Multi-lateral horizontal well with dual-tubing system to improve CO2 storage security and reduce CCS cost

This paper proposes a multi-lateral horizontal well with a dual-tubing (MLHW-DT) system to improve CO2 storage security and reduce the cost of carbon capture and storage (CCS) at a saline aquifer. In CCS, the pro-duction and re-injection of brine are efficient methods of relieving overpressure and improving the CO2 storage security simultaneously. In our previous study, a horizontal well with a dual-tubing (HW-DT) system operating on an onshore platform reduced CCS cost. In this study, the proposed MLHW-DT system is designed to implement the concept of the re-injection of produced brine to improve CO2 storage security while supplementing the shortcomings of the conventional brine production system by reducing CCS cost. When we vary the vertical -horizontal permeability ratio and dip angle of a saline aquifer, the CO2 storage security of the MLHW-DT sys-tem is improved compared with that of the overall HW-DT system because the re-injected brine induces the CO2 plume migration in the lateral direction. Furthermore, the CCS cost of the MLHW-DT system is reduced by 69.4% compared with that of the conventional brine production system if the MLHW is operated on an onshore plat-form. Based on these results, the MLHW-DT is a safe and economical operation system for a CCS project.