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 3

Sensitivity of hydrate saturation to direct temperature measurements, absolute pre- and post-dissociation system pressures, and estimates of volumetric parameter: the absolute pressures are obtained by combination of gauge and ambient pressures. The volume of gas collected at the gas/water collector 𝑉_{𝐺𝑓(𝐺𝑊𝐶)} is obtained with the use of measured height and diameter of the gas column. The volume of hydrate forming gas-filled elements external to the specimen for which the material mass within is forced into the gas/water collector during collection of dissociation products 𝑉_ext is predetermined using mass of water occupying the corresponding volume at full water saturation, density of water, ambient temperature, and pressure. The pore volume of the hydrated host sediment 𝑉_𝑉𝑜 is obtained with the use of specimen dimensions (including height and the diameter), grain density, and mass of dry soil.

Test parameter	Sensitivity in terms of the change in hydrate saturation	Units	Range of validity^a
Pre-dissociation temperature (K) within the hydrated specimen	0.73480982	K^−1	274.15–283.15 K
Postdissociation temperature at the gas/water collector (K)	0.92676320	K^−1	290.15–297.15 K
Ambient room temperature (K)	0.15316374	K^−1	293.15–303.15 K
Pre-dissociation pressure (absolute) (kPa)	0.01702934	kPa^−1	9026.325–9276.325 kPa
Postdissociation pressure (absolute) at the gas/water collector (kPa)	0.59329482	kPa^−1	400–470 kPa
Volume of gas collected at the gas/water collector, 𝑉𝐺𝑓(𝐺𝑊𝐶) (cc)	0.04929067	(cm^3)^−1	5295–5357.5 cc
Volume of hydrate forming gas-filled elements external to the specimen for which the material mass within is forced into the gas/water collector during collection of dissociation products, 𝑉ext (cc)	1.14748275	(cm^3)^−1	21–26 cc
Pore volume of the hydrated host sediment immediately prior to testing, 𝑉𝑉𝑜 (cc)	1.60985040	(cm^3)^−1	143–148 cc

^aWithin the range of validity, hydrate saturation calculated as per section (b) of Table 2 exhibits a linear relationship with the test parameter.