Remediation of CO2 leakage using pressure gradient reversal method: A numerical modelling study

AbstractIt has been suggested that injection of brine above the caprock, at a higher pressure than the CO2 pressure in the reservoir, would create an inverse pressure gradient to reverse the flow direction and increase the solubility of CO2 in the saline water barrier formed, and prevent or limit leakage. The effectiveness of the pressure gradient reversal (PGR) method as a potential remediation technique for CO2 leakage from deep saline aquifers was investigated using a realistic 3D reservoir/caprock model. A hypothetical CO2 storage operation involving CO2 injection at 1 Mt/year for up to 30 years down-dip of a structure high in the model domain was considered. The brine injection simulation results indicate that the performance of PRG is strongly affected by how early leakage is detected from the start of injection (time-to-detection), which in turns is controlled by the detection threshold, leakage pathway permeability and the distance to the injection well. PRG is more effective the earlier leakage is detected and the closer the leakage location is to the injection well