Rock physics calculation and pre-stack inversion of shear modulus parameters for natural gas hydrate-bearing sediments

To accurately estimate gas hydrate content using seismic data, two key problems are needed to be solved: the first is to establish the quantitative relationship between the elastic parameters and physical parameters of hydrate-bearing sediments; the second is to establish the quantitative relationship between seismic pre-stack data and the elastic parameters. In view of the above problems, we combined the microscopic structure of gas hydrate-bearing sediments in Shenhu area on the focus of its characteristics of non-zero shear modulus, used the uncoupled differential effective medium (DEM) theory and patchy saturation theory to carry out the modeling of rock physics, and established the nonlinear relationship between gas hydrate saturation and elastic parameters. Through the analysis of sensitivity and crossplots of elastic parameters, we determined that the shear modulus is a good indicator to the hydrate content. Using the pre-stack Bayesian seismic inversion method, the shear modulus of hydrate-bearing sediments were extracted from the pre-stack seismic data, and the natural gas hydrate was effectively identified. The method in this study can provide a technical support for the identification and prediction of natural gas hydrate in sea areas.