A new pressure management framework for CO2sequestration in deep saline aquifers based on genetic algorithm

CO2sequestration in deep saline aquifer is an effective technology for rapidly reducing CO2emissions. Ensuring safe and successful sequestration in deep saline aquifers necessitates a thorough evaluation and optimization of the sequestration scheme, encompassing injection types, well placement, and well controls, prior to field-scale implementation. The traditional objective of maximizing both economic benefits and CO2sequestration capacity is insufficient when prioritizing sequestration safety. To address this issue, this paper presents a new management framework that focus on uniformly increasing pressure (UIP) to obtain an optimal sequestration scheme for field-scale saline aquifers. In the first stage, the optimal well placement is determined by minimizing the UIP value using genetic algorithm (GA). Subsequently, the optimal well controls are obtained by minimizing the UIP value, building upon the optimal well placement. By comparing the results of each optimization, the optimal injection type is obtained. The proposed framework is tested through the construction of a representative model representing the geological characteristic of Songliao Basin in China and a real field-scale model of the Qing saline aquifer. The results demonstrate that the proposed framework outperforms the conventional direct and three-step optimization strategies to a significant extent. Compared with continuous and intermittent injection, water-alternating-gas method for injecting CO2into saline aquifers exhibits the best performance in minimizing the UIP value. The placement of additional wells with low injection rates in the upper regions of the saline aquifer positively influences the maintenance of a uniform pressure distribution. In comparison to the scheme with maximum CO2sequestration capacity, the sequestration scheme with minimum UIP considerably reduces the contribution of structural trapping contribution while enhancing contributions from dissolved, residual phase and mineral trapping. This study not only sheds light on enhancing the safety of CO2sequestration but also provides a critical reference for other underground geological energy storage projects.