1887
Volume 4, Issue 1
  • E-ISSN:

Abstract

Depleted chalk oilfields may constitute potential CO storage sites, but the remaining oil in the reservoir may pose a risk. This study investigates the effect of supercritical CO (scCO) injection on the oil composition for two different reservoir conditions of the Halfdan chalk field in the Danish North Sea: non-water-flooded (NWF) state and water-flooded (WF) state. Core plugs were cleaned and used for the preparation of two sets of composite cores that were restored to original NWF and WF oil- and brine-saturation conditions. A typical marine North Sea oil was used for restoration. The cores were flooded by scCO under reservoir temperature and pressure conditions. A total of 21 samples were collected from the core plugs and analysed by extended slow heating (ESH) pyrolysis and reflected light microscopy. The ESH showed that most of the oil in the NWF and WF cores was mobilized and removed, decreasing the original oil saturation considerably. Most of the remaining oil after scCO flooding consists of solid bitumen/asphaltenes, in line with low API gravities. The non-movable oil and solid bitumen/asphaltenes were found to amount to 2.22–3.29%, which is very close to the remaining oil saturation after cleaning. This suggests that, in this case, additional precipitation of heavy, non-movable oil (mainly solid bitumen/asphaltenes) induced by scCO may pose a minor risk. Reflected light microscopy showed that lighter oil is commonly concentrated on one side of the stylolites associated with solid bitumen/asphaltenes, suggesting oil flow is hindered and only can cross where the stylolites are absent or thinly developed.

© 2026 The Author(s). Published by The Geological Society of London for GSL and EAGE. All rights, including for text and data mining (TDM), artificial intelligence (AI) training, and similar technologies, are reserved. For permissions: https://www.lyellcollection.org/publishing-hub/permissions-policy. Publishing disclaimer: https://www.lyellcollection.org/publishing-hub/publishing-ethics

Loading

Article metrics loading...

/content/journals/10.1144/geoenergy2025-039
2026-02-27
2026-03-13

  • From This Site

    /content/journals/10.1144/geoenergy2025-039
    dcterms_title,dcterms_subject,pub_keyword
    -contentType:Journal -contentType:Contributor -contentType:Concept -contentType:Institution
    10
    5
Loading full text...

Full text loading...

References

  1. Albrechtsen, T., Andersen, S.J., Dons, T., Engstrøm, F., Jørgensen, O. and Sørensen, F.W.2001. Halfdan: developing non-structural trapped oil in North Sea Chalk. Paper SPE-71322-MS presented at theSPE Annual Technical Conference and Exhibition, September 30–October 3, 2001, New Orleans, Louisiana, USA, doi: 10.2118/71322-MS10.2118/71322‑MS
     https://doi.org/10.2118/71322-MS [Google Scholar]
  2. Allen, M.R., Dube, O.P. et al.2018. Framing and context supplementary material. In: Masson-Delmotte, V., Zhai, P. et al. (eds) Global Warming of 1.5°C. An IPCC Special Report on the Impacts of Global Warming of 1.5°C Above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change, Sustainable Development, and Efforts to Eradicate Poverty. Intergovernmental Panel on Climate Change (IPCC), Geneva, Switzerland, 1SM-1–1SM-17, https://www.ipcc.ch/sr15
     [Google Scholar]
  3. Al-Masri, W.F., Jenei, B., Rudra, A., Sanei, H. and Petersen, H.I.2025. Utilisation of Extended Slow Heating (ESH) pyrolysis and core analysis for determination of oil saturations and porosity correction. Paper SCA2025-1031 presented at the38th International Symposium for the Society of Core Analysts (SCA), 25–29 August 2025, Hannover, Germany, doi: 10.5281/zenodo.1681433010.5281/zenodo.16814330
     https://doi.org/10.5281/zenodo.16814330 [Google Scholar]
  4. Alpern, B., Lemos de Sousa, M.J., Pinheiro, H.J. and Zhu, X.1992. Optical Morphology of Hydrocarbons and Oil Progenitors in Sedimentary Rocks – Relations with Geochemical Parameters. Publicacões do Museu e Laboratório Mineralógico e Geológico da Faculdade de Ciências do Porto Nova Série, 3.
     [Google Scholar]
  5. Anderson, W.G.1986a. Wettability literature survey – Part 1: Rock/oil/brine interactions and the effects of core handling on wettability. Journal of Petroleum Technology, 38, 1125–1144, doi: 10.2118/13932-PA10.2118/13932‑PA
     https://doi.org/10.2118/13932-PA [Google Scholar]
  6. Anderson, W.G.1986b. Wettability literature survey – Part 2: Wettability measurement. Journal of Petroleum Technology, 38, 1246–1262, doi: 10.2118/13933-PA10.2118/13933‑PA
     https://doi.org/10.2118/13933-PA [Google Scholar]
  7. API1998. API RP 40: Recommended Practices for Core Analysis. 2nd edn. American Petroleum Institute (API), Washington, DC.
     [Google Scholar]
  8. Beaubien, S.E., Jones, D.G. et al.2013. Monitoring of near-surface gas geochemistry at the Weyburn, Canada, CO2-EOR site, 2001–2011. International Journal of Greenhouse Gas Control, 16, Suppl. 1, S236–S262, doi: 10.1016/j.ijggc.2013.01.01310.1016/j.ijggc.2013.01.013
     https://doi.org/10.1016/j.ijggc.2013.01.013 [Google Scholar]
  9. Behar, F., Beaumont, V. and De B. Penteado, H.L.2001. Rock-Eval 6 technology: performances and developments. Oil & Gas Science and Technology – Revue d'IFP Energies nouvelles, 56, 111–134, doi: 10.2516/ogst:200101310.2516/ogst:2001013
     https://doi.org/10.2516/ogst:2001013 [Google Scholar]
  10. Bonto, M., Welch, M.J. et al.2021. Challenges and enablers for large-scale CO2 storage in chalk formations. Earth-Science Review, 222, doi: 10.1016/j.earscirev.2021.10382610.1016/j.earscirev.2021.103826
     https://doi.org/10.1016/j.earscirev.2021.103826 [Google Scholar]
  11. Dake, L.P.1978. Fundamentals of Reservoir Engineering. Elsevier, Amsterdam.
     [Google Scholar]
  12. Datta, S.S., Ramakrishnan, T.S. and Weitz, D.2014. Mobilization of a trapped non-wetting fluid from a three-dimensional porous medium. Physics of Fluids, 26, doi: 10.1063/1.486664110.1063/1.4866641
     https://doi.org/10.1063/1.4866641 [Google Scholar]
  13. DEA2009. Denmark's Oil and Gas Production and Subsoil Use 2008. Danish Energy Agency (DEA), Copenhagen.
     [Google Scholar]
  14. DEA2014. Oil and Gas Production in Denmark 2013. Danish Energy Agency (DEA), Copenhagen.
     [Google Scholar]
  15. Emberley, S., Hutcheon, I., Shevalier, M., Durocher, K., Gunter, W.D. and Perkins, E.H.2004. Geochemical monitoring of fluid–rock interaction and CO2 storage at the Weyburn CO2-injection enhanced oil recovery site, Saskatchewan, Canada. Energy, 29, 1393–1401, doi: 10.1016/j.energy.2004.03.07310.1016/j.energy.2004.03.073
     https://doi.org/10.1016/j.energy.2004.03.073 [Google Scholar]
  16. Fabricius, I.L.2007. Chalk: composition, diagenesis and physical properties. Bulletin of the Geological Society of Denmark, 55, 97–128, doi: 10.37570/bgsd-2007-55-0810.37570/bgsd‑2007‑55‑08
     https://doi.org/10.37570/bgsd-2007-55-08 [Google Scholar]
  17. Ghasemi, M., Astutik, W., Alavian, S.A., Whitson, C.H., Sigalas, L., Olsen, D. and Suicmez, V.S.2018. Impact of pressure on tertiary-CO2 flooding in a fractured chalk reservoir. Journal of Petroleum Science and Engineering, 167, 406–417, doi: 10.1016/j.petrol.2018.04.02210.1016/j.petrol.2018.04.022
     https://doi.org/10.1016/j.petrol.2018.04.022 [Google Scholar]
  18. Håkansson, E., Bromley, R. and Perch-Nielsen, K.1974. Maastrichtian chalk of North-West Europe – a pelagic shelf sediment. International Association of Sedimentologists Special Publications, 1, 211–233.
     [Google Scholar]
  19. Hancock, J.M.1975. The petrology of the chalk. Proceedings of the Geologists’ Association, 86, 499–535, doi: 10.1016/S0016-7878(75)80061-710.1016/S0016‑7878(75)80061‑7
     https://doi.org/10.1016/S0016-7878(75)80061-7 [Google Scholar]
  20. Hawthorne, S.B., Miller, D.J., Jin, L., Azzolina, N.A., Hamling, J.A. and Gorecki, C.D.2018. Lab and reservoir study of produced hydrocarbon molecular weight selectivity during CO2 enhanced oil recovery. Energy Fuels, 32, 9070–9080, doi: 10.1021/acs.energyfuels.8b0164510.1021/acs.energyfuels.8b01645
     https://doi.org/10.1021/acs.energyfuels.8b01645 [Google Scholar]
  21. Hawthorne, S.B., Miller, D.J., Grabanski, C.B., Kurz, B.A. and Sørensen, J.A.2019. Hydrocarbon recovery from Williston Basin Shale and mudrock cores with supercritical CO2: Part 1. Method validation and recoveries from cores collected across the basin. Energy & Fuels, 33, 6857–6866, doi: 10.1021/acs.energyfuels.9b0117710.1021/acs.energyfuels.9b01177
     https://doi.org/10.1021/acs.energyfuels.9b01177 [Google Scholar]
  22. Hemmet, M.2005. The hydrocarbon potential of the Danish Continental Shelf. Geological Society, London, Petroleum Geology Conference Series, 6, 85–97, doi: 10.1144/006008510.1144/0060085
     https://doi.org/10.1144/0060085 [Google Scholar]
  23. Huang, D. and Honarpour, M.1998. Capillary end effects in coreflood calculations. Journal of Petroleum Science and Engineering, 19, 103–117, doi: 10.1016/S0920-4105(97)00040-510.1016/S0920‑4105(97)00040‑5
     https://doi.org/10.1016/S0920-4105(97)00040-5 [Google Scholar]
  24. Hwang, R.J. and Ortiz, J.1998. Effect of CO2 flood on geochemistry of the McElroy oil. Organic Geochemistry, 29, 485–503, doi: 10.1016/S0146-6380(98)00057-610.1016/S0146‑6380(98)00057‑6
     https://doi.org/10.1016/S0146-6380(98)00057-6 [Google Scholar]
  25. IPCC2021. Summary for policymakers. In:Masson-Delmotte, V., Zhai, P. et al. (eds) Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Cambridge University Press, Cambridge, UK, 3–32.
     [Google Scholar]
  26. Jarboe, P.J., Candela, P.A., Zhu, W. and Kaufman, A.J.2015. Extraction of hydrocarbons from high-maturity Marcellus shale using supercritical carbon dioxide. Energy & Fuels, 29, 7897–7909, doi: 10.1021/acs.energyfuels.5b0205910.1021/acs.energyfuels.5b02059
     https://doi.org/10.1021/acs.energyfuels.5b02059 [Google Scholar]
  27. Kurz, B.A., Sørensen, J.A. et al.2018. The influence of organics on supercritical CO2 migration in organic-rich shales. In: Unconventional Resources Technology Conference, 23–25 July 2018, Houston, Texas, USA. SPE/AAPG/SEG, 2974–2989, doi: 10.15530/urtec-2018-290274310.15530/urtec‑2018‑2902743
     https://doi.org/10.15530/urtec-2018-2902743 [Google Scholar]
  28. Lake, L.W.1989. Enhanced Oil Recovery. Prentice-Hall, Englewood Cliffs, NJ.
     [Google Scholar]
  29. Leontaritis, K.J. and Mansoori, G.A.1988. Asphaltene deposition: a survey of field experiences and research approaches. Journal of Petroleum Science and Engineering, 1, 229–239, doi: 10.1016/0920-4105(88)90013-710.1016/0920‑4105(88)90013‑7
     https://doi.org/10.1016/0920-4105(88)90013-7 [Google Scholar]
  30. Lind, I., Nykjaer, O., Priisholm, S. and Springer, N.1994. Permeability of stylolite-bearing chak. Journal of Petroleum Technology, 46, 986–993, doi: 10.2118/26019-PA10.2118/26019‑PA
     https://doi.org/10.2118/26019-PA [Google Scholar]
  31. Lucian, A. and Hilfer, R.1999. Trapping and mobilization of residual fluid during capillary desaturation in porous media. Physical Review E, 59, 6819–6823, doi: 10.1103/PhysRevE.59.681910.1103/PhysRevE.59.6819
     https://doi.org/10.1103/PhysRevE.59.6819 [Google Scholar]
  32. Mærsk Oil2014. Final Well Report HDA19/19A. Mærsk Olie og Gas A/S, Copenhagen.
     [Google Scholar]
  33. Megson, J. and Tygesen, T.2005. The North Sea Chalk: an underexplored and underdeveloped play. Geological Society, London, Petroleum Geology Conference Series, 6, 159–168, doi: 10.1144/006015910.1144/0060159
     https://doi.org/10.1144/0060159 [Google Scholar]
  34. Mohammadkhani, S., Anabaraonye, B.U., Afrough, A., Mokhtari, R. and Feilberg, K.L.2021. Crude oil–brine–rock interactions in tight chalk reservoirs: an experimental study. Energies, 14, doi: 10.3390/en1417536010.3390/en14175360
     https://doi.org/10.3390/en14175360 [Google Scholar]
  35. Møller, J.J. and Rasmussen, E.S.2003. Middle Jurassic–Early Cretaceous rifting of the Danish Central Graben. Geological Survey of Denmark and Greenland Bulletin, 1, 247–264, doi: 10.34194/geusb.v1.465410.34194/geusb.v1.4654
     https://doi.org/10.34194/geusb.v1.4654 [Google Scholar]
  36. Olsen, D.2011. CO2 EOR production properties of chalk. Paper SPE-142993-MS presented at theSPE EUROPEC/EAGE Annual Conference and Exhibition, May 23–26, 2011, Vienna, Austria, doi: 10.2118/142993-MS10.2118/142993‑MS
     https://doi.org/10.2118/142993-MS [Google Scholar]
  37. Peters, K.E., Walters, C.C. and Moldowan, J.M.2005. The Biomarker Guide, Volume 2: Biomarkers and Isotopes in Petroleum Systems and Earth History. Cambridge University Press, Cambridge, UK.
     [Google Scholar]
  38. Petersen, H.I. and Hertle, M.2021. Temporal and spatial distribution of original source rock potential in Upper Jurassic–lowermost Cretaceous marine shales, Danish Central Graben, North Sea. Journal of Petroleum Geology, 44, 5–24, doi: 10.1111/jpg.1277610.1111/jpg.12776
     https://doi.org/10.1111/jpg.12776 [Google Scholar]
  39. Petersen, H.I. and Jakobsen, F.C.2021. Lithostratigraphic definition of the Upper Jurassic–lowermost Cretaceous (upper Volgian–Ryazanian) organic-rich and oil-prone Mandal Formation in the Danish Central Graben, North Sea. Marine and Petroleum Geology, 129, doi: 10.1016/j.marpetgeo.2021.10511610.1016/j.marpetgeo.2021.105116
     https://doi.org/10.1016/j.marpetgeo.2021.105116 [Google Scholar]
  40. Petersen, H.I., Hertle, M., Juhasz, A. and Krabbe, H.2016. Oil family typing, biodegradation and source rock affinity of liquid petroleum in the Danish North Sea. Journal of Petroleum Geology, 39, 247–268, doi: 10.1111/jpg.1264510.1111/jpg.12645
     https://doi.org/10.1111/jpg.12645 [Google Scholar]
  41. Petersen, H.I., Al-Masri, W.F., Rudra, A., Mohammadkhani, S. and Sanei, H.2023. Movable and non-movable hydrocarbon fractions in an oil-depleted sandstone reservoir considered for CO2 storage, Nini West Field, Danish North Sea. International Journal of Coal Geology, 280, doi: 10.1016/j.coal.2023.10439910.1016/j.coal.2023.104399
     https://doi.org/10.1016/j.coal.2023.104399 [Google Scholar]
  42. Petersen, H.I., Blinkenberg, K.H., Anderskouv, K., Rudra, A., Zheng, X. and Sanei, H.2024. Spatial distribution of remaining movable and non-movable oil fractions in a depleted Maastrichtian chalk reservoir, Danish North Sea: Implications for CO2 storage. International Journal of Coal Geology, 295, doi: 10.1016/j.coal.2024.10462410.1016/j.coal.2024.104624
     https://doi.org/10.1016/j.coal.2024.104624 [Google Scholar]
  43. Pistiner, A. and Shapiro, M.1993. Capillary end effect in a water saturated porous layer. Transport in Porous Media, 13, 261–275, doi: 10.1007/BF0062244610.1007/BF00622446
     https://doi.org/10.1007/BF00622446 [Google Scholar]
  44. Puntervold, T., Strand, S. and Austad, T.2009. Coinjection of seawater and produced water to improve oil recovery from fractured North Sea chalk oil reservoirs. Energy & Fuels, 23, 2527–2536, doi: 10.1021/ef801023u10.1021/ef801023u
     https://doi.org/10.1021/ef801023u [Google Scholar]
  45. Sanei, H.2020. Genesis of solid bitumen. Science Reports, 10, 15595, doi: 10.1038/s41598-020-72692-210.1038/s41598‑020‑72692‑2
     https://doi.org/10.1038/s41598-020-72692-2 [Google Scholar]
  46. Sanei, H., Wood, J.M., Ardakani, O.H., Clarkson, C.R. and Jiang, C.2015. Characterization of organic matter fractions in an unconventional tight gas siltstone reservoir. International Journal of Coal Geology, 150–151, 296–305, doi: 10.1016/j.coal.2015.04.00410.1016/j.coal.2015.04.004
     https://doi.org/10.1016/j.coal.2015.04.004 [Google Scholar]
  47. Stenshøj, R., Abarghani, A. et al.2023. Hydrocarbon residue in a Danish chalk reservoir and its effects on CO2 injectivity. Marine and Petroleum Geology, 156, doi: 10.1016/j.marpetgeo.2023.10642410.1016/j.marpetgeo.2023.106424
     https://doi.org/10.1016/j.marpetgeo.2023.106424 [Google Scholar]
  48. Surlyk, F.1997. A cool-water carbonate ramp with bryozoan mounds: Late Cretaceous–Danian of the Danish Basin. SEPM Special Publications. 56, 293–307, doi: 10.2110/pec.97.56.029310.2110/pec.97.56.0293
     https://doi.org/10.2110/pec.97.56.0293 [Google Scholar]
  49. Surlyk, F., Dons, T., Clausen, C.K. and Higham, J.2003. Upper Cretaceous. In: Evans, D., Graham, C., Armour, A. and Bathurst, P. (eds) The Millennium Atlas: Petroleum Geology of the Central and Northern North Sea. Geological Society, London, 489–547.
     [Google Scholar]
  50. Thomas, S.2008. Enhanced oil recovery – an overview. Oil & Gas Science and Technology – Revue d'IFP Energies nouvelles, 63, 9–19, doi: 10.2516/ogst:200706010.2516/ogst:2007060
     https://doi.org/10.2516/ogst:2007060 [Google Scholar]
  51. van Buchem, F.S.P., Smit, F.W.H., Buijs, G.J.A., Trudgill, B. and Larsen, P.H.2018. Tectonostratigraphic framework and depositional history of the Cretaceous–Danian succession of the Danish Central Graben (North Sea) – new light on a mature area. Geological Society, London, Petroleum Geology Conference Series, 8, 9–46, doi: 10.1144/PGC8.2410.1144/PGC8.24
     https://doi.org/10.1144/PGC8.24 [Google Scholar]
  52. Yu, T., Gholami, R., Raza, A., Vorland, K.A.N. and Mahmoud, M.2023. CO2 storage in chalks: What are we afraid of?International Journal of Greenhouse Gas Control, 123, doi: 10.1016/j.ijggc.2023.10383210.1016/j.ijggc.2023.103832
     https://doi.org/10.1016/j.ijggc.2023.103832 [Google Scholar]
  53. Zanella, E. and Coward, M.P.2003. Structural framework. In: Evans, D., Graham, C., Armour, A. and Bathurst, P. (eds) The Millennium Atlas: Petroleum Geology of the Central and Northern North Sea. Geological Society, London, 88–125.
     [Google Scholar]
/content/journals/10.1144/geoenergy2025-039
Loading
The effect of supercritical CO2 flooding under two different reservoir conditions on the remaining oil in a fine-grained carbonate reservoir, Danish North Sea
Geoenergy 4, geoenergy2025-039 (2026); https://doi.org/10.1144/geoenergy2025-039
/content/journals/10.1144/geoenergy2025-039
/content/journals/10.1144/geoenergy2025-039
Loading

Data & Media loading...

  • Article Type: Research Article

Most Cited This Month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error