CO2 hydrate stability in oceanic sediments under brine conditions

Carbon capture and storage (CCS) is a critical approach to reducing atmospheric carbon emissions. The United Nations [UN] Climate Change Conference COP26 Glasgow [2021] emphasized setting execution plans to reach the goal of a zero-carbon economy by 2050 as per the Paris Agreement [2015]. CO 2 sequestration in deep-sea sediments in the form of clathrate hydrates is a promising technique as it provides a significant capacity for CO 2 storage. Deep-sea sediments contain high salinity water, which will impair the CO 2 storage capacity and hydrate stability. Therefore, it's essential to examine the effect of salinity on CO 2 hydrate stability in simulated deep-sea sediments to foster real-time field application. In this first-gen experimental work, the stability of CO 2 hydrates across and inside the deep oceanic saline sediments has been evaluated for an extended period [14 days]. An artificial seabed, saturated with saline solution [3.5 wt% NaCl], was created using silica sand inside a high-pressure reactor system and stability tests were conducted at oceanic conditions (10 MPa, 4 °C). In phase 1 , CO 2 hydrates were formed across the seabed by pressurizing the system multiple times to 3.5 MPa using pure CO 2 gas. In phase 2 , the hydrates were immersed in a brine solution [3.5 wt% NaCl] and their stability was observed over 2 weeks [>14 days]. The experimental results indicate that CO 2 hydrates are adequately stable when submerged inside the brine solution and layers of hydrates were visible at the end of 2 weeks of the stability experiment. In phase 3 , a hybrid depressurization heating approach was used at the end of the stability test to confirm the presence of a good quantity of CO 2 hydrates inside the sand bed. • CO 2 hydrate formation kinetics in deep-oceanic sediments saturated in brine. • CO 2 hydrate formation morphology in oceanic sediments saturated in brine. • CO 2 hydrates stability evaluated in deep-ocean sediments submerged in brine.