页岩气体积压裂水平井非稳态产能评价模型

Transient Production Forecasting Model of Multiply Fractured Horizontal Wells in Shale Gas Reservoirs

页岩基质渗透率极低,天然裂缝发育,是一种典型的双重介质。气体在页岩纳米级孔隙中同时存在吸附解吸、扩散和渗流等多种流动机理,同时,天然裂缝渗透率会随地层压力的降低而降低。以平板双重介质模型为基础,综合气体在页岩纳米级基质孔隙中的吸附解吸、扩散和渗流机理,考虑天然裂缝的应力敏感效应,建立了一个页岩气体积压裂水平井非稳态产能评价模型,采用摄动法和Laplace变换,求取了模型的解析解,绘制了典型生产曲线。结果表明,吸附解吸和扩散作用分别影响早期产能和中后期产能,而天然裂缝的应力敏感性影响所有流动阶段的产能。

Shale reservoir is a typical dual media：extremely low permeability matrix and natural fractures.Flow mechanism in shale matrix is complicated,including adsorption desorption,diffusion,seepage,while the natural fracture permeability varies as formation pressure decreases.In this paper,a transient productivity model is built for multi-fractured horizontal shale gas wells based on Bello′s model.An analytical solution is obtained by perturbation method and Laplace conversion,with which typical production curves are drawn.The effects of gas adsorption desorption,diffusion and seepage mechanism in matrix are taken into consideration,and the stress sensitivity of natural fractures is analyzed.The results show that adsorption desorption and diffusion only affect the early and middle-late period production performance,while the stress sensitivity of natural fracture plays a role during all periods.