Gas hydrate equilibrium dissociation conditions in porous media using two thermodynamic approaches

Chen

et al. 2017

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Abstract:The kinetics of methane hydrate formation in marine sediments with different water saturations are important to assess the feasibility of the hydrate production and understand the process of the secondary hydrate formation in the gas production from hydrate reservoir. In this paper, the behaviors of methane hydrate formation in marine sediments from the South China Sea at different water saturation levels were experimentally studied in isobaric conditions. The marine sediments used in the experiments have the mean pore diameter of 12.178 nm, total pore volume of 4.997 × 10 −2 mL/g and surface area of 16.412 m 2 /g. The volume fraction of water in the marine sediments ranges from 30% to 50%. The hydrate formation rate and the final water conversion increase with the decrease of the formation temperature at the water saturation of 40%. At the same experimental conditions, the hydrate formation rate decreases with the increase of the water saturation from 40% to 50% due to the reduction of the gas diffusion speed. At the water saturation of 30%, the hydrate formation rate is lower than that at the water saturation of 40% due to the effect of the equilibrium hydrate formation pressure, which increases with the decrease of the water saturation. The final water conversion is shown to increase with the increase of the water saturation, even the formation process at higher water did not end. The experiments at low water saturation show a better repeatability than that at high water saturation.

Section: Methodsmentioning

confidence: 82%

Section: Methodsmentioning

confidence: 96%

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Methane Hydrate Formation in Marine Sediment from South China Sea with Different Water Saturations

Chen

et al. 2017

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“…When PW decreases from 4.5 to 3.4 MPa, the volume of gas production increases by 20.5%, and when PW decreases from 3.4 to 2.3 MPa, the volume of gas production increases by 13.6%. Additionally, the lowest PW is 2.3 MPa, which is lower than the quadruple point of methane hydrate (2.60 MPa [51]). However, the ice blocking does not happen in this case.…”

Section: Sensitivity Analysis Of Production From Gmgs2-site 8 In Pearmentioning

confidence: 78%

Evaluation of Gas Production from Marine Hydrate Deposits at the GMGS2-Site 8, Pearl River Mouth Basin, South China Sea

Feng

et al. 2016

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Natural gas hydrate accumulations were confirmed in the Dongsha Area of the South China Sea by the Guangzhou Marine Geological Survey 2 (GMGS2) scientific drilling expedition in 2013. The drilling sites of verified the existence of a hydrate-bearing layer. In this work gas production behavior was evaluated at GMGS2-8 by numerical simulation. The hydrate reservoir in the GMGS2-8 was characterized by dual hydrate layers and a massive hydrate layer. A single vertical well was considered as the well configuration, and depressurization was employed as the dissociation method. Analyses of gas production sensitivity to the production pressure, the thermal conductivity, and the intrinsic permeability were investigated as well. Simulation results indicated that the total gas production from the reference case is approximately 7.3ˆ10 7 ST m 3 in 30 years. The average gas production rate in 30 years is 6.7ˆ10 3 ST m 3 /day, which is much higher than the previous study in the Shenhu Area of the South China Sea performed by the GMGS-1. Moreover, the maximum gas production rate (9.5ˆ10 3 ST m 3 /day) has the same order of magnitude of the first offshore methane hydrate production test in the Nankai Trough. When production pressure decreases from 4.5 to 3.4 MPa, the volume of gas production increases by 20.5%, and when production pressure decreases from 3.4 to 2.3 MPa, the volume of gas production increases by 13.6%. Production behaviors are not sensitive to the thermal conductivity. In the initial 10 years, the higher permeability leads to a larger rate of gas production, however, the final volume of gas production in the case with the lowest permeability is the highest.

“…Before hydrate production, the initial hydrate/water/gas saturations (volume) are calculated as 38.5%, 2.2%, and 59.3%, respectively, using the model proposed by Linga et al [13]. During the hydrate production, the temperature of the water bath is maintained at 8.0 °C, and the corresponding equilibrium pressure is calculated to be 5.7 MPa by the fugacity model proposed by Li et al [14]. The temperature of deionized water is raised to the injection temperature (T i = 130 °C) in the pre-heater.…”

Section: Experimental Methodsmentioning

confidence: 99%

Similarity Analysis in Scaling a Gas Hydrates Reservoir

et al. 2013

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A complete set of scaling criteria for gas hydrate reservoir of five-spot well system case is derived from the 3D governing equations, involving the mass balance equation, the energy balance equation, the kinetic model, the endothermic model and the phase equilibrium model. In the scaling criteria, the key parameters of the experiment are the water/gas production rates, the water injection rate, and the production time. By using the scaling criteria, the experimental results can be enlarged to a field scale. Therefore, the experimental results and the scaling criteria could be used to evaluate the hydrate dissociation strategies and the gas production potential of the hydrate reservoir.Keywords: scaling criteria; hydrate reservoir; hydrate production; five-spot well