Study of stress shadow effects in eagle ford shale: Insight from field data analysis
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Copyright 2016 ARMA, American Rock Mechanics Association. Recently, the Eagle Ford shale has become one of the most heavily targeted shale plays. Optimizing the production from wells targeting this play begins with the hydraulic fracture design. Hydraulic fracturing treatments with closely spaced fractures allows for a large area of the formation to be fractured and produced more efficiently. However, fractures spaced too close together suffer from stress shadow effects, which may cause an inefficient fracture completion. Optimal fracture spacing is a crucial aspect to maximize well production. In this paper, we analyzed pressure data recorded during the hydraulic fracturing process of multi-stage horizontal wells in the Eagle Ford field. A gradual increase in the treatment pressure recorded during each successive stage of fracturing is a strong indicator of a stress shadow induced by the fractures. The wells we studied in the Eagle Ford shale did not show the trend of increasing treatment pressure between stages, which may imply that stage spacing is not within the region of stress shadow influence. Furthermore, the extent of a stress shadow induced by opening fractures can be estimated by an analytical solution based on fracture height. Based on the complex geology of interbedded organic rich marl and limestone in the Eagle Ford shale, and stage spacing, we inferred that fracture height in these wells might be limited by the ductile rock in the formation. Since the fracture height is smaller than the stage spacing, this results in a small extent of stress shadow. Furthermore, we built a reservoir model that matches the wells' production and bottomhole pressure data to further quantify the fracture height. The conclusion we obtained is that interbedded ductile layers inhibit the growth of fracture height, resulting in weak stress shadow effects and uniform, planar fractures generated in the formation. Through this study we can provide some critical guidelines on the stage spacing and perforation cluster spacing of wells in similar geologic settings.
