Abstract: The productivity prediction plays an important role in the efficient and rational development of shale gas reservoirs. At present, the researches on the productivity of multi-stage fracturing horizontal wells in shale gas reservoirs at home and abroad does not take into account stress-sensitive effects of natural fractures and hydraulic fracture morphology and seepage characteristics on productivity. Therefore, based on dual medium seepage theory, considering the adsorption, desorption and diffusion mechanisms (pseudo-steady state and transient diffusion) of shale gas in reservoirs and stress-sensitive effects of natural fractures, the shale gas reservoir seepage model is established. The limited conductivity of hydraulic fractures and hydraulic fracture azimuth are considered into the hydraulic fracture model. The source function method is used to discretize the crack, and then the hydraulic fracture model is superimposed. Finally, the two models are coupled to obtain the unstable seepage model and productivity model of the multi-stage fracturing horizontal well in the shale gas reservoir. According to the established shale gas fracturing horizontal well productivity model, the productivity characteristic curve is calculated by programming. The comparative hydraulic simulation results show that the optimal hydraulic fracture conductivity of the shale gas fractured horizontal well which is similar to the example is 15~18 D·cm, the optimal distribution mode of seam length is u-shaped with outer high and inner low, and the optimal fracture spacing distribution is equidistant. The comparison between the simulation results and the field data of shale gas wells also verifies the accuracy of the model. This research is of significance to shale gas development.

Key words: shale gas, multi-stage fracturing horizontal wells, productivity model, stress-sensitive effects, sensitive factor analysis