A New Method to Quantify the Connections Between Wells Based on Pressure and Strain Responses Measured in a Monitoring Well

Abstract Well interference test methods in Multi-Fracture Horizontal Wells (MFHWs) focus on the connectivity and conductivity between the "entire" wells. Practically it is challenging to identify the contribution of each fracture from each cluster in a MFHW. 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. The case study uses field data acquired from the DOE Hydraulic Fracturing Test Site-1 (Phase III) performed in the Eagle Ford shale. A dedicated well with permanent fiber and external pressure gauges installed was used to monitor strain and pressure changes (respectively) during put-on production (so-called "POP") of adjacent wells. A 1D linear flow model was proposed to simulate transient flow within fractures, allowing for the calculation of pressure responses at the monitoring well. By assuming a linear relationship between pressure and strain changes, we were able to match the observed pressure and strain changes to determine fracture connectivity and conductivity between the production and monitoring wells. Using field data from permanent fiber and external pressure gauges, we validated the analytical solution for modeling changes in strain during initial production performance. We note that the pressure and strain changes indicate the same fracture properties. During hydraulic fracturing treatment, 59 fracture hits were identified in the monitoring well, which is 250 ft horizontally from the producing well. During initial production, DSS strain data revealed only 20 fracture connections among 230 clusters between the producing well and the monitoring well. The calculations show fracture conductivities ranging from 0.1 to 15 mD·ft, with 10 connections exceeding 1 mD·ft. This analysis provides an important observation: out of the 230 perforation clusters and considering a well spacing of 250 ft, approximately 26% of the fractures connected from the treatment well to the monitoring well during fracturing, while only about 9% of the fractures remained connected during initial production. This study introduces an innovative interpretation method that can be used to quantify fracture connectivity and conductivity at the cluster level by leveraging advanced monitoring technology in unconventional reservoirs. This approach provides practicing engineers with unique data to optimize the well completion designs and well spacing, thereby enhancing the development and productivity of unconventional reservoirs.