Modeling the physical properties of hydrate-bearing sediments: Considering the effects of occurrence patterns

Investigating the dependence of the physical properties of hydrate-bearing sediments (HBS) on hydrate occurrence patterns and saturation levels is crucial for exploring gas hydrate resources. However, precise analysis of these effects remains challenging due to limitations in current experimental techniques and numerical modeling methods that cannot accurately control the hydrate saturation and distribution patterns. In this work, to address such issues, we propose a novel hybrid modeling approach integrating X-ray CT imaging technology, morphological operation algorithm, and quartet structure generation set method. Then, we generate 75 samples containing pore-floating, cementing, as well as bridging hydrates, each with predefined saturation levels, and comprehensively investigate the effects of the hydrate distribution patterns and saturation on the pore radius, coordination number, correlation functions, permeability, electrical conductivity, and elastic moduli of HBS. The findings indicate that the heterogeneity of pore and throat radius distributions varies across different hydrate types. The increase in pore-floating hydrate leads to the most rapid decline in the pore and throat radii, tortuosity, and pore-space correlation, but it makes the average coordination number larger while the others decrease the number. Moreover, the cementing patterns cause the weakest damage to the permeability and electrical conductivity with low hydrate saturation. When the hydrate saturation is larger than about 45%, the bridging pattern has the greatest effect on the mass transport properties. Furthermore, the pore-floating and bridging patterns cause the largest and smallest increase in the elastic moduli, respectively. The hydrate occurrence pattern causes a larger effect on the bulk modulus than the shear modulus.