Estimating Pore Space Hydrate Saturation Using Dissociation Gas Evolution Measurements: In Relevance to Laboratory Testing of Natural or Artificially Synthesised Hydrate-Bearing Soil Specimens
Table 2
Hydrate saturation estimation with the use of simple and complex primary estimates at measured conditions; (a) complete hydrate formation is achieved in a water-rich environment allowing no free gas to be present immediately prior to testing; (b) complete hydrate formation is achieved in a gas-rich environment allowing no free water to be present immediately prior to testing; (c) incomplete hydrate formation in either water or gas rich environment leaving all three H-Lw-V phases in the system.
Principle of mass balance for methane/hydrate saturation
(a) At completion of hydrate formation in water-rich environment:
Calculated assuming two-phase H-Lw equilibrium under predissociation conditions
( is experimentally determined)
N/A
Calculated assuming two-phase Lw-V equilibrium under postdissociation conditions
Experimentally determined
is calculated assuming two-phase Lw-V equilibrium at conditions applicable to material mass present within . Gas-saturated water within connection tubing is at hydrate forming (or pre-dissociation pressure) and ambient room temperature. is experimentally determined.
N/A
(b) At completion of hydrate formation in gas-rich environment:
N/A
Calculated assuming two-phase H-V equilibrium under predissociation conditions
( is experimentally determined)
Calculated assuming two-phase Lw-V equilibrium under postdissociation conditions
Experimentally determined
is calculated assuming two-phase Lw-V equilibrium at conditions applicable to material mass present within . Vapour within is at hydrate forming (or pre-dissociation pressure) and ambient room temperature. is experimentally determined.
N/A
(c) For hydrate formation in gas-rich environment where the formation is incomplete leaving all H-Lw-V phases in the system:
Thermodynamic state of the system is difficult to define
Calculated assuming two-phase H-Lw equilibrium under pre-dissociation conditions
(neglecting the change in water volume due to gas dissolution + change in water volume due to evaporation into the gas phase) Volume of water consumed in the hydrate formation
Calculated assuming two-phase H-V equilibrium under pre-dissociation conditions
( is experimentally determined)
Calculated assuming two-phase Lw-V equilibrium under post-dissociation conditions
Experimentally determined
is calculated assuming two-phase Lw-V equilibrium at conditions applicable to material mass present within . Vapour within is at hydrate forming (or pre-dissociation pressure) and ambient room temperature. is experimentally determined.
