Helge Hellevang

• 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.  ISSN 2472-3452.  4(2), s 249- 260 . doi: 10.1021/acsearthspacechem.9b00290
• 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
• Haile, Beyene Girma; Czarniecka, Urszula; Xi, Kelai; Smyrak-Sikora, Aleksandra; Jahren, Jens; Braathen, Alvar & Hellevang, Helge (2019). Hydrothermally induced diagenesis: Evidence from shallow marine-deltaic sediments, Wilhelmøya, Svalbard. Geoscience Frontiers.  ISSN 1674-9871.  10(2), s 629- 649 . doi: 10.1016/j.gsf.2018.02.015 Full text in Research Archive.
• Hellevang, Helge; Wolff-Boenisch, Domenik & Nooraiepour, Mohammad (2019). Kinetic control on the distribution of secondary precipitates during CO2-basalt interactions. E3S Web of Conferences.  ISSN 2267-1242.  98 . doi: 10.1051/e3sconf/20199804006
• Morad, Daniel Jan; Nader, Fadi H.; Morad, Sadoon; Rossi, Carlos; Gasparrini, Marta; Alsuwaidi, Mohammad; Al Darmaki, Fatima & Hellevang, Helge (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
• Naseryan Moghadam, Javad; 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 Full text in Research Archive. Show summary

  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.

• 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 Full text in Research Archive. Show summary

  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.

• Olivarius, Mette; Sundal, Anja; Weibel, Rikke; Gregersen, Ulrik; Baig, Irfan; Thomsen, T.B.; Kristensen, Lars; Hellevang, Helge & Nielsen, Lars Henrik (2019). Provenance and sediment maturity as controls on CO2 mineral sequestration potential of the Gassum Formation in Skagerrak.. Frontiers in Earth Science.  ISSN 2296-6463.  7 . doi: 10.3389/feart.2019.00312
• 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.  ISSN 2075-163X.  9(11) . doi: 10.3390/min9110671
• Sætre, Christian; Hellevang, Helge; Riu, Lucie; Dypvik, Henning; Pilorget, C; Poulet, Francois & Werner, Stephanie C. (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
• Veneranda, Marco; Manrique-Martinez, Jose Antonio; Lopez-Reyes, Guillermo; Medina, Jesus E.; Torre-Fdez, Imanol; Castro, Kepa; Madariaga, Juan Manuel; Lantz, Cateline; Poulet, Francois; Krzesinska, Agata Magdalena; Hellevang, Helge; Werner, Stephanie C. & Rull, Fernando (2019). Spectroscopic study of olivine-bearing rocks and its relevance to the ExoMars rover mission. Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy.  ISSN 1386-1425.  223 . doi: 10.1016/j.saa.2019.117360
• Elenius, Maria; Skurtveit, Elin; Yarushina, Viktoriya M.; Baig, Irfan; Sundal, Anja; Wangen, Magnus; Landschulze, Karin; Kaufmann, Roland; Choi, Jung Chan; Hellevang, Helge; Podladchikov, Yuri; Aavatsmark, Ivar & Gasda, Sarah (2018). Assessment of CO2 storage capacity based on sparse data: Skade Formation. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  79, s 252- 271 . doi: 10.1016/j.ijggc.2018.09.004 Full text in Research Archive. Show summary

  Large North Sea aquifers of high quality are the likely major target for 12 Gt of European CO2 emissions that should be stored in the subsurface by 2050. This involves an upscaling of the present combined injection rate from all European projects, which requires careful examination of the storage feasibility. Many aquifers are closed or semi-closed, with storage capacity mainly constrained by consideration of caprock failure criteria. Because the induced overpressure can propagate to sensitive regions far from the injector, the risk of caprock failure must be examined in terms of large volumes and for long times. This poses challenges with respect to fluid-flow simulation in the presence of highly uncertain aquifer properties. In this work, experts on geology, geophysics, geomechanics and simulation technique collaborate to optimize the use of existing data in an efficient simulation framework. The workflow is applied to the large North Sea Skade Formation, with potential for secondary storage and pressure dissipation in the overlying Utsira Formation. Injection at three locations in Skade gives an overall practical capacity of 1–6 Gt CO2 injected over a 50-year period, depending on the reservoir permeability and compressibility. The capacity is limited by local pressure buildup around wells for the lowest estimated reservoir permeability, and otherwise by regional pressure buildup in shallow zones far from the injection sites. Local deformation of clay due to viscoelastoplastic effects do not have an impact on leakage from the aquifer, but these effects may modify the properties of clay layers within the aquifer, which reduces the risk of lateral compartmentalization. Uplift of the seafloor does not impose constraints on the capacity beyond those set by pressure buildup.

• Fazeli, Hossein; Patel, Ravi A. & Hellevang, Helge (2018). Effect of Pore-Scale Mineral Spatial Heterogeneity on Chemically Induced Alterations of Fractured Rock: A Lattice Boltzmann Study. Geofluids.  ISSN 1468-8115. . doi: 10.1155/2018/6046182 Full text in Research Archive. Show summary

  Fractures are the main flow path in rocks with very low permeability, and their hydrodynamic properties might change due to interaction with the pore fluid or injected fluid. Existence of minerals with different reactivities and along with their spatial distribution can affect the fracture geometry evolution and correspondingly its physical and hydrodynamic properties such as porosity and permeability. In this work, evolution of a fracture with two different initial spatial mineral heterogeneities is studied using a pore-scale reactive transport lattice Boltzmann method- (LBM-) based model. The previously developed LBM transport solver coupled with IPHREEQC in open-source Yantra has been extended for simulating advective-diffusive reactive transport. Results show that in case of initially mixed structures for mineral assemblage, a degraded zone will form after dissolution of fast-dissolving minerals which creates a resistance to flow in this region. This causes the permeability-porosity relationship to deviate from a power-law behavior. Results show that permeability will reach a steady-state condition which also depends on transport and reaction conditions. In case of initially banded structures, a comb-tooth zone will form and the same behavior as above is observed; however, in this case, permeability is usually less than that of mixed structures

• Haile, Beyene Girma; Klausen, Tore Grane; Czarniecka, Urszula; Xi, Kelai; Jahren, Jens & Hellevang, Helge (2018). How are diagenesis and reservoir quality linked to depositional facies? A deltaic succession, Edgeøya, Svalbard. Marine and Petroleum Geology.  ISSN 0264-8172.  92, s 519- 546 . doi: 10.1016/j.marpetgeo.2017.11.019
• Haile, Beyene Girma; Klausen, Tore Grane; Jahren, Jens; Braathen, Alvar & Hellevang, Helge (2018). Thermal history of a Triassic sedimentary sequence verified by a multi-method approach: Edgeøya, Svalbard, Norway. Basin Research.  ISSN 0950-091X.  30(6), s 1075- 1097 . doi: 10.1111/bre.12292
• Line, Lina Hedvig; Jahren, Jens & Hellevang, Helge (2018). Mechanical compaction in chlorite-coated sandstone reservoirs - Examples from Middle - Late Triassic channels in the southwestern Barents Sea. Marine and Petroleum Geology.  ISSN 0264-8172.  96, s 348- 370 . doi: 10.1016/j.marpetgeo.2018.05.025 Full text in Research Archive.
• Morad, Daniel Jan; Nader, Fadi H.; Gasparrini, Marta; Morad, Sadoon; Rossi, Carlos; Marchionda, Elisabetta; Al Darmaki, Fatima; Martines, Marco & Hellevang, Helge (2018). Comparison of the diagenetic and reservoir quality evolution between the anticline crest and flank of an Upper Jurassic carbonate gas reservoir, Abu Dhabi, United Arab Emirates. Sedimentary Geology.  ISSN 0037-0738.  367, s 96- 113 . doi: 10.1016/j.sedgeo.2018.02.008
• Morad, Daniel Jan; Nader, Fadi H.; Morad, Sadoon; Darmaki, Fatima AL & Hellevang, Helge (2018). Impact of Stylolitization On Fluid Flow and Diagenesis in Foreland Basins: Evidence from an Upper Jurassic Carbonate Gas Reservoir, Abu Dhabi, United Arab Emirates. Journal of Sedimentary Research.  ISSN 1527-1404.  88(12), s 1345- 1361 . doi: 10.2110/jsr.2018.70
• Nooraiepour, Mohammad; Fazeli, Hossein; Miri, Rohaldin & Hellevang, Helge (2018). Effect of CO2 phase states and flow rate on salt precipitation in shale caprocks — a microfluidic study. Environmental Science and Technology.  ISSN 0013-936X.  52(10), s 6050- 6060 . doi: 10.1021/acs.est.8b00251 Full text in Research Archive. Show summary

  Fracture networks inside the caprock for CO2 storage reservoirs may serve as leakage pathways. Fluid flow through fractured caprocks and bypass conduits, however, can be restrained or diminished by mineral precipitations. This study investigates precipitation of salt crystals in an artificial fracture network as a function of pressure–temperature conditions and CO2 phase states. The impact of CO2 flow rate on salt precipitation was also studied. The primary research objective was to examine whether salt precipitation can block potential CO2 leakage pathways. In this study, we developed a novel microfluidic high-pressure high-temperature vessel to house geomaterial micromodels. A fracture network was laser-scribed on the organic-rich shales of the Draupne Formation, the primary caprock for the Smeaheia CO2 storage in Norway. Experimental observations demonstrated that CO2 phase states influence the magnitude, distribution, and precipitation patterns of salt accumulations. The CO2 phase states also affect the relationship between injection rate and extent of precipitated salts due to differences in solubility of water in CO2 and density of different CO2 phases. Injection of gaseous CO2 resulted in higher salt precipitation compared to liquid and supercritical CO2. It is shown that micrometer-sized halite crystals have the potential to partially or entirely clog fracture apertures.

• Nooraiepour, Mohammad; Haile, Beyene Girma & Hellevang, Helge (2018). Rock physics characterization and geomechanical properties of mudstones rich in siliceous ooze — A case study from the primary caprock for Skade Formation, North Sea, In  SEG Technical Program Extended Abstract 2018.  SEGEAB.  ISBN 978-5-8670-8577-3.  SEG Technical Program Expanded Abstracts 2018.  s 3724 - 3728 Show summary

  This study has investigated rock physics characteristics and geomechanical properties of Middle Miocene mudstones in the Norwegian North Sea as the primary caprock for the Skade CO2 storage reservoir. To evaluate the seal properties, we analyzed collected drill cuttings and measured well logs from well 16/4-1, in addition to an extensive well log database in the Northern North Sea. The studied caprock was identified as siliceous ooze-rich mudstones with low bulk density, high shear wave velocity, and low Vp/Vs ratio. The abundance of siliceous skeletal material resulted in a significant shift from the overall trend of mudstones within the Hordaland Group. The estimated scenarios for S-wave velocity depicted that the ooze-rich mudstones have the highest brittleness of the Hordaland Group semiconsolidated rocks. The more brittle ooze-rich mudstones also indicated the lowest estimation of fracture pressure compared to other scenarios. The research outcomes emphasize the influence of mudstone type and presence of siliceous skeletal material on the macroscale physical properties of shallow semi-compacted mudstones.

• Skurtveit, Elin; Miri, Rohaldin & Hellevang, Helge (2018). Fluid‐Rock Interactions in Clay‐Rich Seals: Impact on Transport and Mechanical Properties, In Stéphanie Vialle; Jonathan Ajo-Franklin & William J. Carey (ed.),  Geological Carbon Storage: Subsurface Seals and Caprock Integrity.  American Geophysical Union (AGU).  ISBN 9781119118657.  Chapter 8.  s 167 - 186 Show summary

  Fluid‐rock interaction in low‐permeable clay‐rich seal units is an important topic for the evaluation of the long‐term seal integrity during geological storage of CO2. In low‐permeable sealing units, the diffusion of CO2 into the matrix is a slow process, and studies of CO2‐initiated fluid‐rock interaction in seals are challenging. In this paper, we present an overview of CO2 transport mechanism and fluid‐rock interaction processes that might alter mechanical and transport properties of seals. The review includes theoretical considerations and simulations, experimentally demonstrated processes, and field examples of flow and fluid‐rock interaction in intact clay‐rich seals as well as for fractures. For clay‐rich seals dominated by minerals like quartz, illite, and smectite, the reactivity due to drop in pH is found to be low, and most reaction observed is found to involve calcite. Only minor porosity changes are observed, and implications for flow and CO2 transport are uncertain due to limited data available. Swelling and shrinking property of smectites due to CO2 sorption and CO2 alterations within fractures in clay‐rich seal is hardly addressed in the literature.

• Sætre, Christian; Hellevang, Helge; Dennehy, Cleona; Dypvik, Henning & Clark, Samantha (2018). A diagenetic study of intrabasaltic siliciclastics sandstones from the Rosebank field. Marine and Petroleum Geology.  ISSN 0264-8172.  98, s 335- 355 . doi: 10.1016/j.marpetgeo.2018.08.026
• Xi, Kelai; Cao, Yingchang; Liu, Keyu; Jahren, Jens; Zhu, Rukai; Yuan, Guanghui & Hellevang, Helge (2018). Authigenic minerals related to wettability and their impacts on oil accumulation in tight sandstone reservoirs: An example from the Lower Cretaceous Quantou Formation in the southern Songliao Basin, China. Journal of Asian Earth Sciences.  ISSN 1367-9120. . doi: 10.1016/j.jseaes.2018.04.025
• Zhang, Shaomin; Cao, Yingchang; Jahren, Jens; Zhu, Rukai; Mao, Zhiguo; Kelai, XI; Muhammad, Kashif & Hellevang, Helge (2018). Pore Characteristics of the Fine-Grained Tight Reservoirs in the Yabulai Basin, Northwestern China. Acta Geologica Sinica.  ISSN 1000-9515.  92(3), s 1170- 1192 . doi: 10.1111/1755-6724.13598
• Hellevang, Helge; Haile, Beyene Girma & Abednego, Tetteh (2017). Experimental study to better understand factors affecting the CO2 mineral trapping potential of basalt. Greenhouse Gases: Science and Technology.  ISSN 2152-3878.  7(1), s 143- 157 . doi: 10.1002/ghg.1619
• Nooraiepour, Mohammad; Haile, Beyene Girma & Hellevang, Helge (2017). Compaction and mechanical strength of Middle Miocene mudstones in the Norwegian North Sea - the major seal for the Skade CO2 storage reservoir. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  67, s 49- 59 . doi: 10.1016/j.ijggc.2017.10.016 Show summary

  This study has investigated petrophysical, acoustic and geomechanical properties of Middle Miocene mudstones in the Norwegian North Sea as the primary caprock for Skade CO2 storage reservoir. To evaluate the seal properties, we analyzed collected drill cuttings and measured well logs from well 16/4-1, in addition to an extensive well log database in the Northern North Sea. The studied caprock was identified as siliceous ooze-rich mudstones with low bulk density, high shear wave velocity, and low Vp/Vs ratio. The abundance of siliceous skeletal material resulted in a significant shift from the overall trend of mudstones within the Hordaland Group. The estimated scenarios for S-wave velocity depicted that the ooze-rich mudstones have the highest brittleness of the Hordaland Group semi-consolidated rocks. The brittleness indices in well 16/4-1 illustrated that the mineralogical composition-based indices significantly overestimate brittleness compared to the elastic-based indices. While the caprock for Skade CO2 storage reservoir showed an overall ductility, the bottom 30 m demonstrated an increased brittleness profile. The more brittle ooze-rich mudstones also indicated the lowest estimation of fracture pressure compared to other scenarios. The research outcomes emphasize on the influence of mudstone type and microstructure on the macroscale physical properties of shallow semi-compacted CO2 caprocks.

• Nooraiepour, Mohammad; Mondol, Nazmul Haque; Hellevang, Helge & Bjørlykke, Knut (2017). Experimental mechanical compaction of reconstituted shale and mudstone aggregates: Investigation of petrophysical and acoustic properties of SW Barents Sea cap rock sequences. Marine and Petroleum Geology.  ISSN 0264-8172.  80, s 265- 292 . doi: 10.1016/j.marpetgeo.2016.12.003 Show summary

  This study investigates petrophysical and acoustic properties of experimentally compacted reconstituted samples of seal sequences from the southwestern Barents Sea. The aggregates were collected from drill cuttings of mudstone and shale formations of two exploration wells, 7220/10-1 (Salina discovery) and 7122/7-3 (Goliat field). The washed and freeze-dried samples were characterized for grain size distributions, geochemical analyses, and mineralogical compositions. A total of 25 compaction tests (12 dry and 13 brine-saturated) were performed with a maximum effective vertical stress of 50 MPa. The laboratory measurements demonstrated that petrophysical and acoustic properties of argillaceous sediments can change within a sedimentary basin and even within a given formation. The results show that the collected aggregates from Goliat field are compacted more compared to Salina discovery. The maximum and minimum compaction are measured in samples collected from Snadd and Fuglen formations, respectively. The final porosity of brine-saturated specimens varies between 5% and 22%. The ultrasonic velocity measurements depict that samples with the same porosity values can have a broad range of velocity values. The resulting compaction trends in this study were compared to published compaction curves for synthetic mixtures of quartz and clay. All compaction trends show higher porosity reduction than the silt fraction with 100% quartz. Comparison of experimental compaction result of each mudstone and shale aggregate with its corresponding acquired well log data helps to delineate the burial history and exhumation in the study area. A net exhumation of 950 m and 800 m is estimated at Salina and Goliat wells, respectively. The outcomes of this study can provide insights for hydrocarbon prospect discovery in a pre-mature sedimentary basin in terms of exploration and production, and also for geological CO2 storage sites. The experimental results may provide information for well log and seismic interpretation, basin modeling and seal integrity of investigated horizons.

• Sundal, Anja; Miri, Rohaldin; Hellevang, Helge; Tveranger, Jan; Midtkandal, Ivar; Zuchuat, Valentin; Aagaard, Per & Braathen, Alvar (2017). Movement of CO 2 charged fluids in low permeability rocks during deformation: migration patterns in the Carmel Formation, Utah. Energy Procedia.  ISSN 1876-6102.  114, s 4537- 4544 . doi: 10.1016/j.egypro.2017.03.1570
• Ahmad, Nawaz; Anders, Wörman; Xavier, Sanchez-Vila; Jerker, Jarsjö; Andrea, Bottacin-Busolin & Hellevang, Helge (2016). Injection of CO2-saturated brine in geological reservoir: A way to enhanced storage safety. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  54(1), s 129- 144 . doi: 10.1016/j.ijggc.2016.08.028
• Hellevang, Helge; Haile, Beyene Girma & Miri, Rohaldin (2016). A Statistical Approach to Explain the Solution Stoichiometry Effect on Crystal Growth Rates. Crystal Growth & Design.  ISSN 1528-7483.  16(3), s 1337- 1348 . doi: 10.1021/acs.cgd.5b01466
• Kirstein, Jens; Hellevang, Helge; Haile, Beyene Girma; Gleixner, Gerd & Gaupp, Reinhard (2016). Experimental determination of natural carbonate rock dissolution rates with a focus on temperature dependency. Geomorphology.  ISSN 0169-555X.  261, s 30- 40 . doi: 10.1016/j.geomorph.2016.02.019
• Miri, Rohaldin & Hellevang, Helge (2016). Salt precipitation during CO2 storage - a review. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  51, s 136- 147 . doi: 10.1016/j.ijggc.2016.05.015
• Naseryan Moghadam, Javad; Mondol, Nazmul Haque; Aagaard, Per & Hellevang, Helge (2016). Effective stress law for the permeability of clay-bearing sandstones by the Modified Clay Shell model. Greenhouse Gases: Science and Technology.  ISSN 2152-3878.  6(6), s 752- 774 . doi: 10.1002/ghg.1612 Show summary

  In this study, the effective stress law for the permeability of two core plugs selected from Berea (Cleveland Quarries, OH, USA) and Knorringfjellet (Longyearbyen, Svalbard, Norway) sandstones is studied experimentally by measuring the core permeability (k) under varying confining stress (σc) and pore pressures (Pp). The obtained results demonstrate that the permeabilities of the two core plugs decrease with increasing σc or decreasing Pp. The effective stress coefficient for the permeability (αk) values are more than 1.0 for both sandstone core plugs indicating higher sensitivity of the permeability with respect to the applied Pp compared to the applied σc. The previously presented models for calculating αk, such as the Clay Free, Clay Shell, and Clay Particle models, are discussed and a new modified Clay Shell model considering spherical geometry is presented to account for the considerable contrast between the elastic moduli of quartz and clay minerals. The discussed models strongly depend on the magnitude of the considered elastic moduli for the clay minerals. While the Clay Shell and Clay Particle models are capable of describing the observed αk values by considering extremely low elastic moduli for clays, the new modified Clay Shell model is capable of predicting αk values by considering moderate to low values of elastic moduli of clays. The increasing trend of αk values by increasing the σc is discussed and a new correlation based on the observed k values for calculation of αk is presented.

• Naseryan Moghadam, Javad; Mondol, Nazmul Haque; Aagaard, Per & Hellevang, Helge (2016). Experimental investigation of seismic velocity behavior of CO2 saturated sandstones under varying temperature and pressure conditions. Greenhouse Gases: Science and Technology.  ISSN 2152-3878.  6(6), s 734- 751 . doi: 10.1002/ghg.1603 Show summary

  Subsurface storage of CO2 into geological formations is considered an important strategy to mitigate increasing atmospheric CO2. Time-lapse seismic monitoring is an integral component of a geological CO2 sequestration project because the seismic behavior of the rock is a function of both mineralogical composition and pore fluid properties. At the uppermost kilometer of the sedimentary basin, CO2 can be present at gaseous, liquid, and supercritical states, with the supercritical and liquid states preferred in CO2 storage operations due to the higher sweep efficiency. In this study, the seismic velocities [both compressional (Vp) and shear (Vs) waves] of two CO2-saturated sandstone core plugs (Red Wildmoor and Knorringfjellet formations) have been measured under a range of temperatures and pressures in which CO2 phase transitions occur. The experiments were done using a uniaxial hydrostatic cell equipped with seismic wave transmitting and receiving transducers. The experimental investigation illustrated that seismic velocities (both Vp and Vs) decreased until the critical point was reached. Further increases in the CO2 pressure above the critical point led to a gradual increasing of Vp while the Vs remained unchanged. The effect of CO2 on the seismic velocity of the sandstone was compared with the effects of N2 and distilled water at the same conditions. It was further indicated that the seismic velocity changes were mainly connected to significant changes of CO2 density and the corresponding bulk rock moduli over the critical point. The observed velocities are in good agreement with Gassmann-predicted velocities as well as literature data.

• Szabo, Zsuzanna; Hellevang, Helge; Kiraly, Csilla; Sendula, Eszter; Kónya, Péter; Falus, György; Török, Szabina B. & Szabó, Csaba (2016). Experimental-modelling geochemical study of potential CCS caprocks in brine and CO2-saturated brine. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  44, s 262- 275 . doi: 10.1016/j.ijggc.2015.11.027
• Xi, Kelai; Cao, Yingchang; Haile, Beyene Girma; Zhu, Rukai; Jahren, Jens; Bjørlykke, Knut; Zhang, Xiangxiang & Hellevang, Helge (2016). How does the pore-throat size control the reservoir quality and oiliness of tight sandstones? The case of the Lower Cretaceous Quantou Formation in the southern Songliao Basin, China. Marine and Petroleum Geology.  ISSN 0264-8172.  76, s 1- 15 . doi: 10.1016/j.marpetgeo.2016.05.001
• Xi, Kelai; Cao, Yingchang; Zhu, Rukai; Haile, Beyene Girma & Hellevang, Helge (2016). Evidences of localized CO2-induced diagenesis in the Cretaceous Quantou Formation, southern Songliao Basin, China. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  52, s 155- 174 . doi: 10.1016/j.ijggc.2016.07.010
• Haile, Beyene Girma; Hellevang, Helge; Aagaard, Per & Jahren, Jens (2015). Experimental nucleation and growth of smectite and chlorite coatings on clean feldspar and quartz grain surfaces. Marine and Petroleum Geology.  ISSN 0264-8172.  68(Part A), s 664- 674 . doi: 10.1016/j.marpetgeo.2015.02.006
• Hellevang, Helge & Aagaard, Per (2015). Constraints on natural global atmospheric CO2 fluxes from 1860 to 2010 using a simplified explicit forward model. Scientific Reports.  ISSN 2045-2322.  5 . doi: 10.1038/srep17352 Full text in Research Archive.
• Miri, Rohaldin; Van Noort, Reinier; Aagaard, Per & Hellevang, Helge (2015). New insights on the physics of salt precipitation during injection of CO2 into saline aquifers. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  43, s 10- 21 . doi: 10.1016/j.ijggc.2015.10.004
• Tambach, TJ & Hellevang, Helge (2015). Discussion on the paper titled "Effect of reactive surface area of minerals on mineralization and carbon dioxide trapping in a depleted gas reservoir" by Bolourinejad et al. (2014). International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  34, s 141- 143 . doi: 10.1016/j.ijggc.2014.12.018
• Xi, Kelai; Cao, Y; Jahren, Jens; Zhu, R; Bjørlykke, Knut; Haile, Beyene Girma; Zheng, L & Hellevang, Helge (2015). Diagenesis and reservoir quality of the Lower Cretaceous Quantou Formation tight sandstones in the southern Songliao Basin, China. Sedimentary Geology.  ISSN 0037-0738.  330, s 90- 107 . doi: 10.1016/j.sedgeo.2015.10.007
• Xi, Kelai; Cao, Y; Jahren, Jens; Zhu, R; Bjørlykke, Knut; Zhang, X; Cai, L & Hellevang, Helge (2015). Quartz cement and its origin in tight sandstone reservoirs of the Cretaceous Quantou formation in the southern Songliao basin, China. Marine and Petroleum Geology.  ISSN 0264-8172.  66(4), s 748- 763 . doi: 10.1016/j.marpetgeo.2015.07.017
• Hellevang, Helge; Aagaard, Per & Jahren, Jens (2014). Will dawsonite form during CO2 storage?. Greenhouse Gases: Science and Technology.  ISSN 2152-3878.  4(2), s 191- 199 . doi: 10.1002/ghg.1378
• Hellevang, Helge; Miri, Rohaldin & Haile, Beyene Girma (2014). New insights into the mechanisms controlling the rate of crystal growth. Crystal Growth & Design.  ISSN 1528-7483.  14(12), s 6451- 6458 . doi: 10.1021/cg501294w
• Miri, Rohaldin; Aagaard, Per & Hellevang, Helge (2014). Examination of CO2–SO2 Solubility in Water by SAFT1. Implications for CO2 Transport and Storage. Journal of Physical Chemistry B.  ISSN 1520-6106.  118(34), s 10214- 10223 . doi: 10.1021/jp505562j
• Miri, Rohaldin; Hellevang, Helge; Braathen, Alvar & Aagaard, Per (2014). Phase relations in the Longyearbyen CO2 Lab reservoir - forecasts for CO2 injection and migration. Norsk Geologisk Tidsskrift.  ISSN 0029-196X.  94(2-3), s 217- 232
• Naseryan-Moghadam, Javad; Mondol, Nazmul Haque; Hellevang, Helge; Johnsen, Øistein & Aagaard, Per (2014). Seismic Response of CO2 Saturated Red Wildmoor Sandstone under Varying Temperatures and Pressures, In EAGE2014 (ed.),  Workshop Proceedings. 76th EAGE Conference & Exhibition.  European Association of Geoscientists and Engineers.  ISBN 978-90-73834-90-3.  Tu G107 15.
• Neubeck, Anna; Duc, Nguyen Thanh; Hellevang, Helge; Oze, Christopher; Bastviken, David; Bacsik, Zoltan & Holm, Nils G. (2014). Olivine alteration and H2 production in carbonate-rich, low temperature aqueous environments. Planetary and Space Science.  ISSN 0032-0633.  96, s 51- 61 . doi: 10.1016/j.pss.2014.02.014
• Hellevang, Helge & Aagaard, Per (2013). Can the long-term potential for carbonatization and safe long-term CO2 storage in sedimentary formations be predicted?. Applied Geochemistry.  ISSN 0883-2927.  39, s 108- 118 . doi: 10.1016/j.apgeochem.2013.09.012
• Hellevang, Helge; Dypvik, Henning; Kalleson, Elin; Pittarello, Lidia & Koeberl, Christian (2013). Can alteration experiments of impact melts from El'gygytgyn and volcanic glasses shed new light on the formation of the Martian surface?. Meteoritics and Planetary Science.  ISSN 1086-9379.  48(7), s 1287- 1295 . doi: 10.1111/maps.12046
• Hellevang, Helge; Pham, Van Thi Hai & Aagaard, Per (2013). Kinetic modelling of CO2-water-rock interactions. International Journal of Greenhouse Gas Control.  ISSN 1750-5836.  15, s 3- 15 . doi: 10.1016/j.ijggc.2013.01.027

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• Nooraiepour, Mohammad; Fazeli, Hossein; Miri, Rohaldin & Hellevang, Helge (2019). Formation dry-out and salt precipitation in porous and fractured media: Laboratory insights on physics and dynamics of CO2-induced halite accumulations. Show summary

  We have conducted a series of microfluidic experiments on the glass and geomaterial micromodels at ambient and HPHT conditions to investigate physics and dynamics of salt precipitation, governing mechanisms, and influencing factors. We have shown that the trapped water films in porous or fractured media have enough continuity and conductivity to transport residual brine to an evaporating front, and cause an increase in the rate and amount of precipitated halite crystals. The pressure gradient imposed by capillary-back flow and imbibition processes can produce significant conductivity and stability of the water films. Laboratory observations suggest that the salt precipitation during CO2 injection is a time-evolving and self-enhancing phenomenon which has the following characteristics: (a) in addition to the aqueous phase, salt crystals can precipitate and grow on the interface of rock and CO2 flow pathway. (b) salt crystals are covered with a thin water film of brine that is attracted by surface energy effects and hydrophilic nature of salt crystals. (c) micrometer-sized salts have a porous structure of densely precipitated aggregates with narrow pore throats between the crystals, which provides a potentially large capillarity to the salt aggregates to imbibe water over long distances. (d) micrometer-sized crystals that precipitate on the interface of solid and CO2 stream enhance the distribution of brine, increase the surface area for evaporation and growth, and hence, accelerate the evaporation rate. (e) evaporation, precipitation, and growth of salt bodies induce further nucleation and precipitation, which in turn contributes to an increase in capillary transport and suction. The results also indicate that CO2 phase states and pressure-temperature conditions govern the magnitude, distribution and precipitation patterns of salt precipitates. Injection of gaseous CO2 resulted in higher salt precipitation compared to liquid and supercritical CO2. The thermodynamic conditions influence salt precipitation via water solubility in CO2, maximum water flux into CO2 stream, and balance between the imposed viscous forces and capillary-driven backflow. The CO2 phase states also affect the relationship between the injection rate and extent of precipitated salts. It is shown the higher the injection flow rate, the lower the salt coverage. A conceptual framework was introduced that suggests salt precipitation may be not only a near-well phenomenon but also a sealing mechanism that can impede CO2 leakage from fracture networks. The research outcome highlights the mechanisms and processes that are crucial to consider during the investigation of salt precipitation induced by CO2 injection because it has implications for both injectivity and containment assessments. For a better reservoir-scale numerical modeling, such mechanisms need to be incorporated and scaled-up in the reservoir simulator. The present approach for modeling salt precipitation using the volumetric approach in the reservoir-scale numerical simulator may not reflect the required physics for investigation of salt precipitation induced by CO2 injection.

• Sundal, Anja; Miri, Rohaldin; Andersen, Odd; Hellevang, Helge; Gregersen, Ulrik; Olivarius, Mette; Nielsen, Lars Henrik; Møyner, Olav; Baig, Irfan; Heeremans, Michel; Lecomte, Isabelle; Nilsen, Halvor Møll; Frykman, Peter & Aagaard, Per (2019). Optimized CO2 storage in sloping aquifers: Estimation of physical and chemical immobilization potential and retardation along migration path in open storage solutions.
• Elenius, Maria; Sundal, Anja; Gasda, Sarah; Aavatsmark, Ivar; Hellevang, Helge; Hermanrud, Christian; Skurtveit, Elin & Midttømme, Kirsti (2018). Storage Capability [FME SUCCESS Synthesis report Volume 1].
• Gasda, Sarah; Elenius, Maria; Skurtveit, Elin; Sundal, Anja; Yarushina, Viktoriya M.; Baig, Irfan; Wangen, Magnus; Landschulze, Karin; Kaufmann, Roland; Choi, Jung Chan; Hellevang, Helge; Podladchikov, Yuri P. & Aavatsmark, Ivar (2018). Skade Case Study.
• Haile, Beyene Girma; Hellevang, Helge & Jahren, Jens (2018). Reservoir quality of the Upper Triassic to Lower Jurassic sediments, NW Barents Shelf. Understanding porosity evolution through diagenesis and sedimentology. Series of dissertations submitted to the Faculty of Mathematics and Natural Sciences, University of Oslo.. 1973.
• Hellevang, Helge; Nooraiepour, Mohammad & Fazeli, Hossein (2018). CO2-H2O-basalt interactions – reactive transport experiments and simulations.
• Miri, Rohaldin; Hellevang, Helge; Aagaard, Per; Kvamme, Bjørn; Skurtveit, Elin & Wangen, Magnus (2018). Critical Factors for Considering CO2 Injectivity in Saline Aquifers [FME SUCCESS Synthesis report Volume 3].
• Nooraiepour, Mohammad; Fazeli, Hossein & Hellevang, Helge (2018). Brine-CO2-Rock Geochemical Interactions: A novel HPHT microfluidic pressure vessel for lab-on-chip investigations.
• Nooraiepour, Mohammad; Fazeli, Hossein; Miri, Rohaldin & Hellevang, Helge (2018). Geomaterial microfluidic experiment at reservoir conditions: Insights on salt precipitation in fractured shale caprocks during CO2 injection. Show summary

  In this study, we have developed a novel microfluidic high-pressure high-temperature vessel to house geomaterial (natural rock or mineral chips) micromodel specimens. Realistic fracture patterns were laser-scribed on the organic-rich shales of Draupne Formation, the primary caprock for the Smeaheia CO2 storage site (the full-scale CCS project) in Norway. The primary research objective was to examine salt precipitation in fracture networks of shale during CO2 injection under different thermodynamic conditions and for various CO2 phase states to investigate whether authigenic precipitation of salt crystals can partially or entirely block potential CO2 leakage pathways in caprocks. Moreover, the impact of CO2 injection flow rate on the extent of salt accumulations was studied. A conceptual framework was introduced that suggests salt precipitation may be not only a near-well phenomenon but also a sealing mechanism that can impede CO2 leakage. We observed that salt crystals precipitate in two distinct forms: (a) large and semi-large single cubic crystals of halite in the aqueous phase, and (b) dense porous aggregates of micrometer-sized halite crystals that form on the interface of rock and CO2 stream. Experimental observations demonstrated that injection of different CO2 phase states affects the magnitude, distribution and salt precipitation patterns. Analysis of the fracture network after complete drying of shale specimen showed that the higher the injection flow rate, the lower the salt coverage. Three drying regimes (diffusive, capillary and evaporative) governed precipitation of salt crystals through stabilized capillary and evaporative fluxes. The CO2 phase states influence the relationship between injection rate and extent of precipitated salts. A higher impact of the rate on salt coverage was found for supercritical- compared to gaseous CO2. Reducing injection flow rate caused the initial salt nuclei to form closer to the inlet and from there toward different branches of fracture pattern. It is shown that bulk and dense aggregates of micrometer-sized halite crystals, that precipitate on the interface of fracture walls and CO2 stream, has the potential to partly or entirely block the fracture aperture and consequently leakage pathways. The development of salt crystals toward the point where leakage begins, the affinity of salt bodies to become connected, and extent of accumulations suggest that the salt precipitation during injection of CO2 into the geologic formations can be considered as a fracture healing mechanism.

• Nooraiepour, Mohammad; Fazeli, Hossein; Miri, Rohaldin & Hellevang, Helge (2018). Salt Precipitation During Injection of CO2 into Saline Aquifers: Lab-on-Chip Experiments on Glass and Geomaterial Microfluidic Specimens. Show summary

  In a full-scale CCS, millions of tons of CO2 must be stored underground. Injection of dry or undersaturated (with respect to water) CO2 leads to dry-out of formation water and salt precipitation. Salt precipitation during CO2 injection into the geological formations causes reduced injectivity and negatively influences reservoir rock properties. It also may have the potential to block CO2 leakage pathways within the fractured caprocks. The present-day reservoir-scale models of salt precipitation consider mechanisms such as water evaporation into CO2 and capillary backflow of water into the dried zone. However, it has been suggested that salt precipitation due to these mechanisms fills only a fraction of the pore network and does not significantly impact the permeability. We report microfluidic experiments on glass-microchips and organic-rich shale specimens to provide insights into the physics and dynamics of salt precipitation at pore-scale and to find the possible explanations for the large-scale salt precipitation observed in the field operations. Moreover, we investigate whether salt crystals can partially or entirely clog fracture apertures and leaking pathways in the seal sequences. The experimental results introduce two interrelated phenomena –self-enhancing of salt growth and water film salt transport, which together remarkably intensify the rate and amount of precipitations. It is shown that salt crystals, although at different rates, grow in both aqueous and gas phases. The salt crystals precipitate in two distinct forms: (a) large single cubic halite crystals in the aqueous phase and (b) dense micrometer-sized halite crystals on the interface of rock and CO2 stream. The micrometer-sized crystals in the gas phase create a microporous medium with large capillarity that can strongly imbibe brine over long distances to the evaporation front via capillary connected water films. It is demonstrated that the CO2 phase states influence magnitude, distribution and precipitation patterns of salt accumulations.

• Nooraiepour, Mohammad; Hellevang, Helge & Mondol, Nazmul Haque (2018). From field-scale to pore-scale: Investigation of caprock properties for CO2 sequestration.
• Nooraiepour, Mohammad; Soldal, Magnus; Park, Joonsang; Mondol, Nazmul Haque; Hellevang, Helge & Bohloli, Bahman (2018). Geophysical Monitoring of Gaseous and Supercritical CO2 Fracture Flow Through a Brine-Saturated Shale Caprock. Show summary

  Pre-existing and induced fractures and faults can play a role as bypass conduits and fast leaking channels in CO2 storage sites. They should therefore be well characterized during site selection, and monitored thoroughly during operation to track the movement and fate of the CO2 plume. Despite to date extensive research on the geophysical properties of brine- and CO2-saturated porous reservoir rocks, changes in acoustic velocity and electrical resistivity during a sole fracture fluid displacement are, however, rather little investigated. Hence, we herein present a laboratory study of core-scale geophysical monitoring during drainage-imbibition cycles of the brine-CO2 system through a shale caprock core sample with a vertical fracture. The experiments were conducted using both gaseous and scCO2 with 4 and 9 MPa pore pressures, respectively, at 12 MPa confining pressure. The tests were performed at 40°C during the loading and unloading stages in order to look into the hysteresis effect. We used a fractured core sample from the Upper Jurassic organic-rich shales of the Draupne Formation, which is the primary caprock for the Smeaheia CO2 storage site – a full-scale CCS project in Norway. The primary objective of the experiment was to compare the geophysical measurements using gaseous and scCO2 drainage-imbibition cycles during the tests in a core-scale experiment. Moreover, we were interested to see how sensitive acoustic velocity and electrical resistance techniques are to the fracture fluid displacement using different CO2 phase states. The outcomes of our high-pressure high-temperature experiment of simultaneous measurements of fracture flow and geophysical properties indicate that potential leakage of injected CO2 through the fractured-shale caprock can be detected in the core-scale laboratory experiments. The performed drainage-imbibition cycles using gaseous and scCO2 resulted in different behaviors in P-wave velocity (Vp) and electrical resistance in axial and radial directions for these two phase states. The measured Vp during the displacement of fracture fluid, CO2-brine subsequent cycles, showed a limited sensitivity in terms of magnitude and relative change. The electrical resistance, on the other hand, shows higher sensitivity and larger variation during fluid displacement along the fracture. It was also observed that the crossplot of Vp versus electrical resistance could detect and even differentiate the different phases during the loading and unloading stages.

• Sacco, Tatiana; Sundal, Anja & Hellevang, Helge (2018). Mass estimation of CO2 trapping potential in the Smeaheia reservoir.
• Sundal, Anja; Hellevang, Helge; Olivarius, Mette; Miri, Rohaldin; Nielsen, Lars-Henrik; Gregersen, Ulrik; Andersen, Odd; Møll-Nilsen, Halvor; Weibel, Rikke & Aagaard, Per (2018). Geological Constraints on the immobilization potential for CO2 in the Gassum Fm. (Skagerrak, Norway).
• Sundal, Anja; Hellevang, Helge & Sacco, Tatiana (2018). CO2 trapping in the Smeaheia reservoir - time mass estimation using geochemical models.
• Yarushina, Viktoriya M.; Van Noort, Reinier; Wangen, Magnus; Skurtveit, Elin; Hermanrud, Christian; Hellevang, Helge; Braathen, Alvar & Kvamme, Bjørn (2018). Potential leakage mechanisms and their relevance to CO2 storage site risk assessment and safe operations [FME SUCCESS Synthesis report Volume 2].
• Bjørlykke, Knut; Jahren, Jens; Mondol, Nazmul Haque; Hellevang, Helge & Aagaard, Per (2017). Mechanical compaction of sand and clay: Constraints from experimental compaction, chemical reactions and fluid flow during burial-An overview.
• Elenius, Maria; Hellevang, Helge; Skurtveit, Elin; Yurushina, Viktoriya; Baig, Irfan; Sundal, Anja; Wangen, Magnus; Landschulze, Karin; Gasda, Sarah Eileen; Kaufmann, Roland; Pettersson, Per & Aavatsmark, Ivar (2017). Storage feasibility in North Sea aquifers.
• Elenius, Maria; Hellevang, Helge; Skurtveit, Elin; Yurushina, Viktoriya; Baig, Irfan; Sundal, Anja; Wangen, Magnus; Landschulze, Karin; Gasda, Sarah Eileen; Kaufmann, Roland; Pettersson, Per & Aavatsmark, Ivar (2017). Workflow for assessment of storage based on sparse data: Skade.
• Elenius, Maria; Hellevang, Helge; Skurtveit, Elin; Yurushina, Viktoriya; Baig, Irfan; Sundal, Anja; Wangen, Magnus; Landschulze, Karin; Gasda, Sarah Eileen; Kaufmann, Roland; Pettersson, Per & Aavatsmark, Ivar (2017). Workflow for evaluation of large-scale CO2 storage feasibility: Skade.
• Haile, Beyene Girma; Jahren, Jens & Hellevang, Helge (2017). New insights about thermally driven diagenetic changes due to the emplacement of magmatic sills into reservoir sediments at Wilhelmøya (Svalbard): Implications for reservoir quality.
• Haile, Beyene Girma; Klausen, Tore Grane; Czarniecka, Urszula; Xi, Kelai; Jahren, Jens; Braathen, Alvar & Hellevang, Helge (2017). Diagenesis of Upper Triassic sandstones, Edgeøya, Svalbard.
• Line, Lina Hedvig; Jahren, Jens & Hellevang, Helge (2017). Diagenesis and Reservoir Quality of Anisian and Carnian channels in the southwestern Barents Sea.
• Line, Lina Hedvig; Jahren, Jens & Hellevang, Helge (2017). Diagenesis and Reservoir quality of Anisian and Carnian channels in the southwestern Barents Sea.
• Line, Lina Hedvig; Jahren, Jens & Hellevang, Helge (2017). Reservoir characterization of Triassic sandstones in the southwestern Barents Sea.
• Moghadam, Javad Naseryan; Mondol, Nazmul Haque; Aagaard, Per & Hellevang, Helge (2017). Determination of CO2-Brine relative permeability curves for CO2 storage sandstone reservoirs.
• Nooraiepour, Mohammad; Fazeli, Hossein & Hellevang, Helge (2017). Effect of CO2 phase state and flow rate on salt formation in shale caprocks – a microfluidics study.
• Zuchuat, Valentin; Midtkandal, Ivar; Braathen, Alvar; Sundal, Anja; Skurtveit, Elin; Hellevang, Helge; Tveranger, Jan; Evans, James & Petrie, Elizabeth (2017). COPASS - CO2 seal bypass.
• Haile, Beyene Girma; Klausen, Tore Grane; Hellevang, Helge; Jahren, Jens & Bjørlykke, Knut (2016). Burial diagenesis of De Geerdalen Formation control by depositional facies distribution, Edgeøya, Svalbard.
• Sundal, Anja; Miri, Rohaldin; Hellevang, Helge; Tveranger, Jan; Midtkandal, Ivar; Zuchuat, Valentin & Braathen, Alvar (2016). Movement of CO2 charged fluids in low permeability rocks during deformation: migration patterns in the Carmel Formation, Utah.
• Sundal, Anja; Petrie, Elizabeth; Hellevang, Helge; Midtkandal, Ivar & Braathen, Alvar (2016). REACTIVE FLUID EXPULSION DURING PROGRESSIVE DEFORMATION IN THE FOLD LIMB OF THE SAN RAFAEL SWELL, UTAH, USA. Show summary

  A series of reaction fronts radiating from fractures are observed in the Navajo Formation in the eastern flank of the San Rafael Swell (monocline structure) in central Utah, USA. Mobilization of metals by reducing fluids and reprecipitation of oxides may be linked to the structural deformation history and the successive opening and closing of fractures and faults, facilitating pumping of fluids. In the field area the Navajo Formation comprises crossbedded sandstone units interpreted as sand dunes deposited in an aeolian environment during early Jurassic. During the Laramide orogeny the sedimentary succession of Jurassic sandstones and mudstones were uplifted and folded over NS striking underlying faults. Later uplift and erosion has exposed the section and the geology may be investigated in numerous cross cutting gullies. Relict plumes sourced from in between bedding surfaces and from fractures are observed at the field locality as successive reaction fronts where oxides have precipitated and formed solid rims, interpreted as resulting from pressure driven intrusion of reducing fluids. Dendritic growth of Mnoxides is observed from solid precipitation fronts, indicating that diffusiondriven transport succeeds advection and carry large mass fractions. Numerous deformation bands in six directional populations are observed to both obstruct and allow fluid migration between generations of expulsion events. The latest generation of fractures is roughly perpendicular to the regional foldaxis, displaces reaction fronts and deformation bands, and do not appear to expel fluids before becoming completely sealed by oxide precipitates, quartz and carbonate. Thus it appears that the bulk part of advective and diffusive mass transfer took place during the earlier stages of deformation. Understanding these processes is of importance in reservoirseal characterization for CO2 storage, as leakage and reactive transport may be quantified in relation to deformation type and force.

• Sætre, Christian; Dypvik, Henning & Hellevang, Helge (2016). Basaltic glass alteration and its reservoir importance.
• Sætre, Christian; Dypvik, Henning; Hellevang, Helge & Werner, Stephanie C. (2016). Earth Mars Analogues - Linking experimental and Martian clays.
• Braathen, Alvar; Anell, Ingrid Margareta; Smyrak-Sikora, Aleksandra Anna; Mulrooney, Mark; Haile, Beyene Girma; Ogata, Kei; Osmundsen, Per Terje; Maher, Harmon; Buckley, Simon John; Hellevang, Helge & Olaussen, Snorre (2015). Tectonic influence on platform infill patterns in the mid-late Triassic, Southern Edgeøya, Svalbard.
• Haile, Beyene Girma; Xi, Kelai; Jahren, Jens; Aagaard, Per; Bjørlykke, Knut & Hellevang, Helge (2015). Burial Diagenesis in Triassic Sandstones: key to understand reservior quality evolution.
• Haile, Beyene Girma; Xi, Kelai; Jahren, Jens; Aagaard, Per; Bjørlykke, Knut & Hellevang, Helge (2015). Burial diagenesis in Triassic siliciclastic reservoirs of the Barents Sea region.
• Hellevang, Helge (2015). Carbon capture and storage (CCS), In Knut Bjørlykke (ed.),  Petroleum Geoscience. From sedimentary environments to rock physics - second edition.  Encyclopedia of Global Archaeology/Springer Verlag.  ISBN 978-3-642-34131-1.  Kapittel 24.  s 591 - 602
• Hellevang, Helge (2015, 18. juni). Hva bestemmer isotopsignaturen til karbon i atmosfæren?. [Internett].  geoforskning.no.
• Hellevang, Helge & Aagaard, Per (2015, 21. april). Kort oppholdstid for karbon i atmosfæren – bevis mot menneskeskapte utslipp?. [Internett].  geoforskning.no.
• Hellevang, Helge; Krafft, Charlotte Gannefors & Dalsbø, Gudmund Anders (2015). FME SUCCESS WP1 – Reservoir.
• Midtkandal, Ivar; Braathen, Alvar; Hellevang, Helge; Skurtveit, Elin & Tveranger, Jan (2015). COPASS - CO2 seal bypass.
• Miri, Rohaldin; Hellevang, Helge; Aagaard, Per & Wangen, Magnus (2015). Effects of CO2-Brine-Rock Interactions on CO2 Injectivity - Implications for CCS.
• Miri, Rohaldin & Hellevang, Helge (2014). Developments in SAFT EOS for Carbon Capture and Storage (CSS).
• Moghadam, Javad Naseryan; Mondol, Nazmul Haque; Hellevang, Helge; Johnsen, Øistein & Aagaard, Per (2014). Seismic response of CO2 saturated Red Wildmoor Sandstone under varying temperatures and pressures. EarthDoc.  (Tu G107)
• Sundal, Anja; Hellevang, Helge; Miri, Rohaldin & Aagaard, Per (2014). On layer specific CO2 plume distributions and variability in mineralization potential.
• Sundal, Anja; Hellevang, Helge; Miri, Rohaldin; Dypvik, Henning; Nystuen, Johan Petter & Per, Aagaard (2014). Variations in mineralization potential for CO2 related to sedimentary facies and burial Depth - a comparative study from the North Sea. Energy Procedia.  ISSN 1876-6102.
• Hellevang, Helge; Jahren, Jens; Haile, Beyene Girma & Aagaard, Per (2013). On the kinetics of digenetic reactions – Diffusion /transport limitations on the K-feldspar to illite conversion during burial diagenesis.
• Jahren, Jens; Haile, Beyene Girma; Hellevang, Helge; Bjørlykke, Knut & Ohm, Sverre Ekrene (2013). Fracture Patterns in Organic Rich Mudstones - Implications for Primary Petroleum Migration. EarthDoc. . doi: 10.3997/2214-4609.20130098

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