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查明煤层气井产气后煤基质收缩变化规律是进行此阶段渗透率变化研究的基础。基于排采过程中表面自由能、有效应力系数、弹性模量的改变对煤基质变形的重要影响,根据表面物理化学、损伤断裂理论分别对表面自由能增量数理模型、有效应力系数数理模型与弹性模量数理模型进行了构建;并基于弹塑性力学对三者的影响进行了叠加,结合樊庄区块地质与压裂排采资料,对气、水两相流阶段煤基质收缩变化规律进行了研究。结果表明:气、水两相流过程中综合表面自由能、有效应力系数与弹性模量影响下的煤基质收缩变形呈近对数形式持续逐步增加。其中表面自由能、有效应力系数对基质收缩变形的影响较大,弹性模量影响较小。排采时在气、水两相流阶段应注意后续气、水补给的连续性。
It is the basis of the research on permeability change in this stage to find out the rule of coal matrix shrinkage after gas production in coalbed methane well. Based on the influence of surface free energy, effective stress coefficient and elastic modulus on the deformation of coal matrix during the process of extraction, according to the surface physicochemical and damage fracture theories, the mathematical model of surface free energy increment, the mathematical model of effective stress coefficient and The mathematical model of elastic modulus is constructed. Based on the elasto-plastic mechanics, the influence of these three factors is superposed. Combined with the data of geology and fracturing in Fanzhuang block, the variation law of coal matrix shrinkage during gas-water two- Study. The results show that the shrinkage deformation of coal matrix under the influence of synthetic surface free energy, effective stress coefficient and elastic modulus in gas-water two-phase flow shows a nearly logarithmic form and continues to increase gradually. Among them, the surface free energy and the effective stress coefficient have a great influence on the shrinkage deformation of the matrix, and the elastic modulus has little effect. Discharge during gas, water phase flow should pay attention to follow-up gas, water supply continuity.