Pore-Scale Numerical Simulation of CO 2 –Oil Two-Phase Flow: A Multiple-Parameter Analysis Based on Phase-Field Method

Rui Song, Yu Tang (), Yao Wang (), Ruiyang Xie and Jianjun Liu
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Rui Song: School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China
Yu Tang: School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China
Yao Wang: School of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang 621010, China
Ruiyang Xie: School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu 610500, China
Jianjun Liu: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China

Energies, 2022, vol. 16, issue 1, 1-24

Abstract: A deep understanding of the pore-scale fluid flow mechanism during the CO 2 flooding process is essential to enhanced oil recovery (EOR) and subsurface CO 2 sequestration. Two-phase flow simulations were performed to simulate the CO 2 flooding process based on the phase-field method in this study. Two-dimensional models with random positions and sizes of grains of circular shape were constructed to reproduce the topology of porous media with heterogeneous pore size distributions in the reservoir rock. A multiple-parameter analysis was performed to investigate the effects of capillary number, viscosity ratio, wettability, density, gravity, interfacial tension, and absolute permeability on the two-phase fluid flow characteristics. The results indicated that when the capillary number and viscosity ratio were large enough, i.e., log Ca = −3.62 and log M = −1.00, the fingering phenomenon was not obvious, which could be regarded as a stable displacement process. CO 2 saturation increased with the increase in the PV value of the injected CO 2 . Once the injected CO 2 broke through at the outlet, the oil recovery efficiency approached stability. Two types of broken behaviors of the fluids were observed during the wettability alternation, i.e., snap-off and viscous breakup. Snap-off occurred when capillary forces dominated the fluid flow process, while viscous breakup occurred with a low viscosity ratio. With a low capillary number, the flooding process of the injected CO 2 was mainly controlled by the capillary force and gravity. With the decrease in the interfacial tension between the fluids and the increase in the permeability of the porous media, the recovery of the displaced phase could be enhanced effectively. In the mixed-wet model, with the increase in the percentage of the nonoil-wetted grains, the intersecting point of the relative permeability curve moved to the right and led to a higher oil recovery.

Keywords: CO 2 flooding; two-phase flow; phase-field method; wettability; capillary number (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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