Validating Refrac Effectiveness with Carbon Rod Conveyed Distributed Fiber Optics in the Barnett Shale for Devon Energy

摘要

This paper presents a diagnostic-driven method of evaluating refracturing (refrac) techniques in unconventional wells. Detailed analysis across the lateral, using intervention based distributed fiber optic (DFO) measurements, allows for a comprehensive understanding of the refrac performance. While there are various approaches to refracing an unconventional well, there is a categorical division of two main strategies: iterations of limited interval re-stimulation or re-stimulate the entire lateral at once. Stage-by-stage refrac, via casing-in-casing or coil tubing with isolation-type packer tool, offers potential control over stimulation distribution but often incurs heavier cost compared to refracing the entire well simultaneously. The economically favorable simultaneous refrac of all stages (Bull head) can be executed at a lower price but at the cost of not knowing the extent of lateral distribution. With several possible approaches for refracing an entire lateral at once, further questions arise regarding which method provides the most laterally uniform re-stimulation and whether the resultant production improvement is from re-stimulated existing or newly created fractures. A major hurdle in both executing and evaluating the success of an all stage simultaneous refrac is the uncertainty of creating new fracture initiation points; furthermore, with complex heterogenic rock, different fracture designs, and different well completions, it is difficult to develop a comprehensive understanding of how well the refrac design worked. Diagnostic validation of the success of a refrac operation, as well as iterative improvements based on those learnings, is fundamental to determining a cost-effective strategy. A strong data set takes the guesswork out of refrac and is the best method for understanding how effective the refrac designs performed. The focus of this paper will be on a case study from a Devon US unconventional well, where a 0.6″ OD, 22,000-foot-long carbon fiber rod was deployed in the Barnett Shale to acquire distributed acoustic (DAS) and temperature (DTS) data for post-refrac evaluation. The case study will explain how distributed fiber optic (DFO) measurements are used to provide a clear and detailed understanding of the refrac effectiveness, illuminating where stimulation went, whether existing fractures alone were re-stimulated or new fractures were initiated, and revealing the corresponding impact on production. These learnings, anchored with other conventional technologies, were applied to further escalate production enhancement in future refrac operations.