Impact of shut-in time on production after hydraulic fracturing in fractured shale gas formation: An experimental study

Abstract Water invasion during hydraulic fracturing can cause water blocking that reduces the permeability of the shale formation matrix. It has been shown that shut-in can solve this problem by allowing the invading water to imbibe into the deeper formation. However, it remains unknown how shut-in time affects the permeability recovery of natural fractures in the shale formation matrix. In this paper, a series of core flooding experiments were conducted to investigate the impact of shut-in time on production in the fractured shale gas formation. According to our experiments, the permeability reduction in fractures caused by water blocking is larger than 80%. The increasing production pressure difference has little help in relieving the water blocking in fractures. The new insight was provided that the shut-in time has little impact on mitigating water damage in fractures. Specifically, although the newly created fractures were observed in spontaneous imbibition, the permeability after water invasion was not recovered. The study gives engineers some recommendations to optimize the shut-in time and reduce the water blocking after hydraulic fracturing in shale gas formation.