Abstract
Detailed knowledge of the effects of temperature on the thermal conductivity ( λ ) of rocks is essential for investigating the geothermal regime of basins and their thermal evolution. In this study, the λ of four rock types (carbonate, clastic, intrusive, and volcanic rocks) were measured at temperatures of 25°C, 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C using the Transient Plane Source (TPS) approach, which is accurate to ±3%. Experimental results demonstrate that the λ of carbonate and clastic specimens decrease strongly with increasing temperature. In contrast, the λ of intrusive and volcanic rocks are relatively insensitive to temperature. The temperature ( T ) dependence of λ can be classified into three groups in terms of the value of λ at 25°C. The first group is composed of rocks characterized by high λ (>4.5 W/m·K) at room temperature, for which the curves of λ − T exhibit a concave pattern. The second group consists of rocks with a moderate λ (2.5~3.5 W/m·K), in which the curves tend to be a straight line. The last group comprises rocks with a low λ (<2.5 W/m·K), exhibiting convex curves. There exists a close relationship between the λ at 25°C and its rate of decrease ( α ). The absolute value of α increases with the λ at 25°C rising. The relationship between the two values can be fitted by the equation y = a x + b 1 / x + c to derive the fitting parameters a , b , and c ; by this equation with known fitting parameters, the λ of the deep carbonate rocks of the Tarim Basin have been estimated.
Highlights
Thermal conductivity of rocks is an essential parameter in many fields such as constraining the dynamic evolution of planets, exploring the thermal state of basins, and utilizing geothermal resource
Majority of samples exhibit a decrease in thermal conductivity with temperature increase, there are considerable discrepancy in the slope dλ/dT and the extent of decrease from 25°C to 300°C among these samples
From the measured thermal conductivity of twenty-eight samples, the following conclusion can be derived: (1) Thermal conductivity of samples at 25°C reveals that the average of λ for carbonate and clastic rocks is greater than that of intrusive rocks and volcanic rocks
Summary
Thermal conductivity of rocks is an essential parameter in many fields such as constraining the dynamic evolution of planets, exploring the thermal state of basins, and utilizing geothermal resource. A large number of studies have been conducted on the calculation of heat flow and temperature in deep strata with demand for the exact data of thermal conductivity in situ, which cannot, be directly measured because of the limitation of current technology. Experimental measurements in high temperature or pressure are the sole approach to attain situ thermal conductivity of rocks. There exist only a few studies focusing on the factors influencing thermal conductivity for rocks in recent years. The experimental results showed that the λ of all samples were between 1.67 and 5.86 W/m·K, and the λ of feldspar aggregates and glasses with low-conductivity increased as temperature rise, whereas those samples having a high conductivity showed a negative temperature dependence. This study seemed to reveal a generalized conclusion that rocks with a relatively high thermal conductivity exhibit a stronger decrease in thermal conductivity with increasing temperature than those with lower λ
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