Novel systematic approach for produced water volume quantification applicable for beneficial reuse

Abstract

Produced water (PW) is an undesirable product generated during oil and gas production. More than 56% of the PW volume generated in the United States is disposed of either into the subsurface non-productive water-bearing reservoir (referred to as Saltwater Disposal well, SWD) or through other means. In the Permian Basin, 38–50% of the PW water volume generated is disposed of into SWD. Using SWDs comes with challenges such as overpressure, loss of injectivity, seismicity, and groundwater contamination. As such, it has become imperative to consider the beneficial reuse of produced water outside the oil and gas industry. Besides the PW volumetric data available in the public domain or some companies' repositories, not much attention is given to the potential volume that will be accessible for beneficial reuse or prediction of future values. Usually, the water–oil ratio (WOR) or water–gas ratio (WGR) is used for this projection (often a generalization of the accurate picture). However, a critical question remains on how much of the PW will be available for beneficial reuse in the coming years. This requires a rigorous method for quantifying and predicting PW obtainable over the long term. As an improvement over existing techniques, this study employs decline-curve analysis (DCA), type-curves method, and historical drilling and production data to develop a new systematic method for quantifying and predicting PW volumes at the basin and other aggregate levels. The applicability and robustness of the proposed method are demonstrated using Permian Basin (in West Texas, US) as a case study due to its uniqueness. The results indicate that the remaining PW in Permian is expected to peak at about 8–16 MMbbl per day in the period 2023–2027, while a total of 34–149 Bbbl of PW would be available for export to external industries over the next 38 years. A retrospective review of PW rates predicted for Permian in previous studies suggests that the approach and results of this new study are improvements over the previous ones. The new method and findings from this work should find relevance in predictions and sustainable management of PW in other petroleum basins in the United States and elsewhere.