Development and application of the modern production decline analysis method in consideration of partial closure of hydraulic fracture

Existing commercial soft ware used for analyzing the production decline of fractured wells doesn't take into consideration the effect of hydraulic fracture closure on oil and gas production rate, so the interpreted fracture length of fractured well is much shorter than the actual length of hydraulic fracture. The production decline model in consideration of partial fracture closure for fractured well was established based on the characteristics of fractured wells, i.e., the partial fracture closure and the nonuniform flow rate in fractures. Then, the unstable production rate of fractured well was solved by means of Newman product, spatial exchange and numerical inversion. Finally, the theoretical chart of production decline was plotted. It is revealed by comparing the production decline model in consideration of partial fracture closure for fractured well with the conventional production decline model for fractured well that the new model is 30%-50% lower than the conventional production decline model in the rate of production decline in the period of unstable flow for it takes the effect of closed fractures into consideration. The curves of both models are approximately coincident in the period of boundary dominated flow. As the partial closure length of fractures increase, the decreasing amplitude of decline rate will increase. The new model is applied to analyze the production decline of fractured wells in tight gas reservoirs, e.g., Sulige and Daniudi. Its fitting results are better than those of conventional decline model, and its interpreted length of closed fractures far from the well can be used to predict the effect of partial fracture closure on the production rate of fractured well.