_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 223581, “A New Method To Quantify the Connections Between Wells Based on Pressure and Strain Responses Measured in a Monitoring Well,” by Jingyu Liu, SPE, and Kan Wu, Texas A&M University, and Ge Jin, Colorado School of Mines, et al. The paper has not been peer reviewed. _ Identifying the contribution of each fracture from each cluster in a multifractured horizontal well can be challenging; however, understanding fracture connections at the cluster level can provide detailed guidance for optimizing completion designs and well spacing. This work proposes a new method to interpret far-field strain change and pressure data to quantify fracture connectivity and properties at the cluster level. Introduction In this study, the authors first analyzed strain and pressure responses during a well interference test in the US Department of Energy’s Hydraulic Fracturing Test Site (HFTS)-1 (Phase III). Based on the assumption of a 1D linear flow equation, a new model was developed to describe early-time pressure changes in the fracture during production. By incorporating the linear relationship between pressure, stress, and strain, the model was extended to capture strain variations along the fracture. The model was then applied to interpret pressure gauge data and corresponding strain measurements, validating its accuracy. Finally, peak responses of strain change and estimated fracture conductivity of individual fractures along the wellbore were identified. Well Setup in HFTS-1 In HFTS-1 (Phase III), a dedicated monitoring well (14H) was drilled and positioned among 10 parent wells and three infill wells to monitor key operations, including the refracturing of parent wells, fracturing of infill wells, and well-interference tests. Among these wells, two parent wells (3H and 5H) were refractured, while the infill wells (11H, 12H, and 13H) were newly drilled. The monitoring well (14H) was equipped with permanent fiber optics and external pressure gauges to collect strain and pressure data during both fracturing and production. The wellbores are aligned approximately parallel to each other. Notably, the heel and toe orientations of monitoring Well 14H differ from those of Wells 3H and 5H. The interference test was conducted by sequentially activating the production wells, starting with the closest well (Well 5H, 250 ft horizontally from the monitoring well) and proceeding to the farthest (Well 11H, 2,000 ft away horizontally). Choke operations were conducted on Wells 5H and 3H. This strategy helped in capturing the pressure and strain responses from the closer-to-farther wells, thereby providing insights into interwell connection by fractures. An overview of strain and pressure data for the wells is provided in the complete paper. Methodology Distributed fiber-optic measurements and external pressure gauges offer new opportunities to measure strain and pressure changes at specific locations along the lateral, enabling more-detailed data collection along the wellbore (Fig. 1). By using fiber-optic measurements and downhole pressure-gauge data installed in monitoring Well 14H, this setup enables monitoring of pressure and strain changes at each individual cluster and location of effective fracture position during well-interference tests. This approach provides input data as well as induced strain and pressure changes at specific locations along the monitoring wellbore.
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