Simulation of Two-Phase Flowback Phenomena in Shale Gas Wells

The gas-water two-phase flow occurring as a result of fracturing fluid flowback phenomena is known to impact significantly the productivity of shale gas well. In this work, this two-phase flow has been simulated in the framework of a hybrid approach partially relying on the embedded discrete fracture model (EDFM). This model assumes the region outside the stimulated reservoir volume (SRV) as a single-medium while the SRV region itself is described using a double-medium strategy which can account for the fluid exchange between the matrix and the micro-fractures. The shale gas adsorption, desorption, diffusion, gas slippage effect, fracture stress sensitivity, and capillary imbibition have been considered. The shale gas production, pore pressure distribution and water saturation distribution in the reservoir have been simulated. The influences of hydraulic fracture geometry and nonorthogonal hydraulic fractures on gas production have been determined and discussed accordingly. The simulation results show that the daily gas production has an upward and downward trend due to the presence of a large amount of fracturing fluid in the reservoir around the hydraulic fracture. The smaller the angle between the hydraulic fracture and the wellbore, the faster the daily production of shale gas wells decreases, and the lower the cumulative production. Nonplanar fractures can increase the control volume of hydraulic fractures and improve the production of shale gas wells.