Production Behavior from Hydrate Bearing Marine Sediments using Depressurization Approach

Abstract A large quantity of natural gas is sequestered in clathrate hydrate form beneath permafrost and continental margin. However, the simultaneous production behavior of gas and water from clathrate hydrate resources in porous media is not well understood. In this study, the gas and water production behavior from hydrate bearing sediment (HBS) using depressurization method is presented. The HBSs of 40% hydrate saturation, 50% water saturation and 10% gas saturation was produced in an excess water environment, and each formation cycle takes around 14 days, achieving a final methane conversion of ∼81%. Upon the formation of quantitatively similar hydrates, the sediments were brought to 281.5 K and exposed to a production pressure of 4.5 MPa. It was found that the localized temperature in several measurement points within the sediment dropped to the equilibrium temperature at the production pressure. By analyzing both gas and water production behavior simultaneously, it was found that hydrate dissociation occurred continuously even after the measured temperatures were stabilized outside the hydrate stability zone. The production profiles were also compared with thermal stimulation results to highlight the distinctive difference in production profile between the two approaches.