Relative permeability to water or gas in the presence of hydrates in porous media from critical path analysis

Most existing models for predicting relative permeability in the presence of hydrate are either empirical or based on simplistic representations of the pore system and hydrate growth. Multiple models are often needed to explain relative permeability behavior observed in the laboratory over different ranges of hydrate saturation. Critical path analysis (CPA) offers a framework for predicting relative permeability based on pore system properties, including the percolation threshold and breadth of the pore size distribution. Using an existing method developed for partially saturated soils, I show that CPA can accurately predict relative permeability to either water or gas over the entire range of measured hydrate saturation for several suites of laboratory measurements. The method does not require any assumption of hydrate growth habit, and assumes that hydrate tends to grow in the largest pores first. This work represents an improvement in understanding the link between pore structure and transport properties of hydrate-bearing sediment.