叠置煤层气系统合采渗透率动态演化特征及其影响因素  

Dynamic evolution and its influencing factors of coal seam permeability during joint gas production of superimposed CBM system

作　　者：彭守建[1] 贾立 许江[1] 郭世超 PENG Shoujian;JIA Li;XU Jiang;GUO Shichao(State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学煤矿灾害动力学与控制国家重点实验室,重庆400044

出　　处：《煤炭学报》2020年第10期3501-3511,共11页Journal of China Coal Society

基　　金：国家科技重大专项资助项目(2016ZX05044-002);国家自然科学基金重点资助项目(51874055);重庆市基础与前沿研究计划资助项目(cstc2016jcyjA0117)。

摘　　要：针对“叠置煤层气系统”这一煤层群地层中普遍发育的煤层气成藏模式,借助重庆大学自主研制的“叠置煤层气系统合采物理模拟实验装置”,设计Ⅰ号、Ⅱ号、Ⅲ号、Ⅳ号模拟煤层的初始气体压力分别为1.0,1.4,1.8,2.2 MPa,通过叠置含气系统煤层气合采物理模拟实验,分析了合采过程中煤层渗透率动态演化特点及其影响因素。结果表明:①合采过程中模拟煤层渗透率变化曲线可分为两类,一类以渗透率先上升后下降再上升为特征,以Ⅰ号和Ⅱ号煤层为代表;另外一类以先下降后上升为特征,以Ⅲ号和Ⅳ号煤层为代表;②合采初期,渗透率差异系数变化显著,中、后期变化不明显,模拟开采结束时Ⅰ,Ⅱ,Ⅲ号煤层相对于Ⅳ号煤层的渗透率差异系数分别为37.5%,26.5%和13.6%,表明合采过程中高储层压力煤层的气体倒灌进入了低储层压力煤层,产生了层间干扰,初期干扰显著,中、后期不明显,煤层受干扰程度随初始气体压力差的加大而增大;③煤层有效应力、煤体温度和煤体变形相互耦合,共同影响着模拟煤层渗透率演化规律,使得4个煤层的渗透率演化呈阶段性变化,其中Ⅳ号煤层渗透率变化影响因素在开采初期以效应力占主导地位,煤体温度和煤体应变分别在渗透率比下降至0.87和0.75时才开始对渗透率演化产生作用。According to the coalbed methane(CBM) reservoir-forming model commonly developed in the coal-bed group stratum of "superimposed CBM system",with the help of the "physical simulation test device for joint production of superimposed CBM system"independently developed by Chongqing University,the simulated initial gas pressures of No.Ⅰ,No.Ⅱ,No.Ⅲ and No.Ⅳ coal seams are designed to be 1.0,1.4,1.8 MPa and 2.2 MPa,respectively.Based on the physical simulation experiment of joint production in the superimposed CBM system,the dynamic evolution characteristics of coalbed permeability and its influencing factors during joint production are analyzed.The results show: ① The permeability curves of CBM joint production in the superimposed CBM system can be divided into two types: one is characterized by increasing permeability first,then decreasing and then increasing,represented by No.Ⅰ and No.Ⅱ coal seam;the other is characterized by first decreasing and then increasing,represented by No.Ⅲ and No.Ⅳcoal seam.② It can be seen that the difference coefficient changes significantly in the initial stage of joint production,but not significantly in the middle and later stages.At the end of production,the difference coefficient of No.Ⅰ,No.Ⅱ and No.Ⅲ coal seam relative to No.Ⅳ coal seam are 37.5%,26.5% and 13.6% respectively,which indicates that the gas pouring into high reservoir pressure coal seam during joint production process is reversed.The low reservoir pressure coal seam produces interlayer interference,which is significant in the initial stage,not obvious in the middle and later stages,and the interference degree increases with the increase of initial gas pressure difference. ③ The coupling of effective stress,temperature and deformation of coal seam affects the evolution of permeability,and makes the permeability evolution of four seams change in stages.The effective stress of No.Ⅳ coal seam occupies the dominant position in the early stage of production,while the temperature and strain of coa

关 键 词：叠置含气系统 煤层气合采 渗透率 有效应力 煤体温度 煤体变形 

分 类 号：P618.11[天文地球—矿床学]