考虑力-热耦合作用的煤岩变形特征与渗透率演化机理研究

Coalbed methane (CBM) resources in China are abundant but the degassing degree is extremely low. This because deformation characteristics and permeability evolution of coal rock during the process of gas production cannot be understood very well especially in the deep coal seam. In this study, experimental research, theoretical analysis, and numerical simulation are used to investigate the deformation characteristics and permeability evolution mechanism of coal under the coupling condition of stress and temperature. Adsorption/desorption deformation of coal under different temperature and deformation and seepage of coal during the process of gas load-unloading are observed by laboratory experiments. The objective are to analyze the influence law of adsorption/desorption process on the expansion/shrinkage deformation of coal, and to study mutual interaction process between adsorption/desorption and deformation of coal, which reveals the evolution mechanism of coal permeability under the coupled effects of temperature, expansion/shrinkage and slippage. .The adsorption/desorption-deformation-permeability coupling model would be established by considering dual-medium mechanics, seepage mechanics, and adsorption theory to analyze the law of permeability in different stages of pore pressure during the process of gas production. The finite element method would be used to develop a calculation program for the evolution process of coal permeability during the coalbed methane extraction process. And numerical simulations would be to verify the theoretical model. The results could provide a theoretical basis and analytical means for improving the recovery of coalbed methane for a broad prospect of application.

当前我国煤层气资源丰富但采收率低，对煤层气开采过程中煤岩变形及渗透率演化规律的研究不足，特别是在深部开采条件方面。本课题拟采用试验研究、理论分析与数值模拟相结合的方法，研究力-热耦合作用下的煤岩变形特征与渗透率的演化机理。开展不同温度作用下的吸附/解吸-变形试验和孔隙压力升降过程中煤岩变形与渗流的试验，分析吸附/解吸过程对煤岩产生的膨胀/收缩变形的影响规律，研究吸附/解吸和煤岩变形互馈作用过程，揭示温度、膨胀/收缩与滑脱效应等多因素耦合作用下煤岩渗透率的演化机理。利用双重介质力学、渗流力学及吸附理论，建立吸附/解吸-变形-渗透率耦合模型，分析煤层气运移过程中煤岩渗透率随不同孔隙压力阶段的变化规律。采用有限元法研发煤层气开采过程中煤岩渗透率演化过程的计算程序，开展数值仿真模拟，试验验证理论模型的可靠性并进行修正。研究成果可为提高煤层气采收率提供理论基础和分析手段，具有广阔的工程应用前景。

煤层气作为一种清洁且经济的能源，其开采与利用不仅可以缓解世界能源问题，也可有效预防煤矿事故的发生。煤岩渗透率参数对煤层气开采具有较大影响，煤岩的开采过程渗透率大小将会受到有效应力大小、滑脱效应、基质变形三方面影响。随深度增加煤岩所受孔隙压力与温度增加，使其吸附/解吸、变形及渗流机制又将更加复杂。因此项目以力热耦合条件下煤岩吸附/解吸-变形-渗透率演化特征为研究主线，依托于西南滇东黔西矿区煤岩，采用煤岩高压吸附/解吸-变形试验系统和进出口端压力可调的煤岩三轴渗流试验平台，模拟煤层气开采过程，开展原煤煤样的吸附/解吸-变形试验和不同温度条件下孔隙压力升降过程中煤岩变形与渗流的试验。揭示了煤岩中的吸附/解吸过程及其对煤岩产生的膨胀/收缩变形的影响机制，进一步厘清煤岩基质膨胀/收缩与滑脱效应引起的煤岩变形对渗透率的影响。基于多孔介质力学、渗流力学及吸附理论等多学科交叉融合，建立力热耦合作用下煤岩吸附/解吸-变形-渗透率耦合模型，阐明煤层气运移过程中在不同温度和孔隙压力阶段煤岩变形与渗透率的变化规律及突变机制。共发表论文57篇，其中SCI/EI收录36篇，申请专利15项，获得软件著作权9项，获2021年重庆市科学技术奖二等奖(排第七)一项。2篇论文获西南五省市区2019年度煤炭学术年会优秀论文，同时获贵州省煤矿瓦斯防治新技术及新装备优秀论文一等奖、二等奖各一项，4篇论文获西南五省市区2020年度煤炭学术年会优秀论文。通过对力热耦合作用下煤岩吸附/解吸-变形-渗流的演化规律进行系统研究，从而为煤岩增透、煤层气增产提供理论基础和技术支持，经济社会效益显著。