Dynamic Behaviors of CO2 Enhanced Shale Oil Flow in Nanopores by Molecular Simulation

作者：Kangjian Tian, Tianyu Wang, Zhengchao Ma, Jintao Weng, Xiaoxia Zhou, Jiacheng Dai, Ye Zhang, Shouceng Tian · 发表于：SPE Journal · 年份：2024 · DOI：10.2118/223974-pa · 被引用次数：9 · 研究领域：Hydrocarbon exploration and reservoir analysis、Atmospheric and Environmental Gas Dynamics、Phase Equilibria and Thermodynamics

Summary With the development of unconventional oil and gas, shale oil has become a significant focus for exploration and development. The mineral composition of shale is notably complex, and the mechanisms underlying carbon dioxide (CO2)-enhanced shale oil flow remain insufficiently understood. While many studies have addressed adsorption in shale oil and gas, research into the dynamic flow of CO2 and shale oil within pore spaces is limited. To investigate the mobility behavior of CO2 and shale oil in nanopores from a microscopic perspective, a dynamic flow model for CO2-enhanced shale oil flow, considering wall adsorption effects, was established by using the Non-Equilibrium Molecular Dynamics (NEMD) method. This model simulated CO2-enhanced shale oil flow within organic nanopores under reservoir conditions and analysed the effects of pore size, temperature, and injection pressure. The results show that shale oil forms four adsorption layers in 4-nm graphene pores, with a density of 2.25 g/cm3 in the first adsorption layer and 0.63 g/cm3 in the free zone, closely aligning with the standard shale oil density of 0.66 g/cm3 at 343 K and 25 MPa, thereby validating the accuracy of the model. The peak density of the first adsorption layer is 3.55 times that of the free zone, highlighting shale oil’s strong adsorption capacity at the pore wall. The study reveals that the diffusion coefficients of CO2 within the pores are 1.05, 1.14, and 1.41 times higher than those of pentane, octa...