Optimization of fracturing parameters in multi-layer and multi-period cube development infill well pad: A case study on a three-layer cube development well pad of Sichuan Basin, SW China

The method for optimizing the hydraulic fracturing parameters of the cube development infill well pad was proposed, aiming at the well pattern characteristic of “multi-layer and multi-period” of the infill wells in Sichuan Basin. The fracture propagation and inter-well interference model were established based on the evolution of 4D in-situ stress, and the evolution characteristics of stress and the mechanism of interference between wells were analyzed. The research shows that the increase in horizontal stress difference and the existence of natural fractures/faults are the main reasons for inter-well interference. Inter-well interference is likely to occur near the fracture zones and between the infill wells and parent wells that have been in production for a long time. When communication channels are formed between the infill wells and parent wells, it can increase the productivity of parent wells in the short term. However, it will have a delayed negative impact on the long-term sustained production of both infill wells and parent wells. The change trend of in-situ stress caused by parent well production is basically consistent with the decline trend of pore pressure. The lateral disturbance range of in-situ stress is initially the same as the fracture length and reaches 1.5 to 1.6 times that length after 2.5 years. The key to avoiding inter-well interference is to optimize the fracturing parameters. By adopting the M-shaped well pattern, the optimal well spacing for the infill wells is 300 m, the cluster spacing is 10 m, and the liquid volume per stage is 1 800 m³.