Shale field development strategies are aimed at increasing recovery factors and thus revolve around well-spacing decisions and hydraulic fracture treatment plans. The hydraulic fracture test site (HFTS) consortium provided invaluable data and insight in terms of the interaction between multiple wellbore pads. Although pressure communication between wellbores during completion and production has been analyzed in previous HFTS studies, relatively little work has been performed to constrain the actual reservoir volume being recovered—this paper addresses an integrated approach to assess the development of the drained rock volume (DRV) and recovery factors. A detailed analysis of flow regime changes, shows when the first fracture pressure interference occurs in each well, and also pinpoints the onset of inter-well pressure interference. Computation of the instantaneous b-value from well rate decline data reveals the occurrence of b-sigmoid patterns, which provide a more detailed indication of the onset of flow regime shifts and pressure interference (with adjacent fractures and well drainage boundaries). Typical changes in water-oil ratios (WOR) and gas-oil ratios (GOR) were also studied, in particular in conjunction with flow regime shifts and bubble point pressure flips during well shut-in tests. Understanding flow regime shifts related to (1) the diffusive advance of pressure transients, and (2) the convective growth of the DRV, can help design more efficient well spacing, cluster staging, perforation design, lateral length and landing targets, fracture design and geometry, etc. to increase hydrocarbon recovery factors.

1. Introduction

The US Department of Energy (DOE) sanctioned in 2014 two major field test sites to study the effects of hydraulic fracturing when applied to hydrocarbon reservoirs with multi-well development. One field project was staged in the Eagle Ford Formation, in a lease region in DeWitt County, Texas (Raterman et al., 2018, 2019); the other so-called HFTS project was located in the Permian Basin (DOE award number DE-FE0024292) and studied well completions in the Wolfcamp Formation, in a lease region in Reagan County, Texas (Ciezobka et al., 2018). Both projects were enabled by consortia of participating companies and research institutions (such as NETL, UT Austin and BEG), matching the DOE funding with subcontracted services and in-kind contributions. The two projects were managed by the Gas Technology Institute based in Des Plaines, Illinois, a non-profit organization which develops, demonstrates, and licenses new energy technologies for private and public clients, with a particular focus on the natural gas industry.

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