14. Hydrocarbon geology and energy

14.1. Geothermal energy and CO2 storage

                       ORAL PRESENTATIONS                    

Assessing European geological CO₂ storage capacity

Karen L. Anthonsen¹ and Niels E. Poulsen^1
1Geological Survey of Denmark and Greenland
Deployment of large scale CCS in Europe is depending on knowledge about location and storage capacity of the most attractive storage areas and thus a reliable CO2 storage atlas is a key tool for planning future CCS operations.

Since the beginning of 1990ties, several studies have attempted to map and estimate the European storage capacity for CO2. Among the most prominent are the Joule II project (Holloway et al. 1996), the GESTCO project from 2004 (Christensen & Holloway, 2004), the CASTOR project (2006), the EU GeoCapacity project (Vangkilde-Pedersen et al. 2009) and the CO2 StoP project (Poulsen et al. 2013).

These projects more or less build on one another, but there are differences between the projects with respect to number of countries included, screening parameters, classification of storage sites and assessment methodology. It is important to recognise the evolution of European CO2 assessments and the challenges related to the methodology (static or probabilistic) for mapping and estimating storage capacities in Europe.

Apart from the European EU co-funded projects, Norway has published an atlas for the Norwegian continental shelf (Halland et al. 2014) and the NORDICCS project made an assessment for the Nordic countries (Anthonsen et al. 2013) and released a joint Nordic CO2 storage web-atlas in 2015. Both United Kingdom and Spain have prepared a national CO2 storage atlas.

References
Anthonsen, K.L., Aagaard, P., Bergmo, P.E.S., Erlström, M., Faleide, J.I., Gislason, S.R., Mortensen, G.M. & Snæbjörnsdottir, S.Ó. 2013: CO2 storage potential in the Nordic region. Energy Procedia 37, 5080-5092. https://data.geus.dk/nordiccs/

Castor project. 2006: Final Report Summary – CASTOR (CO2, from Capture to Storage) Project ID: 502586 Funded under: FP6-SUSTDEV http://cordis.europa.eu/result/rcn/47842_en.html

Christensen, N.P. & Holloway, S. 2004: Geological Storage of CO2 from Combustion of Fossil Fuel. Summary report, 2nd edition. EU Project No. ENK6-CT-1999-00010.

Halland, E.K., Mujezinovic, J., Riis, F. 2014: CO2 Storage Atlas Norwegian Continental Shelf. Norwegian Petroleum directorate. http://gis.npd.no/themes/co2storageatlas/

Holloway, S. (ed) 1996: Joule II Final report: The underground disposal of Carbon dioxide. British Geological Survey, ISBN 0 85272 280 X. EU project no. CT92-0031.

Poulsen, N., Holloway, S., Neele, F., Smith, N.A. & Kirk, K. 2013: CO2StoP Final Report: Assessment of CO2 storage potential in Europe. EU Project no. SI2.611598

Vangklide-Pedersen, T. (ed) 2009: EU GeoCapacity – Assessing European Capacity for Geological Storage of Carbon Dioxide. GeoCapacity Final Report. EU Project no. SES6-518318.

Seismic interpretation of a slopping offshore potential CO2 aquifer; the Gassum Formation in Skagerrak between Norway and Denmark

Ulrik Gregersen¹, Irfan Baig², Anja Sundal², Lars Henrik Nielsen¹, Mette Olivarius¹ and Rikke Weibel^1
1GEUS, ²University of Oslo
The first phase of the project “Optimized CO₂ storage in sloping aquifers – CO₂Upslope” is seismic stratigraphic interpretation of the siliciclastic Upper Triassic–Lower Jurassic Gassum Formation in Skagerrak between Norway and Denmark. The wells Felicia-1, J-1 and 13/1-U-1 provide seismic-well ties for selected lines from eight 2D seismic surveys constituting the database. The work resulted in a detailed interpretation of the top and base of the formation and three sequence stratigraphic horizons within the aquifer (SB5, TS9 and TS10). The formation is mostly less than 100 m thick in the study area, with its thickest parts located in/near the Felicia-1 well (230 m). The formation thins towards east and north and shallows to the north where it is truncated in places. The three internal horizons approach the base of the formation towards north and only TS10 continues into the northernmost part of the study area where it ties near the base of the 13/1-U-1 well. Some minor trough-shaped seismic features within the formation may indicate channel incision. The formation is succeeded by mudstones of the Fjerritslev Formation divided by two internal horizons. Fourteen assigned faults and additional minor faults are interpreted. Most faults are normal faults trending SW–NE and some are associated with ridges/structures formed by regional tectonic events. Most faults slightly offset the Top Gassum horizon and parts of the Fjerritslev mudstones. Succeeding phases of the project involve establishment of a 3D geological model forming the basis for numerical modelling of CO₂ injection, movement and trapping.

A numerical investigation of combined heat storage and extraction in deep geothermal reservoirs

Marton Major¹, Søren Erbs Poulsen² and Niels Balling^1
1Aarhus University, Denmark, ²VIA University College, Campus Horsens, Denmark
Heat storage capabilities of deep sedimentary geothermal reservoirs are evaluated through numerical model simulations. We combine storage with heat extraction in a doublet well system when storage phases are restricted to summer months. The effects of stored volume and annual repetition on energy recovery are investigated. Recovery factors are evaluated for several different model setups and we find that storing 90 °C water at 2500 m depth is capable of reproducing, on average, 67% of the stored energy. In addition, ambient reservoir temperature of 75 °C is slightly elevated leading to increased efficiency. Additional simulations concerning pressure build up in the reservoir are carried out to show that safety levels may not be reached. Reservoir characteristics are inspired by Danish geothermal conditions, but results are assumed to have more general validity. Thus, deep sedimentary reservoirs of suitable properties are found to be viable options for storing access energy for high demand periods.

Keywords: Heat storage, Recovery, Numerical modelling, Geothermal energy, Deep sedimentary reservoirs

Shallow subsurface thermal structure for onshore Denmark

Ingelise Møller¹, Niels Balling² and Claus Ditlefsen^1
1Geological Survey of Danmark and Greenland, Denmark, ²Department of Geoscience, Aarhus University, Denmark
Information of shallow subsurface geothermal conditions is important for number applications including exploitation of shallow geothermal energy, heat storage and cooling as well as of general geoscience interest. Available measured temperatures and thermal conductivities covering Danish onshore areas to a depth of about 300 m have been compiled and analysed. Temperature data from about 50 boreholes, 100-300 m deep and thermal conductivities measured on samples collected at 31 well-characterized outcrops and on core material from 20 boreholes are included. Temperature gradients and thermal conductivities were grouped according to details of lithology over which they were measured.

Significant thermal variations are observed. At a depth of 100 m, temperatures vary between 7.5 and 12 °C and at 200 m, between 9 and 15 °C. Characteristic temperature gradients are in a range of 1 – 4 °C/100 m. Following Fourier’s law of heat conduction (heat flow = thermal conductivity x temperature gradient) a correlation is observed between temperature gradients and thermal conductivities of different lithologies, and a regional estimate of characteristic shallow heat flow in Denmark is obtained. Quartz-rich sand deposits (high thermal conductivity) show low temperature gradients, chalk and limestone intermediate gradients and almost pure clay (low thermal conductivity) high gradients. Mean thermal conductivities range between 0.6 and 6 W/mK. An estimated regional heat flow of about 37 mW/m² is in good agreement with local, classically determined heat-flow values from shallow borehole data. Due to long-term palaeoclimatic effect, this value is significantly below deep background heat flow.

Understanding nature’s secrets and using the new knowledge to solve society’s challenges: insights for CO₂ sequestration

1. L. Svane Stipp¹ and and the Members of the NanoGeoScience Research Section^{1
   1}Nano-Science Center, Department of Chemistry, University of Copenhagen

The electronics revolution has given us tools that can “see” at molecular scale, providing whole new insight into the physical and chemical processes that control the interface between natural solids and fluids (anything that flows, water, oil, CO₂, gases). By understanding how nature works, we find clues to solve some of the challenges that society faces. An important issue is to reduce the CO₂ available in the atmosphere and oceans by converting it to mineral form, where it will be stable for millennia. By understanding the processes that take place at the surfaces of minerals, we can tailor underground gas storage facilities to be more effective and we can build models to predict their safety. What we have learned about CO₂ injection into the basaltic rocks of Iceland has also inspired investigations with mineral fibre insulation and the design of nanoparticles for in situ remediation of contaminated groundwater. Our work is very fundamental and also very applied. We combine experiment with theory, in the lab, the field and at synchrotron radiation facilities.

                       POSTER PRESENTATIONS                    

Regional evaluation of structural collapse in sandstone reservoirs and impact on reservoir quality, a case study from the Entrada Sandstone, Utah, USA

Nikoline Bromander¹, Sigrid Østmo da Costa¹, Elin Skurtveit², James Evans³, Ivar Midtkandal¹, Alvar Braathen¹, Valentin Zuchuat¹ and Anja Sundal^1
1University of Oslo, Norway, ²Norges Geotekniske Institutt (NGI), Norway, ³Dept. of Geology, Utah State University, Logan, Utah, USA
In this study we examine exhumed paleo-reservoirs showing evidence of past CO₂-charged fluid accumulation to better understand processes related to geological sequestration of CO₂ in subsurface siliciclastic reservoirs. Field data was collected from the wet aeolian dune system in the Jurassic Entrada Sandstone in Utah, USA, and in particular the reservoir characteristics of the light-coloured fluvial and aeolian dune interlayers have been evaluated. Bleaching in red rocks is interpreted to have developed in response to reduction and/or dissolution of iron oxides as CO₂-charged fluids from underlying reservoirs escaped through the sedimentary succession. Some light-coloured, highly porous layers contain extensive amounts of deformation bands, which may be associated with structural collapse.

The working hypothesis is that observed reservoir collapse structures (deformation bands) in specific layers is a regional feature related to sedimentary facies. Deformation band distributions and orientations are used to document reservoir collapse. Deformation bands occur in different structural settings; clusters connected to faults cutting the stratigraphy, single deformation bands exclusively in fluvial and aeolian dune interlayers dying out in the over/underlaying facies forming small scale faults in the reservoir, as well as in major meter-scale circular collapse structures. Deformation bands were present in some specific layers throughout the field area, with frequencies from 0 to 18 per meter and the degree of structural collapse increased towards zones of high deformation, e.g. faults. Preliminary results show that collapse structures are regional features exclusively occurring in two types of facies, with the degree of collapse locally determined by structural parameters.

Mass estimation of CO₂ trapping in the Smeaheia reservoir

Tatiana Sacco¹, Anja Sundal² and Helge Hellevang^3
1UiO – University of Oslo, Master student, ²UiO – University of Oslo, Postdoctoral Fellow – Section of Geology and Geophysics, ³UiO – University of Oslo, Associate Professor – Section of Physical Geography and Hydrology
CO₂ storage in saline aquifers is an important measure to reduce anthropogenic greenhouse gas emissions. The Smeaheia reservoir (located east of the Troll field, 50 km offshore) has been proposed by Gassnova and Statoil as a suitable CO₂ sequestration site due to low leakage risk and large storage capacity. The aim of this work is to determine and quantify the temporal distribution of CO₂ in i) mineral phase; ii) dissolved in the formation water; and iii) free phase for specific layers and facies in the Smeaheia reservoir candidate.

The reservoir interval (1.2 to 1.6 km depth) comprises deposits from Middle to Upper Jurassic ages; named Sognefjord, Fensfjord and Krossfjord formations. These are heterogeneous shallow marine and deltaic sandstones. The Draupne Formation consists of marine mudstones and serves as a sealing unit. The Heather Formation comprises silty-claystones with low permeability, interfingering with sandy units.

In addition to the porosity and permeability distribution, the geochemical trapping potential for CO₂ in Smeaheia is considered in this study. The low salinity (TDS~5.6g/l) provides dissolution potential for CO₂, and favor mineral dissolution. High porosity (~30%) and permeability (~500 to 1500mD) cause spreading of a CO₂ plume. Smaller grains yield larger reactive surfaces, accelerating the dissolution of framework minerals (e.g. chlorite, feldspars, pyrite), and thus reactivity is facies dependent. Relatively low temperature (~50 ºC) and pressures (120 – 160 bar) in Smeaheia will affect mineral dissolution kinetics and the potential for subsequent CO₂ trapping through carbonate precipitation (e.g. siderite, ankerite).

References
Dreyer, T., M. Whitaker, J. Dexter, H. Flesche and E. Larsen (2005). “From spit system to tide-dominated delta: integrated reservoir model of the Upper Jurassic Sognefjord Formation on the Troll West Field.” Geological Society, London, Petroleum Geology Conference series, Geological Society of London.

Hellevang, H., V. T. H. Pham and P. Aagaard (2013). “Kinetic modelling of CO2–water–rock interactions.” International Journal of Greenhouse Gas Control 15: 3-15.

Holgate, N. E., C. A.-L. Jackson, G. J. Hampson and T. Dreyer (2013). “Sedimentology and sequence stratigraphy of the Middle–upper Jurassic Krossfjord and Fensfjord formations, troll Field, northern north Sea.” Petroleum Geoscience: 2012-2039.

Patruno, S., G. J. Hampson, C. A. L. Jackson and T. Dreyer (2015). “Clinoform geometry, geomorphology, facies character and stratigraphic architecture of a sand‐rich subaqueous delta: Jurassic Sognefjord Formation, offshore Norway.” Sedimentology 62(1): 350-388.

Pham, V. T. H., P. Lu, P. Aagaard, C. Zhu and H. Hellevang (2011). “On the potential of CO 2–water–rock interactions for CO 2 storage using a modified kinetic model.” International Journal of Greenhouse Gas Control 5(4): 1002-1015.

Sundal, A., H. Hellevang, R. Miri, H. Dypvik, J. P. Nystuen and P. Aagaard (2014). “Variations in mineralization potential for CO2 related to sedimentary facies and burial depth – a comparative study from the North Sea.” Energy Procedia 63: 5063-5070.

Geological constraints on the immobilization potential for CO₂ in the Upper Triassic – Lower Jurassic Gassum Formation (Skagerrak, Norway)

Anja Sundal¹, Helge Hellevang¹, Mette Olivarius², Rohaldin Miri¹, Lars Henrik Nielsen², Ulrik Gregersen², Odd Andersen³, Halvor Møll-Nilsen³, Rikke Weibel² and Per Aagaard^1
1University of Oslo, ²GEUS, ³Sintef
In the CLIMIT-funded “CO₂-Upslope” project, the main objective is to improve reservoir characterization schemes to optimize geological storage of CO₂. Coupled modelling is applied to estimate trapping efficiency and migration distances in order to ensure safe storage in open-boundary, sloping aquifer type reservoirs. The Gassum Formation comprises fluvial to marginal marine sandy and muddy deposits. The prospective reservoir is located in Skagerrak near industrial, onshore CO₂ emission sources. Our estimates of the reaction potential for CO₂ in these sub-arkosic sandstones indicate significant capacity for immobilization of injected gas into fluid and solid phases. The salinity of the formation water is high, and thus the dissolution potential is limited (~0.65 mol/kg), but may be catalyzed by solid carbonate precipitation – driving further dissolution of CO₂. PHREEQ-C simulations in a reservoir setting with 20 % porosity show dissolution of oligoclase and chlorite, providing cations and facilitating precipitation of magnesite, siderite and calcite, trapping more than 5 mol/l carbon after 1000 years. Petrography and geochronology results indicate immature sand with relatively high contents of reactive phases (i.e. feldspar, rock fragments) in the upper part of the Gassum Formation, which dominates on the Norwegian shelf, caused by a shift in provenance area towards the south during the later phases of deposition. Ongoing research activities in “CO₂-Upslope” will further improve the sedimentological, structural and diagenetic model as basis for reservoir simulations. Ultimately, a complete storage scheme tailored to the Gassum Formation and representative of migration assisted CO₂ storage in sloping aquifers will be provided.