Measurement of gas-water relative permeabilities in hydrate systems

Abstract

Gas hydrates are considered to be an alternative energy resource of the future, as they exist in enormous quantities in permafrost and the offshore environment. One of the primary mechanisms involved in hydrate decomposition in porous media is the gas-water two-phase flow in the formations. Despite their importance, these functions are poorly known due to the lack of fundamental understanding of gas-water flows and the difficulty of direct measurements for hydrate systems. As part of a major Alaska gas hydrate project, an experimental apparatus was designed and developed for forming gas hydrates in the laboratory and performing gas-water relative permeability experiments. In this study effective permeability and relative permeability across hydrate saturated consolidated Oklahoma 100 mesh sand and Anadarko field samples were measured. The results suggest that the relative permeability inferred from unsteady state core floods is a lumped parameter which not only includes hydrate saturation but also the effects of dissociation instabilities caused by fluid flow, fine migration and local compaction in porous media at low temperature. Furthermore, these properties are significantly altered by nature of hydrate distribution throughout the specimen, location within the pores, and concentration at specific locations.