Water Permeability of Porous Media Containing Methane Hydrate as Controlled by the Methane-hydrate Growth Process
Hideki Minagawa, Ryo Ohmura, Yasushi Kamata, Jiro Nagao, Takao Ebinuma, Hideo Narita, Yoshihiro Masuda, 2009. "Water Permeability of Porous Media Containing Methane Hydrate as Controlled by the Methane-hydrate Growth Process", Natural Gas Hydrates—Energy Resource Potential and Associated Geologic Hazards, T. Collett, A. Johnson, C. Knapp, R. Boswell
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This chapter seeks to clarify the relation between fluid permeability and methane-hydrate saturation (Sh). The ultimate purpose is to estimate the theoretical expression by the equation K = K0(1 — Sh)N (where K0 is the apparent permeability at Sh = 0 and N is a constant) for input into methane-hydrate numerical simulators. However, the permeability of hydrate-bearing sediment strongly depends on the hydrate saturation, grain-size distribution, porosity, pore-size distribution, hydrate formation method, and so on. To clarify the relation between the permeability and methane-hydrate saturation, we measured the water permeability of methane-hydrate-bearing sediments with different hydrate saturations for three contrasting methane-hydrate formation methods: (1) the connate water reaction method, (2) the gas diffusion method, and the (3) cementing method. The results demonstrate that the rate of decrease in the apparent water permeability (AWP) with increasing methane-hydrate saturation differs for each method of gas-hydrate formation. In addition, the values of K and N in the theoretical expression K = K0(1 — Sh)N were estimated for each production method, and a different N value was obtained for each hydrate formation method. It is apparent that the method of gas-hydrate formation leads to a contrasting geometry of methane-hydrate growth at the pore scale and in turn affects the macroscopic AWP saturation relations.
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In September 2004, the American Association of Petroleum Geologists (AAPG) convened a Hedberg Research Conference in Vancouver, British Columbia, Canada titled "Natural Gas Hydrates: Energy Resource Potential and Associated Geologic Hazards." As a continuation of the Hedberg Research Conference in Vancouver, the conveners of the conference and the editors of this Memoir have worked with more than 150 authors and coauthors to prepare this Memoir on gas hydrates. This publication follows the goals of the Hedberg conference; however, the contents of this Memoir were expanded to include all aspects of gas hydrates in nature. This Memoir contains 39 individual contributions, ranging from long topical summaries to shorter focused research papers. This Memoir has been published in two parts, with digital versions of all the complete research papers included on the enclosed CD. The hardcopy portion of the Memoir includes abstracts and several key figures for each of the contributions along with a complete copy of a gas hydrate technical review. The digital portion of this Memoir has been organized into a series of topical sections consisting of review articles, marine gas hydrate papers, and gas hydrate laboratory and modeling studies. Because of the rapidly emerging worldwide interest in gas hydrates, this comprehensive treatise on the geology of gas hydrates will be valuable to both the gas hydrate research community and exploration/development geologists working in arctic and deep marine environments.