CO2 Seal and Bypass – COPASS

• Braathen, Alvar; Petrie, Elisabeth; Nystuen, Tonje; Sundal, Anja; Skurtveit, Elin & Zuchuat, Valentin [Show all 8 contributors for this article] (2020). Interaction of deformation bands and fractures during progressive strain in monocline - San Rafael Swell, Central Utah, USA. Journal of Structural Geology. ISSN 0191-8141. 141. doi: 10.1016/j.jsg.2020.104219. Full text in Research Archive
• Skurtveit, Elin; Sundal, Anja; Bjørnarå, Tore Ingvald; Soldal, Magnus; Sauvin, Guillaume & Zuchuat, Valentin [Show all 8 contributors for this article] (2020). Experimental investigation of natural fracture stiffness and flow properties in a faulted CO2 bypass system (Utah, USA). Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 125(7). doi: 10.1029/2019JB018917. Full text in Research Archive Show summary

  Fracture stiffness and flow properties have been measured in the laboratory using naturally fractured fault rock samples from the Little Grand Wash fault, Utah, USA. We compare fracture closure and related flow change during isotropic loading of two fractures which have been subject to various amounts of paleo‐reactive flow. The two tested fractures are described as (i) a small‐aperture fracture (0.1 mm) with negligible geochemical alterations of the fracture surface and (ii) a large‐aperture fracture (0.53 mm) where precipitates are observed on the fracture surface. X‐ray imaging is used for quantification of fracture aperture and fracture surface contact distribution. The petrographical characterisation using scanning electron microscopy and x‐ray powder diffraction is performed pre‐test and describes burial and uplift diagenesis as well as pulses of reactive fluid flow within the fault. The stress dependent flow and deformation experiment provides new data on fracture stiffness and flow for naturally developed fractures in siliciclastic rock. Fracture stiffness is found to be highest for the small‐aperture fracture due to its high fracture contact ratio and well‐developed surface mating during closure. For the naturally altered and rougher, large‐aperture fracture, fracture stiffness is lower and a highly stress dependent decay in flow is observed during initial closure. The results illustrate that a natural fracture with high contact ratio and well mated surfaces will close during loading, whereas a fracture associated with high flow rates and affected by previous geochemical alteration maintains a high flow rate compared to the host rock during similar loading.

• Skurtveit, Elin; Miri, Rohaldin & Hellevang, Helge (2018). Fluid‐Rock Interactions in Clay‐Rich Seals: Impact on Transport and Mechanical Properties. In Vialle, Stéphanie; Ajo-Franklin, Jonathan & Carey, William J. (Ed.), Geological Carbon Storage: Subsurface Seals and Caprock Integrity. American Geophysical Union (AGU). ISSN 9781119118657. p. 167–186. doi: 10.1002/9781119118657.ch8. Full text in Research Archive
• Bjørnarå, Tore Ingvald; Skurtveit, Elin & Sauvin, Guillaume (2018). Stress-dependent fracture permeability in core samples: an experimental and numerical study, 52nd US Rock Mechanics / Geomechanics Symposium, 17-20 June 2018, Seattle, Washington. American Rock Mechanics Association (ARMA). ISSN 978-0-9794975-3-7.
• Zuchuat, Valentin; Sleveland, Arve Rein Nes; Sprinkel, Douglas A.; Rimkus, Algirdas; Braathen, Alvar & Midtkandal, Ivar (2018). New insights on the impact of tidal currents on a low-gradient, semi-enclosed, epicontinental basin — the Curtis Formation, east-central Utah, USA. Geology of the Intermountain west (GIW). ISSN 2380-7601. 5, p. 131–165. doi: 10.31711/giw.v5.pp131-165.
• Skurtveit, Elin; Braathen, Alvar; Larsen, Eivind Bernhard; Sauvin, Guillaume; Sundal, Anja & Zuchuat, Valentin (2017). Pressure Induced Deformation and Flow Using CO2 Field Analogues, Utah. Energy Procedia. ISSN 1876-6102. 114, p. 3257–3266. doi: 10.1016/j.egypro.2017.03.1457. Full text in Research Archive Show summary

  Exhumed reservoirs providing evidence of CO2 accumulation and transport in geological history offer a unique possibility to supplement our knowledge on leakage processes observed along faults and fractures. A field location and drill core from Central Utah, USA has been used to characterize mechanical properties and fracture distributions in multiple reservoir-caprock couplets where bleaching pattern around fractures provides evidence of fluid flow. Analysis shows that fractures are mainly observed in low porosity units corresponding to layers with high strength and stiffness. Microstructural characterization substantiates evidence of fracture aperture separated by areas with mineral precipitation clogging aperture. Minerals observed filling fractures are calcite, gypsum and pyrite, suggestive of precipitation from reducing fluids. Fracture aperture distribution and identification of mineralogical changes along the fracture surface provides important input for improved, novel analyses of CO2 transport properties of fractures and faults.

• Sundal, Anja; Miri, Rohaldin; Hellevang, Helge; Tveranger, Jan; Midtkandal, Ivar & Zuchuat, Valentin [Show all 8 contributors for this article] (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, p. 4537–4544. doi: 10.1016/j.egypro.2017.03.1570.

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• Zuchuat, Valentin; Midtkandal, Ivar; Miquel, Poyatos-More; Da Costa, Sigrid; Halvorsen, Kristine Årland & Sundal, Anja [Show all 8 contributors for this article] (2018). Unconformities matter: The spatial and temporal information contained in the J-3 Unconformity and the Curtis Formation, east-central Utah, USA.
• Petrie, Elizabeth; Sundal, Anja; Guiterrez, Marte & Braathen, Alvar (2017). Kinematics of deformation band formation and reactivation associated with a Laramide fault propagation fold.
• Sørensen, Tonje N.; Braathen, Alvar & Skurtveit, Elin (2017). Progressive deformation in monocline, San Rafael Swell, Utah.
• Midtkandal, Ivar; Zuchuat, Valentin; Braathen, Alvar; Sundal, Anja & Evans, James (2017). Syn-sedimentary subsurface liquefaction and collapse; injectites, pseudo-channels and pseudo-clinoforms in the Jurassic Entrada and Curtis Formations, Utah, USA.
• Zuchuat, Valentin; Sleveland, Arve Rein Nes; Rimkus, Algirdas; Braathen, Alvar & Midtkandal, Ivar (2017). Modelling the Sequence Stratigraphic Development of the Upper Jurassic Curtis Formation along the NE Margin of the San Rafael Swell, Central-Eastern Utah, USA: an Example of a Low-Gradient Tidal Basin.
• Zuchuat, Valentin; Midtkandal, Ivar; Braathen, Alvar; Sundal, Anja; Skurtveit, Elin & Hellevang, Helge [Show all 9 contributors for this article] (2017). COPASS - CO2 seal bypass.
• Skurtveit, Elin; Sundal, Anja; Sauvin, Guillaume; Soldal, Magnus; Zuchuat, Valentin & Braathen, Alvar (2017). Fracture flow experiments addressing CO2 migration in fault zone.
• Braathen, Alvar; Skurtveit, Elin; Ogata, Kei; Senger, Kim & Tveranger, Jan (2017). Risking CO2 leakage along faults - what do we know?
• Sleveland, Arve Rein Nes; Zuchuat, Valentin; Rimkus, Algirdas; Midtkandal, Ivar; Sundal, Anja & Braathen, Alvar (2017). Spatial and temporal distribution of tidally modified sandstone reservoirs – implications for CCS and petroleum exploration.
• Zuchuat, Valentin; Midtkandal, Ivar; Da Costa, Sigrid; Sundal, Anja & Braathen, Alvar (2017). Schizophrenia in sedimentology: The J-3 Unconformity and the Curtis Formation, Central-Eastern Utah, USA. Show summary

  The tide-dominated, Upper Jurassic Curtis Formation crops out in Eastern-Central Utah, overlying the continental to marginal marine Entrada Sandstone. The contact between the two sedimentary formations is formally identified as the J-3 Unconformity, which can be traced over significant distances. It has since been regarded as a “simple” subaerial unconformity, followed by a third order transgression within an enclosed basin and the resulting deposition of the tide-influenced Curtis Formation. However, careful inspection of the different facies and their sub-regional correlation clearly shows that the essence of the J-3 Unconformity is not merely characterised by a long-lasting phase of subaerial exposure. It instead displays evidence of an intricate poly-erosional history, happening during short-lived syn-depositional transgressive and regressive periods. The initial bounding surface was locally altered by processes associated with development of the Curtis Formation, and the nature of their impact is strongly process-dependent. Pre-Curtis erosional processes mainly involved aeolian deflation and fluvial incision, creating a basinwide gentle relief. Syn-Curtis erosional mechanisms were controlled by the distribution and magnitude of tidal forces within the basin, resulting in a steeper and more localised relief in comparison with pre-Curtis widespread denudation. Furthermore, sedimentary processes alone can’t explain the present-day relief observed with the J-3 Unconformity. Indeed, tectonic played, at various scale, a key role in the funnelling of the various erosional forces and the distribution of the depocentres, with (i) m-scale grabens and horsts structures, and (ii) hydroplastic sand remobilisation, both observed within the uppermost strata of the Entrada Sandstone, as well as (iii) syn-Curtis sub-regional tectonic uplift. This study shows that reducing an unconformity to a single process is insufficient. Instead, careful mapping and understanding of such a schizophrenic surface can provide a non-negligible amount of information regarding the dynamic of a basin and its subsequent infill.

• 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.

• Guiterrez, Marte; Sundal, Anja & Petrie, Elizabeth (2016). Geomechanical Modeling of Deformation Banding in the Navajo Sandstone, San Rafael Monocline, Utah.
• Skurtveit, Elin; Braathen, Alvar; Larsen, Eivind & Sauvin, Guillaume (2016). Pressure induced deformation and flow using CO2 field analogues, Utah. Show summary

  Geological sequestration of CO2 is steadily maturing towards a stage where it may provide a significant means for mitigating global emissions. A key concern of the general public, potential investors, insurance companies and sequestration site operators is the risk of leakage of injected CO2 from the reservoirs into nearby/overlying groundwater aquifers or hydrocarbon pools, or even to the surface. Existing sequestration sites are generally small and have not been operational for sufficient time to fully forecast and assess leakage scenarios of laterally extensive reservoirs on the time scales relevant for subsurface CO2 storage. Thus the study of exhumed reservoirs showing evidence of CO2 accumulation in geological history offer a unique possibility to supplement our knowledge on leakage processes observed along faults and fractures, and to understand the relevant spatial and temporal scales of CO2 leakage in order to better constrain the failure potential due to injection induced pressure buildup. Natural subsurface CO2 plumes of Utah, USA, are of particular relevance to CO2 storage studies [e.g. Kampman et al., 2013; Ogata et al., 2014] and provide detailed insight into flow of CO2 in subsurface reservoirs. The Little Grand Wash Fault has undergone 400.000 years of CO2 expulsion. A research well drilled by Shell into the damage zone of the fault in 2012 retrieved a complete core of a multi-storied succession of reservoirs and caprocks. The observed patterns of bleaching suggest reducing fluid migrating through tight/low permeability host rock along interconnected fractures, diffusing into the surrounding host rock according to local variations in permeability. The core is cut by several sub-vertical fractures (i.e. fracture corridors) that provided pathways for fluid flow through both reservoir and seals. Fractured core samples from low permeable facies of the Entrada Formation have been selected for further studies on fluid flow along the fracture and interaction with the host rock during fracture controlled leakage. A second case study, the Humbug Flats of the NE San Rafael Swell, is an exhumed stacked reservoir that basically offers an identical stratigraphic and structural setting as the Little Grand Wash Fault. An oblique view into a fault and footwall anticline shows bleaching both along certain layers and up along faults and fractures. In this area, intact samples from selected facies of the Entrada Formation have been sampled for geomechanical characterization of failure criterion. The geomechanical characterization includes uniaxial and indirect tensile strength measurements for four characteristic facies L1-L4 within the Entrada Formation at Humbug Flat field location. Facies L1 and L4 is fluvial plain/overbank deposits with porosity ranging from 8-14 %, L2 is a fluvial sandstone with porosity around 20 % and L3 is a bleached eolian sandstone with 30 % porosity. The tensile strength is in the order of 0.5 to 3.5 MPa, whereas the uniaxial compressive strength (UCS) is 30-40 MPa for L4 and 60-70 MPa for L1. UCS was not measured for L2 whereas for the weak L3 facies, the measured UCS is around 2 MPa with tensile fractures splitting the plug vertically. The results show a good exponential correlation between tensile strength and porosity, with the highest porosity corresponding to the lower strength. 2 From the actively CO2 leaking Little Grand Wash Fault, fractures are sampled with the purpose of measuring the fracture stiffness and stress depended flow potential. Both fractures with a clear zone of bleaching along the fracture and fractures with very limited signs of bleaching were sampled and characterized. Preliminary results from the fracture characterization using computer tomography (CT) show that there is a distinct difference between fractures within extensive bleaching and the non-bleached fractures of the Entrada formation (Figure 1). The unbleached fracture show a small fracture aperture, with several

• Sundal, Anja; Miri, Rohaldin; Hellevang, Helge; Tveranger, Jan; Midtkandal, Ivar & Zuchuat, Valentin [Show all 7 contributors for this article] (2016). Movement of CO2 charged fluids in low permeability rocks during deformation: migration patterns in the Carmel Formation, Utah.
• Midtkandal, Ivar; Braathen, Alvar; Hellevang, Helge; Skurtveit, Elin & Tveranger, Jan (2015). COPASS - CO2 seal bypass.
• Rimkus, Algirdas; Sundal, Anja; Sleveland, Arve Rein Nes; Zuchuat, Valentin; Braathen, Alvar & Midtkandal, Ivar (2015). Sedimentology and reservoir quality of a Middle Jurassic marginal marine succession; the Curtis Formation, southeastern Utah, USA. Show summary

  The objective of this study is to investigate the depositional architecture of the Curtis Formation, and evaluate how the observed facies distributions would affect overall reservoir quality. This tidally influenced marginal marine succession is well exposed in southeastern Utah (Humbug Flats, San Rafael Swell) and provides a high-resolution analogue to subsurface reservoirs. In order to constrain the distribution of reservoir-grade sandstone bodies and characterize their heterogeneities, traditional sedimentological field methods were applied and LIDAR-scan data were collected. Permeability, porosity and diagenetic imprint parameters were evaluated from thin sections and used to constrain the model. The Middle Jurassic (Callovian) Curtis and Summerville formations represent a complex set of vertical and lateral facies transitions from tidal shallow marine and supratidal sabkha deposits, respectively. The Curtis Formation developed in a transgressive to regressive, low-gradient epicontinental setting where vertical stacking of sandstone bodies was limited by accommodation. Determining reservoir quality in tidal sediments is extremely challenging due to complex and heterogeneous sand distribution. In this study of the Curtis Formation, sub-seismic scale reservoir heterogeneities are the main focus. Sedimentological characterization is used for classification of significant structures and layers forming potential baffles to fluid flow within genetically related units. Excellent outcrop quality allowed lateral correlation between log sites, supplemented by conventional photographs and LIDAR imagery. The reservoir quality of Curtis Formation shows a general water-depth related trend: sand-to-mud ratio increases with increasing water-depth during the transgressive phase. The lower succession contains channelized sandstone bodies in a heterolithic matrix, leading to limited connectivity. Tidal flat settimg. High permeability A cleaning upwards trend towards the middle part, corresponds with a transition into a deeper shoreface environment, which in turn represents improved reservoir quality with laterally extensive relatively homogeneous sandstones. The uppermost part displays a dirtying-upwards trend into increasingly heterolithic strata. Lateral connectivity is generally high, whereas siltstone interlayers provide frequent vertical flow baffles. Locally, mud-drapes and shifts in depositional transport directions cause high variance in directional permeability. This depositional model for the Curtis Formation is an inter-well-scale analogue with respect to reservoir property distributions in tidally influenced, heterogeneous reservoirs (e.g. the Tilje, Cook and Knurr formations on the Norwegian continental shelf). Evaluation of the diagenetic imprint proved essential, as reservoir behavior at the original burial depth has to be characterized for relevant comparison. Further studies aim to investigate facies distribution within the succession on a regional scale.

• Zuchuat, Valentin; Midtkandal, Ivar & Braathen, Alvar (2019). Continental to Shallow Marine Transition in a Tide-Dominated, Low Accommodation Basin - Controlling Factors and Depositional Architecture. University of Oslo. Show summary

  Modern tide-dominated, regressive shorelines featuring deltas estuaries and lagoons are well characterised and distinctive from wave or fluvial dominated systems. However, some ancient tidedominated basins and their associated sedimentary successions do not relate well to any of the above-mentioned, present-day systems. The Utah-Idaho Trough a semi-enclosed, narrow, and shallow foreland basin flooded during the Upper Jurassic by the Curtis Sea is one of these exceptions. The main target of this doctoral thesis is the Upper Jurassic, tide-dominated Curtis Formation, which outcrops in east-Central Utah, where it overlies the Middle Jurassic, aeolian deposits of the Entrada Sandstone. The Curtis Formation is defined at its base by the J-3 Unconformity and is conformably overlain by supratidal sabkha deposits of the Summerville Formation. The Entrada-Curtis-Summerville is subdivided into eight facies associations (FA 1-8), with six subfacies associations (FA 1a, 1b, 3a, 3b, 4a, 4b). Based on the specific three-dimensional arrangement of these facies associations, it is proposed to separate the Curtis Formation into three informal subunits: The lower, middle and upper Curtis. The lower Curtis, which consists of upper shoreface to beach deposits (FA 2), mud- (FA 3a) and sand-dominated heterolithic subtidal flat sediments (FA 3b),

• Tveterås, Susanne; Braathen, Alvar; Midtkandal, Ivar & Zuchuat, Valentin (2018). Fault style and deformation mechanisms caused by sand mobility in the Entrada Sandstone and Curtis Formation, Utah, USA. University of Oslo.
• Halvorsen, Kristine; Zuchuat, Valentin; Midtkandal, Ivar & Braathen, Alvar (2018). Sand tectonics – sand mobility linked to faulting and the influence on depositional systems. University of Oslo.
• Da Costa, Sigrid; Zuchuat, Valentin & Midtkandal, Ivar (2018). The complexity of regional erosion; incision, faulting, and deposition during the development of the J-3 unconformity, Utah, USA. University of Oslo.
• Bromander, Nikoline; Sundal, Anja; Midtkandal, Ivar & Zuchuat, Valentin (2018). Facies-controlled reservoir quality and preferential deformation in sandstone reservoirs; a case study from the Entrada Sandstone, Utah, USA. University of Oslo.
• Tveterås, Susanne; Braathen, Alvar; Midtkandal, Ivar & Zuchuat, Valentin (2018). Fault style and deformation mechanisms caused by sand mobility in the Entrada Sandstone. UIO.
• Halvorsen, Kristine; Braathen, Alvar; Midtkandal, Ivar & Zuchuat, Valentin (2018). Sand tectonics – sand mobility linked to faulting and the influence on depositional systems. UIO.
• Bromander, Nikoline; Sundal, Anja; Skurtveit, Elin; Midtkandal, Ivar & Braathen, Alvar (2018). Facies-controlled reservoir quality and preferential deformation in sandstone reservoirs; a case study from the Entrada Sandstone, Utah, USA. UIO.

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