Overview and introduction: Pressure core-sampling and analyses in the 2012–2013 MH21 offshore test of gas production from methane hydrates in the eastern Nankai Trough

This volume describes processes used in and results from laboratory measurements and analyses of core samples taken from methane hydrate-bearing sediments in a methane hydrate concentrated zone in the eastern Nankai Trough. The core analysis program was conducted under a Japan–US collaboration. Several pressure-preserved core samples were recovered as part of the research program that supported the world's first gas production trial from a marine gas-hydrate deposit in the area. To maintain physical properties of the core samples under in situ conditions and not allow the dissociation of the gas hydrates, preservation of the samples under pressure and temperature was necessary during sampling and analyses. To attain this goal, several new techniques were developed and employed for both core sampling and analysis operations. Multidisciplinary measurements for geological, geochemical, petrophysical, and mechanical data were performed on both pressure-preserved and conventional samples. The resulting data allow us to derive integrated and quantitative information about the nature of methane-hydrate-bearing sediments. This data and information are being used for reservoir characterization at the production test site and to improve our understanding of the behavior of methane-hydrate reservoirs during and after gas production.