Variation of Fracture Opening with Pressure -- Key to Well Productivity in Naturally Fractured Reservoirs

摘要

Naturally fractured reservoirs usually developed many scales of fractures, for example, the super-high-permeability flow in big fractures, mid-permeability flow in small fractures and very-low-permeability flow in matrix rock. This results in the subsurface multi-scale flow during the reservoir development. This multi-scale flow makes it tougher to analyze the well productivity than that of a conventional reservoir. In this paper, muti-rate well-testing data were used to calculate the production capacity at different reservoir pressures in naturally fractured reservoirs. The method is exemplified with two wells in a case reservoir. The calculation results are very similar to field production data. We conclude that oil production rate in these kind of reservoirs is not only impacted by both two- phase flow and non-Darcy flow as in conventional reservoirs, but also impacted by the variations of fracture opening. This conclusion can be used to better define the optimal rate for the reservoir under different reservoir pressures, thus further improve our forecast accuracy and overall field development results.