Hydraulic Fracture Propagation under In-Situ Stress Changes: A Weak Plane Identification-Based Study for Shale Gas Reservoirs

The production of mid-depth shale gas wells in Sichuan, China, decreases rapidly. To maintain gas production, infill wells are drilled and fractured to further increase the gas recovery factor. The geometries of infill well fractures are critical to the final production which are significantly affected by the in-situ stresses. According to the simulation results, not only the horizontal stresses, the vertical stresses also change with the parents’ wells production. However, most of the current fracturing simulators only include the impact of horizontal stresses on fracture propagation and are not able to consider the changes of vertical stresses. In this work, the impact of vertical stresses on fracture height growth is included by dynamically identifying the weak planes. As the results demonstrate, the fracture height of fill wells increases due to the loss of weak plane area. Compared to the parents’ wells, infill wells exhibit a 22.88% increase in fracture height and a 69.78% reduction in fracture length, suggesting smaller well spacing may be feasible.