Chalk reservoirs are mainly composed of coccoliths, the remains of algae, which consist of radially arranged, single calcite crystals that are less than a micrometer in diameter. Pores and pore throats are likewise small, making oil production from chalk reservoirs difficult and slow, so a substantial amount of oil is left behind. Inorganic calcite crystals, grown in the laboratory for only a few hours, are 5 or 10 times larger than chalk particles.  Larger particles mean larger pores and pore throats, thus easier oil production.  So the big questions are:  Why has biogenic calcite not recrystallised during the 60 million years it has been exposed to warm, salty water? And can crystal size be modified?  The Nano-Chalk team aimed to find out why, and then use the new information to identify methods to facilitate recrystallisation, thus increasing reservoir particle size and permeability, and ultimately, oil recovery.

We have used nanotechniques to investigate surface composition and pore structure at the sub micrometer scale and found that stability of the coccoliths is likely caused by a thin layer of polysaccarides. Although nanocrystals of clay and intergrowths of silica could play a role, the most effective inhibitor is the polysaccharide that the algae originally used to control biomineralisation.

The venture was high risk – high gain.  However, several spin-offs, such as a method for deriving reservoir parameters from drill cuttings and a high resolution perspective on chalk particle wettability, are already improving understanding of reservoir behaviour.


Papers published:

  1. Controlling biomineralisation with cations
    K.K. Sand, C.S. Pedersen, J. Matthiesen, S. Dobberschütz and S.L.S. Stipp (2017), Nanoscale 9, 12925-12933
  2. Interactions of the Calcite {10.4} Surface with Organic Compounds: Structure and Behaviour at Mineral – Organics Interfaces
    S.S. Hakim, M.H.M. Olsson, H.O. Sørensen, N. Bovet, J. Bohr, R. Feidenhans’l and S.L.S. Stipp (2017), Sci. Rep. 7, 7592
  3. Water Mobility in Chalk: A Quasielastic Neutron Scattering Study
    M.C. Berg, K.N. Dalby, N. Tsapatsaris, D.V. Okhrimenko, H.O. Sørensen, D. Jha, J.P. Embs, S.L.S. Stipp and H.N. Bordallo (2017), Journal of Physical Chemistry C 121, 14088–14095
  4. Calcite Growth Kinetics: Dependence on Saturation Index, Ca2+:CO32–Activity Ratio, and Surface Atomic Structure
    K.K. Sand, D. J. Tobler, S. Dobberschütz, E. Makovicky, K. Larsen, M.P. Andersson and S.L.S. Stipp (2016), Crystal Growth & Design 16, 3602-3612
  5. Modelling how incorporation of divalent cations affects calcite wettability – implications for biomineralisation and oil recovery
    M.P. Andersson, K. Dideriksen, H. Sakuma and S.L.S. Stipp (2016), Scientific Reports 6, 28854
  6. A microkinetic model of calcite step growth
    M.P. Andersson, S. Dobberschütz, K.K. Sand, D.J. Tobler, J.J. De Yoreo and S.L.S. Stipp (2016), Angewandte Chemie 55, 11086-11090
  7. Smaller Calcite Lattice Deformation Caused by Occluded Organic Material in Coccoliths than in Mollusk Shell
    S. Frølich, H.O. Sørensen, S.S. Hakim, F. Marin, S.L.S. Stipp and H. Birkedal (2015)
    Crystal Growth & Design 15, 2761–2767
  8. Repulsive hydration forces between calcite surfaces and their effect on the brittle strength of calcite-bearing rocks
    A. Røyne, K.N. Dalby K.N and T. Hassenkam (2015)
    Geophysical Research Letters 42, 4786-4794
  9. Adsorption of Ethanol and Water on Calcite: Dependence on Surface Geometry and Effect on Surface Behavior
    K.S. Keller, M.H.M. Olsson, M. Yang and S.L.S. Stipp (2015)
    Langmuir 31, 3847-3853
  10. Role of Alginate in Calcite Recrystallization
    L. Z. Lakshtonov, D. A. Belova, D. V. Okhrimenko and S. L. S. Stipp (2015)
    Crystal Growth & Design 15, 419–427
  11. Interaction of alcohols with the calcite surface
    N. Bovet, M. Yang, M. S.Javadi and S. L. S. Stipp (2015)
    Phys. Chem. Chem. Phys. 17, 3490-3496
  12. Biomineralization: Long-Term Effectiveness of Polysaccharides on the Growth and Dissolution of Calcite
    K. K. Sand, C. S. Pedersen, S. Sjöberg, J. W. Nielsen, E. Makovicky and S. L. S. Stipp (2014)
    Cryst. Growth Des.14, 5486–5494
  13. The surface reactivity of chalk (biogenic calcite) with hydrophilic and hydrophobic functional GROUPS
    D. V. Okhrimenko, K. N. Dalby, L. L. Skovbjerg, N. Bovet, J. H. Christensen and S. L. S. Stipp (2014)
    Geochimica et Cosmochimica Acta 128, 212
  14. From Nanometer Aggregates to Micrometer Crystals: Insight into the Coarsening Mechanism of Calcite
    L. N. Schultz, K. Dideriksen, L. Lakshtanov, S. S. Hakim, D. Müter, F. Hausser, K. Bechgaard and Stipp, S. L. S. (2014)
    Crystal Growth & Design 14, 552
  15. Infrared Spectroscopy and Density Functional Theory Investigation of Calcite, Chalk, and Coccoltihs – Do We Observe the Mineral Surface
    M. P. Andersson, C. P. Hem, L. N. Schultz, J. W. Nielsen, C. S. Pedersen, K. K. Sand, D. V. Okhrimenko, A. Johnsson and S. L. S. Stipp (2014)
    J. Phys. Chem. A 118, 10720-10729
  16. Preferential Adsorption of Hydrocarbons to Nanometer-Sized Clay on Chalk Particle Surfaces
    L. Skovbjerg, D. V. Okhrimenko, J. Khoo, K. Dalby, T. Hassenkam, E. Makovicky and S. Stipp (2013)
    Energy & Fuels 27, 3642
  17. High surface area calcite
    L. Schultz, M. Andersson, K. Dalby, D. Müter, D. V. Okhrimenko, H. Fordsmand and S. Stipp (2013)
    Journal of Crystal Growth 371, 34
  18. Energies of the Adsorption of Functional Groups to Calcium Carbonate Polymorphs: The Importance of -OH and -COOH Groups
    D. V. Okhrimenko, J. Nissenbaum, M. Andersson, M. Olsson and S. Stipp (2013)
    Langmuir 29, 11062
  19. Adsorption properties of chalk: contributions from calcite and clays
    Denis V. Okhrimenko, Kim N. Dalby, Susan L.S. Stipp (2013)
    Procedia Earth and Planetary Science 7, 632
  20. Non-Destructive Identification of Micrometer-Scale Minerals and Their Position Within A Bulk Sample
    H. O. Sorensen, S. S. Hakim, S. Pedersen, B. C. Christiansen, Z. I. Balogh, C. P. Hem, I. S. Pasarin, S. Schmidt, U. L. Olsen, J. Oddershede, C. Frandsen, R. Feidenhan’l and S. L. Stipp (2012)
    Canadian Mineralogist 50, 501
  21. Nano sized clay detected on chalk particle surfaces
    L. Skovbjerg, T. Hassenkam, E. Makovicky, C. Hem, M. Yang, N. Bovet and S. Stipp (2012)
    Geochimica et Cosmochimica Acta 99, 57
  22. Crystallization of CaCO3 in Water-Alcohol Mixtures: Spherulitic Growth, Polymorph Stabilization, and Morphology Change
    Sand, K., Rodriguez-Blanco, J., Makovicky, E., Benning, L., and Stipp, S. (2012)
    Crystal Growth & Design 12, 842

and many more