The strength and rheology of methane clathrate hydrate

Abstract

[1] Methane clathrate hydrate (structure I) is found to be very strong, based on laboratory triaxial deformation experiments we have carried out on samples of synthetic, high-purity, polycrystalline material. Samples were deformed in compressional creep tests (i.e., constant applied stress, s), at conditions of confining pressure P = 50 and 100 MPa, strain rate 4.5 Â 10 À8 _ e 4.3 Â 10 À4 s À1 , temperature 260 T 287 K, and internal methane pressure 10 P CH4 15 MPa. At steady state, typically reached in a few percent strain, methane hydrate exhibited strength that was far higher than expected on the basis of published work. In terms of the standard high-temperature creep law, _ e = As n e À(E*+PV*)/RT the rheology is described by the constants A = 10 8.55 MPa Àn s À1 , n = 2.2, E* = 90,000 J mol À1 , and V* = 19 cm 3 mol À1 . For comparison, at temperatures just below the ice point, methane hydrate at a given strain rate is over 20 times stronger than ice, and the contrast increases at lower temperatures. The possible occurrence of syntectonic dissociation of methane hydrate to methane plus free water in these experiments suggests that the high strength measured here may be only a lower bound. On Earth, high strength in hydratebearing formations implies higher energy release upon decomposition and subsequent failure. In the outer solar system, if Titan has a 100-km-thick near-surface layer of highstrength, low-thermal conductivity methane hydrate as has been suggested, its interior is likely to be considerably warmer than previously expected.

Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluation of Technology and Potential

“…Working from a solid foundation of knowledge obtained from earlier studies (Sloan and Koh, 2008;Boswell, 2007), researchers gained a greater understanding of the complexity of hydrate accumulations through laboratory work (Waite et al, 2002;Durham et al, 2003;Winters et al, 2004;Gupta et al, 2006), numerical simulation analyses (Moridis and Reagan, 2007a,b;Moridis and Sloan, 2007), and national and international collaborative field experiments (Dallimore and Collett, 2005) (see discussion in following sections of this paper), and began the development of the precursors to tomorrow's hydrate exploration and evaluation technologies. By 2005, it was clear that, given certain reservoir conditions, production of methane from hydrate was technically feasible and potentially commercially viable through specially tailored application of existing technologies (Boswell, 2007).…”

“…China has pursued gas hydrates R&D for more than a decade (Fan et al, 2005) and conducted its initial drilling and coring program in the South China Sea in early 2007. That expedition found saturations of gas hydrate up to 40% in undeformed, clay-dominated sediments at a number of sites .…”

Feasibility of Large-Scale Ocean CO2 Sequestration

“…Researchers hypothesized that the bubble fabric forms when hydrate-coated gas bubbles collect during ascent through the sediment. Pure methane hydrate is much stronger than ice (Durham et al 2003); however, a bubble fabric likely has a very different geomechanical response. Although the presence of free gas has a solid foundation, the reason for it is still debatable.…”

Field Testing of Gas Hydrates - An Alternative to Conventional Fuels

“…Gas hydrates are seen as future generation energy resource [2]. Keeping into this various studies have been reported gas hydrates as potential energy resource [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. According to USA department of energy, if only feeble amount of the methane stored in the hydrates can be obtained, it will be more than the current domestic supply of USA of natural gas [17,18].…”

“…It is estimated that under the sea huge amount of methane of the order of trillion in the form of gas hydrate is present [1]. Hydrates are naturally occurring materials that are present on submarine continental margins and regions of Arctic permafrost [2][3][4]. Their presence is also supposed to be on large icy to medium-sized moons of the outer solar system [5,6] and also on the polar regions of Mars [7,8].…”