Physical properties of hydrate‐bearing sediments

Abstract

[1] Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate-bearing sediments to changes in mechanical, thermal, or chemical boundary conditions. These predictions are vital for mitigating borehole, local, and regional slope stability hazards; optimizing recovery techniques for extracting methane from hydrate-bearing sediments or sequestering carbon dioxide in gas hydrate; and evaluating the role of gas hydrate in the global carbon cycle.

A theoretical model for predicting the spatial distribution of gas hydrate dissociation under the combination of depressurization and heating without the discontinuous interface assumption

“…The in-situ data show that the magnitudes of the pressures and the temperature in the production wells normally stay at (1.8-7.3) Â 10 6 Pa and 3.4 Â 10 2 K respectively. In addition, the magnitudes of the density, the specific heat and the thermal conductivity of HBS naturally stayed at (0.9-2.6) Â 10 3 kg/m 3 , (0.8-4.2) Â 10 3 J/kg/K and (1.0-4.0) Â 10 0 W/m/K respectively (Sun et al, 2005;Waite et al, 2009). Besides, the parameters in the absolute and relative permeability models and the model of intrinsic kinetic of GH dissociation are constant (Table 2).…”

“…5.00 ϕ 0.25 Κ 0 (mD) 1.00 Table 2 Properties of the hydrate-bearing sediment (Sun et al, 2005;Waite et al, 2009). and the temperature after TInF obviously increases because of the energy transferred from the production well.…”

“…Based on HCoF, Zone II can be further separated into two subzones: a heating subzone, and a following non-heating subzone. The temperature in the heating subzone increases as the heat can be directly provided by the production well, while the temperature in the non-heating subzone decreases and approaches the equilibrium temperature at pressure P well because of the endothermic nature of GH dissociation (Sloan and Koh, 2007;Waite et al, 2009). Therefore, the heat for GH dissociation is provided by the heat conduction from the production well in the heating subzone, and by the sensible heat of HBS in the non-heating subzone.…”

“…HBS can vary from Darcy to Millidarcy (Sun et al, 2005;Waite et al, 2009;Dai et al, 2011) in nature, Π 2 can change in several orders around one, causing the gas flow becomes from faster to slower than the conductive heat transfer. Unlike Π 2 , Π 3 naturally exceeds one, a fact that indicates that the water flow is usually slower than the conductive heat transfer.…”

“…GH dissociation, a phase transition from solid to liquid and gas, may result in dramatical changes of petrophysical, geophysical, and geochemical properties of hydratebearing sediments (HBS) during gas recovery from GH (Waite et al, 2009). Therefore, it is of great importance to have a thorough understanding of the spatial distribution of GH dissociation in sediments, size of the dissociation region and location of the dissociation front in particular Anderson et al, 2008;Ikegami et al, 2008;Primiero et al, 2008).…”