Numerical simulation of shut-in and flowback in shale gas tridimensional platform wells considering complex fractures

The formation of complex fractures in shale gas reservoirs under the tridimensional well network development mode increases the complexity of fluid flow mechanism in the reservoir, leading to unclear effects of the productive system on production capacity. This article establishes a shut-in and flowback numerical model of shale gas tridimensional wells based on complex fracture morphology and verifies the accuracy of the model based on on-site microseismic and production data. The paper simulated the dynamic production characteristics of a well network under different productive systems and analyzed the impact of shut-in time and flowback rate on the overall productivity of platform wells. Research has shown the following: After the completion of shale gas well fracturing, closing the well is beneficial for full interaction between the fracturing fluid and reservoir. The optimal action time is 30 days. The treatment period is closely related to the shut-in time. Under conditions of long horizontal sections and slow treatment speed, the shut-in time should be shortened. The initial flowback rate of the well has a significant impact on the energy depletion rate of the formation. In the low flowback rate mode, it can improve the stable production capacity, increase the overall cumulative production of the well network, and the optimal flowback rate before fracture closure is 35.7 t/d, and after closure it is 40 t/d. The parameter optimization of the shut-in and flowback rate in the shale gas well network provide a theoretical basis for determining the fractured production system.