Characterization of the sediments in a gas hydrate reservoir in the northern South China Sea: Implications for gas hydrate accumulation

Abstract

As a potential major energy resource, gas hydrates are widely found in sub-oceanic sediments and could play an important role in the future of fuels. Many studies have been applied on gas hydrates reservoir to understand its accumulation as well as potential industrial values, while the characteristics of sediments favoring gas hydrates accumulation are still unclear. Here, we investigate a gas hydrates reservoir in Shenhu area, Pearl River Mouth Basin, South China Sea (SCS), studying reservoir sediments features to understand controlling factors of gas hydrates accumulation. We sampled sediments of drilling site W19 in this area, which has thick, high saturation gas hydrate layers, for sediments' physical properties analysis (including the grain size, mineral composition, and specific surface area), as well as biological abundance in the gas hydrate-bearing layer and adjacent layers. The results show fine-grained turbidite sediments characterized by poor sorting, high foraminifera abundance, and low clay mineral content, are beneficial to gas hydrate accumulation, while suspended sediments characterized by fine sorting, high calcareous ultra-microfossil abundance, and high clay mineral content, are not conducive to gas hydrate accumulation. Based on these results, we propose that the gas hydrate accumulation in the SCS is controlled by multiple factors, including the sedimentary processes, sorting, biological abundance, mineral composition, and specific surface area. It could potentially reveal the regularity of gas hydrate accumulation on a global scale.