四川盆地页岩储层中CO_(2)/CH_(4)竞争吸附规律的影响因素  

Influential factors on competitive adsorption between CO_(2) and CH_(4) in shale reservoirs of Sichuan Basin

作　　者：马欣健 向祖平[1] 朱诗杰 芮红琴 宋振龙 胡俊骉 MA Xinjian;XIANG Zuping;ZHU Shijie;RUI Hongqin;SONG Zhenlong;and HU Junbiao(Chongqing University of Science and Technology,Chongqing 401331,China)

机构地区：[1]重庆科技学院

出　　处：《天然气勘探与开发》2023年第3期117-122,共6页Natural Gas Exploration and Development

摘　　要：我国川渝地区页岩气开发面临采收率低的开发瓶颈,有研究表明页岩储层中注入CO_(2)可置换出吸附在有机质干酪根上的CH_(4)而提高页岩气采收率,但其关键的CO_(2)/CH_(4)竞争吸附规律尚不明确。为提高注CO_(2)开采页岩气技术的可行性,采用分子模拟(MS)方法,模拟页岩储层Ⅱ型干酪根中CO_(2)/CH_(4)气体在不同条件下的竞争吸附行为,引入CO_(2)/CH_(4)置换效率作为评价参数,分析不同因素对CO_(2)/CH_(4)竞争吸附的影响规律,研究结果表明:①干酪根中不同官能团上的吸附位对CO_(2)分子、CH_(4)分子的相互作用能不同。②CO_(2)/CH_(4)置换效率随CO_(2)/CH_(4)浓度比、压力的上升而增大;温度与CO_(2)/CH_(4)置换效率并无太大影响。③由于干酪根中不同官能团上的吸附位对CO_(2)分子、CH_(4)分子的相互作用能不同,导致CO_(2)/CH_(4)浓度比较大或压力相对较高时,CO_(2)/CH_(4)置换效率上升幅度减缓。④结合开发成本考虑,在注CO_(2)开发页岩储层过程中CO_(2)/CH_(4)浓度比、地层压力均不宜过高。Shale gas development in Sichuan and Chongqing areas is stepping into a bottleneck period with low recovery efficiency.Studies suggest that injecting CO_(2) into shale reservoirs can displace CH_(4) adsorbed on kerogen to further increase this efficiency.The key mechanisms on competitive adsorption between CO_(2) and CH_(4),however,have not yet been made clear.So,adsorption behaviors ofⅡ-type kerogen in these shale reservoirs under different conditions were simulated by using molecular simulation(MS)to promote the feasibility of CO_(2) injection.The displacement efficiency between CO_(2) and CH_(4) as a parameter was employed to evaluate the influence of different factors on this competitive adsorption.Results indicate that(i)adsorption sites on different functional groups in kerogen have various interaction between CO_(2) and CH_(4) molecules;(ii)the displacement efficiency increases with the concentration ratio and pressure of both them,but it is less sensitive to temperature;(iii)since the sites have different interaction between CO_(2) and CH_(4) mole-cules,the growth of displacement efficiency may slow down when the concentration ratio is big or the pressure is relatively high;and(iv)the concentration ratio of both CO_(2) and CH_(4) and the formation pressure should not be too high during CO_(2) injection in an effort to save costs in shale gas development.

关 键 词：干酪根 竞争吸附 分子模拟 

分 类 号：TE37[石油与天然气工程—油气田开发工程]