Characterization of Gas-Hydrate Sediment: In Situ Evaluation of Hydrate Saturation in Pores of Pressured Sedimental Samples

Abstract:

Hydrate saturation of gas-hydrate bearing sediment is a key of gas production from natural gas-hydrate reservoir. Developable natural gas-hydrates by conventional gas/oil production apparatus almost exist in unconsolidated sedimental layer. Generally, hydrate saturations of sedimental samples are directly estimated by volume of gas generated from dissociation of gas hydrates in pore spaces, porosity data and volume of the sediments. Furthermore, hydrate saturation can be also assessed using velocity of P-wave through sedimental samples. Nevertheless, hydrate saturation would be changed by morphological variations (grain-coating, cementing and pore-filling model) of gas hydrates in pore spaces. Jin et al.[1,2] recently observed the O-H stretching bands of H₂O molecules of methane hydrate in porous media using an attenuated total reflection IR (ATR−IR) spectra. They observed in situ hydrate formation/dissociation process in sandy samples (Tohoku Keisya number 8, grain size of ca. 110 μm). In this presentation, we present IR spectroscopy approach to in situ evaluation of hydrate saturation of pressured gas-hydrate sediments. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan.

[1] Jin, Y.; Konno, Y.; Nagao, J. Energy Fules, 2012, 26, 2242-2247.

[2] Jin, Y.; Oyama, H.; Nagao, J. Jpn. J. Appl. Phys. 2009, 48, No. 108001.