First-time implementation of multiple flowback DFITs (“DFIT-FBA”) along a horizontal well

Abstract

The DFIT flowback analysis (DFIT-FBA) method is a new approach for obtaining closure pressure (pc), a proxy for minimum in-situ stress, reservoir pressure (pr), and well productivity index (J) estimates in a fraction of the time required by conventional (pump-in/falloff) DFITs. The time and cost efficiency associated with the DFIT-FBA method provides an opportunity to conduct multiple field tests without delaying drilling and completion programs. The primary novelty of the current study is the first-time demonstration of the implementation and analysis of multiple DFIT-FBA tests along a horizontal well completed in an unconventional reservoir to investigate variations in pc, pr, and J. Furthermore, new corrections are introduced for the DFIT-FBA method to account for perforation friction, tortuosity, and wellbore unloading during the flowback stage of the test.Three DFIT-FBA tests were performed in the studied lateral, including at the toe, at a middle stage and near the heel of the lateral. Minimum in-situ stress, pore pressure, and well productivity index estimates were successfully obtained for all the DFIT-FBA tests and verified with the results of a conventional DFIT, also performed at the toe of the studied well. The new corrections for friction and wellbore unloading improved the accuracy of the closure and reservoir pressures by 4%. Furthermore, the results of flowing material balance analysis demonstrate that wellbore unloading might cause significant over-estimation of the well productivity index.Considerable variation in well productivity index was observed from the toe stage to the heel stage (along the lateral) for the studied well, as determined using DFIT-FBA. This variation has significant implications for hydraulic fracture design optimization, particularly treatment pressures and volumes.