实现页岩气藏有效开发的关键在于页岩储层渗流机理的研究和产能模型的建立，但页岩气藏孔渗结构具有强烈的多尺度性，渗流机理复杂；纳米级孔隙存在克努森扩散，解吸介质变形等情形。同时，在增产改造过程中形成的复杂裂缝网络形态也对页岩气多尺度流动特征及页岩气产能造成不同程度的影响。建立了页岩气藏体积压裂后，水力裂缝与天然裂缝耦合条件下的产能预测模型，综合考虑吸附、解吸、扩散、裂缝网络等非线性流动效应的作用，并分别运用有限差分、嵌套性有限差分方法及牛顿拉普森迭代法进行求解。最后，结合我国某页岩区块实际井对体积压裂后产能进行影响因素分析。该模型对页岩气藏水平井压裂设计、压裂参数优化以及产能评价研究都具有一定的指导意义。
The seepage mechanism and productivity model of shale gas reservoirs is the critical and scientific issue to develop the shale gas reservoirs effectively.The pore structures of shale possess the strong multi-scale characteristic,and complexity of seepage mechanisms.Knudsen diffusion,matrix deformation,stress sensitivity,non-Darcy flow and complex fracture network stimulated by hydraulic fracturing technology have certain effects on the multi-scale flow characteristic and productivity model. Firstly,this paper establishes a model of apparent permeability with the consideration of adsorption,diffusion,viscous flow,rock deformation,adsorption layer.On the basis of this proposed models,the influences of some related parameters,such as rock deformation,adsorption layer,on capillary radius and apparent permeability are analyzed.Secondly,for the different fracture pattern of multi-stage fractured horizontal well and volumetric fracturing horizontal well,with the consideration of gas adsorption,diffusion,matrix deformation,stress sensitivity and non-Darcy flow,two productivity prediction models are established based on the coupled hydraulic fractures and natural fractures.Finite difference method,Newton-Rapson iterative method and embed discrete fracture method are respectively employed to solve those two models.Finally,the orthogonal test design is employed to identify and analyze the dominated factors among the relevant parameters,such as fracture spacing,fracture half length,fracture numbers,fracture conductivity,permeability,and so on.The results can provide some certain guidance for the optimization of stimulated treatment in shale gas reservoirs.
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