Zhang Yingnan, Dou Xiangji, Zhou Wenteng, Lu Chang
School of Civil Engineering, Qingdao University of Technology, Qingdao, 266520, China.
School of Petroleum and Natural Gas Engineering, Changzhou University, Changzhou, 213164, China.
Sci Rep. 2025 May 15;15(1):16970. doi: 10.1038/s41598-025-02095-8.
Developing unconventional reservoirs through gas injection has become increasingly popular in recent years. Among the various injector gases, hydrocarbon gas is considered one of the most promising fluids for use in the EOR process. In this study, molecular dynamics simulations have been utilized to generate insights into the tight oil migration under six different hydrocarbon gas composition ratios. Simulation results indicate that the migration process of the oil-gas mixture occurs in stages, but the overall states of all systems remain relatively consistent. As the proportion of heavy components (ethane and propane) in the hydrocarbon gas increases, the threshold migration resistance of each system exhibits a pattern of initially decreasing and then increasing. The mechanism underlying the nonlinear evolutionary trend of migration resistance was clarified through analyzing dynamic interactions and interfacial tension characteristics. The essence lies in the fact that the hindrance effect caused by increasingly stronger oil/gas-pore interactions eventually outweighs the drag reduction effect induced by the gradual reduction of oil/gas-water interfacial tension. Based on migration characteristics and sensitivity factors, we propose that the optimal hydrocarbon gas composition ratio for methane/ethane/propane is in the range of 80/10/10 to 70/15/15. Overall, this study focuses on employing molecular dynamics simulations to analyze the oil-gas migration characteristics at the nanoscale, aiming to provide more detailed insights for microscopic analysis and theoretical support for tight oil development.
近年来，通过注气开发非常规油藏越来越受到关注。在各种注入气体中，烃类气体被认为是用于提高采收率（EOR）过程中最有前景的流体之一。在本研究中，利用分子动力学模拟来深入了解六种不同烃类气体组成比例下的致密油运移情况。模拟结果表明，油气混合物的运移过程分阶段进行，但所有系统的总体状态保持相对一致。随着烃类气体中重组分（乙烷和丙烷）比例的增加，各系统的运移阻力阈值呈现出先降低后升高的趋势。通过分析动态相互作用和界面张力特性，阐明了运移阻力非线性演化趋势的机理。其实质在于，油/气-孔隙相互作用不断增强所导致的阻碍作用最终超过了油/气-水界面张力逐渐降低所带来的减阻作用。基于运移特性和敏感因素，我们提出甲烷/乙烷/丙烷的最佳烃类气体组成比例范围为80/10/10至70/15/15。总体而言，本研究着重利用分子动力学模拟来分析纳米尺度下的油气运移特性，旨在为微观分析提供更详细的见解，并为致密油开发提供理论支持。
