温度冲击对煤系叠置气藏合采兼容性的影响规律与机理研究

The coal-bearing gas of the late paleozoic coal-bearing formation has the characteristics of multi-layered, multi-cycle, superimposed reservoir-forming, and complex diagenetic thermal evolution and later transformation, so that the geological conditions, reservoir structure and lithology of coal-bearing gas reservoirs are complex. The low porosity, strong heterogeneity, high clay mineral content and low permeability result in high cost and low efficiency of single gas source, and the co-mining has high requirements for geological compatibility between reservoirs. Aiming at the key scientific issue of geological compatibility of co-mining, the paper puts forward the research idea of changing the inter-layer geological compatibility by temperature variation. The project intends to use the research methods of theoretical analysis and experiment, focusing on the effects of temperature variation threshold, waveform, irradiation time, cycle number on typical rock formations (coal, mud shale, sandstone) samples. The effects of temperature variation on the pore fracture structure, surface properties, adsorption and desorption, permeability and slipstream of the typical rock samples were analyzed. The research results will provide theoretical, methodological and technical support for enhancing the permeability of soft, deep high stress and structurally affected reservoirs, and improving the inter-layer compatibility of coal-bearing gas co-mining.

我国晚古生代含煤地层的煤系气具有多层段、多旋回、叠置成藏的特点，并且复杂的成岩热演化与后期改造，使其气藏的地质条件、储层结构与岩性具有复杂性，低孔隙率、强非均质性、高黏土矿物含量和低渗透率导致了单一气源的开采成本高、效率低，而合采对储层间地质兼容性的要求较高。针对合采地质兼容性的关键科学问题，提出采用温度冲击改变层间地质兼容性的研究思路。项目拟采用理论分析和实验相结合的方法，重点研究温度冲击的阈值、波形、作用时间、循环次数等对典型岩层（煤、泥页岩、砂岩）试样的作用效果；分析温度冲击对典型岩层试样孔裂隙结构、表面性质、吸附解吸、渗透性、层内滑脱的影响规律及机理。研究成果将为提高松软、深部高应力和受构造影响储层的渗透性和改善煤系气合采的层间兼容性，实现高效抽采提供理论、方法与技术支持。

我国煤系气藏储层结构复杂，具有微孔发育、非均质性强、黏土矿物含量高和渗透性差的特性，使得对单一含气系统的开采成本高、效率低。因此，如何提高煤系储层的渗透性与兼容性是开发煤系气的关键问题。考虑煤岩类材料热胀冷缩及其不同矿物组分对温度响应的不协调性，提出采用温度冲击方法改变煤系储层吸附解吸与渗透性的研究思路。重点研究了高低温冲击作用对研究区域煤系地层储层煤岩的物化电力学特性的改变效果及规律，建立煤系典型储层无烟煤原样和温度冲击改性样的甲烷吸附解吸率、吸附解吸速率和物性之间的相关性，以及原样和温度冲击改性样的孔隙结构演化特征，并优化出温度冲击的温度阈值、作用时间、冲击速率和循环次数等参数。结果表明：高低温循环冲击作用减弱了煤岩基体间的束缚力，打破了其原有的静态平衡，促使煤岩试样孔裂隙发育、扩展、连通和次生裂隙的萌生，冲击作用有助于微小孔裂隙扩展形成较大的宏观裂隙；温度冲击4因素对煤岩甲烷吸附-解吸特性，以及表面基团、煤-水接触角和表面能、煤的孔隙结构影响由强到弱的排序为温度升降速率（温差）、高低温作用时间、循环次数。研究结果可为采用温度冲击方法改变煤系储层对气体的解吸与渗透特性、提高单一储层的抽采效率和叠置气藏合采的兼容性提供理论依据和工程应用的技术支持。