Thermal Conductivity of Frozen Sediments Containing Self-Preserved Pore Gas Hydrates at Atmospheric Pressure: An Experimental Study

Abstract

The paper presents the results of an experimental thermal conductivity study of frozen artificial and natural gas hydrate-bearing sediments at atmospheric pressure (0.1 MPa). Samples of hydrate-saturated sediments are highly stable and suitable for the determination of their physical properties, including thermal conductivity, due to the self-preservation of pore methane hydrate at negative temperatures. It is suggested to measure the thermal conductivity of frozen sediments containing self-preserved pore hydrates by a KD-2 needle probe which causes very little thermal impact on the samples. As shown by the special measurements of reference materials with known thermal conductivities, the values measured with the KD-2 probe are up to 20% underestimated and require the respective correction. Frozen hydrate-bearing sediments differ markedly in thermal conductivity from reference frozen samples of the same composition but free from pore hydrate. The difference depends on the physical properties of the sediments and on changes in their texture and structure associated with the self-preservation effect. Namely, it increases proportionally to the volumetric hydrate content, hydrate saturation, and the percentage of water converted to hydrate. Thermal conductivity is anisotropic in core samples of naturally frozen sediments that enclose visible ice-hydrate lenses and varies with the direction of measurements with respect to the lenses. Thermal conductivity measurements with the suggested method provide a reliable tool for detection of stable and relict gas hydrates in permafrost.

Heat and water flux modeling in an earth dam

“…For silty sand having quartz content of 64%, the water content of 15%, and dry density of 1.77 g/cm 3 , reported thermal conductivity of 1.04 W/mK at the unfrozen state and 1.61 W/mK at the frozen state of À6°C. (Chuvilin & Bukhanov 2019). The thermal conductivity of sand collected from two places had avalue of 1.9, 1.25 at 20% water content.…”

“…Experimental investigations were carried, and an application range of various soil thermal conductivity was recommended, based on various soil states, texture, and water content. Chuvilin & Bukhanov (2019) conducted an experimental study to determine the thermal conductivity of frozen soil at gas pressure below equilibrium using a KD-2 needle probe which caused a little impact on the soil samples in the study area. Kurz et al (2017) presented experimental laboratory results to estimate the thermal conductivity of frozen and unfrozen soil samples of clay, silt, and peat subjected to seasonal freezing and thawing at the study area.…”

Non-Isothermal Kinetic Model of the Methane Hydrate Dissociation Process at Temperatures Below Ice Melting Point

“…Here m is the mass, kg; indices H, I, G refer to hydrate, ice, and gas, respectively; r is the rate of gas formation during decomposition of the hydrate, kg/s; j g is the loss of gas mass due to mass transfer with the environment, kg/s. The thermal conductivity of a hydrate particle is of the order of 0.5 W/m/K [44]. Therefore, at moderate heating rates, it can be assumed with good accuracy that the Biot number for particles of the order of 1 mm is quite small.…”

Insights into the climate-driven evolution of gas hydrate-bearing permafrost sediments: implications for prediction of environmental impacts and security of energy in cold regions

“…31 Although ETC of gas hydrate-bearing sediments has been extensively investigated at unfrozen conditions, little work has been carried out at frozen conditions to the best of our knowledge. [32][33][34][35] There is also another challenge when investigating the thermal response of natural gas hydrate-bearing sediments: how to distinguish methane hydrates from water despite their quite similar intrinsic thermal conductivity values. 23 In this article, we report experimental measurements of the elastic wave velocities and ETC of methane hydrate-bearing permafrost sediment samples at a typical range of temperature in permafrost and different hydrate saturations (up to 60%).…”