Analysing sand-dominated channel systems for potential gas-hydrate-reservoirs using an AVO seismic inversion technique on the Southern Hikurangi Margin, New Zealand

Gas hydrates have recently been recognised as a class of unconventional petroleum resource and the economic viability of gas production from hydrates is now being viewed as a realistic possibility within the next decade. Therefore, potential offshore hydrate accumulations in the world-class endowed gas hydrate province, the Hikurangi Margin, New Zealand, represent a significant medium- to long-term opportunity to meet the country's future energy requirements.In this paper we delineate a potential gas hydrate reservoir in the East Coast Basin, New Zealand and quantitatively estimate its gas hydrate concentrations from 2D seismic data with no well information available.The target is interesting for exploration since it shows evidence for gas-hydrate bearing sands, in particular, buried channel systems. We use a combined analysis of high-resolution velocity analysis, amplitude-versus-offset (AVO) attribute and AVO inversion to investigate whether we can identify regions that are likely to contain highly concentrated gas hydrates and whether they are likely to be sand-dominated. To estimate hydrate concentrations we apply a rock physics model.Our results indicate the presence of several – up to 200 m thick – zones that are likely to host gas hydrates, with one location predicted to consist of high-permeable channel sands and an inferred gas hydrate saturation of ∼25%. These findings suggest significant amounts of gas hydrates may be present in high-quality reservoirs on this part of the margin.

► 2D seismic data is examined for gas hydrate deposits, offshore New Zealand.
► We perform velocity analysis, AVO attributes & inversion and rock-physics modelling.
► Our results indicate the presence of gas hydrates.
► We predict high-permeable channel sands with a gas hydrate saturation of 25%.