Rapid Refracturing Candidate Selection in Shale Reservoirs Using Drainage Volume and Instantaneous Recovery Ratio
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Copyright 2016, Unconventional Resources Technology Conference (URTeC). Production performance for unconventional shale reservoirs generally show an early high flow rate followed by a steep decline. Refracturing the underperforming wells is an economical practice to mitigate the flow rate decline and maximize reservoir deliverability, especially at the current low oil price environment. Selecting the correct candidates for refracturing is a crucial step for refracturing jobs. Despite the experience that has been gained in refracturing candidate selection for conventional reservoirs and unconventional tight reservoirs, very little literature is currently available about refracturing candidate selection for multistage hydraulic fractured horizontal wells. An efficient refracturing candidate selection approach is proposed in this paper based on competition between the produced volume and the drainage volume. The well drainage volume is calculated based on pressure and production data, which measures how much reservoir volume is accessed by the well. Instantaneous Recovery Ratio (IRR), defined as the ratio of produced volume to the drainage volume, is proposed in this paper to measure how quickly or efficiently the accessed volume is being produced. Wells are qualitatively ranked based on their drainage volume and IRR after sufficient production time. Accordingly, well production performance can be compared and refracturing candidates can be selected. Proposed drainage volume calculation and IRR can efficiently measure the effectiveness of fracture stimulation. The proposed refracturing candidate selection approach is first validated through coupled fluid flow and geo-mechanical simulation, which can account for stress shadow and stress change due to depletion for modeling of the refracturing process. Candidate selection approach is then applied to Eagle Ford shale wells. Results suggest that maximum potential candidate seems to be the well with relatively large drainage volume but with poor depletion rate. The advantage of the proposed approach is that all calculations are based on pressure and production data, which is purely data driven without any presumptive flow regimes. The result of our refracturing candidate selection criteria is compared to that of previous approaches based on production and completion indices. The proposed approach by this paper can select consistent underperforming wells but additionally can differentiate the wells by giving possible underlining reasons for underperforming. Thus, more appropriate refracturing jobs can be designed accordingly to maximize the chance of refracturing success.
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Proceedings of the 4th Unconventional Resources Technology Conference
