含煤层气储层物性与压裂液微观特性动态耦合作用机理研究

Hydraulic fracturing is an effective method to extract coalbed methane by clearing the crack system and well bore from the coal reservoir with low permeability, low porosity and low pressure on the surface. The key issue to ensure the open path for increasing gas production is to take account of reservoir damage as well as improve permeability of formation. Based on classic theories of hydrological mechanics, soil mechanics, thermodynamics, numerical simulation and experiments were adopted in this research project to build the mathematic model of coupling hydrological field/ stress field/ thermal field for fracturing fluid invasion process. T+F (TOUGH2+FLAC3D) numerical simulation was applied to analyze response law of geomechanical behaviors under the effect of multi-field coupling, also the synthetical seepage simulation test for hydraulic fracturing was developed to master the dynamic response of macro-mechanical performances, and performance of heat and mass transfer, rheological property was analyzed by fracturing fluid (SEM) before test and after fracturing fluid invasion, and reveal the coupling law between the geomechanical behaviors of formation and microstructure of fracturing fluid. The research has an important significance of theory for increasing recovery efficiency, and also to be a theory guide for wellbore stability of coalbed and log response.

压裂法是地面开采低渗、低孔、低压煤层中煤层气的有效手段之一，通过沟通煤岩层中天然裂隙系统且连通至井孔，提高储层产气能力。在改善储层渗透性的前提下又能降低压裂液对储层的伤害，从而保证气体导流通道的畅通是提高采气量的关键所在。 本项目基于渗流力学、土力学、热力学经典理论，采用数值模拟和实验相结合的方式，建立渗流场/应力场/温度场（H+M+T）耦合作用下压裂液侵入煤岩层的数学模型；采用T+F (TOUGH2+FLAC3D) 耦合数值模拟方式分析多场多相作用下煤岩层各物性参数之间的关联；通过压裂过程综合渗流模拟试验，掌握煤岩层宏观力学表现随压裂液侵入的动态响应特征；根据压裂液微观结构（SEM）实验，分析压裂液侵入前后其传热传质和流变性特征。从而揭示煤岩层物性与压裂液微观结构的宏观表现之间的耦合规律。本研究对提高煤层气采收率具有重要的理论意义，同时也可为煤岩层井壁稳定性、测井响应提供理论指导。

压裂法是地面开采低渗、低孔、低压煤层中煤层气的有效手段之一，通过沟通煤岩层中天然裂隙系统且连通至井孔，提高储层产气能力。在改善储层渗透性的前提下又能降低压裂液对储层的伤害，从而保证气体导流通道的畅通是提高采气量的关键所在。本项目基于渗流力学、土力学、热力学经典理论，采用数值模拟和实验相结合的方式，建立多场耦合作用下压裂液侵入煤岩层的数学模型,分析压裂液侵入过程中对煤岩层的作用机理。通过三轴加载水力压裂试验，掌握煤岩层宏观力学表现随压裂液侵入的动态响应特征, 分析不同载荷、流量作用下，压裂过程中岩样裂隙形成，扩展过程，从而确定煤岩层物性与压裂液微观结构的宏观表现之间的耦合规律。本研究对提高煤层气采收率具有重要理论意义，同时也可为煤岩层井壁稳定性、测井响应提供理论指导。