The low permeability of clayey-silt hydrate reservoirs in the South China Sea affects the thermal and pressure conductivity of the reservoir, which is difficult to spread to the far end of the wellbore and achieve com...
The low permeability of clayey-silt hydrate reservoirs in the South China Sea affects the thermal and pressure conductivity of the reservoir, which is difficult to spread to the far end of the wellbore and achieve commercial gas production. In this respect, enhancing the permeability to assist depressurization is necessary. Hydraulic fracturing is a promising reservoir stimulation method for gas hydrate reservoirs. Up to now, majorities of research focus on the fracability of hydrate-bearing sandy sediments, but the studies rarely involved fracture propagation characteristics of clayey-silt sediments in the hydrate dissociation area. In this paper, three sets of hydraulic fracturing experiments under different confining pressure were carried out using the clayey-silt sediments in the Shenhu Area. Computed tomographic (CT) images indicated that clayey-silt sediments could be artificially fractured, and the fracturing fluid could induce tensile fractures and local shear fractures. A multimorphological fracture zone occurred near the borehole. Furthermore, the greater the confining pressure imposed, the greater the breakdown pressure was, and the microfracture arose more easily. The fractures at the top were generally wider than those at the bottom with the same confining pressure. The experimental results could reveal the fracture initiation and propagation mechanism of clayey-silt sediments and provide theoretical support for hydraulic fracture in the hydrate dissociation area.
The heat injection during depressurization is a crucial technique for sustaining the long-term gas production rate of natural gas hydrates. To analyze the production patterns and mechanisms of hydrate dissociation und...
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Three hundred gas samples recovered from SHSC-4 during China's first gas hydrate production test in the South China Sea were examined for gas component and isotopic composition. According to the gas chromatography...
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Three hundred gas samples recovered from SHSC-4 during China's first gas hydrate production test in the South China Sea were examined for gas component and isotopic composition. According to the gas chromatography analysis, all the gas samples from SHSC-4 are predominated by CH4, with minor N-2 + O-2, as well as trace amounts of CO2, C2H6, and C3H8. No H2S was detected. The molecular and isotopic data of the gas samples fall into the region of mixed origin on the plot of C-1/(C-2 + C-3) - C-13(1), which is close to the microbial origin. The discrimination diagram of C-13(1) - D-CH4 shows that the methane in all of the samples is of microbial origin, and is derived from the CO2 reduction.
Excessive carbon dioxide emissions pose a global environmental issue, and carbon sequestration technology offers a solution. This study proposes a novel approach for carbon dioxide sequestration in the overlying layer...
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