Study on the effects of natural gas hydrate cementation mode on the physical properties of rocks

In order to investigate the effects of the natural gas hydrate cementation mode on the physical properties of rocks, three-dimensional digital rocks with different hydrate cementation modes were constructed using the process simulation method and algorithm of hydrate cementation and growth; the finite element method and lattice Boltzmann method were then used to simulate the physical properties of rocks. The results show that the hydrate cementation mode has a great influence on the rock conductivity, stiffness and pore connectivity, controlling resistivity, the elastic modulus, permeability and other physical property parameters of rock respectively. Under the same hydrate saturation conditions, rock with hydrate occurring in the throats has a high resistivity, high elastic modulus and high permeability; whereas rock with hydrate precipitating within pores has low resistivity, low elastic modulus and low permeability. Among the three simulated hydrate cementation mode scenarios, the resistivity and elastic modulus all increase with the increase of hydrate saturation, however, rock permeability decreases with the increase of hydrate saturation. Rock with hydrate occurring in the pore throats is the most sensitive mode to the electricity and elasticity parameters of the three cementation modes, and rock with hydrate precipitating within pores is the most sensitive mode to permeability.