Analyzing the effects of inhomogeneity on the permeability of porous media containing methane hydrates through pore network models combined with CT observation

The permeability of porous media containing gas hydrates is of crucial importance in predicting the fluid flow behavior and gas production capacity during the exploitation of gas hydrate resource. Gas hydrates are generally unevenly distributed in the natural samples, the inhomogeneity of which could have significant impacts on the permeability properties. So here we extend our study on the permeability of heterogeneous hydrate-bearing porous media using pore network models combined with X-ray computed tomography (CT). The effects of varying pore/throat radii, non-even distribution of hydrates and fluid flow directions on the absolute and relative permeability are discussed. It is indicated that the rather high water saturation would significantly impact the gas permeation, which is not favorable for gas production. The microstructures of pores and throats would likely differ even under similar porosities; some pores may not have sufficient throats connected to them, limiting the fluid flow. The absolute permeability could also significantly vary with flow directions; the direction favorable for gas flow may not be true for water flow. This finding can be of help in case a preferential gas production is more required rather than water in the field test.