| Citation: |
Yun-xin Fang, Jing-an Lu, Jin-qiang Liang, Zeng-gui Kuang, Yun-cheng Cao, Duo-fu Chen, 2019. Numerical studies of gas hydrate evolution time in Shenhu area in the northern South China Sea, China Geology, 2, 49-55. doi: 10.31035/cg2018054
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Numerical studies of gas hydrate evolution time in Shenhu area in the northern South China Sea
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Abstract
Although the Shenhu sea area has been a topic and focus of intense research for the exploration and study of marine gas hydrate in China, the mechanism of gas hydrate accumulation in this region remains controversial. The formation rate and evolution time of gas hydrate are the critical basis for studying the gas hydrate formation of the Shenhu sea area. In this paper, based on the positive anomaly characteristics of chloride concentration that measured in the GMGS3-W19 drilling site is higher than the seawater value, we numerically simulated the gas hydrate formation time of GMGS3-W19 site. The simulation results show that the gas hydrate formation rate positively correlates with the chloride concentration when the hydrate reaches the measured saturation. The formation time of gas hydrate in the GMGS3-W19 site is approximately 30 ka. Moreover, the measured chloride concentration is consistent with the in-situ chloride concentration, indicating that the formation rate of gas hydrate at the GMGS3-W19 site is very fast with a relatively short evolution time.
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Keywords:
- Shenhu /
- South China Sea /
- Numerical simulation /
- Formation rate
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References
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Yun-xin Fang, Jing-an Lu, Jin-qiang Liang, Zeng-gui Kuang, Yun-cheng Cao, Duo-fu Chen, 2019. Numerical studies of gas hydrate evolution time in Shenhu area in the northern South China Sea, China Geology, 2, 49-55. doi: 10.31035/cg2018054
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Figure 1.
Distribution of the GMGS3-W19 site in the Shenhu area (b) in the northern South China Sea (a, modified from Li JF et al., 2018).
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Figure 2.
Fitted porosity and temperature of the W19 site.
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Figure 3.
Simulated gas hydrate saturation (a), chlorine concentration (b), methane gas flux (c) and temperature (d) under the model conditions of k=0.04 kg2/(m3·a·mol), qg, z=220=−0.0065 kg/(m2·a), and t=150 ka. The dotted line of Fig. 3b is the chloride concentration that has been diluted after the gas hydrate is dissociated.
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Figure 4.
Simulated gas hydrate saturation (a), chloride concentration (b), methane gas flux (c) and temperature (d) under the conditions of constant k=1.0 kg2/(m3·a·mol), natural gas flux qg, z=220=−0.15 kg/(m2·a), and t=5 ka. The dotted line of Fig. 4b is the chlorine concentration that has been diluted after the gas hydrate is dissociated, indicating that the negative chloride anomaly is insignificant. The dashed line in Fig. 4d represents the background temperature while the solid line refers to the model temperature.
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Figure 5.
Simulated gas hydrate saturation (a), chloride concentration (b), methane gas flux (c) and temperature (d) under the model conditions of rate constant k=0.15 kg2/m3·a·mol, gas flux qg, z=220= −0.015 kg/m2·a, and t=30 ka. The dotted line in Fig. 5b is the chlorine concentration that has been diluted after the gas hydrate is dissociated, indicating that the negative chloride anomaly is insignificant.