Due to the tight nature of the matrix in shale plays, the drainage area does not extend far into the reservoir and is defined by the shape and size of the hydraulic fractures. As a consequence of this, wells typically exhibit steep decline rates and one of the prevalent ways to arrest the decline of a field is to drill and complete more wells. However, re-fracturing is slowly gaining a foothold in the industry, and our study has shown tremendous re-frac potential in the Bakken and Eagle Ford. In this study, we analyzed horizontal wells from the Bakken and Eagle Ford to identify existing re-fractured wells and estimated incremental recovery, followed by an economic analysis, to show re-fracturing as a viable alternative to drilling new wells.

Production and completions data was retrieved from public sources for all horizontal wells in the Bakken and the Eagle Ford formations, and a proprietary algorithm was applied to identify wells with a production signature that is consistent with a recompletion event. These wells were individually screened and confirmed as being re-fractured or not. Production metrics were defined to understand the performance of the wells before and after re-fracturing. Cross plots were made between these parameters to understand trends between the ratios of production decline rates and b-factors before and after re-fracturing, taking into account the time of re-completion. Decline curves were fit to the production of these wells to estimate the incremental estimated ultimate recovery (EUR) upon re-fracturing, and a net present value (NPV) analysis was done to determine commercial viability.

A majority of the identified potentially re-fractured wells had positive incremental NPV based on the EUR increase, which was 53% and 69%, on an average, for the Eagle Ford and Bakken respectively. From the existing re-fractured wells that were analyzed, it was found that there was no discernible correlation between the time an operator produces a well before being refractured and the various performance metrics that were analyzed. Also, good decline curve fits were found without changing the b-factors post-refrac and secant decline rates were typically lower after re-fracturing.

The results show the potential of re-completing wells and increasing reserves without drilling new wells based on actual field examples, showing an alternative field development strategy to the current practice of replacing older wells with newly drilled ones. Also, if re-fracturing is to be implemented on a larger scale, wells must be completed so as to make subsequent recompletions much easier, thereby encouraging use of novel casing and diverting agent technologies. Positive economics shows the huge potential of cost savings with re-stimulation and makes a ‘second wave’ of Eagle Ford/Bakken production possible.

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