Numerical modeling of methane hydrate accumulation with mixed sources in marine sediments: Case study of Shenhu Area, South China Sea
Numerical modeling of methane hydrate accumulation with mixed sources in marine sediments: Case study of Shenhu Area, South China Sea
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海洋沉积物中混合源甲烷水合物聚集的数值模拟——以南海神狐海域为例
DOI：
10.1016/j.margeo.2020.106142
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发表时间：
2020-05
期刊：
影响因子：
2.9
通讯作者：
Tian Hailong
中科院分区：
文献类型：
--
作者：
Zhu Huixing;Xu Tianfu;Zhu Zhenyu;Yuan Yilong;Tian Hailong
南海神狐海域发现的天然气水合物被认为具有巨大的开发潜力，成为研究热点。然而，该地区天然气水合物长期动态聚集演化过程的细节仍不清楚。在本研究中，我们通过将生物产甲烷模块引入到现有模拟器 TOUGH+HYDRATE 的框架中，开发了一个数值模型来预测海洋沉积物中天然气水合物的积累。应用一维动力学模型再现了神狐地区SH2地点天然气水合物的形成过程。考虑了沉积物的埋藏和相关现象（例如，温度的演变、沉积物压实以及随后沉积物孔隙度和渗透率的降低、流体排出）。模拟结果表明，常规有机碳与甲烷的转换系数（CC）为0.15，原位生物甲烷的量不足以形成该位置检测到的高度饱和的水合物，剩余的甲烷（91.4%）由流体的向上流动供给。大约1.5 Ma发生的构造运动为流体垂直运移创造了通道。利用已证实的水合物饱和度剖面和从回收岩心样品中测量的孔隙水氯度，确定向上流体中的孔隙水和甲烷气体通量分别为2×10(-10)kg/s.m(2)和1×10(-11)kg/s.m(2)。沉积物中水合物的分布受孔隙水盐度的显着影响。盐对水合物形成的抑制作用，使三相（即固体水合物、甲烷气体和孔隙水）平衡压力向实际孔隙水压力转移，可能是水合物富集区出现三相共存带的主要原因。此外，水通量和盐的扩散率通过影响天然气水合物富集区孔隙水的盐度，对天然气水合物的形成产生深远的影响。该研究成果对指导海洋天然气水合物勘探和资源评价具有重要意义。
The natural gas hydrates detected in Shenhu Area, South China Sea are considered to have great potential for exploitation and to become a research hotspot. However, details of the dynamic accumulation and evolution processes of gas hydrate over a long time in this area remain unclear. In this study, we developed a numerical model to predict the accumulation of gas hydrates in the marine sediments by introducing the biogenic methanogenesis module to the framework of the existing simulator TOUGH+HYDRATE. A one-dimensional dynamic model was applied to reproduce the formation of gas hydrate at site SH2 in Shenhu Area. The burial of sediments and associated phenomena (e.g., evolution of temperature, sediment compaction and consequent reduction in sediment porosity and permeability, fluid expulsion) are taken into account. Modeling results indicate that with the conventional conversion coefficient (CC) of organic carbon to methane of 0.15, the amount of in-situ biogenic methane is not sufficient to form the highly saturated hydrate detected at this location and the remaining methane (91.4%) is supplied by the upward flow of fluids. The tectonic movement that took place about 1.5 Ma created pathways for the fluids to migrate vertically. The pore water and methane gas fluxes in the upward fluids were determined as 2 x 10(-10) kg/s.m(2) and 1 x 10(-11) kg/s.m(2), respectively, using the proved hydrate saturation profile and measured pore water chlorinity from recovered core samples. The distribution of hydrate in the sediments is significantly influenced by pore water salinity. The inhibitory effect of salt on hydrate formation, which shifts the pressure of three-phase (i.e., solid hydrate, methane gas and pore water) equilibrium to actual pore water pressure, could be the major reason for the appearance of a three-phase co-existence zone in the hydrate concentrated zone. Additionally, the water flux and diffusivity of salt have a profound effect on the formation of gas hydrate by affecting the salinity of pore water in the gas hydrate concentrated zone. The results of this study are of great significance for guiding marine gas hydrate exploration and resource evaluation.
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影响因子：
5.3
作者：
A. Milkov;G. Dickens;G. Claypool;Youngjoo Lee;W. Borowski;M. Torres;Wenyue Xu;H. Tomaru;A. Tréhu
通讯作者：
A. Milkov;G. Dickens;G. Claypool;Youngjoo Lee;W. Borowski;M. Torres;Wenyue Xu;H. Tomaru;A. Tréhu
DOI：
--
发表时间：
1992-12
期刊：
--
影响因子：
--
作者：
C. Clayton
通讯作者：
C. Clayton
影响因子：
4.2
作者：
S. Wegner;K. J. Campbell
通讯作者：
S. Wegner;K. J. Campbell
DOI：
--
发表时间：
2002
期刊：
--
影响因子：
--
作者：
M. Light;C. Solana
通讯作者：
M. Light;C. Solana
DOI：
10.2118/2116-pa
发表时间：
1970-02
期刊：
Journal of Petroleum Technology
影响因子：
--
作者：
H. L. Stone
通讯作者：
H. L. Stone