Three internationally-partnered research well programs in 1998, 2002, and 2007-08 studied the Mallik gas hydrate accumulation in the Mackenzie Delta, Canada, and have allowed successful extraction of subpermafrost core samples with significant amount of hydrates. Gas hydrate bearing intervals were logged with a comprehensive suite of tools and their producibility was tested in 2002 using thermal stimulation and in 2007/08 using depressurization techniques. Thus, the Mallik gas hydrates are well-characterized and are ideal targets for testing geophysical imaging techniques. Here, we apply acoustic impedance inversion to 3D seismic data acquired over the Mallik area to characterize gas hydrate occurrences and to help define their spatial extent away from well control. The inversion method converts reflections into acoustic impedances from which velocity and hydrate saturation were estimated. The extent and geometry of the two lower hydrate zones were mapped with high confidence and show a distribution controlled by local geology. Correlation between the uppermost hydrate zone and the 3D seismic data could not be established with confidence, because of geological heterogeneity and/or inappropriate seismic imaging. The heterogeneity of the Mallik gas hydrates was parameterized following a method based on multivariate conditional stochastic simulation of well-logging data. Following this method, multi-dimensional heterogeneous models of petrophysical properties (Vp, Vs and density) of hydratebearing sediments were constructed and used to assess effects of heterogeneity on gas hydrate volume estimates. Models including small-scale heterogneities provide volume estimate nearly an order of magnitude lower than earlier estimates which did not include effect of heterogeneity.

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