Pore Connectivity Between Organic and Inorganic Matter in Shale: Network Modeling of Mercury Capillary Pressure
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Each of the two major mineral components found in shale samples—organic matter (OM) and inorganic matter (iOM)—has a distinct pore system revealed by scanning electron microscope images, low-pressure nitrogen adsorption, and high-pressure mercury injection tests. Although a vast amount of research has been conducted to detect and measure pore sizes in OM and iOM separately, the connectivity of the pores in these two components remains unclear. In permeability models, pore connectivity between OM and iOM components plays an important role in studying and predicting fluid flow. We studied pore connectivity between OM and iOM by developing pore-network models to mimic the composite nature of distributed OM patches in shale. Input parameters to generate network models were porosity, pore- and throat-size distribution, and total organic content. Mercury injection and capillary-pressure curves were then simulated through generated network models using percolation theory. To study the effects of pore connectivity between OM and iOM, we changed the size and locale of OM patches in the generated network models. Simulation results showed that the locale of OM affects mercury saturation (location and numbers of invaded pores) at given applied pressures. To study the effect of pore-size overlap between OM and iOM pores, we simulated mercury injection for two groups of constructed pore networks: non-overlapping and overlapping. In non-overlapping cases, first all iOM pores were invaded with mercury; then, only OM pores at very high pressure were invaded. In overlapping cases, OM and iOM pores can be invaded simultaneously because some of the pores have similar sizes in both components. The simulated capillary-pressure curves show distinct behavior in the non-overlapping and overlapping cases. Non-overlapping capillary-pressure curves show a sudden increase when OM pores are invaded, whereas overlapping capillary-pressure curves are smoother. Results of this work increase understanding of the connectivity of pores from measured capillary-pressure curves for further implementation in permeability-predictive models.
KeywordsNanopore Shale Organic matter Mudrock Pore connectivity
Both authors contributed equally to this work. FJ conceived the problem and supervised the project. AA performed the modeling. AA and FJ drafted the manuscript. This work was supported partly by the NanoGeosciences Laboratory and by the Mudrock Systems Research Laboratory (MSRL) consortium at the Bureau of Economic Geology, the University of Texas at Austin. MSRL member companies are Anadarko, BP, Cenovus, Centrica, Chesapeake, Chevron, Cima, Cimarex, Concho, ConocoPhillips, Cypress, Devon, Encana, Eni, EOG, Equinor (formerly “Statoil”), EXCO, ExxonMobil, Hess, Husky, Kerogen, Marathon, Murphy, Newfield, Penn Virginia, Penn West, Pioneer, Samson, Shell, Talisman, Texas American Resources, The Unconventionals, US Enercorp, Valence, and YPF. We would like to thank Drs. S. Ruppel and S. Peng for their constructive comments. Publication was authorized by the Director, Bureau of Economic Geology.
- Clerke, E.A., Mueller, H.W., Phillips, E.C., et al.: Application of Thomeer hyperbolas to decode the pore systems, facies and reservoir properties of the Upper Jurassic Arab D Limestone, Ghawar field, Saudi Arabia: a “Rosetta Stone” approach. GeoArabia 13(4), 113–160 (2008)Google Scholar
- Fatt, I.: The network model of porous media I. Capillary pressure characteristics. Trans. AIME 207, 144–159 (1956)Google Scholar
- Fawzi, A., Ford, M., Coleman, M.: Tight oil production pushes U.S. crude supply to over 10% of world total. U.S. Energy Information Administration. http://www.eia.gov/todayinenergy/detail.cfm?id=15571 (2014). Accessed 8 Aug 2017
- Gibbs, J.W.: The Collected Works of J. Willard Gibbs. Yale University Press, New Haven (1957)Google Scholar
- Javadpour, F., Ettehadtavakkoli, A.: Gas transport processes in shales. In: Rezaee, R. (ed.) Fundamentals of Gas Shale Reservoirs. Wiley, Hoboken (2015)Google Scholar
- Javadpour, F., Fisher, D., Unsworth, M.: Nanoscale gas flow in shale sediments. JCPT 46, 55–61 (2007)Google Scholar
- Kale, S., Rai, C.S., Sondergeld, C.H.: Rock typing in gas shales. SPE 134539, SPE Annual Technical Conference and Exhibition, Florence, Italy, 19–22 Sept (2010)Google Scholar
- Sakhaee-Pour, A., Bryant, S.: Gas permeability of shale. Adv. Water Resour. 15, 401–409 (2012)Google Scholar