Helge Hellevang

• Hellevang, Helge; Nooraiepour, Mohammad; Sednev-Lugovets, Anton & Dziadkowiec, Joanna (2026). Crystal Growth in Porous Media. InterPore Journal. 3(3). doi: 10.69631/9kd53x06. Fulltekst i vitenarkiv Vis sammendrag

  Crystalline silicate minerals and carbonates make up 90% to 95% of the Earth's lithosphere, the rigid outermost shell comprising the crust and uppermost solid mantle. Crystalline materials are continuously modified by fluid–rock interactions including crystal growth occurring along fractures and within pore spaces. Crystals form under conditions dictated by extrinsic factors, such as temperature, pressure, fluid composition, and pore confinement, as well as intrinsic factors such as crystal structure, chemical bonding, and anisotropy. While the thermodynamic stability and structure of crystals are well established, their rates of heterogeneous nucleation and growth remain poorly constrained. This is particularly true in porous media, where nucleation is frequently a distinct and rate-limiting step rather than a negligible precursor to growth, especially where non-classical pathways preclude a single, well-defined interfacial free energy. In this commentary, we outline how crystal nucleation and growth in porous media control pore-scale structure, flow, and transport, and we evaluate how these processes can be represented in numerical models across scales. We examine the distinct roles of nucleation pathways, growth kinetics, interfacial and confinement effects, and crystallization pressure in governing transient porosity, stress localization, and self-organized crystalline networks. Furthermore, we discuss how fluid flow and mixing modulate where and when these processes occur. These principles are illustrated through examples spanning well-controlled synthetic crystal growth in materials science to geo-energy and geoscience applications, such as basaltic CO2 mineralization, where probabilistic nucleation, reactive transport, and evolving pore architecture jointly control macroscopic behavior. Finally, we assess the potential of machine learning and surrogate modeling approaches to bridge the persistent gap between molecular-scale mechanisms and field-scale predictions. By emphasizing mechanistic understanding over system-specific details, our goal is to help porous media scientists judge when crystallization is likely to matter, and to guide the selection of modeling approaches that remain both physically grounded and computationally tractable. WHY THIS PAPER MATTERS Crystal nucleation and growth can progressively clog pore spaces, redirect fluid pathways, and transform the mechanical and transport behavior of porous rocks across scales. Is it possible to use information we have about nanoscale processes to predict reservoir-scale changes? This InterPore Commentary article synthesizes how confinement, interfacial free energies, and crystallization pressures control where crystals appear, how fast they grow, and when they damage or seal flow networks in natural and engineered systems. It then outlines how machine learning can be used to connect molecular, pore, and field scales for predictive modeling.

• Hellevang, Helge; Fischer, Cornelius; Nooraiepour, Mohammad; Molins, Sergi; Masoudi, Mohammad & Prasianakis, Nikolaos I. (2026). Bridging Nanoscopic Surface Heterogeneity and Macroscopic Nucleation Rates: A Perspective on Probabilistic Approaches. Crystal Growth & Design. ISSN 1528-7483. doi: 10.1021/acs.cgd.6c00312. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Predicting the number of newly formed crystals and their spatial distribution on surfaces or within pore spaces matters across many fields, from structural biology to coupled fluid flow and reactive transport in porous media to atmospheric physics. Nucleation occurs at molecular and nanoscopic scales, yet classical nucleation theory (CNT) provides an averaged, macroscopic description, and a growing body of experimental observations is inconsistent with CNT predictions. Probabilistic nucleation models have been developed to predict mineral formation in reactive porous geochemical systems and to generate uncertainty estimates, for example, of how mineral growth affects fluid flow. However, the probability density functions of nucleation rates or induction times that underlie these models remain poorly constrained and are not grounded in the intrinsic nanoscopic physicochemical mechanisms underlying the observed macroscopic behavior. This perspective reviews recent advances in mineral nucleation research, focusing on modeling in coupled reactive transport systems, and examines how the large uncertainties reported for macroscopic nucleation rates may be linked to the extent and spatial distribution of surface sites with contrasting reactivity, such as kinks, steps, and terraces. Building on this, we propose a framework that integrates site-specific nucleation probabilities and explicitly accounts for polymorph selection to enable deterministic prediction of macroscopic nucleation rates from intrinsic surface properties. While the resulting parameter space is extensive, recent advances in machine learning, combined with high-throughput experimentation and simulation, suggest that such predictive, multiscale models are now within reach.

• Dąbrowski, Karol M.; Nooraiepour, Mohammad; Masoudi, Mohammad; Soomro, Ahsan N.; Smulski, Rafał & Barbacki, Jan [Vis alle 8 forfattere av denne artikkelen] (2026). Pore-scale salt precipitation during CO2 injection: How additives and interfacial tension govern crystallization? International Journal of Greenhouse Gas Control. ISSN 1750-5836. 154, s. 104695–104695. doi: 10.1016/j.ijggc.2026.104695. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad; Derluyn, Hannelore; Senechal, Pascale; Moonen, Peter & Hellevang, Helge (2026). Halite precipitates as porous crystalline networks, not dispersed crystals: Self-enhancing growth mechanisms during CO₂ storage in saline aquifers. Chemical Engineering Journal. ISSN 1385-8947. 543, s. 1–15. doi: 10.1016/j.cej.2026.178165. Fulltekst i vitenarkiv Vis sammendrag

  Salt precipitation during CO₂ injection into saline aquifers obstructs flow-controlling pore throats and reduces injectivity, yet reactive transport models assume dispersed, non-porous crystals with negligible fluid flow impact. Here, we demonstrate that halite develops three-dimensional porous networks with 40 ± 15% internal porosity through self-enhancing growth mechanisms. Time-lapse X-ray micro-computed tomography and spectral imaging reveal preferential nucleation at gas-liquid interfaces, where porous hydrophilic aggregates generate capillary suction that draws brine films toward precipitation sites, thereby accelerating growth and expanding the reactive surface area in a positive feedback loop. Spectral tomography identifies two-stage precipitation: dense macrocrystalline cores formed under moderate supersaturation and evaporation, surrounded by microcrystalline overgrowths from rapid late-stage dynamics that produce umbrella-like crusts encapsulating residual brine. This porous architecture explains why modest bulk porosity reduction causes disproportionate permeability decline, as aggregates preferentially obstruct flow percolation pathways rather than uniformly cementing grains or filling pore space. Five interconnected mechanisms drive self-enhancing growth across nano- to centimeter scales: interface nucleation, secondary porous structure formation, steep concentration gradients, hydrophilic substrate film maintenance, and capillary-driven solute delivery. Pore network quantification delivers the first three-dimensional structural characterization of halite growth architecture under GCS-relevant conditions, resolving pore diameter distributions of 20–200 μm, mean coordination numbers of 5, and reactive surface areas averaging 0.04 mm2 per pore – parameters currently absent from reactive transport models yet essential for predicting injectivity impairment and containment integrity at operational storage scales.

• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2026). Carbon Mineralization in CO2–Seawater–Basalt Systems: Reactive Transport Dynamics and Vesicular Pore Architecture Controls. Langmuir. ISSN 0743-7463. 42(16), s. 11435–11456. doi: 10.1021/acs.langmuir.6c00958. Fulltekst i vitenarkiv Vis sammendrag

  Carbon mineralization in basaltic rocks offers a promising pathway for rapid, permanent CO2 storage, yet fundamental controls on reactive transport, precipitation patterns, and permeability evolution under seawater conditions remain poorly constrained. This study integrates flow-through column experiments at 80 °C with CO2-acidified seawater, geochemical modeling, and multiscale pore imaging (SEM-EDS and micro-CT) to elucidate mineralization dynamics in basaltic glass. Results demonstrate that carbonate precipitation is nucleation-limited and kinetically controlled rather than thermodynamically driven or growth-dominated, forming discrete patchy accumulations despite sustained supersaturation. An order-of-magnitude reduction in flow rate (0.05 to 0.005 mL/min) was required to achieve visible precipitation, highlighting residence time as the primary control. Postexperiment characterization identified calcium carbonate and inferred smectite-like clays, with dissolution-induced surface roughening and localized precipitation evident across the column. Seawater chemistry further complicates mineralization kinetics and efficiency relative to freshwater systems. Micro-CT analysis of three vesicular basalt facies revealed low coordination numbers (modal = 2) and serial connectivity, contrasting sharply with higher-coordination sandstone networks. The connected porosity (1.3–32%) differs significantly from the total segmented porosity (18–42%), demonstrating that network topology, rather than total porosity, controls permeability. Pore-scale observations thus indicate that precipitation may render basalts inherently more vulnerable to permeability impairment from modest, distributed precipitation. We explore end-member precipitation-induced clogging scenarios in which small, distributed precipitates cause disproportionately severe permeability loss compared to large, isolated masses. These findings underscore the need for probabilistic reactive transport frameworks that incorporate realistic pore topologies and nucleation barriers, which are fundamentally different from conventional CCS in sedimentary reservoirs, to improve predictions of injectivity and long-term carbon mineralization performance in mafic formations.

• Masoudi, Mohammad; Meyra, Ariel G.; Nooraiepour, Mohammad; Nezhad, Mohaddeseh Mousavi; Hassanpouryouzband, Aliakbar & Hellevang, Helge (2026). Revisiting Hydrogen Sorption–Desorption in Natural Rocks. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 65(6), s. 2984–3026. doi: 10.1021/acs.iecr.5c02081. Fulltekst i vitenarkiv Vis sammendrag

  Hydrogen sorption and desorption in natural rocks are increasingly referenced across subsurface energy and environmental applications, including underground hydrogen storage, natural hydrogen exploration, geological hydrogen generation, and radioactive waste containment. However, the extent to which these physical interactions influence hydrogen behavior in geological materials remains poorly understood. This review examines current experimental and theoretical studies (atomistic simulation and isotherm modeling) of hydrogen sorption and desorption in natural rocks. We evaluated reported sorption capacities and their variability across different lithologies alongside the influencing parameters and the occurrence of hysteresis. Additionally, we modeled all available data using multiple isotherm models to identify the best-fitting formulations. By synthesizing results across diverse methods and geological settings, we identify where physical sorption–desorption is likely to matter, where it is negligible, and what this means for understanding hydrogen transport and retention in the subsurface. Additionally, we provided practical implications of adsorption–desorption, identified critical data gaps, and proposed future research directions to advance the understanding of hydrogen behavior in geological formations.

• Huang, Weikai; Xi, Kelai; Cao, Yingchang; Shan, Xiang; Cui, Zhicheng & Hellevang, Helge (2025). Mechanisms of feldspar dissolution and associated authigenic mineral precipitation in coal measure tight sandstone reservoirs: Insights using a reaction-transport numerical model incorporating organic chelation. Advances in Geo-Energy Research. ISSN 2207-9963. 18(1), s. 51–68. doi: 10.46690/ager.2025.10.05. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Dąbrowski, Karol M.; Masoudi, Mohammad; Kuczyński, Szymon; Song, Zezhang & Lothe, Ane Elisabet [Vis alle 7 forfattere av denne artikkelen] (2025). Geological CO2 storage assessment in emerging CCS regions: Review of sequestration potential, policy development, and socio-economic factors in Poland. International Journal of Greenhouse Gas Control. ISSN 1750-5836. 148, s. 1–25. doi: 10.1016/j.ijggc.2025.104524. Fulltekst i vitenarkiv Vis sammendrag

  Emerging carbon capture and storage (CCS) markets face critical challenges in developing systematic methodologies to assess geological CO2 storage potential under conditions of limited data availability, evolving regulatory frameworks, and nascent infrastructure development. This study establishes an integrated assessment framework for lower-maturity CCS regions that combines geological characterization, storage capacity assessment, regulatory analysis, and socio-economic evaluation through a structured approach adaptable to diverse global contexts. Poland serves as a representative case study, with its coal-reliant economy exemplifying the decarbonization challenges facing emerging regions while meeting European Union climate mandates, and its geological setting offering substantial sequestration opportunities across three major sedimentary regions. Through multidisciplinary analysis synthesizing scattered geological data, policy developments, CCUS value chain dynamics, and stakeholder perspectives, we systematically evaluate CO2 storage potential and demonstrate framework application. Analysis reveals that onshore saline aquifers and depleted hydrocarbon fields provide significant storage capacity, while offshore Baltic Basin sites face logistical and environmental regulatory constraints. Current assessments encounter limitations including sparse data, restricted research access, and inadequate industry-academia collaboration, preventing basin-scale analyses from advancing to higher storage readiness levels and undermining business decision-making reliability. This study contributes a replicable methodology extending beyond Poland to lower-maturity CCS regions worldwide, providing decision-makers with tools for storage assessment, policy development, and stakeholder engagement that support evidence-based deployment strategies. Success in emerging markets requires coordinated advancement across technical characterization, regulatory clarity, infrastructure development, and public engagement, with transparent governance and inclusive community participation as critical enablers for sustainable CCS implementation.

• Dąbrowski, Karol; Nooraiepour, Mohammad; Masoudi, Mohammad; Smulski, Rafał; Hellevang, Helge & Nagy, Stanisław (2025). Understanding Salt Precipitation Dynamics during CO2 Injection into Saline Aquifers using Microfluidic Experiments. I EAGE (Red.), 86th EAGE Annual Conference & Exhibition, June 2-5, 2025, Toulouse, France. European Association of Geoscientists and Engineers (EAGE). doi: https:/www.earthdoc.org/content/papers/10.3997/2214-4609.202510377. Fulltekst i vitenarkiv Vis sammendrag

  This study investigates salt precipitation dynamics using microfluidic experiments, simulating CO2-brine flow in porous media. The results show that salt crystallization is influenced by factors such as capillary backflow, fluid flow, and the interaction between CO2 and brine. Salt precipitation occurs not only where brine was initially present but also in upstream areas due to capillary flow dynamics, highlighting the complexity of these processes. Variations in salinity and flow rates further affect the crystallization behavior, influencing the size, shape, and distribution of salt deposits. These findings emphasize the need for a comprehensive understanding of crystallization mechanisms to improve CO2 sequestration strategies and mitigate unwanted salt precipitation in saline aquifers. Incorporating spatial variability and flow dynamics into models will enhance predictive capabilities and guide operational strategies.

• Masoudi, Mohammad; Nooraiepour, Mohammad; Blom, Richard; Xi, Kelai; Cerasi, Pierre & Hellevang, Helge (2025). Evaluating Hydrogen Sorption in Shale: Effects of Mineral Composition and Sample Treatment. I EAGE (Red.), 86th EAGE Annual Conference & Exhibition, June 2-5, 2025, Toulouse, France. European Association of Geoscientists and Engineers (EAGE). doi: https:/www.earthdoc.org/content/papers/10.3997/2214-4609.202510554. Fulltekst i vitenarkiv Vis sammendrag

  Understanding hydrogen adsorption on clay minerals is vital for optimizing hydrogen energy applications, including storage, natural hydrogen exploration, and also waste containment. However, safety concerns such as high diffusivity and invisible flame risks limit data on hydrogen’s interaction with various natural settings. This study presents the hydrogen adsorption capacities of four clay-rich shale samples from the Norwegian Continental Shelf (NCS) and three pure clay fractions. Utilizing a high-pressure gas adsorption analyzer, we obtained hydrogen sorption isotherms and found that non-dried clay samples had lower hydrogen sorption due to competition with water molecules. The sorption data were analyzed using Freundlich, Langmuir, and Toth models, with the Freundlich model providing the best fit. These findings highlight the complexities involved in hydrogen interactions with natural materials and underscore the need for careful modeling and analysis.

• Nooraiepour, Mohammad; Polański, Krzysztof; Masoudi, Mohammad; Bohloli, Bahman & Hellevang, Helge (2025). CO2-Induced Salt Crystallization in Sandstone Reservoirs: Significance for Mechanical Properties and Containment in Saline Aquifers. I EAGE (Red.), 86th EAGE Annual Conference & Exhibition, June 2-5, 2025, Toulouse, France. European Association of Geoscientists and Engineers (EAGE). doi: https:/www.earthdoc.org/content/papers/10.3997/2214-4609.202510772. Fulltekst i vitenarkiv Vis sammendrag

  Effective predictive modeling of CO₂ storage sites requires a comprehensive understanding of the physico-chemical processes and the challenges of scaling up operations. In high-salinity aquifers, CO₂ injection can significantly reduce injectivity due to pore clogging from salt precipitation. This study investigates the effects of CO₂-induced salt crystallization on the geomechanical properties of sandstone reservoirs. We examine the geochemical and mechanical coupling effects through CO₂-brine-rock interactions, utilizing two experimental paths: treatment with (a) CO₂-acidified brine and (b) supercritical injection leading to salt crystallization. High-pressure, high-temperature (HPHT) triaxial tests were conducted on Boise Buff (BB) and Torrey Red (TR) sandstones, representative of North Sea CO₂ storage candidates. The results showed up to a 50% reduction in Young’s and shear moduli, with TR sandstones being more susceptible due to their lower porosity and higher stiffness. An increase in ductility suggests mechanical weakening and potential storage integrity risks. These findings highlight the containment and integrity challenges posed by salt crystallization in (hyper)saline aquifers beyond injectivity issues, emphasizing potential mechanical failure risks due to pressure buildup. The study underscores the importance of incorporating geochemical interactions into CO₂ storage assessments and reservoir management strategies to mitigate these risks.

• Masoudi, Mohammad; Nooraiepour, Mohammad; Blom, Richard; Xi, Kelai; Cerasi, Pierre & Hellevang, Helge (2025). Impact of hydration on hydrogen sorption in clay minerals and shale caprocks: Implications for hydrogen energy and waste storage. International Journal of Hydrogen Energy. ISSN 0360-3199. 99, s. 661–670. doi: 10.1016/j.ijhydene.2024.12.247. Fulltekst i vitenarkiv Vis sammendrag

  Understanding hydrogen sorption on clay minerals is crucial for hydrogen energy applications such as surface and subsurface storage, natural hydrogen exploration, and waste storage. However, safety issues surrounding hydrogen gas handling limit the availability of comprehensive data. This study investigates hydrogen sorption in various geomaterials, including four shale caprocks from the Norwegian Continental Shelf and three reference pure clay fractions. We have conducted thorough sample characterization, low-temperature nitrogen sorption, and high-pressure high-temperature hydrogen sorption tests on both dried and non-dried samples. The results highlight the higher hydrogen uptake capacity of swelling clays, particularly montmorillonite. Non-dried clay samples demonstrated reduced hydrogen sorption, likely due to competition between hydrogen and water for sorption sites within the clay structure. Freundlich, Langmuir, and Toth models were employed to analyze the experimental hydrogen isotherms, with the Freundlich model providing the best fit due to the linear or convex-downward nature of the isotherms. Based on our results, we suggest that in a fully water-saturated medium, the sorption of hydrogen on clay minerals is very low, and it is unlikely to significantly affect hydrogen transport.

• Dąbrowski, Karol M.; Nooraiepour, Mohammad; Masoudi, Mohammad; Zając, Michał; Kuczyński, Szymon & Smulski, Rafał [Vis alle 9 forfattere av denne artikkelen] (2025). Surface wettability governs brine evaporation and salt precipitation during carbon sequestration in saline aquifers: Microfluidic insights. Science of the Total Environment. ISSN 0048-9697. 958, s. 1–13. doi: 10.1016/j.scitotenv.2024.178110. Fulltekst i vitenarkiv Vis sammendrag

  Carbon sequestration in deep saline aquifers is a promising strategy for reducing atmospheric CO2 emissions. However, salt precipitation triggered by the evaporation of formation brine into injected supercritical CO2 can cause injectivity and containment issues in near-wellbore regions. Predicting the distribution of precipitated salts and their impact on near-wellbore properties remains challenging. This study investigates the influence of surface wettability on CO2-induced halite precipitation and growth within hydrophilic and hydrophobic microfluidic chips designed to mimic rock-structure porous geometries. A series of high-pressure brine-CO2 flow experiments, direct microscopic observations, and detailed image processing were conducted to explore how substrate wettability affects salt precipitation. The experiments show that wettability markedly controls residual brine relocation, film flow movement, solute consumption, and salt formation. Tracking halite precipitation dynamics revealed distinct crystal formation signatures: hydrophilic chips exhibited irregular, larger aggregation patches, while the hydrophobic network showed more numerous, smaller, and limited aggregations. Large individual crystals were observed in both chips, with a notable dominance in the hydrophobic one. Crystallization dynamics varied, with nucleation and growth occurring earlier, progressing faster, and forming bulkier aggregates in the hydrophilic chip. Despite these differences, the three identified temporal stages of brine evaporation and halite surface coverage were comparable. Spatial analysis along the chips indicated that crystal aggregation properties, such as size and distribution, were position-dependent, with hydrophilic chips exhibiting greater probabilistic variability. These observations underscore the impact of surface wettability on salt precipitation through brine accessibility and capillarity, with implications for mitigating and remediating salt issues in saline aquifers.

• Masoudi, Mohammad; Emmel, Benjamin; Betken, Benjamin; Cerasi, Pierre; Ahmed, Elyes & Stroisz, Anna Magdalena [Vis alle 9 forfattere av denne artikkelen] (2025). Feasibility of Hydrogen Storage in Depleted Hydrocarbon Reservoirs in Norway. I EAGE (Red.), 86th EAGE Annual Conference & Exhibition (Workshop Programme), June 2-5, 2025, Toulouse, France. European Association of Geoscientists and Engineers (EAGE). doi: 10.3997/2214-4609.2025101675. Fulltekst i vitenarkiv Vis sammendrag

  Underground hydrogen storage (UHS) in geological formations (aquifers, salt caverns, and depleted reservoirs) is a promising large-scale solution, with capacities reaching terawatt-hours. Depleted reservoirs are especially suitable due to well-characterized geological structures, existing wells and surface facilities, reduced cost of field exploration and decommissioning, lower investment cost, and proven sealing capabilities. To assess the feasibility of offshore UHS in Norway for powering platforms with renewables, interdisciplinary research has been conducted under the HyStorm project and the Hydrogeni FME Centre, combining experimental and modeling approaches to evaluate H2 storage potential in depleted offshore reservoirs. This paper summarizes completed and ongoing work within these projects, focusing on hydrogen storage in depleted oil and gas reservoirs. The studies include: 1. Evaluation of the hydrogen storage potential of shut-down fields on the Norwegian Continental Shelf. 2. Phase behaviour and black-oil simulations to model fluid dynamics in reservoir systems. 3. Hydrogen sorption/desorption experiments on clay minerals and shale caprocks. 4. Measurements of hydrogen and hydrogen-methane mixture viscosity for flow characterization. 5. Risk assessment of legacy wells and their potential impact on storage security. 6. Long-term reservoir sandstone and caprock shale exposure experiments, followed by post-exposure analysis using gas chromatography, XRD, and acoustic/rock mechanical tests.

• Nooraiepour, Mohammad; Polański, Krzysztof; Masoudi, Mohammad; Kuczyński, Szymon; Derluyn, Hannelore & Nogueira, Liebert Parreiras [Vis alle 9 forfattere av denne artikkelen] (2024). Potential for 50% Mechanical Strength Decline in Sandstone Reservoirs Due to Salt Precipitation and CO2–Brine Interactions During Carbon Sequestration. Rock Mechanics and Rock Engineering. ISSN 0723-2632. 58, s. 1239–1269. doi: 10.1007/s00603-024-04223-8. Fulltekst i vitenarkiv Vis sammendrag

  Predictive modeling of CO2 storage sites requires a detailed understanding of physico-chemical processes and scale-up challenges. Dramatic injectivity decline may occur due to salt precipitation pore clogging in high-salinity aquifers during subsurface CO2 injection. This study aims to elucidate the impact of CO2-induced salt crystallization in the porous medium on the geomechanical properties of reservoir sandstones. As the impact of salt precipitation cannot be isolated from the precursor interactions with CO2 and acidified brine, we present a comprehensive review and discuss CO2 chemo-mechanical interactions with sandstones. Laboratory geochemical CO2–brine–rock interactions at elevated pressures and temperatures were conducted on two sandstone sets with contrasting petrophysical qualities. Interaction paths comprised treatment with (a) CO2-acidified brine and (b) supercritical injection until brine dry-out, salt crystallization, and growth. Afterward, the core samples were tested in a triaxial apparatus at varying stresses and temperatures. The elastic moduli of intact, CO2-acidified brine treated, and salt-affected sandstones were juxtaposed to elucidate the geochemical–geomechanical-coupled impacts and identify the extent of crystallization damages. The salt-affected sandstones showed a maximum of 50% reduction in Young’s and shear moduli and twice an increase in Poisson’s ratio compared to intact condition. The deterioration was notably higher for the tighter reservoir sandstones, with higher initial stiffness and lower porosity–permeability. We propose two pore- and grain-scale mechanisms to explain how salt crystallization contributes to stress localization and mechanical damage. The results highlight the potential integrity risk imposed by salt crystallization in (hyper)saline aquifers besides injectivity, signaling mechanical failure exacerbated by pressure buildup.

• Xi, Kelai; Cao, Yingchang; Zhu, Rukai; Xin, Honggang; Dan, Weidong & Hellevang, Helge (2024). Integration of diagenesis, porosity evolution, and oil emplacement in lacustrine tight sandstone reservoirs: A review with illustrative cases from the major oil-bearing basins in China. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 108(4), s. 691–718. doi: 10.1306/12212322063. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Hassanpouryouzband, Aliakbar; Hellevang, Helge & Haszeldine, R. Stuart (2024). Lined rock caverns: A hydrogen storage solution. Journal of Energy Storage. ISSN 2352-152X. 84(Part B). doi: 10.1016/j.est.2024.110927. Fulltekst i vitenarkiv Vis sammendrag

  The inherent intermittency of renewable energy sources frequently leads to variable power outputs, challenging the reliability of our power supply. An evolving approach to mitigate these inconsistencies is the conversion of excess energy into hydrogen. Yet, the pursuit of safe and efficient hydrogen storage methods endures. In this perspective paper, we conduct a comprehensive evaluation of the potential of lined rock caverns (LRCs) for hydrogen storage. We provide a detailed exploration of all system components and their associated challenges. While LRCs have demonstrated effectiveness in storing various materials, their suitability for hydrogen storage remains a largely uncharted territory. Drawing from empirical data and practical applications, we delineate the unique challenges entailed in employing LRCs for hydrogen storage. Additionally, we identify promising avenues for advancement and underscore crucial research directions to unlock the full potential of LRCs in hydrogen storage applications. The foundational infrastructure and associated risks of large-scale hydrogen storage within LRCs necessitate thorough examination. This work not only highlights challenges but also prospects, with the aim of accelerating the realization of this innovative storage technology on a practical, field-scale level.

• Cao, Yingchang; Xi, Kelai; Niu, Xiaobing; Lin, Miruo; Ma, Weijiao & Zhang, Zehan [Vis alle 7 forfattere av denne artikkelen] (2024). Lamina-scale diagenetic mass transfer in lacustrine organic-rich shales and impacts on shale oil reservoir formation. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 108(7), s. 1327–1356. doi: 10.1306/12212323018. Fulltekst i vitenarkiv
• Meng, Jie; Li, Changdong; Zhang, Shuang; Hellevang, Helge & Xiang, Linyu (2024). New computational method for calculating of water droplet–clay contact angles: Based on molecular dynamics. Applied Clay Science. ISSN 0169-1317. 252. doi: 10.1016/j.clay.2024.107343. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Polanski, Krzysztof; Masoudi, Mohammad; Kuczyński, Szymon; Derluyn, Hannelore & Nogueira, Liebert Parreiras [Vis alle 9 forfattere av denne artikkelen] (2024). Assessing salt precipitation and weak acid interaction in subsurface CO2 injection: Potential 50% strength decline in near-wellbore reservoir sandstones. arXiv. doi: 10.48550/arXiv.2401.14852. Fulltekst i vitenarkiv Vis sammendrag

  Predictive modeling of CO2 storage sites requires a detailed understanding of physico-chemical processes and potential challenges for scale-up. Dramatic injectivity decline may occur due to salt precipitation pore clogging in high-salinity reservoirs, even over a short time frame. This study aims to elucidate the adverse impact of CO2-induced salt crystallization in porous media on the geomechanical properties of near-wellbore reservoir sandstones. As the impact of salt precipitation cannot be isolated from the precursor effects of interaction with CO2 and carbonic acid, we initiated our study by a comprehensive review of CO2 chemo-mechanical interactions with sandstones. We conducted laboratory geochemical CO2-brine-rock interactions at elevated pressures and temperatures on two sets of porous sandstone with contrasting petrophysical qualities. Two paths were followed: treatment with (a) CO2-acidified brine at 10 MPa fluid pressure and 60C for 7 days, and a second subset continuation with (b) supercritical injection until complete dry-out and salt precipitation. Afterward, the core samples were tested in a triaxial apparatus at varying stresses and temperatures. The elastic moduli of intact, CO2-reacted, and salt-damaged sandstones were juxtaposed to elucidate the extent of crystallization damages. The salt-affected specimens showed a maximum of 50 percent reduction in Young's and shear moduli and twice an increase in Poisson's ratio compared to intact condition. The deterioration was notably higher for the tighter rocks with higher initial stiffness.

• Masoudi, Mohammad; Nooraiepour, Mohammad; Deng, Hang & Hellevang, Helge (2024). Mineral precipitation and geometry alteration in porous structures: How to upscale variations in permeability-porosity relationship? EarthArXiv preprint platform. doi: 10.31223/X56Q41. Fulltekst i vitenarkiv Vis sammendrag

  Porous materials in natural and engineered environments are subject to morphological changes resulting from interacting chemical and physical processes. The complexity of coupled flow, transport, and chemical processes that occur on different temporal and spatial scales makes it difficult to predict the resulting porosity and permeability alterations. Delineating the controls of mineral precipitation reactions is particularly challenging because it requires the implementation of nucleation criteria and precipitation attributes. By conducting pore-scale simulations, we studied how the amount and stochastic distribution of crystallites, controlled by nucleation, affect the pore geometry and permeability in two-dimensional porous structures. The observed relationships between porosity and permeability show characteristics that differ from ones that are typically applicable in dissolving porous media because of the clogging effect. Additionally, we propose a stochastic framework that upscales the co-evolution of permeability and porosity across length scales. This framework enables precise communication of clogging behavior to continuum-scale simulations based on statistical probability distributions of permeability-porosity variations.

• Sun, Xiaolong; Liu, Keyu; An, Senyou; Hellevang, Helge; Cao, Yingchang & Alcalde, Juan [Vis alle 10 forfattere av denne artikkelen] (2024). A review of experimental investigations on salt precipitation during CO2 geological storage. Geoenergy Science and Engineering. ISSN 2949-8929. 244. doi: 10.1016/j.geoen.2024.213451. Fulltekst i vitenarkiv Vis sammendrag

  Salt precipitation due to formation drying is a critical secondary alteration process that significantly impairs reservoir injectivity in the context of CO2 geological storage. In this work, salt precipitation during CO2 injection is reviewed primarily through various experimental studies. First, the experimental systems for salt precipitation studies, namely core-flooding, microfluidic-chip, static batch, and surface drying experimental systems, have been described to present their respective experimental procedures and merits, as well as corresponding applications. Subsequently, following the general description of the formation mechanisms of salt precipitation, the macro and micro salt distribution patterns at the reservoir and pore scales have been summarized. Finally, and most importantly, this study provides a comprehensive analysis of the controlling factors for salt precipitation, categorized into four different groups, according to the brine, rock, gas, and injection scenario aspects. Among all these factors, brine salinity, CO2 injection rate and initial reservoir properties are considered the most critical in determining the amount and distribution of precipitated salts and the degree of injectivity impairment. The effects of multi-scale reservoir heterogeneity and rock wettability on salt precipitation are attracting growing consideration, while the brine and gas composition studies are receiving less attention due to their relatively minor influences on reservoir alteration. Due to the limited specimen sizes, the ex-situ brine replenishment may be underestimated in core-flooding and microfluidic-chip experiments. This may result in a potentially significant underestimation of the volume of local salts and the potentially inaccurate prediction of the drying process during CO2 injection in many such experiments.

• Masoudi, Mohammad; Nooraiepour, Mohammad; Deng, Hang & Hellevang, Helge (2024). Mineral Precipitation and Geometry Alteration in Porous Structures: How to Upscale Variations in Permeability-Porosity Relationship? Energy & Fuels. ISSN 0887-0624. 38(11), s. 9988–1001. doi: 10.1021/acs.energyfuels.4c01432. Fulltekst i vitenarkiv Vis sammendrag

  Porous materials in natural and engineered environments are subject to morphological changes resulting from interacting chemical and physical processes. The intricate nature of these coupled processes, occurring at various temporal and spatial scales, poses challenges in predicting alterations in porosity and permeability. Delineating the controls of mineral precipitation reactions is particularly challenging because it requires the implementation of nucleation criteria and growth mechanisms. By conducting pore-scale simulations, we investigated the impact of the amount and stochastic distribution of crystallites, controlled by nucleation, on pore geometry and permeability in two-dimensional porous structures. The observed relationships between porosity and permeability exhibit characteristics that differ from the ones that are typically applied in dissolving porous media because of the clogging effect. Additionally, we propose a stochastic framework that upscales the coevolution of permeability and porosity across length scales. This framework enables the upscaling of clogging behavior to continuum-scale simulations based on statistical probability distributions of permeability–porosity variations.

• Hellevang, Helge; Nooraiepour, Mohammad & Masoudi, Mohammad (2023). Mineral nucleation and growth in porous and fractured media. Goldschmidt Conference Abstracts. Fulltekst i vitenarkiv Vis sammendrag

  Early simulation works on carbonization during CO2 storage overpredicted the amount and rate of mineral formation because of unrealistic growth models based on transition state theory (TST), where surface areas for growth were assumed to be present from day one. Inspired by [1], we made our first nucleation-growth model a decade ago [2], providing a zero-dimensional averaged kinetic nucleation-growth model for the continuum scale. This model provided some information on lag time for the onset of mineral growth, which is essential to understand why the lack of mineralization in short-term laboratory experiments cannot be extrapolated in time. The continuum-scale models, however, lack the potential to predict how the pore space geometries change and, thereby, how the permeability-porosity relationship changes in complex ways. Recent efforts have been to implement mineral nucleation and crystal growth in pore-scale models, using classical nucleation theory (CNT) and statistically derived expressions for the induction time of the formation of stable growing crystallites. In the new expressions, the probability of creating a crystallite at each surface site (solid surface area in the pore space) is estimated based on a normal distribution centered around the mean induction time value [τ] (symmetric between t= 0 and 2τ). This has been implemented and tested in 2D pore-scale models, showing strong mutual relations and impacts of transport and crystallization in porous media [3-4]. Another emerging field for nucleation-growth research is how the number of crystallites (or aggregates) and their spatial distribution control the evolution of porosity-permeability relations. 2D nucleation-growth Monte Carlo-type pore-scale RTMs show that the permeability-porosity relationship and the associated uncertainty depend on the number of crystallites (Figs. 1, 2). The relationship evolves predictably if the number of crystallites is small or large. If, on the other hand, the number of crystals is in an intermediate range, the permeability-porosity dynamics vary stochastically and are highly uncertain.

• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2023). Nucleation and Crystal Growth on the Secondary Substrate. I Médici, Ezequiel F. & Otero, Alejandro D. (Red.), Album of Porous Media. Springer. ISSN 9783031238000. doi: 10.1007/978-3-031-23800-0_14. Fulltekst i vitenarkiv
• Zając, Michał; Nagy, Stanisław; Kuczyński, Szymon; Dabrowski, Karol M.; Smulski, Rafal & Hellevang, Helge [Vis alle 8 forfattere av denne artikkelen] (2023). Multicomponent and multiphase CO2-brine system in microfluidic characterised in situ by Raman spectroscopy, 84th EAGE Conference & Exhibition 2023. European Association of Geoscientists and Engineers (EAGE). doi: 10.3997/2214-4609.2023101024. Fulltekst i vitenarkiv Vis sammendrag

  Deep-saline aquifers could be instrumental in the geological storage of carbon dioxide due to their relatively good reservoir properties, high volume, and prevalence. However, there are a few difficulties which should be overcome to obtain effective stores in such reservoirs. Most problems are related to formation damage caused by salt precipitation. Due to the complexity of such systems, it is necessary to identify crucial processes, phenomena, factors, and products. In our work, we present a novel platform to trace precipitation ‘in situ’ using microfluidics and Raman spectroscopy. We have built a set in which we can investigate not only the salt deposition phenomenon in pores or microchannels by visual observation but also, because of Raman spectroscopy, determine the kinetics of reactions, carbon dioxide solubility, phase composition, and crystal composition. On the basis of our research, we have identified intensive clogging of pores and fast growth of crystals on the rock-like grain boundaries and bottlenecks. Furthermore, in a 20% weight NaCl solution we have found precipitated carbonates, for example, nitrate. Our results can broaden our understanding of CCS in high-saline aquifers and contribute to the development and common use of this process.

• Nooraiepour, Mohammad; Masoudi, Mohammad; Hellevang, Helge; Dąbrowski, Karol; Kuczyński, Szymon & Zając, Michał [Vis alle 8 forfattere av denne artikkelen] (2023). Why is it critical to revisit significance and consequences of salt precipitation during CO2 injection? 84th EAGE Conference & Exhibition 2023. European Association of Geoscientists and Engineers (EAGE). doi: 10.3997/2214-4609.2023101162. Fulltekst i vitenarkiv Vis sammendrag

  Among the candidates for CO2 sequestration, deep saline aquifers are considered the best option because of their storage capacity and proximity to emission sources. Injection of large volumes (million tons scale) of supercritical CO2 into the geological formations causes evaporation of formation water near wellbores and precipitation of salt crystals inside the porous medium. CO2-induced salt precipitation can substantially threaten sequestration in saline aquifers. Most available experimental, numerical and theoretical works have focused on predicting the salt's location and amount. However, less attention is given to the precipitation physics, growth dynamics, and behavior of the fluid-solid interface near the evaporation/precipitation front. We report a series of experiments to provide new insights, beyond the current understanding, into the dynamics of brine evaporation and salt growth and to challenge the current understanding that might not be entirely representative of the field conditions. The research outcome highlights the interplay of complex processes (some of which are not yet fully characterized) crucial in investigating salt precipitation induced by million-tons-scale CO2 injection. The observed characteristics call for further in-depth investigation because, in the context of subsurface CO2 storage, we need to redefine how we see injectivity impairment due to salt precipitation.

• Masoudi, Mohammad; Nooraiepour, Mohammad & Hellevang, Helge (2023). Salt Precipitation during Geological CO2 Storage: Effect of Access to Continuous Brine Source. EarthArXiv preprint platform. doi: 10.31223/X5J68G. Fulltekst i vitenarkiv Vis sammendrag

  During CO2 storage, the near-wellbore environment experiences significant chemical, physical, thermal, and mechanical perturbations. Therefore, it is crucial to characterize the coupled thermo-hydro-mechanical-chemical (THMC) processes in this region through representative experimental tests and numerical simulations to maximize the safety and cost-efficiency of CO2 storage. One common shortcoming of current experimental methods is failing to facilitate access and replicate the in-situ brine sources within geological repositories, particularly saline aquifers. This failure can significantly alter the dynamics and dimensionality of mineral/crystal growth in porous reservoir rocks due to the availability and continuity of solute. To address this issue, we designed surface mineral precipitation tests and large-scale sandbox experiments to investigate salt precipitation and growth under two different scales and regimes in porous geometries. The laboratory results indicated massive salt accumulation close to the injection port and underlined the effect of solute availability and continuity on intensifying severity of salt accumulation. The observed continued growth highlights the importance of designing representative laboratory experiments in exploring fluid-rock interactions during carbon sequestration in the subsurface geological media.

• Hellevang, Helge; Ippach, Mats Rouven; Westermann, Sebastian & Nooraiepour, Mohammad (2023). Formation of giant Siberian gas emission craters (GECs). EarthArXiv preprint platform. doi: 10.31223/X59Q3K. Fulltekst i vitenarkiv Vis sammendrag

  The recent discovery of eight giant gas escape craters (GECs) in the Russian Yamal and Gydan peninsulas has challenged researchers for the past decade. Despite numerous proposed models, ranging from meteor impacts to gas explosions, none provide a comprehensive explanation for why the GECs are found only in this specific region. This study proposes a new general model for the formation of GECs in which local permafrost thinning is linked to the local geology, i.e., discrete conductive faults bring natural gas and heat to the base permafrost, deforming and melting the base leading to the development of domal gas and heat traps. Atmospheric warming results in further local thinning and eventually mechanical collapse. The morphology of the GECs initially reflects the concentric deformation above domal base-permafrost structures but are after a short time disguised by water and sediment infill, and over time peatification, and cannot be distinguished from e.g., thermokarst lakes. Thus, the true number of GECs may largely exceed those already discovered.

• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2023). Experimental and Numerical Description of Mineral Precipitation Dynamics on Heterogeneous Substrate Surfaces. EarthArXiv preprint platform. doi: 10.31223/X5SQ49. Fulltekst i vitenarkiv Vis sammendrag

  Mineral precipitation reactions are critical in reactive transport studies of porous media due to their significant impacts on flow and transport properties. Understanding the nucleation process, a probabilistic phenomenon that determines the location and distribution of solid formation in space and time domains, is essential for accurately comprehending the effect of mineral precipitation on porous media surfaces. To this end, this paper presents microfluidic laboratory experiments and reactive transport modeling of mineral precipitation dynamics under different physicochemical conditions and substrate surface properties. Our results demonstrate the importance of the spatial and temporal location and distribution of nucleation and growth events when the interplay among several determining parameters is inevitable. We show mineral precipitation on primary and secondary substrate surfaces under different supersaturations and temperatures. Our high-resolution EDS-SEM surface maps identify the favorable sites and competing locations for attracting solute concentration and continued growth, providing valuable insights into the mineral precipitation mechanism.

• Ma, Pengjie; Lin, Chengyan; Dong, Chunmei; Ren, Lihua; Jahren, Jens & Hellevang, Helge [Vis alle 7 forfattere av denne artikkelen] (2023). Effect of faulting on diagenetic processes in the silicate-sulfate-carbonate system: A case study from the Bonan Sag of Jiyang Depression, Bohai Bay Basin. Marine and Petroleum Geology. ISSN 0264-8172. 147. doi: 10.1016/j.marpetgeo.2022.105985. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2022). Precipitation-Induced Geometry Evolution During Reactive Transport: Experimental and Numerical Insights into Stochastic Dynamics of Mineral Growth, 83rd EAGE Annual Conference & Exhibition 2022. European Association of Geoscientists and Engineers (EAGE). ISSN 9789073834125. doi: 10.3997/2214-4609.202210470. Fulltekst i vitenarkiv Vis sammendrag

  Crystal nucleation, precipitation, and growth during a reactive fluid flow and solute transport are critical in many natural and industrial systems. Mineral growth is a prime example where (geo)chemical reactions give rise to geometry evolution in porous media. Motivated by the importance of incorporating stochastic dynamics of nucleation, crystallization, and growth kinetics in studying a variety of multiphase and multiscale processes occurring in geo-environmental and geo-energy systems, this work presents experimental and numerical results delineating geometry evolution induced by mineral precipitation. A total of 27 microfluidic experiments (3×3×3 sets of supersaturation-temperature-time) extend the understanding of factors controlling crystal nucleation and growth rates, the impact of ambient and aqueous phase properties, and the substrate characteristics. For numerical simulations, we used the Lattice Boltzmann Method (LBM) to solve the advection-diffusion-reaction equation for tracking the concentration of different species. We developed a reactive transport model based on our recently proposed probabilistic nucleation and crystal growth theory. The results indicated the probabilistic nature of the process, which is affected by the physiochemistry of the aqueous phase and governed by fluid-solid surface interactions. We underscore the importance of theoretical reactive transport models considering the probabilistic nature of nucleation events before crystal formation.

• Masoudi, Mohammad; Nooraiepour, Mohammad & Hellevang, Helge (2022). The Effect of Preferential Nucleation Sites on the Distribution of Secondary Mineral Precipitates, 83rd EAGE Annual Conference & Exhibition 2022. European Association of Geoscientists and Engineers (EAGE). ISSN 9789073834125. doi: 10.3997/2214-4609.202210445. Fulltekst i vitenarkiv Vis sammendrag

  In the process of mineral nucleation and growth, substrate surface properties and substrate types introduce favorable areas where nucleation events are more likely to occur. The preferential sites for mineral nucleation exist because of the lower interfacial free energy between the precipitating phase and the substrate. In this work, we used a pore-scale Lattice Boltzmann (LB)-based reactive transport model incorporated with the developed probabilistic nucleation model in our previous works to investigate the role of the interfacial free energy between the nucleating phase and the substrate on the nucleation and growth of secondary minerals. We also used Shannon entropy to assess the spatial randomness and the evolution path of the systems as solid phases form. The results showed that the developed model can accurately capture the selective behavior of nucleation processes in the presence of preferential sites. The simulation results demonstrate the importance of using a probabilistic nucleation model to capture the correct physics of this phenomenon. It is also concluded that the probabilistic nucleation models are more relevant in environments with longer induction times.

• Nooraiepour, Mohammad; Masoudi, Mohammad; Shokri, Nima & Hellevang, Helge (2022). Precipitation-induced Geometry Evolution in Porous Media: Numerical and Experimental Insights based on New Model on Probabilistic Nucleation and Mineral Growth. 16th Greenhouse Gas Control Technologies Conference 2022 (GHGT-16). doi: 10.2139/ssrn.4272555. Fulltekst i vitenarkiv Vis sammendrag

  Precipitation and growth of solid phases during a reactive fluid flow and solute transport are critical in many natural and industrial systems. Mineral nucleation and growth is a prime example where (geo)chemical reactions give rise to geometry evolution in porous media. The precipitation reactions can reduce the amount of void space, alter pore space connectivity and morphology, modify tortuosity, deteriorate permeability, and change the fluid flow and solute transport. Additionally, precipitation events reshape the available surface area for growth, leading to changes in reactivity, reaction progress, and reaction rates. The target is to ideally limit the mineral growth in many applications, such as avoiding damage to reservoir permeability due to solid precipitation near CO2 injection wells. In other cases, maximizing mineral growth in porous media can be highly favorable, such as sealing fractured caprocks or increasing mineral trapping in the sequestration sites. Understanding, controlling, and predicting this reactive transport phenomenon is challenging because it requires coupling flow, transport, and chemical processes often characterized by different temporal and spatial resolutions. Nucleation is the pre-growth process that controls the primary position of any mineral precipitation and subsequent growth dynamics. Mineral nucleation is a probabilistic process where crystals might nucleate anywhere given similar conditions, such as surface properties, supersaturation, and temperature. It is imperative to use a probabilistic approach or an upscaled physically sound representation to understand the effect of mineral precipitation on porous medium hydrodynamics. Motivated by the importance of incorporating stochastic dynamics of nucleation and growth kinetics in studying various multiphase and multiscale processes occurring in geo-environmental and geo-energy systems, this paper provides numerical and experimental insights into the recently proposed probabilistic nucleation model. We present laboratory experiments (microfluidic and flow-through column reactor) and pore-scale reactive Lattice Boltzmann Method (LBM) numerical simulations. As variations in the properties of the porous medium are intimately linked to the spatial distribution of the precipitation events, we quantify the evolution of experimental and numerical modeled systems at different physiochemical conditions by mapping the disorder of the system (Shannon's entropy) induced by the spatial mineral distributions across time. We use experimental and numerical results to show the importance of the spatial and temporal location and distribution of nucleation and growth events, particularly when the interplay among several determining parameters is inevitable. The results show that probabilistic nucleation contributes to broad stochastic distributions in both amounts and locations of crystals in temporal and spatial domains.

• Ahmadigoltapeh, Sajjad; Abdolahi, Saeed; Jahren, Jens; Miri, Rohaldin & Hellevang, Helge (2022). Drivers of Low Salinity Effect in Carbonate Reservoirs Using Molecular Dynamic Simulation. Journal of Molecular Liquids. ISSN 0167-7322. 360. doi: 10.1016/j.molliq.2022.119490. Fulltekst i vitenarkiv Vis sammendrag

  Low salinity water (LSW) flooding has yielded promising results in improving the enhanced oil recovery (EOR) techniques in sandstone and carbonate reservoirs. Despite various studies and advances, the main mechanism behind the oil displacement in the rock-brine-oil system is unclear. To get a better understanding of the governing mechanisms, we used the molecular dynamic (MD) method to simulate a system including calcite-brine-oil under two different scenarios. At T=300 K and T=360 K each scenario is completed during 40 ns using a canonical ensemble. The results show that all mono/divalent ions are hydrated initially. Furthermore, Na+, Cl− and H2O molecules reside close to the calcite surface and their positions show little change at different time steps. However, the position of divalent ions is dynamic depending on the simulation time steps. Ca2+, which is initially detected at 2.35 Å above the solid surface at T=300 K and T=360 K, migrates away by time. On the other hand, Mg2+ and SO42− which are invisible up to t = 16 ns even at the radius of 10 Å, move gradually toward the surface with time and consolidate their position after oil displacement. Namely, prior to oil displacement, a shift in Na+, Cl− and Ca2+ locations is noticed, and the trend of double electric layer (EDL) is extended, which might be the cause of oil displacement. The findings of this study are applicable in the improvement of EOR technology, water resource treatment and contaminant transfer from geological systems, dealing with solid solutions such as ocean-soil systems.

• Ahmadigoltapeh, Sajjad; Rahman, Md Jamilur; Mondol, Nazmul Haque & Hellevang, Helge (2022). Artificial Neural Network-Based Caprock Structural Reliability Analysis for CO2 Injection Site—An Example from Northern North Sea. Energies. 15(9). doi: 10.3390/en15093365. Fulltekst i vitenarkiv Vis sammendrag

  In CO2 sequestration projects, assessing caprock structural stability is crucial to assure the success and reliability of the CO2 injection. However, since caprock experimental data are sparse, we applied a Monte Carlo (MC) algorithm to generate stochastic data from the given mean and standard deviation values. The generated data sets were introduced to a neural network (NN), including four hidden layers for classification purposes. The model was then used to evaluate organic-rich Draupne caprock shale failure in the Alpha structure, northern North Sea. The train and test were carried out with 75% and 25% of the input data, respectively. Following that, validation is accomplished with unseen data, yielding promising classification scores. The results show that introducing larger input data sizes to the established NN provides better convergence conditions and higher classification scores. Although the NN can predicts the failure states with a classification score of 97%, the structural reliability was significantly low compare to the failure results estimated using other method. Moreover, this indicated that during evaluating the field-scale caprock failure, more experimental data is needed for a reliable result. However, this study depicts the advantage of machine learning algorithms in geological CO2 storage projects compared with similar finite elements methods in the aspect of short fitting time, high accuracy, and flexibility in processing different input data sizes with different scales.

• Ahmadigoltapeh, Sajjad; Abdolahi, Saeed; Miri, Rohaldin & Hellevang, Helge (2021). Extension of PC-SAFT equation of state to include mineral surface effect in fluid properties using molecular dynamic simulation. Sustainable Energy Technologies and Assessments. ISSN 2213-1388. 48. doi: 10.1016/j.seta.2021.101624. Fulltekst i vitenarkiv Vis sammendrag

  In the vicinity of fluid-mineral interfaces a transition zone exist in which the order and packing of the molecules differ from that of the bulk phase where the distribution of intermolecular forces exhibit a more homogenous form. To develop an understanding of the thermodynamic properties in the fluid-mineral interface molecular dynamic (MD) simulation was conducted for the water-calcite system. To predict the water properties near the calcite wall, we have defined a contribution for Helmholtz energy extended from PC-SAFT equation of state (EOS). The new energy contribution depends on the confinement parameters i.e. potential of fluid-wall interaction, confinement degree, bulk density, and fraction of confined molecules estimated by MD simulation. The outcomes of MD simulation exhibit the layering transition of water on the water-calcite interface. In addition, MD simulation confirm the energy deviation within the layering transition zone, where the calcite adsorbs the water molecules. In this approach, the modified PC-SAFT showed a good agreement with MD observations. The results of this study can contribute to a better understanding of fluid behavior at the fluid-mineral interface. In addition, this technique is a valuable tool that can be used to estimate solubility limits in multicomponent fluid processing and pipeline transport.

• An, Senyou; Erfani, Hamidreza; Hellevang, Helge & Niasar, Vahid (2021). Lattice-Boltzmann simulation of dissolution of carbonate rock during CO2-saturated brine injection. Chemical Engineering Journal. ISSN 1385-8947. 408. doi: 10.1016/j.cej.2020.127235. Fulltekst i vitenarkiv
• Ahmadigoltapeh, Sajjad; Miri, Rohaldin; Aagaard, Per & Hellevang, Helge (2021). Extension of SAFT equation of state for fluids confined in nano-pores of sedimentary rocks using molecular dynamic simulation. Journal of Molecular Liquids. ISSN 0167-7322. 348. doi: 10.1016/j.molliq.2021.118045. Fulltekst i vitenarkiv Vis sammendrag

  Confined fluids in nano-mineral pores show notably different thermodynamic behavior compared with those of the same fluid in bulk. We have extended an equation of state (EoS) inspired by statistical association fluid theory (SAFT) to incorporate the fluid-mineral effect into the pure fluid properties confined in the nanopore. The established EoS is coupled with a Helmholtz free energy contribution which is a function of confinement characteristics: the potential of fluid-mineral interaction, bulk-like density and CF. The novel fitting parameter CF relies on the local properties of confined fluid and measures the density fraction within the layering and bulk-like zones, i.e., . The first-principle molecular dynamics (MD) simulation was utilized to estimate the confinement parameters. At T = 300 K, 350 K, 400 K, and 450 K, the NVT ensemble was applied to simulate slit-pore calcite with a continuous and homogeneous surface in contact with water, with pore widths ranging from 1.5 nm to 5 nm. After running each NVT ensemble for 6 ns, the energy and density of confined water were analyzed, and a deviation was discovered with different behavior from what had previously been reported. Coupling CF parameter with proposed EoS improves the absolute relative errors (ARE) at low temperatures up about 50%, leading to a good agreement between modified SAFT EoS and MD results. The methodology described here may be extended to include a mixture of associating fluids such as those found in oil composition and implemented in all SAFT versions.

• Nooraiepour, Mohammad; Fazeli, Hossein; Masoudi, Mohammad & Hellevang, Helge (2021). Effect of Mineral Heterogeneity on Fracture Dissolution in Carbonate-Rich Caprocks During Subsurface Co2 Injection. I SPE, , (Red.), SPE Europec featured at 82nd EAGE conference and exhibition, October 18-21, 2021, Amsterdam, The Netherlands. Society of Petroleum Engineers. ISSN 9781613997918. doi: 10.3997/2214-4609.202011174. Fulltekst i vitenarkiv Vis sammendrag

  Chemical interactions between CO2, brine and caprock-forming minerals might lead to the dissolution of the fractures present in the caprock of CO2 storage sites. One factor that can affect the chemically induced fracture alterations is mineral heterogeneity in the caprock. In this study, we investigate the effect of mineral heterogeneity on fracture dissolution of four carbonate-rich caprock samples, having different levels of heterogeneity, where CO¬2-rich brine flows through the fractured caprocks. A HPHT geomaterial microfluidic experimental setup is used to monitor the evolution of the fractures. Results indicate that the homogeneous caprock samples, i.e. the samples that are mainly composed of calcite, show a uniform fracture wall dissolution while fracture wall roughness increases for heterogeneous samples. The effluent chemistry analyses show that the sample-scale calcite dissolution rate decreases over time, which can be due to the mass transfer limitations in the boundary layer near the fracture wall (for the homogeneous sample) or in the altered layer formed around the fracture (for the heterogeneous samples). Microfluidic experiments were also done for one carbonate-rich fine-grained shale sample, which showed no detectable fracture alteration. However, the effluent analysis for the shale sample confirmed the calcite dissolution.

• Hellevang, Helge; Line, Lina Hedvig; Eide, Christian Haug; Jahren, Jens Sigurd & Haile, Beyene Girma (2021). Insights into past tectonism from authigenic quartz. Geochemical Perspectives Letters. ISSN 2410-339X. 19, s. 27–31. doi: 10.7185/geochemlet.2130. Fulltekst i vitenarkiv Vis sammendrag

  Authigenic quartz grains carry information that is diagnostic for the thermal history and thereby the burial depth and uplift of sediments. Recycled quartz grains with embayed or rounded authigenic remnants have been observed globally, but the value of these grains in unravelling past tectonism is presently underexplored. In this study, we launch a new method to demonstrate that cathodoluminescence (CL) in combination with fluid inclusion data and textural characteristics of authigenic quartz can provide important information about past tectonic activity. Vital in the method is the realisation that recycled quartz grains can be distinguished from other quartz grains by their geochemical CL fingerprint, allowing tracking of uplifted source terrains in a direction towards higher fractions of the recycled grains. Furthermore, regional mapping can reveal both intra-basinal recycling as well as recycled grains transported into the basin from external sources. The new proposed method is simple and does not require more than a standard Scanning Electron Microscope equipped with a CL detector, available at many geoscientific institutions worldwide. This innovative approach applies to a wide section of geoscientific disciplines, and complement and supplement other conventional methods used for unravelling past tectonism.

• Xi, Kelai; Cao, Yingchang; Haile, Beyene Girma; Zhu, Ning; Liu, Keyu & Wu, Songtao [Vis alle 7 forfattere av denne artikkelen] (2021). Diagenetic variations with respect to sediment composition and paleo-fluids evolution in conglomerate reservoirs: A case study of the Triassic Baikouquan Formation in Mahu Sag, Junggar Basin, Northwestern China. Journal of Petroleum Science and Engineering. ISSN 0920-4105. 197. doi: 10.1016/j.petrol.2020.107943. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad; Shokri, Nima & Hellevang, Helge (2021). Probabilistic Nucleation and Crystal Growth in Porous Medium: New Insights from Calcium Carbonate Precipitation on Primary and Secondary Substrates. ACS Omega. 6(42), s. 28072–28083. doi: 10.1021/acsomega.1c04147. Fulltekst i vitenarkiv Vis sammendrag

  Knowledge of crystal nucleation and growth is paramount in understanding the geometry evolution of porous medium during reactive transport processes in geo-environmental studies. To predict transport properties precisely, it is necessary to delineate both the amount and location of nucleation and precipitation events in the spatiotemporal domain. This study investigates the precipitation of calcium carbonate crystals on a heterogeneous sandstone substrate as a function of chemical supersaturation, temperature, and time. The main objective was to evaluate solid formation under different boundary conditions when the solid–liquid interface plays a key role. New observations were made on the effect of primary and secondary substrates and the role of preferential precipitation locations on the rock surfaces. The results indicate that supersaturation and temperature determine the amount, distribution pattern, and growth rate of crystals. Substrate characteristics governed the nucleation, growth location, and evolution probability across time and space. Moreover, substrate surface properties introduced preferential sites that were occupied and covered with solids first. Our results highlight the complex dynamics induced by substrate surface properties on the spatial and temporal solute distribution, transport, and deposition. We accentuate the great potentials of the probabilistic nucleation model to describe mineral formation in a porous medium during reactive transport.

• Fazeli, Hossein; Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2021). Effect of Mineral Heterogeneity on Fracture Dissolution in Carbonate-Rich Caprocks During Subsurface Co2 Injection. EAGE extended abstracts. doi: 10.3997/2214-4609.202011174. Fulltekst i vitenarkiv Vis sammendrag

  Chemical interactions between CO2, brine, and caprock-forming minerals might lead to dissolution of the fractures present in the caprock of CO2 storage sites. One factor that can affect the chemically induced fracture alterations is mineral heterogeneity in the caprock. In this study, we investigate the effect of mineral heterogeneity on fracture dissolution of four carbonate-rich caprock samples, having different levels of heterogeneity, where CO¬2-rich brine flows through the fractured caprocks. A HPHT geomaterial microfluidic experimental setup is used to monitor the evolution of the fractures. Results indicate that the homogeneous caprock samples, i.e. the samples that are mainly composed of calcite, show a uniform fracture wall dissolution while fracture wall roughness increases for heterogeneous samples. The effluent chemistry analyses show that the sample-scale calcite dissolution rate decreases over time, which can be due to the mass transfer limitations in the boundary layer near the fracture wall (for the homogeneous sample) or in the altered layer formed around the fracture (for the heterogeneous samples). Microfluidic experiments were also done for one carbonate rich finegrained shale sample, which showed no detectable fracture alteration. However, the effluent analysis for the shale sample confirmed the calcite dissolution.

• Ma, Pengije; Lin, Chengyan; Jahren, Jens; Dong, Chunmei; Ren, Lihua & Hellevang, Helge (2021). Cyclic zoning in authigenic saddle dolomite-ankerite: Indications of a complex interplay between fault-rupturing and diagenetic alteration. Chemical Geology. ISSN 0009-2541. 559. doi: 10.1016/j.chemgeo.2020.119831. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2021). Probabilistic nucleation governs time, amount, and location of mineral precipitation and geometry evolution in the porous medium. Scientific Reports. 11. doi: 10.1038/s41598-021-95237-7. Fulltekst i vitenarkiv Vis sammendrag

  One important unresolved question in reactive transport is how pore-scale processes can be upscaled and how predictions can be made on the mutual effect of chemical processes and fluid flow in the porous medium. It is paramount to predict the location of mineral precipitation besides their amount for understanding the fate of transport properties. However, current models and simulation approaches fail to predict precisely where crystals will nucleate and grow in the spatiotemporal domain. We present a new mathematical model for probabilistic mineral nucleation and precipitation. A Lattice Boltzmann implementation of the two-dimensional mineral surface was developed to evaluate geometry evolution when probabilistic nucleation criterion is incorporated. To provide high-resolution surface information on mineral precipitation, growth, and distribution, we conducted a total of 27 calcium carbonate synthesis experiments in the laboratory. The results indicate that nucleation events as precursors determine the location and timing of crystal precipitation. It is shown that reaction rate has primary control over covering the substrate with nuclei and, subsequently, solid-phase accumulation. The work provides insight into the spatiotemporal evolution of porous media by suggesting probabilistic and deterministic domains for studying reactive transport processes. We indicate in which length- and time-scales it is essential to incorporate probabilistic nucleation for valid predictions.

• Masoudi, Mohammad; Fazeli, Hossein; Miri, Rohaldin & Hellevang, Helge (2021). Pore scale modeling and evaluation of clogging behavior of salt crystal aggregates in CO2-rich phase during carbon storage. International Journal of Greenhouse Gas Control. ISSN 1750-5836. 111. doi: 10.1016/j.ijggc.2021.103475. Fulltekst i vitenarkiv Vis sammendrag

  The optimal CO2 storage operation requires high permeability in the near-well region in order to keep it safe and cost-efficient. Nucleation and growth of salt crystals driven by the evaporation of formation water into under-saturated (dry) super-critical CO2 streams result in the changes in porosity and permeability of the near well-bore area. Permeability reduction is one of the main reasons for injectivity losses in the context of CO2 storage in saline aquifers. According to recent studies, during CO2 storage, salt crystals grow in two different forms: 1) single, large crystals in the aqueous phase, and 2) aggregates of micro-meter size salt crystals in the CO2-rich vapor phase. All previous numerical studies at pore-scale have addressed the formation of single, large crystals in the aqueous phase. In this work we have developed a 3D pore-scale reactive transport solver based on a D3Q19 advection-diffusion Lattice-Boltzmann model. The model takes for the first time salt nucleation into consideration via a new probabilistic approach to simulate the formation of micro-meter size salt crystal aggregates in the CO2-rich phase and their effect on changes in pore morphology and permeability. Comparing the results of porosity-permeability relations with some of the well-known clogging models, confirms the need for a new clogging model to capture the permeability reduction caused by salt aggregates.

• Ma, Pengjie; Lin, Chengyan; Ren, Lihua; Jahren, Jens Sigurd; Dong, Daotao & Yu, Guoding [Vis alle 10 forfattere av denne artikkelen] (2021). Linkage and growth of the independent and coherent faults: Insight into the effect of relay ramps on sedimentation patterns in the northern Bonan Sag, Bohai Bay Basin. Marine and Petroleum Geology. ISSN 0264-8172. 127. doi: 10.1016/j.marpetgeo.2021.104985. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Sundal, Anja & Hellevang, Helge (2021). Estimation of Mutual Solubility of CO2-H2O in Saline Aquifer Systems Using ePC-SAFT Equation of State. I Røkke, Nils Anders & Knuutila, Hanna K (Red.), TCCS–11. CO2 Capture, Transport and Storage. Trondheim 22nd–23rd June 2021. Short Papers from the 11th International Trondheim CCS Conference. SINTEF akademisk forlag. ISSN 9788253617145. Fulltekst i vitenarkiv Vis sammendrag

  A primary assessment of mutual solubility of CO2 and water for estimated max and min temperatures and pressures of the prospective reservoir formations of Aurora; Cook (at >2650 m depth) and Johansen (at >2700 m depth) have been done using ePC-SAFT equation of estate. Mole fraction of CO2 in H2O ranges from 0.025 to 0.027, and H2O in CO2 form 0.016 to 0.023 over pressure-temperature ranges of 265 – 283 bar and 95 – 110 °C. The potential for drying out effects (H2O to CO2) is significant, and there would be risk of salt precipitation in the near well area.

• Sætre, Christian; Hellevang, Helge; Dennehy, C. & Dypvik, Henning (2021). Reactive transport modelling of an intra-basalt sandstone reservoir, Rosebank, UK. Scientific Reports. 11(1). doi: 10.1038/s41598-021-86421-w. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The Rosebank field, located in the Faroe-Shetland Basin, contains producible hydrocarbons in intra-basaltic siliciclastic reservoirs. The volcanic-reservoir interface is poorly studied and the geochemical system, as a function of distance from the basalt, is largely unknown. The current paper applies a geochemical model coupling mineral dissolution and precipitation with element diffusion to investigate the geochemical system in time and space from the basalt-sandstone interface. Earlier studies indicate few negative effects on reservoir properties despite the proximity to a reactive volcanic lithology. The causes of this minimal impact have not been studied. The numerical simulations in this study expand on the knowledge demonstrating that precipitation of authigenic phases at the basalt-sandstone interface buffer the formation water solution for key elements, which hamper the transport of solutes and subsequent precipitation of secondary minerals within the reservoir. Saturation index values over the simulated period indicate that precipitation of authigenic phases should not extend beyond the basalt-sandstone interface. This shows that diffusion alone is not enough to reduce the reservoir quality due to increased precipitation of secondary phases. The basalt dissolution rate varies according to the silica concentration. The combined effects on silica concentration by diffusional fluxes, mineral precipitation and dissolution, control the basalt dissolution rate, and there are no differences in the results between high and low basalt reactive surface area.

• Dypvik, Henning; Hellevang, Helge; Krzesinska, Agata Magdalena; Sætre, Christian; Viennet, Jean-Christophe & Bultel, Benjamin Gabriel Rene [Vis alle 13 forfattere av denne artikkelen] (2021). The Planetary Terrestrial Analogues Library (PTAL) – An exclusive lithological selection of possible martian earth analogues. Planetary and Space Science. ISSN 0032-0633. 208. doi: 10.1016/j.pss.2021.105339. Fulltekst i vitenarkiv Vis sammendrag

  The Planetary Terrestrial Analogues Library (PTAL) is a dedicated lithological collection that currently consists of 102 terrestrial rock samples selected to be possible Mars analogues. The ultimate goal is improving future remote mineralogical and petrological analysis on Mars and other planetary bodies based on selected analysis such as Near- Infrared Reflectance Spectroscopy (NIR), Raman spectroscopy, Laser Induced Breakdown Spectroscopy (LIBS) and X-ray diffraction (XRD). Most international standards applied in the remote martian mineralogical and petrological analysis have so far been based on single, pure mineral analysis, with minimal interferences from other naturally occurring minerals. Here we present detailed lithological sample evaluations based on field appearance along with optical and XRD analysis of key terrestrial rock types. The detailed mineralogical and petrological descriptions give good basis for more complete lithological understanding. In combination with NIR, LIBS and Raman analysis of the very same samples PTAL aims at improving mineralogical and petrographical information from future rovers on Mars e.g. NASA's Mars2020-Perseverance and ESA and Roscosmos's ExoMars - Rosalind Franklin. The PTAL sample collection covers exclusively collected volcanic, magmatic and various sedimentary rocks and regoliths from well-known locations all over the world. These samples have a general composition comparable to what is currently known from Mars. The strength of this sample collection is its origin as common whole rock samples, in which minerals occur in their natural settings. It thereby allows studying possible detection interferences and a comparison of the sensitivity of the different techniques. The collection, in addition, forms the base for various alteration studies to better understand and explain alteration and weathering conditions on Mars. The complete results and sample preparations will be available to all scientists interested.

• Fazeli, Hossein; Masoudi, Mohammad; Patel, Ravi A.; Aagaard, Per & Hellevang, Helge (2020). Pore-Scale Modeling of Nucleation and Growth in Porous Media. ACS Earth and Space Chemistry. 4(2), s. 249–260. doi: 10.1021/acsearthspacechem.9b00290. Fulltekst i vitenarkiv
• Fazeli, Hossein; Nooraiepour, Mohammad & Hellevang, Helge (2020). Microfluidic Study of Fracture Dissolution in Carbonate-Rich Caprocks Subjected to CO2-Charged Brine. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 59(1), s. 450–457. doi: 10.1021/acs.iecr.9b06048. Fulltekst i vitenarkiv Vis sammendrag

  Investigating fracture evolutions triggered by chemical interactions in caprocks of CO2 storage sites is of great importance when caprock integrity is concerned. Mineral heterogeneity is one of the factors affecting fracture evolution. We present results from flow-through experiments deploying a unique high pressure geo-material microfluidic cell to monitor the fracture evolution of four carbonate-rich caprocks: (1) a homogeneous carbonate-rich sample, (2) a heterogeneous carbonate-rich sample, (3) a heterogeneous carbonate-rich shale sample, and (4) a heterogeneous carbonate-rich organic shale sample, representing different levels of mineral heterogeneity. The results show rather smooth fracture wall dissolution for the homogeneous rock sample. For the heterogeneous sample without shale, however, an altered layer is formed around the fracture that leads to an increase in the fracture roughness. Chemical analyses of effluent solutions demonstrate a decrease in the bulk dissolution rate of calcite over time at a constant flow rate. For the two carbonate-rich shale samples, visual observations using optical microscopy showed little changes in fracture dissolution, although analysis of effluent chemistry confirmed calcite dissolution.

• Masoudi, Mohammad; Miri, Rohaldin; Hellevang, Helge & Kord, S. (2020). Modified PC-SAFT characterization technique for modeling asphaltenic crude oil phase behavior. Fluid Phase Equilibria. ISSN 0378-3812. 513. doi: 10.1016/j.fluid.2020.112545. Fulltekst i vitenarkiv Vis sammendrag

  The perturbed-chain version of Statistical Association Fluid Theory (PC-SAFT) emerged as a powerful tool to study the phase behavior of complex fluids such as polymers and asphaltene. In spite of this, it has not gained widespread acceptance in the industry because of its sophisticated oil characterization procedure. In fact, the predictive performance of the current characterization methods is limited and not all-inclusive as they use a large number of fitting parameters and/or a non-integrated procedure. In this study, a convenient and easy-to-use procedure for crude oil characterization is proposed, assuming asphaltene as a combination of poly-nuclear aromatics, benzene derivatives, and saturates. To achieve the best match between measured and model predictions, a simple and robust Trust-Region based optimization method is used. A set of weighting factors is also used based on uncertainties in experimental data. Additionally, it is showed that the poor agreement between the measured amounts of precipitated asphaltene (from filtration test) and thermodynamic model predictions —tuned toward experimental asphaltene onset pressure data— is because of the inherent difference between the accuracy of the experimental methods. The performance of the proposed method is evaluated against reliable literature data of three frequently used crude oils which have been previously characterized over wide range of temperature, pressure, and compositions, and a reservoir fluid sample taken from a southwestern Iranian reservoir. The results are encouraging if compared to the available characterization procedures in the literature.

• Line, Lina Hedvig; Müller, Reidar; Klausen, Tore Grane; Jahren, Jens & Hellevang, Helge (2020). Distinct petrographic responses to basin reorganization across the Triassic–Jurassic boundary in the southwestern Barents Sea. Basin Research. ISSN 0950-091X. 32(6), s. 1463–1484. doi: 10.1111/bre.12437. Fulltekst i vitenarkiv Vis sammendrag

  A general shift towards higher mineralogical and textural maturity changes the reservoir character across the Triassic–Jurassic transition in the southwestern Barents Sea basin (SWBSB), largely affecting the hydrocarbon prospectivity in the region. Petrographic and geochronological provenance data presented in this paper suggest that the shift from mineralogically immature to mature sandstones initiated during the deposition of the Norian–Rhaetian Fruholmen Formation, and varies with basin location. Strong contrasts between the Fruholmen Formation and underlying formations are associated with proximity to the rejuvenated Caledonian and Fennoscandian hinterlands and are mainly restricted to the southern basin margins. In the basin interior, subtle petrographic variations between the Fruholmen Formation and older Triassic sandstones reflect a distal position relative to the southern hinterland. The long‐lived misconception of a regional compositional contrast in the Arctic at the turn of the Norian can be attributed to higher sampling frequency associated with hydrocarbon exploration activity along the southern basin margins, and masking by increased annual precipitation and subsequent reworking during the Jurassic. Geothermal signatures and rearrangement of ferric clay material across the Carnian–Norian transition support a recycled origin for the Fruholmen Formation in the basin interior. As the closest tectonically active region at the time, the Novaya Zemlya fold‐and‐thrust belt represents the best provenance candidate for polycyclic components in Norian–Rhaetian strata. In addition to recycling in the hinterland during the Late Triassic, local erosion of exposed intrabasinal highs and platforms at the Triassic–Jurassic transition represents a second process where thermodynamically unstable mineral components originally sourced from the Uralides may be removed. Textural and mineralogical modification may also have occurred in marginal‐marine depositional environments during periods with elevated sea level. Mature sediment supply from the rejuvenated hinterland in the south, multiple cycles of reworking and gradual accumulation of polycyclic grains have likely led to the extreme compositional maturity registered in the Tubåen, Nordmela and Stø formations in the SWBSB. It is likely that increased annual precipitation since the latest Carnian had an amplifying effect on sandstone maturation across the Triassic–Jurassic boundary, but we consider the effect to be inferior compared to provenance shifts and reworking. Findings from this study are important for understanding compositional and textural maturity enhancement processes in siliciclastic sedimentary basins.

• Haile, Beyene Girma; Line, Lina Hedvig; Klausen, Tore Grane; Olaussen, Snorre; Eide, Christian Haug & Jahren, Jens [Vis alle 7 forfattere av denne artikkelen] (2020). Quartz overgrowth textures and fluid inclusion thermometry evidence for basin-scale sedimentary recycling: An example from the Mesozoic Barents Sea Basin. Basin Research. ISSN 0950-091X. 33(3). doi: 10.1111/bre.12531. Fulltekst i vitenarkiv Vis sammendrag

  Sedimentary recycling has the potential to obscure source-to-sink relationships, provenance interpretations, burial history reconstructions and robust reservoir quality predictions in siliciclastic sedimentary basins. Here, we integrate petrographic and cathodoluminescence microtextures with fluid inclusion thermometry in quartz overgrowths to identify sedimentary recycling and to constrain the potential provenance candidate for recycled grains in Lower Mesozoic sandstone of the western Barents Sea basin. Four diagenetic imprints were recognized as proof of sediment recycling: (a) microtextural surface properties of overgrowths, (b) the presence of overgrowths at sutured grain contacts, (c) reversed diagenetic sequences and (d) fluid inclusions within quartz overgrowths. The diagenetic imprints confirm delivery of recycled sediments across the western Barents Sea basin. Their widespread distribution across the basin suggest that the recycled grains were derived from a drainage basin with regional-scale sediment dispersal potential during the latest Triassic. Furthermore, the drainage basin must have contained sedimentary rocks. Prior to surface exposure, the precursor sedimentary basin was subjected to burial temperatures exceeding 130°C, whereby syntaxial quartz overgrowths precipitated. This temperature indicates an uplift of around 3–4 km, which represents a significant tectonic event. Recycled quartz grains can provide insights on their provenance as they retain direct temperature records. The geothermal signatures and geographically widespread distribution of recycled quartz exclude spatially restricted intrabasinal highs and higher-temperature crystalline rocks as provenance candidates for the recycled grain portion. Our data support the contemporaneous Novaya Zemlya Fold and Thrust Belt as the most likely provenance candidate in the region. The integrated approach demonstrated herein can be used to constrain sediment recycling and partly eroded provenance candidates in sedimentary basins of equivalent setting worldwide, particularly in quartz-rich strata susceptible to sediment supply from older uplifted sedimentary basins.

• Sundal, Anja & Hellevang, Helge (2019). Using Reservoir Geology and Petrographic Observations to Improve CO2 Mineralization Estimates; Examples from the Johansen Formation, North Sea, Norway. Minerals. 9(11). doi: 10.3390/min9110671. Fulltekst i vitenarkiv Vis sammendrag

  Reservoir characterization specific to CO2 storage is challenging due to the dynamic interplay of physical and chemical trapping mechanisms. The mineralization potential for CO2 in a given siliciclastic sandstone aquifer is controlled by the mineralogy, the total reactive surface areas, and the prevailing reservoir conditions. Grain size, morphologies and mineral assemblages vary according to sedimentary facies and diagenetic imprint. The proposed workflow highlights how the input values for reactive mineral surface areas used in geochemical modelling may be parameterized as part of geological reservoir characterization. The key issue is to separate minerals both with respect to phase chemistry and morphology (i.e., grain size, shape, and occurrence), and focus on main reactants for sensitivity studies and total storage potentials. The Johansen Formation is the main reservoir unit in the new full-value chain CO2 capture and storage (CCS) prospect in Norway, which was licenced for the storage of CO2 as of 2019. The simulations show how reaction potentials vary in different sedimentary facies and for different mineral occurrences. Mineralization potentials are higher in fine-grained facies, where plagioclase and chlorite are the main cation donors for carbonatization. Reactivity decreases with higher relative fractions of ooidal clay and lithic fragments.

• Sætre, Christian; Hellevang, Helge; Riu, Lucie; Dypvik, Henning; Pilorget, C & Poulet, Francois [Vis alle 7 forfattere av denne artikkelen] (2019). Experimental hydrothermal alteration of basaltic glass with relevance to Mars. Meteoritics and Planetary Science. ISSN 1086-9379. 54(2), s. 357–378. doi: 10.1111/maps.13214. Fulltekst i vitenarkiv Vis sammendrag

  Phyllosilicates, carbonates, zeolites, and sulfates on Mars give clues about the planet's past environmental conditions, but little is known about the specific conditions in which these minerals formed within the crust and at the surface. The aim of the present study was to gain increased understanding on the formation of secondary phases by hydrothermal alteration of basaltic glass. The reaction processes were studied under varying conditions (temperature, pCO2, water:rock ratio, and fluid composition) with relevance to aqueous hydrothermal alteration in fully and partly saturated Martian basalt deposits. Analyses made on reaction products using X-ray diffraction (XRD) and scanning electron microscope (SEM) were compared with near infrared spectroscopy (NIR) to establish relative detectability and spectral signatures. This study demonstrates that comparable alteration minerals (phyllosilicates, carbonates, zeolites) form from vapor condensing on mineral surfaces in unsaturated sediments and not only in fully water-saturated sediments. In certain environments where water vapor might be present, it can alter the basaltic bedrock to a suite of authigenic phases similar to those observed on the Martian surface. For the detection of the secondary phases, XRD and SEM-EDS were found to be superior to NIR for detecting and characterizing zeolites. The discrepancy in detectability of zeolites between NIR and XRD/SEM-EDS might indicate that zeolites on Mars are more abundant than previously thought.

• Fazeli, Hossein; Patel, Ravi A.; Ellis, Brian R & Hellevang, Helge (2019). Three-Dimensional Pore-Scale Modeling of Fracture Evolution in Heterogeneous Carbonate Caprock Subjected to CO2-Enriched Brine. Environmental Science and Technology. ISSN 0013-936X. 53(8), s. 4630–4639. doi: 10.1021/acs.est.8b05653. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Mondol, Nazmul Haque & Hellevang, Helge (2019). Permeability and physical properties of semi-compacted fine-grained sediments – A laboratory study to constrain mudstone compaction trends. Marine and Petroleum Geology. ISSN 0264-8172. 102, s. 590–603. doi: 10.1016/j.marpetgeo.2019.01.019. Fulltekst i vitenarkiv Vis sammendrag

  Permeability and physical properties of fine-grained clastic sediments show a wide range of variations. Despite rather intensive research, the impact of grain size distribution and mineralogical composition of individual rock constituents is not thoroughly investigated. We performed mechanical compaction of brine-statured reconstituted borehole cuttings and synthetic quartz-clay mixtures to study the evolution of properties in fine-grained clastic sediments during burial. The primary objective was to examine whether the hydraulic and physical properties of fine-grained sediments could be described and constrained by binary quartz-clay mixtures. The synthetic binary mixtures were prepared by mixing quartz with non-swelling (kaolinite) and strongly-swelling (smectite) clays, which can represent the endmember properties within the clay minerals. In addition to vertical permeability, physical and seismic properties, stress-dependence of permeability, and two-phase relative permeability of brine-oil system were investigated. Experimental results show that grain size distribution and mineralogical composition control the vertical permeability. A well-constrained porosity-permeability bound is defined, where the compaction trends of pure quartz and quartz-smectite 15:85 (wt %) mixtures describe the maximum and minimum boundaries, respectively. The quartz-clay mixtures, however, fail to provide bounds to constrain the broad range of variations in physical and seismic properties of reconstituted aggregates, and consequently natural mudstones. It is crucial to incorporate microstructure into the permeability prediction models because the experiments indicated that the microscale characteristics control the macroscale fluid flow properties.

• Moghadam, Javad Naseryan; Nooraiepour, Mohammad; Hellevang, Helge; Mondol, Nazmul Haque & Aagaard, Per (2019). Relative permeability and residual gaseous CO2 saturation in the Jurassic Brentskardhaugen Bed sandstones, Wilhelmøya Subgroup, western central Spitsbergen, Svalbard. Norwegian Journal of Geology. ISSN 2387-5844. 99(2). doi: 10.17850/njg005. Fulltekst i vitenarkiv Vis sammendrag

  This study investigates fluid-flow properties of the low-permeability Brentskardhaugen Bed (Knorringfjellet Formation), Wilhelmøya Subgroup, western central Spitsbergen, Svalbard. To evaluate the two-phase relative permeability of the water-CO2 system, we performed unsteady state core-flooding experiments using deionised water and gaseous CO2. The absolute permeability and residual fluid saturations were also studied. Moreover, a core plug of the Berea sandstone was tested as a reference sample. The core-flooding experiments recorded microDarcy permeability values (0.022–0.039 mD) for various differential pressures (4 to 12 MPa). The poor grain sorting and the abundance of cement were the main factors controlling the low matrix permeabilities. Closure of sub-micron fractures was the likely reason for reduced permeability with increasing effective stresses. The experimental measurements showed that CO2 fractional flow reached unity at relatively low CO2 saturation (approximately 0.35–0.45). The irreducible water saturation and trapped CO2 saturation were 56% and 23%, respectively. The corresponding endpoint CO2 and water relative permeability were 0.18 and 0.47, respectively. The results, therefore, demonstrate low endpoint CO2 saturation and low relative permeability, in addition to high CO2 fractional flow at high water saturation. The trapped CO2 saturation was relatively high, which suggests a high CO2 immobilisation capability of the Wilhelmøya Subgroup sandstones. Moreover, a lower relative permeability was observed for gaseous CO2 compared to published results for supercritical CO2. In addition, the examined core sample showed a higher trapped CO2 saturation and higher endpoint CO2 relative permeability compared with the porous and permeable Berea sandstone.

• Gasda, Sarah Eileen; Aavatsmark, Ivar; Bohloli, Bahman; Hellevang, Helge; Nordbotten, Jan Martin & Wangen, Magnus [Vis alle 18 forfattere av denne artikkelen] (2019). Protection of Caprock Integrity for Large-Scale CO2 Storage on the Norwegian Continental Shelf. International Journal of Greenhouse Gas Control. ISSN 1750-5836. doi: 10.2139/ssrn.3365962. Fulltekst i vitenarkiv Vis sammendrag

  Large-scale CO2 storage requires advanced understanding of the geomechanical response of the caprock subject to pressure build- up in the reservoir. CO2 injection into basin systems will need to approach rates of 100 Mt/y in order to achieve significant reduction in worldwide emissions and realize the large capacity of saline aquifers. High pressure build-up is expected, which may activate existing fractures and faults in the seal and create leakage pathways for the CO2 plume. New fractures may also evolve at higher pressures. To avoid creating leakage pathways for the CO2 plume, the pressure must be kept under an upper bound that is determined by the caprock weakest point or initial stress. To date, there has been great uncertainty in critical knowledge needed for planning and execution of safe large-scale CO2 storage projects. Within the PROTECT project, we advance methods and reduce uncertainty regarding the mechanical response. The research study focuses on three subareas: data collection, experimental studies and computational tasks. The studies are performed at small scale (scale of individual cracks, cm to m) and at large scale (reservoir or basin scale, 10 m to km). Data are synthesized, and a benchmark study of large-scale geomechanical simulation is performed. The Utsira Formation on the Norwegian continental shelf has been used as a common case study for integration and benchmarking activities. Finally, recommendations are made for future research based on knowledge gained in this study.

• Morad, Daniel Jan; Nader, Fadi H.; Morad, Sadoon; Rossi, Carlos; Gasparrini, Marta & Alsuwaidi, Mohammad [Vis alle 8 forfattere av denne artikkelen] (2019). Limited thermochemical sulfate reduction in hot, anhydritic, sour gas carbonate reservoirs: The Upper Jurassic Arab Formation, United Arab Emirates. Marine and Petroleum Geology. ISSN 0264-8172. 106, s. 30–41. doi: 10.1016/j.marpetgeo.2019.04.023. Fulltekst i vitenarkiv

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• Nooraiepour, Mohammad; Masoudi, Mohammad; Derluyn, Hannelore; Senechal, Pascale; Moonen, Peter & Hellevang, Helge (2025). Role of Continuous Brine Access on Salt Precipitation Dynamics ─ Implications for Injectivity and Containment Integrity during Geological CO2 Storage. doi: https:/deca.upc.edu/ca/projectes/cryspom/abstracts-cryspom25.pdf/view. Fulltekst i vitenarkiv Vis sammendrag

  Geological carbon storage emerges as a critical strategy for mitigating climate change via capturing and storing human-made CO₂ emissions. Salt precipitation during CO₂ injection in saline aquifers can cause pore clogging near the wellbore, reducing permeability and increasing pressure buildup, which may find significant consequences for injectivity, containment integrity, and the overall safety and efficiency of CO₂ storage operations. While increasingly more literature focuses on CO₂-induced salt precipitation, the underlying physics, growth dynamics, and fluid-solid interface behavior remain elusive. This study investigates the role of continuous brine access on pore-scale salt precipitation dynamics, significance for self-enhancing growth nature, and its broader implications for injectivity and containment criteria. Using laboratory techniques, including microfluidics, a Hele-Shaw cell, a flow-through system, a large-scale sandbox setup, and a triaxial geomechanical cell we explore the mechanisms governing brine evaporation and salt crystal growth, their pore occupancy and chemo-mechanical couplings. A key finding is the critical role of continuous brine sources, which significantly alter salt nucleation and growth dynamics by controlling solute availability and continuity through water film movement. Laboratory results reveal substantial salt accumulation near the injection port, emphasizing the importance of solute vailability in exacerbating salt accumulation severity. Two mechanisms accelerate growth dynamics. First, evaporation shifts the gas-liquid interface from larger to finer pores, expanding the surface area for brine evaporation and salt formation. Second, hydrophilic, hygroscopic halite crystals, nucleating on existing precipitates as secondary substrates via probabilistic nucleation, amplify reactive surface area and create a feedback loop. Salt crystallization can weaken reservoir rock, reducing mechanical strength and increasing susceptibility to shear failure. This weakening, evidenced by reduced Young’s and shear moduli, may lower the fracture gradient, posing a risk of unintentional fracturing during injection. By elucidating the role of continuous brine access on precipitation dynamics and the interplay of hydro-mechanical-chemical processes, the research offers insights for optimizing injection strategies and enhancing containment integrity. The findings underscore the need to incorporate these mechanistic aspects into reservoir-scale models to predict better and manage the impacts of salt precipitation on subsurface injection operations.

• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2025). Salt precipitation dynamics in saline aquifers during geological CO2 storage: Role of continuous brine access and its implications for injectivity and containment integrity. Water-rock interaction: the International Symposium on Water-Rock Interaction : Proceedings. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Nooraiepour, Mohammad & Hellevang, Helge (2025). Bridging numerical predictions and experimental realities: CO2 mineralization in basaltic rocks. Water-rock interaction: the International Symposium on Water-Rock Interaction : Proceedings. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2023). How probabilistic nucleation controls spatiotemporal dynamics and dimensionality of mineral growth in porous media? Fulltekst i vitenarkiv
• Masoudi, Mohammad; Nooraiepour, Mohammad & Hellevang, Helge (2023). How does probabilistic nucleation control the spatiotemporal distribution of minerals in porous media? Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2023). Predictive modeling of reactive transport processes during CO2 sequestration: Geometry alteration induced by mineral dissolution and precipitation. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2023). Pore-scale investigation into dynamics of salt crystal nucleation, precipitation and growth in porous media during CO2 sequestration in saline aquifers Content. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2023). Nucleation and mineral precipitation during reactive flow and transport: I nsights into porous media geometry alteration. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Nooraiepour, Mohammad & Hellevang, Helge (2023). Assessment of hydrogen uptake ability of clay-rich caprocks. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2023). CO2-induced mineralization in porous reactive system: Implications for mineral precipitation and growth in basaltic layers. Fulltekst i vitenarkiv
• Masoudi, Mohammad & Hellevang, Helge (2023). Near injector salt scale buildup in CCS due to CO2 plume drying of aquifer. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Ahmed, Elyes; Raynaud, Xavier Marcel & Hellevang, Helge (2023). Is salt precipitation an issue during geological storage of hydrogen in saline aquifers? from thermodynamic perspective using PC-SAFT EoS. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Nooraiepour, Mohammad & Hellevang, Helge (2022). How the Probabilistic Nature of the Nucleation Process Affects and Controls the Distribution of Mineral Precipitates in Porous Media. Fulltekst i vitenarkiv Vis sammendrag

  Nucleation and growth of secondary mineral phases is of great importance in a variety of processes in different fields. Mineral precipitation alters the morphology and hydrodynamics of the porous media by blocking the pore and throats and changing the tortuosity and permeability of flow paths. Even reaction rates are affected by the reshaping of available reactive surfaces. Any mineral precipitation process begins with the nucleation, which is a probabilistic phenomenon. It is often overlooked in studying the reactive transport phenomena. Nucleation controls the location and timing of crystal formation in a porous structure. The spatial distribution of stable secondary nuclei is crucial to precisely predict the hydrodynamics of the porous medium after mineral precipitation. Thus, a deeper understanding of the mineral nucleation and growth process is essential and it is necessary to develop a new probabilistic nucleation approach that could produce more reliable results. Accordingly, we have developed a new probabilistic nucleation model and incorporated it into a pore-scale Lattice Boltzmann reactive transport model to investigate the effect of various factors such as saturation ratio, flow rate, temperature, interfacial free energy, nucleation rate, and growth rates on the distribution of precipitated secondary minerals. In our model, the probabilistic induction time statistically spreads around the measured or reported induction time, either obtained from experiments or approximated by the exponential nucleation rate equation suggested by the classical nucleation theory (CNT). We provide a detailed explanation on how to implement the developed probabilistic nucleation approach into pore-scale reactive transport models. We also gave a thorough description of each parameter of the probabilistic nucleation model and how to measure or calculate them for different fluid and rock systems. Additionally, we used a new approach to measure the disorder of the spatial mineral distributions. The developed models provide new insights into the spatiotemporal evolution of porous media during mineral precipitation. Furthermore, the outcomes provide the basis for implementing mineral nucleation and growth for reactive transport modeling across timescales and length-scales.

• Nooraiepour, Mohammad; Masoudi, Mohammad; Shokri, Nima & Hellevang, Helge (2022). Heterogeneous nucleation and precipitation on solid surfaces: Experimental observation of calcium carbonate formation on primary and secondary substrates. Fulltekst i vitenarkiv Vis sammendrag

  Mineral nucleation and growth are prime examples of (geo)chemical reactions giving rise to geometry evolution during reactive flow and transport in porous media. The precipitation reactions can reduce porosity, alter pore space connectivity and morphology, modify tortuosity, and deteriorate permeability. Therefore, change the fluid flow and solute transport. Additionally, precipitation reshapes the available surface area for growth, leading to changes in the system's reactivity, reaction progress, and reaction rates. As the probabilistic nucle-ation model highlights, it is necessary to delineate both amount and location of nucleation and precipitation events in the spatiotemporal domain for precise prediction of changes in transport properties. This work aims to improve the understanding of factors controlling crystal nucleation and growth rates, the impact of ambient and aqueous phase properties, and the substrate characteristics. To explore the effect of solute concentration, temperature, and experimental elapsed time on the surface coverage area and the number of precipitated crystals , we carried out a total of 27 mineral synthesis experiments on the surface of heterogeneous quartz-rich sandstone with a solution stoichiometry of close to 1 (Ca/CO3 ≈ 1). The tests were performed at three temperatures (T = 20, 40, and 60℃) and three supersaturations (Ω = 15, 50, and 130x). The principal objective was to evaluate solid formation at different controlling conditions when the solid-liquid interface plays a key role. Effects of primary and secondary substrates and control imposed by preferential precipitation locations are identified and discussed. The results indicate that supersaturation and temperature imposed control on the amount, distribution pattern, and growth rate of crystals while the phenomenon still being probabilistic. Substrate characteristics governed the nucleation and crystal growth location and stochastic dynamics across time and space evolution. Moreover, substrate surface properties introduced preferential sites that were occupied and covered with solids first. For reactive transport modeling, in addition to porous medium's geometry and aqueous phase properties, a stochastic nucleation and growth model is necessary to implement substrate surface properties and compute solute transport and fluid flow for different spatial and temporal locations distinctively.

• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2022). new probabilistic framework for nucleation and mineral growth in porous media helps bridge between different spatial and temporal scales— Theory, experiments and simulations. Fulltekst i vitenarkiv
• Ahmadigoltapeh, Sajjad; Miri, Rohaldin; Aagaard, Per & Hellevang, Helge (2022). Corrigendum to “Extension of SAFT equation of state for fluids confined in nano-pores of sedimentary rocks using molecular dynamic simulation” [J. Mol. Liquids (348) (2022) 118045] (Journal of Molecular Liquids (2022) 348, (S0167732221027707), (10.1016/j.molliq.2021.118045)). Journal of Molecular Liquids. ISSN 0167-7322. 367. doi: 10.1016/j.molliq.2022.120440. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Nooraiepour, Mohammad & Hellevang, Helge (2022). On the effect of probabilistic nucleation on the distribution of mineral precipitates in porous media. EGU General Assembly Conference Abstracts. doi: 10.5194/egusphere-egu22-8398. Fulltekst i vitenarkiv
• Hellevang, Helge; Masoudi, Mohammad & Nooraiepour, Mohammad (2022). To what degree can the spatial distribution of secondary minerals in porous media be determined? Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad & Hellevang, Helge (2022). Reactive transport in porous media: How solid precipitation shapes geometry evolution? Fulltekst i vitenarkiv
• Haile, Beyene Girma; Line, Lina Hedvig; Klausen, Tore Grane; Olaussen, Snorre; Eide, Christian Haug & Jahren, Jens [Vis alle 7 forfattere av denne artikkelen] (2021). Identifying and constraining sedimentary recycling from microscopic fluid inclusions in quartz overgrowth. Fulltekst i vitenarkiv
• Sundal, Anja; Meneguolo, Renata & Hellevang, Helge (2021). CO2 storage – dynamic trapping mechanisms due to mineralization. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad & Hellevang, Helge (2021). Solid and Salt Precipitation Kinetics during CO2 Injection into Reservoir. Fulltekst i vitenarkiv
• Ahmadigoltapeh, Sajjad; Abdolahi, Saeed; Miri, Rohaldin & Hellevang, Helge (2021). Extension of SAFT equation of state to include calcite wall effect in water properties within water-calcite interface using molecular dynamic simulations. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Nooraiepour, Mohammad; Berntsen, Andreas Nicolas & Hellevang, Helge (2021). A new probabilistic nucleation model to predict crystal growth in porous medium. Fulltekst i vitenarkiv Vis sammendrag

  A new probabilistic nucleation model to predict crystal growth in porous medium Tuesday, 1 June 2021 15:10 (15 minutes) Nucleation is the first step of any mineral precipitation and crystal growth process. It is often overlooked in studying the reactive transport phenomena. Nucleation controls the location and timing of crystal formation in a porous structure. The spatial distribution of stable secondary nuclei is crucial to predict hydrodynam-ics of the porous medium after mineral precipitation precisely. To better understand the nucleation process, we developed a new probabilistic nucleation approach in which the induction time is considered a random variable. The random induction time statistically spreads around the measured or reported induction time, either obtained from experiments or approximated by the exponential nucleation rate equation suggested by the classical nucleation theory. In this work, we utilized inputs from the classical nucleation theory. In our model, both location and time of nucleation are probabilistic, affecting transport properties in different time-and length-scales. We developed a pore-scale Lattice Boltzmann reactive transport model and implemented the new probabilistic nucleation model to investigate the effect of nucleation rate and reaction rate on the extent, distribution, and precipitation pattern of the solid phases. The simulation domain is a 2D substrate with an infinite source of the supersaturated solution. We use Shannon entropy to measure the disorder of the spatial mineral distributions. The results of the simulations show that all the reactions follow similar random behavior with different Gauss-Laplace distributions. The simulation scenarios start from a fully ordered system with no solid precipitation on the substrate (entropy of 0). Entropy starts to increase as the secondary phase precipitates and grows on the surface until it reaches its maximum value (entropy of 1). Afterward, the overall disorder declines as more surface areas are getting covered, and eventually, entropy approaches a constant value. The research results indicate that the slower reactions have longer windows of the probabilistic regime before entering the deterministic regime. The outcomes provide the basis for implementing mineral nucleation and growth for reactive transport modeling across timescales and length-scales.

• Nooraiepour, Mohammad & Hellevang, Helge (2021). Coupled THMC processes during subsurface CO2 injection. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Nooraiepour, Mohammad; Berntsen, Andreas Nicolas & Hellevang, Helge (2021). How to bridge between different time and length scales using a new probabilistic approach for mineral nucleation and growth. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad; Masoudi, Mohammad; Fazeli, Hossein & Hellevang, Helge (2021). Geometry evolution and fracture alteration controlled by spatial mineral heterogeneity during CO2 sequestration -A reactive transport study. Fulltekst i vitenarkiv Vis sammendrag

  Geological CO2 storage and CCS have a crucial role in reducing CO2 emission and therefore mitigating climate change. One of the prerequisites for selecting CO2 storage sites is a low permeability caprock preventing potential CO2 leakage and migration from the storage reservoir. The presence of fractures in the caprock can adversely affect the sealing capacity of caprocks. Chemical interactions between CO2, brine, and caprock-forming minerals can cause fracture evolution, which results in changes in the transmissivity of fractures within the sealing layers. One factor that can affect the chemically induced fracture alterations is mineral het-erogeneity in the caprock. In the present work, we investigate the effect of mineral heterogeneity on fracture geometry evolution when CO2-rich brine flows through a single fracture scribed on different carbonate-rich caprock samples. The rock samples have different carbonate contents and different levels of mineral hetero-geneities. They can represent carbonate-rich caprocks such as some intervals of the Upper Jurassic (Kimmerid-gian) Draupne shales, the caprock for Smeaheia CO2 storage in Norway. An HPHT geomaterial microfluidic experimental setup is used to monitor the evolution of the fractures. Results indicate that the homogeneous caprock samples, i.e., the samples mainly composed of calcite, show a uniform fracture wall dissolution while fracture wall roughness increases for heterogeneous samples. The effluent chemistry analyses show that the sample-scale calcite dissolution rate decreases over time, which can be due to the mass transfer limitations in the boundary layer near the fracture wall (for the homogeneous sample) or the altered layer formed around the fracture (for the heterogeneous samples). Microfluidic experiments were also done for one carbonate-rich fine-grained shale sample, which showed dissolution of calcite with no macroscopic fracture alteration during the ten-day experiment. This indicates that in shale samples where the carbonate minerals, mainly calcite, are armored with other slow reacting minerals such as clays, the rate of fracture geometry evolution will be prolonged, which might be a positive point for the caprock integrity. However, the confirmed fluid-rock geochemical interactions within the shaly sample in a short time frame call for further investigations on the consequent impacts on caprock samples' geomechanical-hydrological properties for more extended periods relevant for subsurface CO2 storage. The microfluidic experiments are also used to validate a reactive transport model. The model will then be utilized to study changes in transport properties of different samples during experiments. The LBM-based model outputs, such as porosity-permeability relationships, can inform reactive models at larger scales to develop a better predictive numerical simulator for processes involved in CO2 storage projects.

• Nooraiepour, Mohammad & Hellevang, Helge (2021). Reactive transport and geometry evolution of the porous medium: A geochemical perspective. Fulltekst i vitenarkiv
• Sundal, Anja; Meneguolo, Renata; Kruber, Claudia; Olsen, Elin & Hellevang, Helge (2021). Geological site assessment: geochemical review of the Aurora Storage Complex, Northern Lights project, North Sea. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Parvin, Saeed; Miri, Rohaldin; Kord, Shahin & Hellevang, Helge (2021). Implementation of PC-SAFT Equation of State into MRST Compositional for Modelling of Asphaltene Precipitation. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Fazeli, Hossein; Miri, Rohaldin & Hellevang, Helge (2021). Toward Probabilistic Modeling of Halite Nucleation and Growth during Carbon Storage Process: Pore Scale Modeling. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Fazeli, Hossein; Miri, Rohaldin & Hellevang, Helge (2020). Probabilistic Modeling of Halite Nucleation and Growth in Porous Media: Pore Scale Modeling. Fulltekst i vitenarkiv
• Hellevang, Helge; Nooraiepour, Mohammad; Masoudi, Mohammad & Fazeli, Hossein (2020). Statistical Model for Mineral Nucleation and Growth. Fulltekst i vitenarkiv
• Masoudi, Mohammad; Parvin, Saeed; Miri, Rohaldin & Hellevang, Helge (2020). Implementation of ePc-SAFT Equation of State into MRST Compositional for Modelling of Salt Precipitation during CO2 Storage in Saline Aquifers. Fulltekst i vitenarkiv
• Weber, Ulrich Wolfgang; Sundal, Anja; Hellevang, Helge & Kipfer, Rolf (2020). Experiences from the ICO2P Project applied to Migration Monitoring of Injected CO2. Fulltekst i vitenarkiv
• Nooraiepour, Mohammad & Hellevang, Helge (2020). Solid precipitation in porous reservoir rocks near the injection well: State of the art. Fulltekst i vitenarkiv
• Hellevang, Helge; Miri, Rohaldin & Masoudi, Mohammad (2021). Near Wellbore Processes during Carbon Capture, Utilization, and Storage (CCUS): An Integrated Modeling Approach. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Carbon capture and storage (CCS) is a relatively new technology that captures CO2 before it reaches the atmosphere and safely stores it underground. CO2 storage will achieve significant climate change mitigation, only if it is implemented on a very large scale with considerable injection rates. To achieve a high injection rate, we need to ensure that the near wellbore area is clean because all the injected CO2 needs to pass through this zone before entering the reservoir. Clogging these paths reduces injectivity (ease of injection) and requires costly mitigation measures. In this PhD project, numerical models are developed at different scales to improve our understanding of near-well processes during CO2 storage and their effects on injectivity. It addresses the following research topics: 1. Thermodynamic modeling of complex systems: results showed that mutual solubilities of CO2 and H2O can provide a primary assessment of the possible risk of salt precipitation. 2. Continuum scale modeling of CO2 storage: results showed that the selected porosity-permeability relation is a significant source of uncertainty for simulation of injectivity impairment during CO2 injection. 3. Pore-scale modeling of mineral nucleation and growth: results showed that mineral nucleation should be modelled using a probabilistic approach to better predict the hydrodynamic properties of porous media. 4. Pore-scale modeling of salt aggregates formation during carbon storage: results showed that widely used porosity-permeability relations were unable to cover the clogging behavior of salt aggregates, indicating the need for developing a proper clogging model in this context.

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