CONJUNCTIVE INJECTION OF CO2 AND WASTEWATER IN A HETEROGENEOUS POROUS FORMATION

One of the major obstacles to development, implementation, and deployment of carbon capture and storage (CCS) is cost. As a result, sustainably combining CCS with existing technologies to make CCS less costly or even profitable is vital. This article proposes a CCS strategy in which captured anthropogenic carbon dioxide (CO2) and treated municipal wastewater are simultaneously injected into a confined saline aquifer. Numerical simulations of conjunctive injection of CO2 and wastewater into a confined saline aquifer were conducted under heterogeneous conditions. Simulation results were evaluated based on spatial distributions of gas saturation, and pressure, over an injection period of 10 years. Results from the simulation of CO2-wastewater injection (3214 tons/day) into a carbonate saline aquifer predict very low gas saturations and enhancement of dissolved CO2 mass fraction as a result of the dissolution of CO2 into wastewater and native brine. Vertical baffling of the CO2 plume was achieved due to vertical heterogeneity of the injection zone thereby reducing reliance on caprock integrity in ensuring CO2 storage security. Comparison of simulation results of conjunctive CO2-wastewater injection to those of single phase CO2 and wastewater injection suggest that coinjection of CO2 and wastewater in deep confined saline aquifers enhances CO2 storage efficiency and security.