Dual-objective enhancement of CO2 injection and hydrate conversion for CO2 solid sequestration in submarine sediments via penicillin G sodium solution pre-injection

CO 2 hydrate provides an important way for the long-term stable CO 2 geological sequestration considering CO 2 has potential self-sealing ability in submarine hydrate stable zone. However, the insufficient displacement efficiency of pore water and hydrate conversion rate pose significant challenges to ensuring long term CO 2 injection and hydrate sequestration under shallow burial sediments. Here, to enhance CO 2 injection into water-saturated sediments and hydrate conversion, we report a novel self-emulsification injection approach via penicillin G sodium solution pre-injection, which enables the rapid dispersion of injected CO 2 into the pore water as micro- and nano-sized CO 2 droplets in submarine sediments. The effects of liquid CO 2 injection rate, flow distance, sediment particle size, and reagent dosage on droplet dispersion were quantitatively analyzed. On this basis, we further tested its complex behaviors of displacement flow and hydrate formation. The results indicate that compared to conventional liquid CO 2 injection, self-emulsification injection effectively reduces injection pressure by 25 %–49 % and achieves the CO 2 storage density up to 181 kg/m 3 , indicating that this method is more suitable for rapid and large-scale CO 2 injection on the seabed. Moreover, the sufficiently small CO 2 microdroplets generated by self-emulsification flow almost eliminate the interphase hydrate membrane effect, thereby increasing the CO 2 hydration rate to over 70 %. This provides a guarantee for the effective establishment of CO 2 hydrate sealing cap in shallow seabed sediments. Given its comprehensive excellent performance, the self-emulsification injection technology is expected to significantly advance the hydrated CO 2 sequestration.