CO2注入对煤储层应力应变与渗透率影响的实验研究  

Experimental study of the influences of CO_2 injection on stress-strain and permeability of coal reservoir

作　　者：牛庆合 曹丽文[1] 周效志[1,2] NIU Qinghe;CAO Liwen;ZHOU Xiaozhi(School of Resources and Geosciences,China University of Mining and Technology,Xuzhou 221116,China;Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process of the Ministry of Education,China University of Mining and Technology,Xuzhou,221008,China)

机构地区：[1]中国矿业大学资源与地球科学学院,江苏徐州221116 [2]中国矿业大学煤层气资源与成藏过程教育部重点实验室,江苏徐州221008

出　　处：《煤田地质与勘探》2018年第5期43-48,共6页Coal Geology & Exploration

基　　金：国家重点研发计划项目(2018YFB0605600);国家自然科学基金重点项目(41330638)

摘　　要：以沁水盆地成庄矿煤样为研究对象,利用实验室自主研发的CO_2注入与煤层气强化开采实验模拟装置进行不同有效应力和CO_2吸附压力下的煤岩渗透率测试。实验结果表明,煤岩的裂隙压缩系数受到CO_2吸附的影响,初始状态下、亚临界CO_2吸附和超临界CO_2吸附煤样裂隙压缩系数分别为0.066、0.086和0.089。引起裂隙压缩系数改变的原因主要有两方面:CO_2和煤中矿物反应提高了煤基质的不连续性;CO_2软化了煤基质同时降低了煤岩的力学性质。利用考虑吸附应变以及内部膨胀系数的渗透率模型对实测渗透率进行拟合,发现有效应力和内部膨胀系数成正比。CO_2吸附压力和有效应力的增大均提高了煤岩的内部膨胀系数,这影响了煤岩孔裂隙的开度,降低了煤储层的渗透率,并最终降低CO_2在煤储层中的可注性。Based on the coal samples of Chengzhuang coal mine in Qinshui basin,the permeability tests under various effective stresses and CO2 adsorption pressures of coal were conducted by using the independent-developed experimental simulation device for CO2 injection and enhanced coalbed methane recovery.The results indicate that the fracture compressibility of coal is affected by CO2 adsorption,the fracture compressibility coefficients of coal under initial state,subcritical CO2 adsorption and supercritical CO2 adsorption are 0.066,0.086 and 0.089.Two reasons are concluded as:the reaction of CO2 and minerals in coal improves the internal discontinuity of coal matrix;CO2 softens the coal matrix and reduces its elastic modulus.The fitting results of measured permeability by adopting the permeability model considering adsorption swelling strain and internal swelling coefficient show that the effective stress is proportional to the internal swelling coefficient.CO2 adsorption effect blocks some pores and fractures,effective stress not only compress fracture structure but also advances the internal swelling coefficient.The combination of the two effects reduces the injectivity of CO2 into coal seam,especially for injecting high pressure CO2 into coal reservoirs with high effective stress.

关 键 词：CO2-ECBM 渗透率 吸附膨胀 有效应力 超临界CO2 

分 类 号：TE377[石油与天然气工程—油气田开发工程]