Optimization of enhanced oil recovery operations in unconventional reservoirs

The U.S. Department of Energy is promoting the development of technologies that tackle gas flaring activity in oil production. Among these technologies, injection of flare gas into the reservoir to stimulate production of oil and capture the injected gas has received attention. Accordingly, this study contributes to understanding the economic and environmental implications of implementing enhanced oil recovery (EOR) in shale oil development to reduce gas flaring. A systematic optimization-based methodology is proposed to fully integrate the development of a shale oil field along with EOR projects. The framework optimizes decisions such as drilling schemes, workover of depleted production wells, pipeline and processing infrastructure, location of injection sites, injection rates, and duration of EOR operations. The pertinence of implementing EOR in the Bakken area is addressed through a typical production unit with 18 wellpads, which is further extended to 4 production units (72 wellpads). Results reveal consistent values across different development scales for operational variables such as percentage of wellpads undergoing EOR, incremental produced oil, percentage of total gas production used for injection, and average gas flaring. Conversion of depleted wellpads is preferred over installation of new injection wells. A global sensitivity analysis revealed the dominant role of EOR efficiency over Capex, Opex, and gas-oil ratio. EOR greatly favors the economics and the reduction of gas flaring but it is insufficient to comply with local flaring targets. Nonetheless, the implementation of EOR in combination with taxation tariffs is an adequate mechanism to reduce gas flaring and comply with regulatory targets.