不同初始储层压力下CO_(2)驱替CH_(4)试验研究  

An experimental study of CH_(4) displacement by CO_(2) under varying initial reservoir pressures

作　　者：许江[1,2] 蒋石宇 彭守建[1,2] 王忠晖 陈嘉璇 牛慧婷 XU Jiang;JIANG Shiyu;PENG Shoujian;WANG Zhonghui;CHEN Jiaxuan;NIU Huiting(State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400044,China;State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学煤矿灾害动力学与控制全国重点实验室,重庆400044 [2]重庆大学复杂煤气层瓦斯抽采国家地方联合工程实验室,重庆400044

出　　处：《煤田地质与勘探》2025年第4期94-105,共12页Coal Geology & Exploration

基　　金：中央高校基本科研业务费项目(2022CDJQY-011);国家自然科学基金面上项目(52274174);重庆市自然科学基金面上项目(cstc2024ycjh-bgzxm0114)。

摘　　要：【目的】为揭示注二氧化碳强化煤层气开采(CO_(2)-ECBM)过程中的储层参数演化规律及初始储层压力对煤层气注气开采效果的影响。【方法】利用多场耦合煤层注气增产物理模拟试验系统,开展了恒定注气压力2.0 MPa和初始储层压力分别为1.5、1.0和0.5 MPa的注CO_(2)驱替CH_(4)试验研究,探讨了CO_(2)驱替CH_(4)过程中储层压力、温度和体积应变等多物理场参数的时空演化规律及其驱替效果,并在分析其作用机制的基础上对CO_(2)驱替CH_(4)过程进行了阶段划分。【结果和结论】结果表明:(1)在驱替过程中,注气井储层压力高于生产井储层压力,且压差随初始储层压力增大而增大,最大值为0.34 MPa,而储层平衡压力随初始储层压力增大而减小。(2)储层温度在距离注气井越近的位置越早上升,且初始储层压力越小温度上升速率越大,储层平衡温度随初始储层压力增大而减小。(3)储层体积应变演化可划分为缓慢上升、急速上升、趋于平缓3个阶段,储层体积应变随初始储层压力增大而减小。(4)在驱替过程中,初始储层压力从0.5 MPa依次增至1.0、1.5 MPa时,CH_(4)采收率由91.00%依次降至88.48%、86.81%,随初始储层压力增大呈现减小趋势,与之相反,CO_(2)突破时间和CO_(2)封存效率随初始储层压力增大而增大。驱替过程各阶段作用机制不同,阶段1 (CO_(2)未突破阶段)和阶段2 (CO_(2)突破阶段)的CH_(4)累积体积、CO_(2)封存体积随着初始储层压力的增加而增加,均占整个驱替过程中CH_(4)累积体积、CO_(2)封存体积的80%以上。研究成果为构建煤层气高效开采协同CO_(2)地质封存一体化技术提供理论依据。[Objective] This study aims to reveal the evolutionary patterns of reservoir parameters during the CO_2-enhanced coalbed methane(CO_2-ECBM) recovery and the impact of initial reservoir pressure on CBM recovery by gas injection.[Methods] Based on the multi-field coupling-based physical simulation experiment system of gas injection into coal seams for production growth,this study conducted experiments of CH_(4) displacement by CO_(2) under a constant gas injection pressure of 2.0 MPa and initial reservoir pressures of 1.5 MPa,1.0 MPa,and 0.5 MPa.Accordingly,this study explored the spatiotemporal evolutionary patterns of multiphysical field parameters such as reservoir pressure,temperature,and volumetric strain during CH_(4) displacement by CO_2,as well as the displacement effects.Moreover,this study divided the displacement process into three stages(i.e.,stages 1,2,and 3) by analyzing the interaction mechanisms.[Results and Conclusions] The results indicate that in the displacement process,the reservoir pressure in the injection well was higher than that in the production well.Their pressure difference increased with the initial reservoir pressure,with a maximum of 0.34 MPa.In contrast,the reservoir equilibrium pressure decreased with an increase in the initial reservoir pressure.The reservoir temperature rose earlier at a location closer to the injection well,and it rose at a higher rate under a lower initial reservoir pressure.Furthermore,the reservoir equilibrium temperature decreased with an increase in the initial reservoir pressure.The evolutionary process of reservoir volumetric strain was divided into three stages:slow increase,rapid increase,and stabilization,and the reservoir volumetric strain decreased with an increase in the initial reservoir pressure.During the displacement,as the initial reservoir pressure increased from 0.5 MPa to 1.0 MPa and then to1.5 MPa,the CH_(4) recovery decreased from 91.00 % to 88.48 % and then to 86.81 %,showing a decreasing trend with increasing initial reservoir pressure.I

关 键 词：CO_(2)-ECBM 初始储层压力 储层参数演化 驱替效果 多场耦合 真三轴应力状态 

分 类 号：TD712[矿业工程—矿井通风与安全]