This paper discusses the application of massively-parallel GPU flow-simulation to rapidly compare alternate reservoir development cases in the Bakken/Three Forks using vertically offset stacks of horizontal wells. Compared with conventional CPU flow simulation, Graphics Processing Units (GPUs) used as general purpose processors allow much faster run times and larger models (10+ million cells). Larger flow simulation models can retain important details of reservoir characterization (hydro-frac SRV + natural fractures + matrix), allowing investigation of many alternative development cases such as closely spaced, vertically offset stacked wells with interfering hydro-frac stages. These multi-pad horizontal well cases are often difficult to simulate due to model active cell size limits or impractical due to project time constraints.

This study aims to investigate three key what-if scenarios that are of current operational and economic significance. In particular, we investigate the impact of hydraulic fracture height, delayed drilling of the vertically offset horizontal wells, as well as horizontal well interference between Middle Bakken and Three Forks. The simulations are run on a GPU based simulator allowing us to take advantage of its high computational efficiency and reduced simulation run times, and to retain geomodel geological detail.

For the flow-sim examples presented in this work, we use a detailed Bakken and Three Forks geomodel based on NDIC public data. We demonstrate how the optimized GPU formulation provides the ability to run multiple fine-scale realizations with offset stacked groups of Bakken and Three Forks horizontal well sets to address vertical hydro-frac SRV uncertainty. Furthermore, we investigate several development cases that provide economic scenarios for future production from Bakken/Three Forks play.

Multi-million cell GPU flow-sim models are shown to run at least an order of magnitude faster than current parallel CPU algorithms for the same large Bakken/Three Forks combined models. Our fast full-physics simulations enable investigation of a wide range of what-if scenarios, thereby providing a better insight into several aspects of production from the complex Bakken/Three Forks play including hydraulic fracture interactions.

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