Permeability properties of hydrate-bearing sediments: Competition and conversion in hydrates growth

The permeability of reservoirs is an important factor restricting CO2 sequestration and CH4 hydrate exploitation, which is predicted by the hybrid models. However, these hybrid models fail to provide the calculation method and physical meaning of the weight parameters. Additionally, pore structure controls permeability by affecting the hydrates growth modes. In this work, a competition parameter was used to describe the modes evolution with increasing saturation, and its value range was determined using natural and laboratory samples. Then, the relationship between saturation, competition parameter, newly formed hydrates, and cumulatively formed hydrate was analyzed, respectively. The results indicate that a competitive cumulative effect exists in hydrates growth. Sh corresponding to the first derivative (equal to 1) of the ratio of PF hydrates in the newly formed hydrates is twice the first derivative maximum value of weighting parameter. This competition model could predict the mode evolution in hydrates growth and provide a new idea for industrial exploitation and simulation calculation.