Strategic Multi-Bench Child Well Placement Amid Parent Well Production-Induced Stress Depletion in the Permian Basin
Authors: Gong Yiwen , McMahon Timothy P. 
Published: January 2025

The growing interest in closely spaced drilling units (DSUs) highlights the need to understand well performance under interference conditions in shale oil reservoirs, particularly in the Permian Basin. Over time, studies of the impact of well completion optimization on production performance, along with studies of parent-child interference have become more mature, and increasingly effective diagnostic tools, such as fiber optics, pressure diagnostics, radioactive tracers, and production logs are being used to guide parent-child well placement strategies. However, the geomechanical effects of stress reduction due to pressure depletion and its influence on child well placement remain underexplored and could potentially play an important role in future well planning.

In this study, we examined this effect using wells from the Hydraulic Fracture Test Site 1 (HFTS1) in the Midland Basin to demonstrate the geomechanical impacts on child wells at representative spacings, derived from basin-wide well spacing statistics. Additionally, we consider the relationship between depletion and production performance as a key factor in both early- and late-stage evaluations. Our objective is to analyze the hydraulic fracture growth characteristics of bi-wing fracture propagation. We began with hydraulic fracture propagation simulations for two representative horizontal wells as parent wells in Wolfcamp A and Wolfcamp B formations. This was followed by coupled flow and geomechanical simulations to assess the production performance of these parent wells, yielding insights into changes in the principal stresses during production.

After a comprehensive analysis of modern well spacing distributions and depletion patterns in recently-completed horizontal wells within the Wolfcamp across the Midland Basin, we evaluated potential child well placement strategies at various horizontal spacings (400 ft, 600 ft, 800 ft, 1200 ft) and stacked placement scenarios (400 ft horizontal spacing with 100 ft and 200 ft vertical offsets), with production beginning at different times during the parent well’s production life (1 year, 5 years). We then assessed the asymmetric hydraulic fracture growth metrics in each scenario. The results show that when completing Wolfcamp A child wells during the early stages (1 year) of parent well production, asymmetric growth of hydraulic fractures is not highly sensitive to horizontal distance from the parent well. However, at later stages (5 years), Wolfcamp A child wells display greater sensitivity to spacing compared to Wolfcamp B child wells. Additionally, staggered well placement proves more beneficial for Wolfcamp A child wells over those in the Wolfcamp B. To mitigate asymmetric growth effectively, earlier placement of child wells during the parent well’s production life is recommended. Through this integrated fracturing-geomechanics-reservoir simulation workflow, we provide insights into the impact of various child well placement strategies on both short-term and long-term stimulated reservoir volume (SRV) generation, offering valuable guidance for optimizing reservoir potential in the Permian Basin’s shale oil formations.