Development of reactive-transport models simulating the formation of a silica gel barrier under CO2 storage conditions

Abstract

Geological storage of carbon dioxide (CO2) is a means of reducing greenhouse gas emissions. Key to the successful implementation of this technology is the ability to prevent CO2 leakage from the storage reservoir. One promising leakage abatement technology involves forming a geochemical barrier through reaction of an alkaline sodium silicate solution with CO2-enriched water or supercritical CO2. To investigate the feasibility of this technology at the field scale, three reactive-transport models were developed. The first simulations replicated previous laboratory studies (Castañeda-Herrera et al., 2018a), the second and third predicted the formation of a radial shield around the well and an impermeable silica gel layer serving as a flow diverter above the CO2 injection point. Good agreement with the experimental results was observed. Results also show the pH-dependent silica gel formation and its location deep in the reservoir strongly depend on the rate and the sequence of reagent injection as well as their efficient mixing in the reservoir. An alternative field application of the silica gel barrier is proposed to enhance capillary trapping beneath a lateral flow diverter. The application of silica gel barriers could make CO2 sequestration both safer and more efficient, enhancing further uptake of carbon capture and storage.