The fluid migration system and gas hydrate enrichment and accumulation in southern South China Sea

doi:10.3969/j.issn.1001-909X.2025.01.005

Abstract

Abstract:

The Zengmu-Beikang Basin, located in the southern South China Sea, was formed under a complex geological background, with a large number of oil and gas reservoirs developed, and various types of fluid flow structures widely distributed. Seismic data indicate that the fluid flow system composed of gas chimneys, faults, tubular channels, mud volcanoes, and mud diapirs in the southern South China Sea may be related to the accumulation of gas hydrates. Seabed seepage and bottom simulating reflection (BSR) indicate the possible existence of gas hydrates. The formation of gas chimneys originates from hydraulic fracturing caused by deep oil-gas accumulation, which transports fluids to shallow areas. The gas chimneys are related to BSR, indicating the enrichment of gas hydrates. Faults developed in deep and were connected to potential source rocks or reservoirs, thus accumulating a large amount of shallow gas and gas hydrates around the faults. Pockmark is also an indicative structure for seabed seepage and an area where cold seepage gas hydrates are usually enriched. The formation of mud volcanoes and mud diapirs not only leads to vertical fluid migration, but also triggers the shallow strata deformation and fault development. Therefore, the development areas of mud volcanoes and mud diapirs are also potential areas for gas hydrate enrichment. In addition, this article uses the volume method to estimate the gas hydrate resources in the Zengmu-Beikang Basin in the southern South China Sea. The results show that the gas hydrate resources in the Zengmu-Beikang Basin are approximately 1.62×10¹³ m³. The Zengmu-Beikang Basin has strong potential for gas hydrate resources and is a region worthy of attention for future gas hydrate exploration activities.

Key words: southern South China Sea, Zengmu-Beikang Basin, fluid flow, gas hydrate, oil-gas exploration

CLC Number:

P744.4

WANG Xiuping, YANG Pengcheng, LIU Fangyuan. The fluid migration system and gas hydrate enrichment and accumulation in southern South China Sea[J]. Journal of Marine Sciences, 2025, 43(1): 47-56.

Figures/Tables 7

Fig.1 Water depth and tectonic unit division map of Zengmu-Beikang Basin in southern South China Sea (Figure was redrawn from the reference [13].)

Fig.2 Comprehensive stratigraphic histogram of Zengmu Basin in southern South China Sea (Figure was redrawn from the reference [16].)

Fig.3 BSR seismic profiles related to gas chimneys and faults (Figures were redrawn from the references [13] and [17].)

Fig.4 Seismic reflection characteristics and pattern of tubular channels developed on the deep flow drift bodies of carbonate rocks (Figures were redrawn from the reference [13].)

Fig.5 Topographic characteristics, seismic reflection characteristics and formation pattern of submarine pockmarks (Figures were redrawn from the reference [23].)

Fig.6 Seismic reflection and seabed topography characteristics of mud volcanoes and mud diapirs (Figures were redrawn from the reference [22].)

Fig.7 Distribution map of seabed temperature (a) and geothermal gradient (b) in the South China Sea, and thickness of hydrate stability zone in southern South China Sea (c)

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