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Identifying Remaining Bakken/Three Forks Prospects Using Geologic, Engineering and Dynamic Well Spacing Data

Abstract

One of the more mature unconventional resource plays, the Williston Basin has over ten thousand hydraulically fractured, horizontal wells spanning the Middle Bakken and Three Forks formations. With fewer and fewer new, standalone well locations remaining in the basin, focus has shifted towards understanding the dynamics of geologic sweet-spots, in a heavily developed environment. In other words, in the context of original oil in place (OOIP) models, how do we optimize recovery factors by economically increasing drainage volumes and efficiencies, through the addition of infill wells and the refracturing of existing producing wells. Previous studies have highlighted the importance of TOC, thermal maturity, depth and thickness when modeling expected well performance across the Bakken/Three Forks play. The volume of statistics surrounding the variable completion designs of these horizontal wells and their subsequent production performance, in particular geologic settings, has spawned various efforts to model well performance using multivariate analytics. Such techniques have allowed operators to more optimally “right size” well designs for specific geologic conditions. However, the Bakken/Three Forks challenge has evolved from modeling individual, isolated well performance - to comprehending the complex interaction of multiple horizontal wells, across multiple targeted landing zones. A geologic framework of the Bakken and Three Forks formation depths and thicknesses, is developed from geologic interpretation of numerous vertical wells; augmented with geochemical and well log data to highlight prospect variability. Against this geologic backdrop, this study looks at well interactions that include “frac hits”, driven by per-well injections of water volumes of 250,000+ bbl; as well as estimates of production interference. Well spacing metrics have been developed to characterize the dynamic impact of: vertical and lateral well spacing; length of well overlap; cumulative adjacent well footage; and more. Calibration of spacing impact is achieved using multi-variate analytic techniques that model multi-well performance by comparing geologic attributes, drilling and completions parameters, and a suite of dynamic well spacing metrics. The results of this study highlight remaining Bakken/Three Forks prospects and the importance of considering the timing of infill wells and recompletions, in addition to lateral and vertical spacing, in unconventional field development.