Integrated Reservoir Simulation and Discrete Fracture Network Modeling for Produced Water Source Identification in Tight Reservoirs, Case Study from the Bakken Formation, Williston Basin

ABSTRACT The Bakken reservoir in the Williston Basin recorded an increase in produced water volume, previous research suggested two possible reasons: Bakken formation pressure depletion allowing for more water migration and fractures propagation FP enabling fluid flow from the upper Lodgepole and/or from the lower Three Forks formations. The aim of this study is to investigate the two theories and to identify the best match with the real production data. An integrated reservoir model and a discrete fracture network DFN have been used for this purpose, wells and literature data from a Bakken reservoir field were associated to build the reservoir model and then compiled with natural fractures network generated using a DFN modeling tool. The assessment included four production cases: from the Bakken formation only, from the Bakken and Three Forks formations with downside FP, from the Bakken and Lodgepole formations with upside FP, and simultaneously from the three layers. The simulated models were evaluated using monthly production rates and cumulative volumes. Producing from the Bakken and Lodgepole formations case resulted in a good match, whereas the other three scenarios requested an unreasonable range of parameters for history matching. The third model's tight match establishes fracture propagation through the Bakken and Lodgepole formations as the most likely source of produced water. Natural pressure depletion of the Bakken formation and downside fracture propagation are implausible due to the unrealistic values required to match the models. This study might be expanded to include more fields to gain a more comprehensive knowledge of the Bakken produced water sources, and the outcomes serve as a guide for future wells implementation and development. INTRODUCTION In 2021, the United States oil and gas industry generated 25.86 Bbbls of produced water (GWPC, 2022). Effective management of produced water is crucial for the industry's sustainability and cost efficiency.