Bulk thermal conductivity of stable and dissolved methane hydrate-bearing zones

Abstract

Measurements of thermal conductivities in fully methane hydrate- and water saturated samples at steady state and no flow conditions are presented. The results were compared with four theoretical soil conductivity models, and their agreement in the presence of free gas was determined by experiments on partially- and fully methane saturated samples. Bulk thermal conductivity (k b) measurements at a steady temperature state led to accurate results, as they reduce the error of local heterogeneities or measurements inaccuracies by averaging a set of independent measurements. The geometric mean and the mixing model by Johansen (1975) resulted in close approximations of k b in fully hydrate- and water saturated conditions, while the former was preferred over the latter for its simplicity and reduced empiricism. However, in partially saturated sediment, the theoretical models tended to overestimate the effect of the free gas phase on the heat transfer mechanism, as the measured k b at 65 and 100% gas saturation was only slightly below that in the stable hydrate zone. A numerical simulation with the bulk thermal conductivity of 2.6 w/(mK) matched the measured temperature evolution in the transient phase. Free convection had no effect on the heat transfer in gas production scenarios from hydrate reservoirs, neither in stable- nor dissociated zones. This is an abstract of a paper presented at the Proceedings of the Twenty-Second International Offshore and Polar Engineering Conference (Rhodes, Greece 6/17-22/2012).