Using Thermal Conductivity to Build Better Geothermal Data

Presented by guest speaker Joseph de Luca


Thermal conductivity geothermal power plant

Geothermal power plant

Geothermal energy utilizes the flow of heat through the Earth to produce clean electricity with a minimized surface environmental footprint. This is currently achieved either through using hydrothermal resources natively present in deep subsurface fractures and pores, or by injecting water into hot, dry rock at depth and using the newly heated water for turbine-powered electricity generation. To be economically viable, sufficient heat must be available at shallow subsurface depths to minimize the expensive drilling and pumping costs associated with geothermal production, meaning steep geothermal gradients are required. In regions that are not tectonically or volcanically active, any geothermal potential lies in (1) decay heat from radiogenic intrusive rocks, or in (2) elevated heat flow through moderate-temperature sedimentary basins coupled with low thermal conductivity rocks acting as insulators in the basin fill. Where geothermal gradients in sedimentary basins are promising, thermal conductivity and effusivity must be assessed to create heat flow models and reconstruct the thermal history in the basin.

This webinar highlights the use of C-Therm’s TCkit, a low-cost capable kit that employs the Transient Plane Source (TPS) technique for doing basic thermal conductivity work – including geological samples, on an ongoing study aimed at developing geothermal gradient maps. The TPS technique does not require a contact agent, which might be particularly important to note when dealing with different levels of porosity in the samples.

For the region in the study, previous maps of geothermal gradients have not drawn from very extensive datasets, with some papers making assertions on geothermal potential based on information taken from as few as five drilling reports. The updated maps and databases pull critically assessed information from over 790 well and drilling reports primarily covering the southeastern half of the region. For comparison with existing thermal conductivity ranges of particular rock types, the study also tabulates measured thermal conductivities of nine rock types taken from core in selected boreholes across the region: Carboniferous – Triassic sandstone, mudstone, conglomerate, anhydrite, limestone, halite, and potash; Devonian granite, and Triassic basalt. Results from the sedimentary rocks are in general agreement with previously published work, which will be discussed in the webinar.


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