As a kind of unconventional gas reservoir, there are some special characteristics compared with conventional gas reservoir, as the ultra-low porosity, ultra-low permeability, self-generation and self-storage, adsorption, low or no natural production capacity, long production cycle, and large change in recovery rate. Based on the investigation of a large number of relevant scientific literatures, the differential equation of shale gas seepage is derived by considering the influence of adsorption desorption and slippage in matrix pores and the mechanism of stress sensitivity and abnormal diffusion under complex fractures, and the seepage model of fractured horizontal well in shale gas reservoir under the mechanism of abnormal diffusion of complex fractures is established. By applying the point source function method to study the unstable productivity in shale gas reservoir, the productivity prediction model of fractured horizontal well w ith complex fracture system is obtained, and the relevant influencing factors are analyzed. It is found that anomalous diffusion, desorption diffusion and stress sensitivity have significant effects on productivity. Desorption diffusion in matrix and fractal diffusion in complex fractures are the main influencing factors. The influence of fracture stress sensitivity after fracturing cannot be ignored. Finally, the case study for a horizontal well in the field shows the accuracy and reliability of this new model.
展开▼
