| Citation: |
Yao-hong Shi, Qian-yong Liang, Jiang-pin Yang, Qing-meng Yuan, Xue-min Wu, Liang Kong, 2019. Stability analysis of submarine slopes in the area of the test production of gas hydrate in the South China Sea, China Geology, 2, 276-286. doi: 10.31035/cg2018122
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Stability analysis of submarine slopes in the area of the test production of gas hydrate in the South China Sea
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Abstract
In this paper, the mechanical properties of gas hydrate-bearing sediments (GHBS) were summarized and the instability mechanism of submarine hydrate-bearing slope (SHBS) was analyzed under the background of the test production of gas hydrate in the northern part of the South China Sea. The strength reduction finite element method (SRFEM) was introduced to the stability analysis of submarine slopes for the safety of the test production. Two schemes were designed to determine the physical and mechanical parameters of four target wells. Through the division of the hydrate dissociation region and the design of four working conditions, the range and degree of hydrate dissociation at different stages during the test production were simulated. Based on the software ABAQUS, 37 FEM models of SHBS were set up to analyze and assess the stability of the submarine slopes in the area of the test production. Necessary information such as safety factors, deformation, and displacement were obtained at different stages and under different working conditions. According to the calculation results, the submarine slope area is stable before the test production, and the safety factors almost remains the same during and after the test production. All these indicate that the test production has no obvious influence on the area of the test production and the submarine slopes in the area are stable during and after the test production.
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References
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Yao-hong Shi, Qian-yong Liang, Jiang-pin Yang, Qing-meng Yuan, Xue-min Wu, Liang Kong, 2019. Stability analysis of submarine slopes in the area of the test production of gas hydrate in the South China Sea, China Geology, 2, 276-286. doi: 10.31035/cg2018122
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Figure 1.
Locations of the test production wells.
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Figure 2.
Seismic reflection maps of the profiles of the test production wells. a–seismic reflection map of Well SHSC-1; b–seismic reflection map of Well SHSC-2; c–seismic reflection map of Well SHSC-3; d–seismic reflection map of Well SHSC-4.
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Figure 3.
Division of drilling influence areas.
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Figure 4.
FEM model and FEM mesh of Well SHSC-4 (Scheme 1). a–FEM model; b–FEM mesh.
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Figure 5.
FEM model and FEM mesh of Well SHSC-4 (Scheme 2). a–FEM model; b–FEM mesh.
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Figure 6.
Contours of the plastic zone under different reduction coefficients (Well SHSC-4, during test production, Condition 4, Scheme 1). a–Plastic zone when Fr=1.0; b–plastic zone when Fr=3.406; c–plastic zone when Fr=4.754; d–plastic zone when Fr=4.769.
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Figure 7.
Relationship between reduction coefficient Fr and displacement of characteristic point (Condition 1, Scheme 1).
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Figure 8.
Contour of displacement (Fr=4.800, Well SHSC-4, Scheme 1).