Exhaustive brine production and complete CO storage in Jianghan Basin of China.

Pressure buildup limits CO injectivity and storage capacity and pressure loss limits the brine production capacity and security, particularly for closed and semi-closed formations. In this study, we conduct a multiwell model to examine the potential advantages of combined exhaustive brine production and complete CO storage in deep saline formations in the Jiangling Depression, Jianghan Basin of China. Simulation results show that the simultaneous brine extraction and CO storage in saline formation not only effectively regulate near-wellbore and regional pressure of storage formation, but also can significantly enhance brine production capacity and CO injectivity as well as storage capacity, thereby achieving maximum utilization of underground space. In addition, the combination of brine production and CO injection can effectively mitigate the leakage risk between the geological units. With regard to the scheme of brine production and CO injection, constant pressure injection is much superior to constant rate injection thanks to the mutual enhancement effect. The simultaneous brine production of nine wells and CO injection of four wells under the constant pressure injection scheme act best in all respects of pressure regulation, brine production efficiency, CO injectivity and storage capacity as well as leakage risk mitigation. Several ways to further optimize the combined strategy are investigated and the results show that increasing the injection pressure and adopting fully penetrating production wells can further significantly enhance the combined efficiency; however, there is no obvious promoting effect by shortening the well spacing and changing the well placement. [ABSTRACT FROM AUTHOR]