Widespread subseafloor gas hydrate in the Barents Sea and Norwegian Margin

Abstract

The distribution and concentration of subseafloor natural gas hydrate across margins is not well understood, because these systems are challenging to image and quantify remotely. Furthermore, it is unknown if shallow hydrate systems are linked to deeper oil and gas reservoirs. Herein, we analyze petroleum industry well logs with data in the gas hydrate stability zone and find that low concentrations of hydrate commonly occur below the seafloor in the Barents Sea and the Norwegian Margin. We observe hydrate in half of analyzed industry wells using a set of conservative criteria that requires a resistivity increase of at least 0.5 Ωm above background resistivity. Hydrate accumulations occur significantly above the base of the hydrate stability zone, in layers with thicknesses ranging from tens of centimeters to tens of meters. Moreover, we find that there is no relationship between wells with hydrate accumulations and deeper oil and gas reservoirs; hydrate is just as likely to occur above identified oil and gas reservoirs as in areas with dry holes (i.e., no oil or gas reservoir). We argue the low concentration of hydrate, the occurrence of hydrate significantly above the base of the gas hydrate stability zone, and the lack of association between hydrate occurrence and deeper oil and gas reservoirs implies that the gas in these hydrate systems is likely transported via diffusion and is primarily microbial in origin.