基于分子动力学模拟的致密储层CO_(2)/N_(2)换油机理研究  

Mechanism of CO_(2)/N_(2) oil exchange in tight reservoirs based on molecular dynamics simulation

作　　者：陈汉钊 吴正彬 李轩 舒坤 蒋恕[1] 陈掌星 CHEN Hanzhao;WU Zhengbin;LI Xuan;SHU Kun;JIANG Shu;CHEN Zhangxing(Hubei Key Laboratory of Oil and Gas Exploration and Development Theory and Technology,China University of Geosciences(Wuhan),Wuhan 430074,China;Department of Chemical and Petroleum Engineering,University of Calgary,Calgary T2N 1N4,Alberta,Canada;No.9 Oil Production Plant,CNPC Changqing Oilfield Company,Yinchuan 750006,China;Research Institute of Exploration&Development,PetroChina Tuha Oilfield Company,Hami Xinjiang 839009,China)

机构地区：[1]中国地质大学(武汉)油气勘探开发理论与技术湖北省重点实验室,武汉430074 [2]Department of Chemical and Petroleum Engineering,University of Calgary,Calgary T2N 1N4,Alberta,Canada [3]中国石油长庆油田分公司第九采油厂,银川750006 [4]中国石油吐哈油田公司勘探开发研究院,新疆哈密839009

出　　处：《地质科技通报》2025年第1期36-47,共12页Bulletin of Geological Science and Technology

基　　金：国家自然科学基金项目(52404046,42130803);湖北省自然科学基金项目(2024AFD385);武汉市知识创新专项-曙光计划项目。

摘　　要：利用分子动力学模拟来研究致密油的赋存状态以及CO_(2)置换致密油的机理。采用蒙特卡洛法和分子动力学模拟算法,建立了不同相对分子质量烷烃在岩石壁面的赋存状态模型,研究了烷烃分子在不同岩石壁面的赋存特征,分析了CO_(2)和N_(2)置换致密油的微观机理。模拟温度和压力条件(343.13 K、20 MPa)选取四川盆地致密储层的温度和压力条件。测得石英壁面和方解石壁面中,C7在CO_(2)中的扩散系数分别为1.88×10^(−5) m/s^(2)和1.83×10^(−5) m/s^(2),在N_(2)中分别为6.4×10^(−6) m/s^(2)和9.01×10^(−6) m/s^(2)。结果将CO_(2)置换致密油的效果明显好于N_(2)。随着相对分子质量的增加,烷烃分子从岩石壁面置换的难度增大,方解石壁面对烷烃分子的吸附作用要强于石英壁面。根据本研究模拟结果将CO_(2)置换机理大致分为4个阶段:分子扩散阶段、竞争吸附阶段、乳化溶解阶段以及混相阶段(低相对分子质量烷烃)。[Objective]This research aims to investigate the storage state of tight oil and the mechanism of its replacement by CO_(2) through molecular dynamics simulations.[Methods]The Monte Carlo method and molecular dynamics simulation algorithms were utilized to model the storage state of alkanes with varying molecular weights on rock surfaces.These models facilitate the examination of the storage characteristics of alkane molecules on different types of rock surfaces and analyze the micromechanisms of tight oil replacement by CO_(2) and N2.The simulated temperature and pressure conditions(343.13 K and 20 MPa)were chosen to reflect the conditions in tight reservoirs of the Sichuan Basin.[Results]The diffusion coefficients of C7 in CO_(2) were measured at 1.88×10^(−5) m/s^(2) and 1.83×10^(−5) m/s^(2) for the quartz and calcite surfaces,respectively.In contrast,the coefficients in N_(2) were lower,measuring 6.4×10^(−6) m/s^(2) and 9.01×10^(−6) m/s^(2) for the same surfaces.[Conclusion]These findings indicate that CO_(2) is significantly more effective than N2 in displacing tight oil.The challenge of displacing alkane molecules from rock surfaces increases with the relative molecular weight of the alkane.In addition,alkane molecule adsorption on the calcite surface is greater than on the quartz surface.Based on the experimental results presented in this paper,the CO_(2) replacement mechanism can be broadly categorized into four stages:molecular diffusion,competitive adsorption,emulsification and dissolution,and a mixed-phase stage(involving low-molecular-weight alkanes).

关 键 词：致密油 CO_(2) N_(2) 赋存状态 驱油机理 分子动力学模拟 

分 类 号：TE357.45[石油与天然气工程—油气田开发工程]