【作者】 刘彦飞； 汤达祯； 李松； 胡雄； 朱学光； 马良； 许浩； 陶树；

【Author】 Liu Yanfei;Tang Dazhen;Li Song;Hu Xiong;Zhu Xueguang;Ma Liang;Xu Hao;Tao Shu;School of Energy Resources,China University of Geosciences(Beijing);Coal Reservoir Laboratory of National Engineering Research Center of CBM Development & Utilization,China University of Geosciences(Beijing);Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism,Ministry of Education;Basic Experiment Center of China United Coalbed Methane National Engineering Research Center Co.Ltd.;

【机构】 中国地质大学(北京)能源学院； 煤层气开发利用国家工程研究中心煤储层实验室； 海相储层演化与油气富集机理教育部重点实验室； 中联煤层气国家工程研究中心有限责任公司基础试验中心；

【摘要】 在煤层气开采过程中,煤岩力学性质对煤储层改造和煤储层渗透率动态变化有重要的影响。通常将煤岩看作弹脆性介质,在地应力较小的情况下是合理的。但是,随着煤层气开采深度不断加大,地应力也相应增大,煤岩不可避免会表现出一定塑性变形特征。为了研究深部煤岩力学变形行为,基于不可逆热力学理论,引入非关联的塑性流动法则和损伤演化法则,建立了煤岩的弹塑性损伤本构模型。同时开展了不同围压（0,5MPa,10MPa,15MPa,20MPa）下的煤岩三轴应力应变实验。结果显示,煤岩在应力加载过程中会产生一系列的变形响应,具体分为:初始压缩阶段、弹性变形阶段、塑性变形阶段和峰后破坏阶段。随着围压增大,屈服强度（σ_y）和抗压强度(σ_peak)非线性增大,弹性模量（E）先快速增大后增速趋缓,泊松比（v）则先快速减小后缓慢减小。煤岩本构模型的数值模拟结果与试验结果符合得很好,该模型可用于深部煤储层力学性质的相关研究。更多还原

【Abstract】 The mechanical behavior of coal has an important influence on coal reservoir stimulation and the dynamic change of coal reservoir permeability during coalbed methane（CBM） production.Generally,coal is regarded as an elastic-brittle material,which is reasonable when the surrounding stress is small.However,with the increasing depth of CBM exploitation,the in-situ stress increases continuously,so the coal will inevitably show some plastic behavior.Based on irreversible thermodynamics,a coupled elastoplastic damage constitutive model for coal was established by introducing the non-associated plastic flow laws and the damage evolution rules.In this work,uniaxial and triaxial compression tests of coal under various confining pressures（P_c） were carried out for further investigation of mechanical behavior.The results show that coal samples have a series of deformation responses during the loading process,which can be classified into four phases,i.e.initial compression phase,elastic deformation phase,plastic deformation phase and post peak failure phase.Both the yield stress（σ_y） and the peak stress(σ_peak) increase nonlinearly as P_c increases.Additionally,with increasing P_c,the elastic modulus（E） increases at a decreasing rate,while the Poisson’s ratio（v） decreases at a decreasing rate.The numerical simulation result of the model is in good agreement with the experimental measurements,and the model can be used for further investigation of the mechanical properties of deep coal reservoirs under different in-situ stress conditions during the exploitation of CBM.更多还原