CO2 storage capacity in laboratory simulated depleted hydrocarbon reservoirs – Impact of salinity and additives

Abstract

A number of depleted hydrocarbon reservoirs in Alberta, Canada provide an opportunity for enhanced CO2 storage density because the reservoir conditions favor CO2 gas hydrate crystal formation. A laboratory simulation study was conducted to study this process and assess the impact of injection method, presence of additives and salinity on the CO2 storage density. Results indicated constant flow rate followed by constant pressure CO2 injection enhanced CO2 hydrate formation compared to constant pressure gas injection. It was noted that 85 % of the original water in the reservoir formed CO2 hydrate after 24 h experiments and that figure rose to 90 % after a 120 h period. Certain amount of tapioca starch and Polyvinylpyrrolidone (PVP) added to the water prevented the hydrate formation in the earlier stage (delay of the onset of hydrate nucleation but subsequently more CO2 was stored as hydrate in the reservoir compared to the inhibitor-free systems. Hydrate formation in saline reservoirs was reduced compared to pure water conditions. The hydrate technology provides an improved CO2 storage density.