The depletion of conventional hydrocarbon reservoirs has prompted the oil and gas industry to search for unconventional resources such as shale gas/oil reservoirs. In shale rocks, considerable amounts of hydrocarbon reside in nanoscale pore spaces. As a result, understanding the multiphase flow of wetting and non-wetting phases in nanopores is important to improve oil and gas recovery from these formations. This study was designed to investigate the threshold capillary pressure of oil and water displacements in a capillary dominated regime inside nanoscale pores using nonequilibrium molecular dynamics (NEMD) simulations. The pores have the same cross-sectional area and volume but different cross-sectional shapes. Oil and water particles were represented with a coarse grained model and the NEMD simulations were conducted by assigning external pressure on an impermeable piston. Threshold capillary pressures were determined for the drainage process (water replaced by oil) in different pores. The molecular dynamics results are in close agreements with calculations using the Mayer-Stowe-Princen (MS-P) method which has been developed on the premise of energy balance in thermodynamic equilibrium. After the drainage simulations, a change in wall particles’ wettability from water-wet to oil-wet was implemented based on the final configuration of oil and water inside the pore. Waterflooding simulations were then carried out at the threshold capillary pressure. The results show that the oil layer formed between water in the corner and in the center of the pore is not stable and collapses as the simulation continues. This is in line with the predictions from the MS-P method.
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21 November 2014
Research Article|
November 19 2014
Molecular dynamics of wetting layer formation and forced water invasion in angular nanopores with mixed wettability
Mohammad Sedghi;
Mohammad Sedghi
a)
Department of Chemical and Petroleum Engineering,
University of Wyoming
, 1000 East University Avenue, Laramie, Wyoming 82071, USA
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Mohammad Piri;
Mohammad Piri
Department of Chemical and Petroleum Engineering,
University of Wyoming
, 1000 East University Avenue, Laramie, Wyoming 82071, USA
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Lamia Goual
Lamia Goual
Department of Chemical and Petroleum Engineering,
University of Wyoming
, 1000 East University Avenue, Laramie, Wyoming 82071, USA
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J. Chem. Phys. 141, 194703 (2014)
Article history
Received:
August 11 2014
Accepted:
November 03 2014
Citation
Mohammad Sedghi, Mohammad Piri, Lamia Goual; Molecular dynamics of wetting layer formation and forced water invasion in angular nanopores with mixed wettability. J. Chem. Phys. 21 November 2014; 141 (19): 194703. https://doi.org/10.1063/1.4901752
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