Enhanced CO2 injection and hydrate conversion in unsealed submarine sediments for CO2 hydrate sequestration by CO2-H2O emulsion injection

CO 2 hydrate provides an important alternative solution for CO 2 geological sequestration. However, fingering flow of liquid CO 2 and hydrate membrane effect can severely restrict flowing CO 2 conversion to hydrate. Here we report an enhanced CO 2 hydrate sequestration method via CO 2 -H 2 O emulsion injection, and its effectiveness has been proven in a three-dimensional system. Compared to liquid injection, emulsion injection demonstrated higher displacement efficiency of pore water and larger sweep area, finally increasing CO 2 sequestration density by 142 %. The highly dispersed CO 2 micro-droplets significantly increase CO 2 -H 2 O contact capability and weakens the hydrate membrane effect, thereby greatly increasing the rate and quantity of hydrate conversion. For different water contents, the highest CO 2 sequestration density of 148 kg/m 3 is achieved at 40 % water content, with hydrated CO 2 accounting for 71.45 %. The excellent performance of CO 2 -H 2 O emulsion provides a green and high-efficient approach to CO 2 hydrate sequestration.