A Monte Carlo Model of Gas-Liquid-Hydrate Three-phase Coexistence Constrained by Pore Geometry in Marine Sediments

Gas hydrates form at relatively high pressures in near-surface, organic-rich marine sediments, with the base of hydrate stability field and onset partial gas saturation determined by temperature increases depth. Because pore-scale curvature wetting effects, transition between free occurrence need not take place a distinct depth or boundary, but instead can be characterized zone finite thickness which methane bubbles crystals coexist same aqueous solution. Previous treatments have idealized pores as spheres cylinders, real sediment grains irregular, largely convex walls that enable highly curved surfaces and/or within given pore to change varying conditions. In partially hydrate-saturated for example, gas–liquid surface energy perturbs equilibrium an amount proportional bubble-surface curvature, causing commensurate solubility liquid phase. This is also constrained coexisting hence volume occupied As result, three-phase depends only on space geometry, levels gaseous phases. We evaluate local geometrical constraints synthetic 3D packing spherical particles resembling granular relate changes relative proportions phases conditions, demonstrate how boundaries are displaced function size, while level. The predicted varies from tens hundreds meters, inversely dependent host grain dramatically when near complete gas, requiring interfacial curvatures become large.