Rock-physics models of hydrate-bearing sediments in permafrost, Qilian Mountains, China

摘要

Rock-physics models are constructed for hydrate-bearing sediments in the Qilian Mountains permafrost region using the K-T equation model,and modes Ⅰ and Ⅱ of the effective medium model.The K-T equation models the seismic wave propagation in a twophase medium to determine the elastic moduli of the composite medium.In the effective medium model,mode Ⅰ,the hydrate is a component of the pore inclusions in mode Ⅰ and in mode Ⅱ it is a component of the matrix.First,the P-wave velocity,S-wave velocity,density,bulk modulus,and shear modulus of the sediment matrix are extracted from logging data..Second,based on the physical properties of the main components of the sediments,rockphysics model is established using the K-T equation,and two additional rock-physics models are established assuming different hydrate-filling modes for the effective medium.The model and actual velocity data for the hydrate-bearing sediments are compared and it is found that the rock-physics model for the hydrate-filling mode Ⅱ well reproduces the actual data.