Gas chimneys are zones ofenhanced permeability, typically associated with high levelsof gas flux, but many of the mechanisms involved are unclear. Recent work in the Uk hasfocussed on characterizing a gas chimney in the UK through a unique anisotropy experimentThe proiect used Ocean Bottom Seismic with a variety of sources tuned to different frequenciesaiming to detect the frequency-dependence of anisotropy, Frequency-dependent anisotropy hasbeen tied theoretically to permeability and fracture scale lengths.

within the chimney and at a reference site. We measured shear-wave splitting and P-waveattenuation anisotropy, which varied markedly with frequency, with apparent correlation to fluidand fracture properties. Modelling ofthe results provided a plausible interpretation in terms ofthe fluid flow regime.