As the urgency to combat climate change intensifies, developing innovative and efficient carbon-sequestration strategies to capture and store CO2 from industrial sources has become a critical priority. This paper reviews the simultaneous supercritical (SC) CO2-brine aquifer injection (SAI) and water-alternating-gas (WAG) methods for geologic carbon sequestration and proposes a novel integration with saltwater-disposal wells (SWDs).
SAI-WAG Method
The SAI-WAG strategy incorporates two scenarios: concurrent injection of CO2 and treated wastewater into a geological formation through a dual-structured well for disposal purposes, or alternating injection of treated water and CO2 by a single- or dual-string assembly. The latter scenario mirrors traditional WAG processes, which combine conventional waterflooding and CO2-injection methods into what is known as CO2-SWAG. Simultaneous injection also is called CO2-SWAG.
Compared with CO2-WAG injection, CO2-SWAG injection provides better control over fluid mobility and enables more-stable gas displacement. Despite these advantages, SWAG injection presents challenges, including high costs for well completion, equipment, operations, and complex design.
The SAI-WAG strategy offers significant economic advantages by eliminating the need to drill additional wells for geological carbon-storage activities.
