煤层处置CO_2的二元气-固耦合数值模拟  

Numerical Simulation of Coupled Binary Gas-Solid InteractionD uring Carbon Dioxide Sequestration in a Coal Bed

作　　者：冯启言[1,2] 周来[1,2] 陈中伟[3,4] 刘继山[3,4] 

机构地区：[1]中国矿业大学环境与测绘学院,江苏徐州221116 [2]江苏省资源环境信息工程重点实验室,江苏徐州221008 [3]中国矿业大学深部岩土力学与地下工程国家重点实验室(中国矿业大学),江苏徐州2211163 [4]澳大利亚西澳大利亚大学燃料,石油与能源研究中心

出　　处：《高校地质学报》2009年第1期63-68,共6页Geological Journal of China Universities

基　　金：江苏省自然科学基金项目(BK2007034);江苏省研究生培养创新工程项目(2006);中国矿业大学青年科研基金项目(2006)

摘　　要：利用不可开采煤层处置二氧化碳可以有效控制温室气体的排放量并可驱动和增加煤层气资源的开采量。二氧化碳注入煤层处置后引入一个复杂的CH4-CO2二元气体与煤体的气固耦合问题,耦合了二元气体竞争吸附、竞争扩散,气体渗流以及煤体变形过程。基于COMSOLMultiphysics建立了二元气固耦合的有限元数值模型,并应用数值模拟实验对二元气固耦合进行了机理分析。模拟结果表明,CO2注入煤层后不断驱替CH4,CH4组分明显减少;气体吸附引起的煤层膨胀量可以抵消部分有效应力引起的压缩变形,由于CH4-CO2二元气体较单一CH4引起的煤层吸附膨胀量大,二氧化碳注入煤层后可以缓解煤层的压缩变形;不同孔隙压力条件下,吸附膨胀与孔隙压力两者竞争作用引起的煤层净变形不同,而净变形也控制着煤层孔隙压力和渗流率的变化,煤层渗透整体呈现先降后升,模拟进行到4.66×107s时煤层渗透率发生反弹。The prospect of geological sequestration and storage of CO2 as a means of reducing global emission of this greenhouse gas and enhancing coalbed methane recovery （ECBM） has recently attracted worldwide interest due to the global warming and the resource shortage. Complicated coupled binary gas-solid interaction arises during carbon dioxide sequestration in a coal seam, which combines effects of CO2-CH4 counter adsorption, CO2-CH4 counter diffusion, binary gas flow and coal bed deformation. Through solving a set of coupled field governing equations, a novel full coupled Finite Element （FE） model was established by COMSOL Multiphysics. The new FE model was applied to the quantification of coal porous pressure, coal permeability, gas composition fraction and coal displacement when CO2 was injected in a CH4 saturated coal bed. Numerical results demonstrate that CH4 is swept by the injected CO2 accompanied by coal volumetric deformation. Compared to the single CH4 in situ, CH4- CO2 counter-diffusion induced coal swelling can make more compensation for coal shrinkage due to effective stress. Competing influences between the effective stress and the CH4-CO2 counter-diffusion induced volume change governs the evolution of porous pressure and permeability, which is controlled by the porous pressure correspondingly. Initially, the coal permeability keeps descending due to the coal swelling. Afterwards, it behaves rising when the porous pressure dominates the coal deformation. In this simulation, coal permeability rebounded at the 4.66 × 10^7s. This achievement extends our ability to understand the coupled multi-physics of the CO2 geological sequestration and CO2 enhanced coal bed methane recovery under field conditions.

关 键 词：二氧化碳 甲烷 二元气固耦合 地质处置 数值模拟 

分 类 号：P618.11[天文地球—矿床学] X141[天文地球—地质学]