Water Flowback RTA Analysis to Estimate Fracture Geometry and Rank the Shale Quality
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AbstractRecently, flowback data analysis enabled us to evaluate important fracture parameters including fracture conductivity and volume in unconventional reservoirs. To perform the analysis, diagnostic plots, straight-line techniques, and history-matching techniques have been used. Immediate water and gas production usually occurs on flowback in shale gas wells. In this paper, a novel workflow is developed for the analysis of water flowback data and early-time production of shale gas wells. This analysis then helps to define the movable water and the applicability of the soaking process on the shale gas well.Rate transient analysis (RTA) combined with decline curve analysis (DCA) was used to analyze different shale gas wells. Effective fracture volume and geometry were calculated from the RTA analysis. Estimated ultimate water recovery was calculated from DCA. The calculated water-in-place and the estimated ultimate water recover (EURw) will be compared against the injected fracturing fluid.Water RTA result show that in the case of shale wells with no movable formation water, gas kick off early, and boundary dominated flow (BDF) was observed. In addition, these wells performance improved with soaking process. On the other hand, if initial formation water saturation is higher than the connate water, water production will be from the frac fluid and formation water. As a result, gas kick off delays and transient flow regimes are expected. Soaking process can have a negative impact on the well performance if the movable water saturation is high.Honoring the flowback data can help to estimate the fracture geometry and to judge the quality of the shale formation quality and its validity for soaking process.
