Thermal conductivity rocks

Varying rock thermal conduction If there is one type of rock that is conducting more heat than the surrounding rock, the rock with greater heat conduction will stay warmer than the surrounding one. In such cases water would be trapped and overpressure would occur when freezing. 

In fractured or cracked rocks, thermal conductivity is additionally influenced by the properties of crack-filling materials, fracture porosity, geometry, and distribution. 

Doveton, J.H., 1986. Log Analysis of Subsurface Geology. John Wiley Sons, New York. Drury, M.J., Jessop, A.M., 1983. The estimation of rock thermal conductivity from mineral content— an assessment of techniques. Zbl. Geol. PaliionL Teil 1, 35-48. 1983 H 1/2. Duffaut, K., Landro, M., 2007. Vp/Vs ratio versus differential stress and rock consolidation a comparison between rock models and time-lapse AVO data. Geophysics 72 (5), C81-C94. Dunham, R.J., 1962. Classification of carbonate rocks according to depositional texture. In Ham, W.E. (Ed.), Classification of Carbonate Rocks—A Symposium. AAPG Memoirs, 1, American Association of Petroleum Geologists, Tulsa OK/USA, pp. 108-121. 

Popov, Y.A., Pribnow, D.F.C., Sass, J.H., Williams, C.F., Burhardt, H., 1999. Characterization of rock thermal conductivity by high resolution optical scanning. Geothermics 28, 253-276. 

Wrong assumption about thermal properties of the rock, i.e., thermal conduction. 

Air temperature variations are reasonably well-reflected in the soil surface but disappear rapidly in depth at 50 cm depth daily variations are hardly significant, and only seasonal temperature fluctuations are registered. Almost similar situations occur in hard consolidated rocks. Those, although having a somewhat higher thermal conductivity than loose materials, do not... 

Uddin et al. (2008b) conducted several depressurization simulations for the Mallik 5L-38 well. Their results showed that the Mallik gas hydrate layer with its underlying aquifer could yield significant amounts of gas originating entirely from gas hydrates, the volumes of which increased with the production rate. However, large amounts of water were also produced. Sensitivity studies indicated that the methane release from the hydrate accumulations increased with the decomposition surface area, the initial hydrate stability field (P-T conditions), and the thermal conductivity of the formation. Methane production appears to be less sensitive to the specific heat of the rock and of the gas hydrate. 

Groundwater has a huge capacity to store heat (4181 J/kg/K). Rocks and minerals have a lesser (around 800 J/kg/K Mellon 2001), but still significant, heat capacity. They also have a certain thermal conductivity and these properties allow them to act as enormous subsurface heat storage and exchange reservoirs. Table 1 provides some examples of specific heat capacities and thermal conductivities. This heat, stored in the geological environment, can be extracted, manipulated and utilized. 

Table 1. The thermal conductivity anti specific volumetric heat capacity of selected rocks and minerals ...

Data from inter alia Sundbcrg 1991), Banks Robins (2002). Halliday Resnick (1978). Italics show recommended values cited by Eskilson el at. (2000). Note that thermal conductivity increases with quartz content, and that most rock materials have a specific heal capacity of around 800 J/kg/K, or slightly over 2 MJ/m /K (compare with copper at only 386 J/kg/K). 

Another proof of the importance of temperature is the fact that there is often a strict relationship between the run of isovols and the run of isotherms in deep profiles, both being influenced no doubt by the varying thermal conductivity of the different rocks. The strong influence of temperature on the rank of coal is obvious in the case of contact-metamorphic coals, whose rank increases distinctly when approaching the intrusive body. Apart from these geological observations, all experiments on artificial coalification have shown that temperature is the decisive factor in the coalification process. Thermodynamic and reaction kinetic considerations (9) also support this opinion. 

The low thermal conductivity of polyurethanes, plus the ease of application and structural properties of foamed-in-place materials, affords great freedom of design. As a result, rigid polyurethane foams have displaced rock wool and glass wool in freezers and refrigerators. 

Fountain D. M., Salisbury M. H., and Furlong K. P. (1987) Heat production and thermal conductivity of rocks from the Pikwitonei-Sachigo continental cross section, central Manitoba implications for the thermal structure of Archean crust. Can. J. Earth Sci. 24, 1583-1594. 

The thermal conductivity of a porous medium is a function of density, porosity, grainsize, shape, cementation, mineral composition and nature of the pore fillers (Somerton, 1992), i.e. the thermal conductivity is different for different types of rock. The heat flow in an inhomogeneous porous medium under conductive equilibrium conditions is given by... 

K-Tmleff = SL5/I (Lj/Kj) = effective thermal conductivity of the inhomogeneous porous medium of total thickness Az Ki = thermal conductivity of a rock unit of thickness Lj SLi = Az... 

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