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Analysis of cross-well fracture hits in DJ Basin, Colorado using low-frequency DAS data



In this study, we analyze low-frequency DAS (LF-DAS) data of two fiber wells monitoring two zipper-fraced injection wells in DJ Basin, Colorado. Interpreting the fracture hits yields insights into the fracture geometry across and within two formations, the Niobrara and Codell, where the studied wells are located. This observation indicates that the length of hydraulic fractures in the Codell formation is more than twice of that in the Niobrara. Furthermore, we observe consistent vertical fracture connections between the two formations. Although we interpret that the observed fracture-geometry difference is caused by differences in geologic properties and pressure in the two formations, further geological and geomechanical interpretation is needed to validate this hypothesis. By correlating fracture hit timing with pumping curves, we estimate the cumulative injection volume needed for the fracture to propagate from the perforation location to two offset fiber wells. Because one fiber well is three times further from the injection well than the other, it took less time and injection volume for fractures to arrive at the nearer fiber well, despite the nearer well being in a different formation. Overall, the injection volume is proportional to the fiber well distance, but varies greatly among fracture hits of the same stage. These observations from the LF-DAS data reveal the complexity of the fracture geometry in the studied area. These insights may also help engineers to optimize the well spacing and completion design.