Experimental Investigation of Methane Gas Production from Methane Hydrate

Abstract

A 72 L large-scale reactor vessel was designed, manufactured, and built to investigate the gas production from methane gas hydrates. Methane hydrates were successfully formed within the reactor using pure methane gas and deionized water in a sand matrix with grain sizes between 100 and 500 μm. Hydrate formation tests resulted in formation at 2.2 °C around 600 psi. Mass balance calculations show that 11% of the pore space volume was occupied by hydrate. Measurements and simulations suggest that hydrate was initially formed at the top section of the reactor followed by formation within the lower part of the sediment. A cooling effect was observed during the dissociation via depressurization experiments, caused by the endothermic dissociation reaction. The observed temperature decrease of the system was between 4.0 and 0.8 °C. During the hydrate dissociation tests, a transition regime showing an increased gas production from 9.5 to 13 L/min within a very narrow range of temperature between −1.6 and −1.2 °C and pressure between 310 and 360 psi was recorded. In addition, the temperature was observed to jump to 0 °C in an extremely short time period. The interpretation of this phenomenon is ice formation in the transition regime where hydrate decomposes to gas and ice instead of gas and liquid. This is the first experimental observation of this phenomenon.

Review of natural gas hydrates as an energy resource: Prospects and challenges

“…During depressurization to 2.3 MPa, a stage of which the temperature of hydrate sample falls below freezing point was identified, and gas recovery was observed to increase during that stage. The increased gas recovery at low temperature was consistent with previous theoretical [136] and experimental studies [137], which is explained by a simultaneous dissociation of hydrate into water, ice and gas.…”

Analyzing the process of gas production for natural gas hydrate using depressurization

“…Both concluded that the success of gas production was strongly dependent on the effective permeability and initial temperature of sediments. However, little work has analyzed the effects of natural gas hydrate reformation and ice generation on gas production, phenomena that are commonly observed when employing depressurization [25,26].…”

Numerical analysis of methane hydrate decomposition experiments by depressurization around freezing point in porous media

“…Yang et al [26] carried out the hydrate dissociation experiment at a constant wellbore pressure of 1.0 MPa in a middle-sized cylindrical reactor, and found that the hydrate dissociation and gas production rates were both affected by the formed ice below the freezing point. Zhou et al [27] observed a cooling effect during methane hydrate dissociation via depressurization experiments in a 72 L large-scale reactor vessel. The temperature was found to jump to 0°C in an extremely short period because of ice formation.…”