Learnings from the Hydraulic Fracturing Test Site (HFTS) #1, Midland Basin, West Texas - A Geomechanics Perspective

Abstract: The Hydraulic Fracture Test Site (HFTS) #1 is a field-based hydraulic fracturing research experiment performed in the Midland Basin, West Texas. This hydraulic fracturing research is centralized around eleven horizontal wells fractured with over 400 stages in the Upper and Middle Wolfcamp formations as well as two refractured parent wells. 600 feet of core was obtained by drilling through the stimulated rock volume at the test site. HTFS#1 provided a unique platform to collect a rich dataset that includes surface seismic and downhole microseismic monitoring, downhole tiltmeters, in situ proppant placement assessment using core sampling, pressure interference tests, exhaustive core fracture description, proppant distribution from fracture faces, and downhole pressure gauge data during production. This has led to a series of publications in which findings, lessons, learnings, and challenges from this research have been shared to the community by the consortium members. The objective of this study is to analyze this dataset from a geomechanics perspective. We modeled pressure depletion and stress change on the two parent wells after 15 months of production using a one-way coupled approach. Simulation results indicate that no significant stress rotation occurred after this period of depletion. Microseismic depletion delineation (MDD) has recently been recognized as a potentially effective technique to estimate the depleted region. In this dataset, we observed the MDD phenomenon during the recompletions of the parent wells. Using the Mohr-Coulomb failure criterion, we developed a failure margin model to evaluate geomechanical conditions under which MDD occurs and to calculate the pressure depletion needed to trigger MDD. In the industry, bottom hole pressure (BHP) data from unconventional reservoirs are sparse, which limits our ability to understand the coupling processes that are spatiotemporally complex. Conversely, HFTS#1 provides a rare opportunity to perform detailed analyses based on the high-quality BHP data from 11 wells in two Wolfcamp formations. Key observations are presented from the real-time pressure gauge data, which allows mechanistic models to be developed to optimize drawdown strategy. This comprehensive dataset provided a better understanding on how geomechanics plays a significant role in field development of unconventional reservoirs.