Mechanism of shale oil displacement by CO2 in nanopores: A molecular dynamics simulation study

Zhengbin Wu, Zhe Sun, Kun Shu, Shu Jiang, Qiyang Gou, Zhangxing Chen

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Utilizing CO2 to enhance shale oil recovery has a huge potential and thus has gained widespread popularity in recent years. However, the microscopic mechanisms of CO2 enhancing shale oil recovery remain poorly understood. In this paper, the molecular dynamics simulation method is adopted to investigate the replacement behavior of CO2 in shale oil reservoirs from a micro perspective. Three kinds of n-alkanes are selected as the simulative crude oil in silica nanopores. Molecular dynamics models are established to study the occurrence patterns of different alkanes on the rock surface and the alkane[1]stripping characteristics of CO2. The fluid density, mean square displacement and centroid variation are evaluated to reveal the effect of CO2 on alkanes. The results indicate that different alkanes exhibit varying occurrence characteristics of oil film on the rock surface of the shale reservoir. Specifically, a higher carbon number leads to a thicker oil film. Through the alkane molecular gaps, CO2 penetrates the alkane molecular system and reaches the rock surface to effectively strip the oil film of different alkane molecules. CO2 will more readily mix with the stripped oil molecules and displace them from the rock surface when the carbon number is small. The process for CO2 replacing crude oil on the rock surface can be divided into four typical stages, namely, CO2 diffusion, competitive adsorption, emulsification and dissolution, and CO2-alkanes miscible phase (for light alkanes). This study contributes to the improvement of micro-scale enhanced oil recovery mechanisms for shale oil via CO2 injection and provides a guidance for enhancing shale oil recovery by using CO2.

Document Type: Original article

Cited as: Wu, Z., Sun, Z., Shu, K., Jiang, S., Gou, Q., Chen, Z. Mechanism of shale oil displacement by CO2 in nanopores: A molecular dynamics simulation study. Advances in Geo-Energy Research, 2024, 11(2): 141-151.


Shale oil, molecular dynamics simulation, micro mechanisms, enhanced oil recovery

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Alafnan, S. Carbon dioxide and methane sequestration in organic-rich shales: Nanoscale insights into adsorption and transport mechanisms. Journal of Energy Resources Technology, 2022, 144(7): 073010.

Alfarge, D., Wei, M., Bai, B. Factors affecting CO2-EOR in shale-oil reservoirs: Numerical simulation study and pilot tests. Energy & Fuels, 2017, 31(8): 8462-8480.

Cui, F., Jin, X., Liu, H., et al. Molecular modeling on Gulong shale oil and wettability of reservoir matrix. Capillarity, 2022, 5(4): 65-74.

Dong, X., Xu, W., Liu, H., et al. Molecular insight into the oil displacement mechanism of CO2 flooding in the nanopores of shale oil reservoir. Petroleum Science, 2023a, 20: 3516-3529.

Dong, X., Xu, W., Liu, H., et al. On the replacement behavior of CO2 in nanopores of shale oil reservoirs: Insights from wettability tests and molecular dynamics simulations. Geoenergy Science and Engineering, 2023b, 223: 211528.

Fang, T., Zhang, Y., Ma, R., et al. Oil extraction mechanism in CO2 flooding from rough surface: Molecular dynamics simulation. Applied Surface Science, 2019, 494(15): 80-86.

Feng, Q., Xu, S., Xing, X., et al. Advances and challenges in shale oil development: A critical review. Advances in Geo-Energy Research, 2020, 4(4): 406-418.

Gou, Q., Xu, S., Chen, Z. Full-scale pores and micro-fractures characterization using FE-SEM, gas adsorption, nano-CT and micro-CT: A case study of the Silurian Longmaxi Formation shale in the Fuling area, Sichuan Basin, China. Fuel, 2019, 253(1): 167-179.

Guo, H., Wang, Z., Wang, B., et al. Molecular dynamics simulations of oil recovery from dolomite slit nanopores enhanced by CO2 and N2 injection. Advances in Geo-Energy Research, 2022, 6(4): 306-313.

Huang, T., Cheng, L., Cao, R., et al. Molecular simulation of the dynamic distribution of complex oil components in shale nanopores during CO2-EOR. Chemical Engineering Journal, 2024, 479: 147743.

Jin, L., Hawthorne, S., Sorensen, J., et al. Advancing CO2 enhanced oil recovery and storage in unconventional oil play-experimental studies on Bakken Shales. Applied Energy, 2017, 208: 171-183.

Jin, Z., Firoozabadi, A. Methane and carbon dioxide adsorption in clay-like slit pores by Monte Carlo simulations. Fluid Phase Equilibria, 2013, 360: 456-465.

Liu, B., Wang, C., Zhang, J., et al. Displacement mechanism of oil in shale inorganic nanopores by supercritical carbon dioxide from molecular dynamics simulations. Energy & Fuels, 2017, 31: 738-746.

Michael, G., Vello, K., Phil, D. Opportunities for using anthropogenic CO2 for enhanced oil recovery and CO2 storage. Energy and Fuels, 2013, 27(8): 4183-4189.

Pathak, M., Huang, H., Meakin, P., et al. Molecular investigation of the interactions of carbon dioxide and methane with kerogen: Application in enhanced shale gas recovery. Journal of Natural Gas Science and Engineering, 2018, 51: 1-8.

Qin, Y., Yang, X., Zhu, Y., et al. Molecular dynamics simulation of interaction between supercritical CO2 fluid and modified silica surfaces. Journal of Physical Chemistry C, 2008, 112(33): 12815-12824.

Santos, M., Franco, L., Castier, M., et al. Molecular dynamics simulation of n-alkanes and CO2 confined by calcite nanopores. Energy & Fuels, 2018, 32(2): 1934-1941.

Sheng, J. Critical review of field EOR projects in shale and tight reservoirs. Journal of Petroleum Science and Engineering, 2017, 159: 654-665.

Sui, H., Zhang, F., Zhang L., et al. Competitive sorption of CO2/CH4 and CO2 capture on modified silica surfaces: A molecular simulation. Science of The Total Environment, 2024, 908: 168356.

Sun, S., Liang, S., Liu, Y., et al. A review on shale oil and gas characteristics and molecular dynamics simulation for the fluid behavior in shale pore. Journal of Molecular Liquids, 2023, 376: 121507.

Wang, H., Su, Y., Wang, W., et al. CO2-oil diffusion, adsorption and miscible flow in nanoporous media from porescale perspectives. Chemical Engineering Journal, 2022a, 450: 137957.

Wang, H., Wang, X., Jin, X., et al. Molecular dynamics simulation of diffusion of shale oils in montmorillonite. The Journal of Physical Chemistry C, 2016a, 120(16): 8986-8991.

Wang, R., Bi, S., Guo, Z., et al. Molecular insight into replacement dynamics of CO2 enhanced oil recovery in nanopores. Chemical Engineering Journal, 2022b, 440: 135796.

Wang, S., Feng, Q., Javadpour F., et al. Oil adsorption in shale nanopores and its effect on recoverable oil-in-place. International Journal of Coal Geology, 2015, 147-148: 9-24.

Wang, S., Javadpour, F., Feng, Q. Molecular dynamics simulations of oil transport through inorganic nanopores in shale. Fuel, 2016b, 171: 74-86.

Wang, S., Yao, X., Feng, Q., et al. Molecular insights into carbon dioxide enhanced multi-component shale gas recovery and its sequestration in realistic kerogen. Chemical Engineering Journal, 2021, 425: 130292.

Wan, Y., Jia, C., Lv, W., et al. Recovery mechanisms and formation influencing factors of miscible CO2 huff-n-puff processes in shale oil reservoirs: A systematic review. Advances in Geo-Energy Research, 2024, 11(2): 88-102.

Xue, C., Ji, D., Cheng, D., et al. Adsorption behaviors of different components of shale oil in quartz slits studied by molecular simulation. ACS Omega, 2022, 7(45): 41189-41200.

Yan, Y., Dong, Z., Zhang, Y., et al. CO2 activating hydrocarbon transport across nanopore throat: Insights from molecular dynamics simulation. Physical Chemistry Chemical Physics, 2017, 19(45): 30439-30444.



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