In this study, we focus on the fluid production behavior of water-saturated hydrate-bearing sediments with hydrate saturation around 40% induced by depressurization below the quadruple point of CH4 H2O, which was rarely reported in the open literature. We conducted a series of experiments with ultra-deep depressurization of 1.0 MPa, 1.5 MPa and 2.1 MPa to investigate the gas and water production profiles. Ultra-fast gas production was observed with staged water production profile. Ice formation and secondary hydrate formation was likely based on the temperature measurement. However, the concurrence of ice formation did not promote the gas production significantly due to the large driving force that has already been induced by the ultra-deep depressurization. Various hydrate saturations between 20-60 vol% and pressure drawdown rates were also employed to further optimize the production condition below the quadruple point in the full paper.
Keywords Natural Gas Hydrate, Ultra-deep Depressurization,Quadruple Point, Water-Saturated Hydrate-bearing Sediments, Fluid production, Heat Transfer