Gas clathrate hydrate water cavities: (a) pentagonal dodecahedron , (b) tetrakaidecahedron , (c) hexakaidecahedron , (d) irregular dodecahedron , and (e) icosahedron .
Burning methane hydrate snowball on the grill (left, courtesy of P. Walz, MBARI, the Monterey Bay Aquarium Research Institute). Crystal structure of sI methane hydrate comprised of and cages with methane guest molecules in blue (right, Ref. 3).
Schematic showing predicted sigma ranges (sigma is effectively the size of the molecule), where a sI to sII transition (thermodynamic) occurs in a binary system of two sI formers. Reprinted with permission from K. C. Hester, Ph.D. thesis, Colorado School of Mines, 2007.
Cartoon of PVCap interacting with a partial hydrate cage.
Raman cell showing the hydrate morphology: (a) before and (b) after the unexpected transformation. Reprinted with permission from J. M. Schicks, R. Naumann, J. Erzinger, K. C. Hester, C. A. Koh, and E. D. Sloan, J. Phys. Chem. B 110, 11468 (2006). Copyright © 2006, American Chemical Society.
Very high pressure (0.3–2.1 GPa) structural changes in gas hydrates at room temperature. Numerical values (adjacent to square boxes) indicate transition pressures. Hexagonal (sH) and tetragonal (sT) hydrate phases are distinct from sH and sT hydrate structures found at normal pressures (Ref. 1. Reprinted with permission from H. Hirai, T. Tanaka, K. Kawamura, Y. Yamamoto, and Y. Yagi, J. Phys. Chem. Solids 65, 1555 (2005). Copyright © 2006, Elsevier.
The locations of natural gas hydrate deposits on shore within and beneath the permafrost, and off shore along the continental margins. Reprinted with permission from K. Kvenvolden.
Resource pyramids of arctic and oceanic hydrated deposits (left) and all other conventional resources (right) in the United States. Reprinted with permission from R. Boswell and T. Collett, 2006.
Recovered cores containing gas hydrates from Arctic deposits from Mount Elbert, Alaskan North Slope (top left; reprinted with permission from R. Boswell and T. Collett, 2006) and the Mallik Well, MacKenzie Delta, Canada (bottom left; reprinted with permission from T. S. Collett, M. Riedel, J. R. Cochran, R. Boswell, P. Kumar, and A. V. Sathe, unpublished), and from an oceanic deposit in the Krishna-Godavari Basin, India (right; courtesy of M. R. Walsh, CSM).
Hydrate production methods of depressurization (left), thermal stimulation (middle; for inhibitor injection, hot fluids can be replaced with methanol, glycols, or other chemicals), and exchange (right).
Mallik2002 short-term production test showing the gas flare from gas produced from hydrate under the permafrost. Reprinted with permission from S. R. Dallimore, T. S. Collett, eds., Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program. Copyright © 2005 by Scott Dallimore and Tim Collett.
The effect of the hydrate formation method on the hydrate growth mechanism. The physical properties of hydrate-bearing sediment depend on the size and distribution of hydrate (black) relative to the sediment grains (gray). Redrawn with permission from W. F. Waite et al., in press.
Physical (white and yellow hydrate, top) and chemical (Raman spectra: white hydrate) heterogeneities of hydrate mounds in Barkley Canyon. The white hydrate has components up to isobutane in all specimens. Reprinted with permission from K. C. Hester, Ph.D. thesis, Colorado School of Mines, 2007.
Structural properties of clathrate hydrates (Ref. 1).
Comparison of the mechanical, thermal, and physical properties of ice, sI, and sII hydrates (Ref. 1).
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