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Linking Sequence Stratigraphy and Rock Mechanics for the Unconventional Permian Tight Oil Play in the Delaware Basin: A Hierarchical Tool for Predicting Fracture Barriers and Stimulation Zones

Abstract

The Permian unconventional plays in the Delaware Basin are most often considered cost plays, resulting in a tendency to be parsimonious with the acquisition of formation evaluation data and other services that facilitate reservoir characterization, especially within a factory approach to development. A meaningful sequence stratigraphic framework is key to projecting observations into predictions where well data is sparse. A sequence stratigraphic framework for this play was constructed from core, high definition image logs, and log based mineralogy models to predict fracture stimulation zone trends. The stratigraphic framework has been linked to pertinent rock mechanic properties, such as Poisson's ratio, Young's moduli, and closure stress that enable the characterization of frac barriers across the basin. The framework describes high frequency sequences (4th and 5th order) that can be grouped into lower-order composite sequences and correlated for at least 10s of kilometers across the basin. The stratigraphic model predicts both: 1.) distribution and vertical dispersion of facies with the best reservoir characteristics and; 2.) occurrence of thick successions of facies prone to bearing high closure stress that are likely frac barriers. The stratigraphic framework is calibrated to a series of fracture propagation models. In more proximal settings, carbonate-prone high stand (HST) systems tracks tend to be fracture barriers, while the transgressive stand (TST) tends to include lower stressed and thinly bedded siliciclastic facies favored as reservoir targets. In more distal basin settings, the low stand (LST) system tract becomes well expressed and tends to be less favored as a reservoir target and often becomes a succession of geomechanically tough rock that also behaves as a frac barrier. The sequence stratigraphic framework provides excellent perspective for regional opportunity identification and helps to fill interpretive gaps when comprehensive formation evaluation data is not available.