Experiments on methane hydrates formation in seabed deposits and gas recovery adopting carbon dioxide replacement strategies

Topic of this work is to carry out studies to deepen the knowledge of the CO2-CH4 replacement process, using a laboratory scale apparatus designed to reproduce marine hydrate sediments. Nine tests were performed, at three different hydrate saturation levels: 10, 20 and 30%. Temperature profiles over time allow to determine the spatial distribution of the formed hydrates in the sediment. At 10% and 20% hydrates saturation the reaction always starts in the upper part of the reactor, but the massive formation occurred in the lower and the middle area. When saturation reached 30%, reaction heat was mainly produced in the upper part of the reactor. Three CO2-CH4 replacement tests were carried out at 10% hydrate saturation. During the tests both temperature and pressure were modified to cause the CH4 hydrates dissociation and the CO2 hydrates formation. At the end of the replacement process, CO2 stored was in the range 31–42% of the total CO2 injected, and the exchange efficiency was in the range 1.30–1.45.