Replacement of methane from quartz sand-bearing hydrate with carbon dioxide-in-water emulsion

The replacement of CH(4) from its hydrate in quartz sand with 90:10, 70:30, and 50:50 (W(CO2):W(H2O)) carbon dioxide-in-water (C/W) emulsions and liquid CO(2) has been performed in a cell with size of empty set 36 x 200 mm. The above emulsions were formed in a new emulsifier, in which the temperature and pressure were 285.2 K and 30 MPa, respectively, and the emulsions were stable for 7-12 h. The results of replacing showed that 13.1-27.1%, 14.1-25.5%, and 14.6-24.3% of CH(4) had been displaced from its hydrate with the above emulsions after 24-96 It of replacement, corresponding to about 1.5 times the CH(4) replaced with high-pressure liquid CO(2). The results also showed that the replacement rate of CH(4) with the above emulsions and liquid CO(2) decreased from 0.543, 0.587, 0.608, and 0.348 1/h to 0.083, 0.077, 0.069, and 0.063 1/h with the replacement time increased from 24 to 96 h. It has been indicated by this study that the use of CO(2) emulsions is advantageous compared to the use of liquid CO(2) in replacing CH(4) from its hydrate

Simulation of the Decomposition of Natural Gas Hydrate in Porous Media by Hot Water Injection

As a reference of the recovery of natural gas hydrates by hot water injection, the decomposition of natural gas hydrates in sediments due to heat stimulation was simulated experimentally and numerically. It is supposed the radial diffusion model describes the decomposition of natural gas hydrates in sediments owing to hot water injection, and the hydrate decomposition is a one-order reaction. Combining the rate equation of the decomposing reaction with the rate equation of the heat transfer and heat balance equation, the relationship between the accumulative quantity of methane and decomposing time t was obtained i.e.. n(o) - n(H) = 2.7 x 10(-2) (theta(3) - 10)(1/2)t(3/2). By comparing the results from the experiment and numerical simulation, it was found that, under the experimental conditions, the rate coefficient of hydrate decomposition was 2.675x10(-4) mol/(m(2)-Pa.min), which was found to be consistent with the experimental results

Determination of appropriate condition on replacing methane from hydrate with carbon dioxide

This paper is intended to determine the appropriate conditions for replacing CH(4) from NGH with CO(2). By analyzing the hydration equilibrium graphs and geotherms, the HSZs of NGH and CO(2) hydrate, both in permafrost and under deep sea, were determined. Based on the above analysis and experimental results, it is found that to replace CH(4) from NGH with gaseous CO(2), the appropriate experimental condition should be in the area surrounded by four curves: the geotherm, (H-V)(CO2), (L-V)(CO2) and (H-V)(CH4), and to replace CH4 from NGH with liquid CO(2), the condition should be in the area surrounded by three curves: (L-V)(CO2), (H-L)(CO2) and (H-V)CH4. For conditions in other areas, either CO(2) can not form a hydrate or CH4 can release little from its hydrate, which are not desirable results. (c) 2008 Elsevier Ltd. All rights reserved

Use of electrical resistance to detect the formation and decomposition of methane hydrate

The changes of electrical resistance (R) were studied experimentally in the process of CH4 hydrate formation and decomposition, using temperature and pressure as the auxiliary detecting methods simultaneously. The experiment results show that R increases with hydrate formation and decreases with hydrate decompositon. R is more sensitive to hydrate formation and decompositon than temperature or pressure, which indicates that the detection of R will be an effective means for detecting natural gas hydrate (NGH) quantitatively