Identification of pore-filling gas hydrate deposits in marine sediments based on amplitude-versus-angle study

Abstract

Gas hydrate is regarded as an alternative energy source to fossil fuels in the future. In particular, the pore-filling gas hydrate has the advantages of wide distribution and large reserves, which is of great significance for commercial exploitation. We focus on the amplitude-versus-angle (AVA) patterns of reflection interfaces overlying by different pore-filling minerals deposits in order to identify gas hydrate from marine sediments. The AVA responses of different reflection models are obtained based on rock physics model and approximated Zoeppritz equation. The theoretical results show class III AVA patterns for pore-filling gas hydrate deposits and class IV AVA patterns for other pore-filling minerals deposits. In addition, we analyze the effect of gas saturation and different minerals saturation on the AVA patterns. The prestack seismic data of sites GMGS2-08 and GMGS2-16 in South China Sea is processed and the common reflection point (CRP) gathers are applied to verify our theoretical results. The AVA patterns of actual reflection interface overlying by pore-filling gas hydrate deposits and other pore-filling minerals deposits are class III and IV, respectively, in agreement with theoretical results. And the class IV AVA responses for reflection interfaces overlying by fracture-filling gas hydrate studied by predecessors are also tested in our study area. We then propose a new approach to identify pore-filling gas hydrate from marine sediments by AVA analysis.

Keywords

• Gas hydrate
• AVA analysis
• Rock physics model
• Shuey’s equation