煤层气藏全流固耦合数学模型

为准确表征煤层复杂的地质力学效应，根据多重孔隙介质力学特征和多过程运移特点，来构建煤层气藏三孔双渗全流固耦合数学模型，并基于所研发的全隐式有限体积数值模拟器，进一步研究地质力学效应对孔渗参数和煤层气产能的影响。结果表明，有效应力效应与基质收缩作用均可影响裂缝渗透率，且作用方向相反：有效应力效应的作用强度在开发初期大于基质收缩作用，但在后期发生逆转，导致渗透率先减小后增大，最终值甚至可达初始值的数倍；随着煤岩杨氏模量增大，有效应力效应减弱，煤层气日产量增大，产气高峰出现时机提前，随着Langmuir体应变量增大，基质收缩作用增强，同样煤层气日产量增大，产气高峰出现时机提前。全流固耦合数学模型能够更准确地刻画煤层复杂流固耦合作用，这对煤层气产能预测具有重要意义。

A fully coupled fluid flow and geomechanics model for coalbed methane reservoir

To more accurately characterize the complex geomechanical effects in coalbed methane reservoir,a fully coupled triple porosity dual permeability fluid flow and geomechanics model was established with consideration of poroelastic properties and multi-process transportation. The corresponding numerical solver was constructed by the fully implicit finite volumetric method,and the impacts of geomechanics on porosity and permeability and methane production were investigated. The results show that both effective stress effect and matrix shrinkage can significantly affect fracture permeability,but in opposite direction. The dominate factor is effective stress effect compared with matrix shrinkage at the early stage of primary production,but latter turns to matrix shrinkage,which makes fracture permeability firstly decreases and then rebound. The final permeability can even reach several times of its original value. As Young's modulus increases,the effective stress effect recedes,which creates bigger and earlier peak gas production. As the Langmuir strain increases,the matrix shrinkage is strengthened,which creates bigger and earlier peak gas production. The fully coupled fluid flow and geomechanics model can describe the complex fluid-structure interaction of coalbed methane reservoir more accurately,which is of great significance to the prediction of CBM productivity.