CO2 foam to enhance geological storage capacity in hydrocarbon reservoirs

Geological CO2 storage is an emerging topic in energy and environmental community, which is, as a commonly-accepted sense, considered a powerful approach to mitigate the global carbon emissions during the transition to net-zero. The geological media initially considered cover the saline aquifers, oil and gas reservoirs, coal beds, and potentially basalts. Up to now only the first two choices have been proven to be the most capable storage sites and successfully implemented at pilot/commercial scales. Here, novel strategies were proposed for the first time, by synthesizing and utilizing new high-dryness CO2 foam, to enhance geological CO2 storage capacity in oil and gas reservoirs. As a major storage site, the oil and gas reservoirs ranked only second to the saline aquifer, due to their huge underground spaces, and more importantly, spontaneous economic benefits by injecting CO2 for geological storage. However, at any development stage, particularly late stage with high water cut, CO2 injection usually tends to cause gas channeling and therefore result in low-efficient storage. In this paper, a series of dynamic evaluation experiments are carried out to investigate the effect of newly-synthesized high-dryness CO2 foam in oil and gas reservoirs. A comprehensive set of parameters, including the fluid production volume, rate, efficiency, pressure, porous media weight, water cut, mobility reduction factor, oil-gas-water ternary phase saturation, etc., are specifically analyzed. The lab results show that when the foam quality is 85 %, the oil recovery performance and gas phase saturation reach their highest values, of 82.68 % and 75.36 %, respectively; meanwhile, the water consumption is at the lowest level, 43.88 g/mol, for the CO2 storage in oil and gas reservoirs. This indicates the synthesized high-dryness CO2 foam, attributed to its superb stability, modifies the mobility ratio, suppresses the viscous fingering, and finally results in higher oil recovery and more CO2 storage. Similar work has been done for the reservoirs with permeabilities from high to low levels. The study provides experimental evidences that suggest benefits from applying CO2 flooding in oil and gas reservoirs.