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 two-phase 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, rock-physics 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.
