Abstract

Refracturing continues to provide operators with the opportunity to add production at a fraction of the cost to drill and complete a new well. Various re-stimulation designs and diversion techniques are currently being utilized to maximize contact with previously un-stimulated rock. Optimizing this process involves evaluating all available diagnostic, pressure and production data and determining the optimum design that maximizes recovery. This paper describes how these diagnostic technologies have been employed to evaluate and optimize refracs in four major North American basins.

The process of refracturing and recompleting wells continues to improve. Much of this improvement comes from the optimization of techniques through completion diagnostics. Diagnostics provide data that can quantify the amount of the lateral treated and the effectiveness of diversion. Operators are focused on bridging the gap between the completion methods commonly used at the time the well was originally completed and the methods of today. Application of completion diagnostics also assists in identifying opportunities to further reduce the cost of the project while achieving similar results. In this study, proppant tracing followed by spectral gamma ray logging was employed to evaluate the effectiveness of the refracs, the extent of new rock contacted, the benefits of reperforating, and various diversion methodologies.

Diagnostic results from 121 vertical (34) and horizontal (87) refracs covering 16 different formations and 26 different operators were analyzed and compared based on stimulation effectiveness and performance. The wells were then grouped by well type, formation and the basic refracturing technique that was utilized. In addition to the macroscopic data interpretation; four case histories are presented from the Barnett Shale, Permian Basin, Eagle Ford, and Haynesville. These case histories include before and after reservoir production matching with fracture half-length and effective conductivity calculations along with the diagnostic analysis of new and existing perforation coverage, diversion effectiveness, and ultimately the % incremental estimated ultimate recovery (EUR).

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