页岩气藏三重介质模型压力动态分析及其应用

Pressure dynamic analysis and application of triple medium model for shale gas reservoir

不同于常规气藏,页岩气藏储层及页岩气的储存、运移都具有十分复杂的特性,其气体渗流过程描述也相当困难。为了解页岩气储层气体的流动规律、井底压力动态及影响因素,进而有效地开发页岩气,文中对页岩气藏渗流规律进行了研究,并基于双重介质模型,建立了新的三重介质模型。新模型考虑了页岩气吸附机理,假设基质为双重孔隙介质,且带有微裂缝,微基质和裂缝之间有气体流动;对方程进行了离散化差分,通过Matlab编程进行求解,讨论了3个系统的窜流系数、弹性储容比,以及裂缝与基质渗透率比对井底压力的影响;最后通过对比现场实际数据,使建立的模型得到有效验证。

Unlike conventional gas reservoir, shale gas reservoir, migration and storage process are very complicated and particular,which lead to the complexity of seepage process description. In order to obtain a better understanding of shale gas flow rule, the dynamic of bottom pressure of shale gas well and influencing factors to develop shale gas efficiently, the seepage law is researched and a triple medium model is built. The new model is based on shale gas adsorption mechanism, assuming the matrix blocks a dual porosity media with micro fractures, and gas flow between sub-matrix and fractures. Using discretization difference, the equation is solved by the matlab programming, the cross flow coefficient of three systems, storativity-ratio and the effect of permeability ratio of fracture to matrix on pressure are discussed, finally the model is validated by in situ data.