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This study aims to experimentally investigate the potential of solubility trapping mechanism in increasing CO2 storage during EGR by CO2 injection and sequestration in conventional natural gas reservoirs. A laboratory core flooding process was carried out to simulate EGR on a sandstone core at 0, 5, 10wt% NaCl formation water salinity at 1300 psig, 50 o C and 0.3ml/min injection rate. The results show that CO2 storage capacity was improved significantly when solubility trapping was considered. Lower connate water salinities (0 and 5 wt%) showed higher CO2 solubility from IFT measurements. With 10% connate water salinity, the highest accumulation of the CO2 in the reservoir was realised with about 70% of the total CO2 injected stored; an indication of improved storage capacity. Therefore, solubility trapping can potentially increase the CO2 storage capacity of the gas reservoir by serving as a secondary trapping mechanism in addition to the primary structural and stratigraphic trapping and improving CH4 recovery.

A core flooding experiment was carried out to simulate an Enhanced Gas Recovery (EGR) process to inject supercritical Carbon Dioxide (SCO2) into a core sample saturated with methane (CH4). This was done to investigate the flow behaviour of the injected SCO2 at the flow conditions when the injection orientation was switched from horizontal to vertical during the CH4 displacement. From the results, it was found that gravity has significant effects on the flow behaviour of SCO2 at lower flowrates; more pronounced is the seemingly lower permeability in the horizontal orientation compared with the vertical orientation. So the choice of the injection pattern or direction during EGR by SCO2 injection for the purpose of additional recovery of CH4 and subsequent sequestration of the injected CO2 should be made in conjunction with the determination of optimum injection rate for efficient injectivity.Fifth CO 2 Geological Storage Workshop

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