Prediction of Thermal Conductivity of Underground Rocks from P-Wave Velocity of Ultrahigh-Pressure Metamorphic Rocks
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摘要: 岩石热导率是了解地球内部热传导过程的重要参数之一, 但热导率的测量在室内和野外都比较复杂.如何利用容易获得的岩石物理参数(如超声波速度) 来估算岩石的热导率就显得非常重要.通过对中国大陆科学钻探(CCSD) 主孔655件样品热导率和超声波速度的相关分析, 把样品分为新鲜榴辉岩、退变质榴辉岩、副片麻岩和正片麻岩4类, 并分别建立了利用岩石P波速度估算热导率的计算方程.回归计算表明, 榴辉岩热导率和P波速度之间的相关性较大, 相关系数在0.7左右, 片麻岩显示的相关系数比较小, 在0.4~0.5之间.鉴于样本数量较大, 这种结果足以表明热导率和P波速度之间可以用给定的线性关系来表达.为了检验获得的方程, 在CCSD主孔中选取典型的岩性单元, 利用测得的P波速度估算相应的热导率, 结果显示估算值和实测热导率平均值非常接近, 表明利用P波估算岩石热导率的方程是可行和实用的, 为本区和相似地区大地热流和热结构计算提供了热导率的计算方法和依据, 因而具有重要的岩石物理学和地球物理意义.Abstract: The relationship between thermal conductivity and ultrasonic velocity has been analyzed by using 655 samples from scientific boreholes drilled in Donghai, eastern China. The samples are classified into 4 different types: fresh eclogite, retrograde eclogite, orthogneiss and paragneiss. We established equations that enabled us to predict thermal conductivity from measuring the P-wave velocity of each type of rock. The regression analysis of thermal conductivity vs. ultrasonic velocity yields a correlation coefficient of about 0.7 for eclogite and 0.5-0.4 for gneiss. The result shows that the linear equation is sufficient to describe the relationship between thermal conductivity and ultrasonic velocity. For verifying these equations, we chose several typical lithology units of the CCSD mainhole to estimate thermal conductivity from P-wave velocity. The calculated values are consistent with the measured average value of thermal conductivity, which means these equations can be used to infer thermal conductivity for underground rocks through P-wave velocity in the Donghai region or similar area. These results are of great significance for thermal conductivity selection in thermal structure analysis or heat flow calculations.
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表 1 不同岩石热导率K和纵波速度Vp的回归分析结果
Table 1. Regression analysis of thermal conductivity versus P-wave velocity of different rocks
表 2 利用P波计算得到的热导率和实测热导率平均值的对比
Table 2. Comparison of measured thermal conductivity with calculated values from P-wave velocity
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[1] Burkhardt, H., Honarmand, H., Pribnow, D., 1995. Testmeasurements with a new thermal conductivity boreholetool. Tectonophysics, 244 (1-3): 161-165. doi: 10.1016/0040-1951(94)00224-W [2] Chapman, D. S., 1986. Thermal gradients in the continental crust. In: Dawson, J. B., ed., The nature of the lower continental crust. Geological Society Special Publication, 24: 63-70. [3] Chi, Q. H., Yan, M. C., 1998. Radioactive elements of rocks in North China platform and the thermal structure and temperature distribution of the modern continental lithosphere. ChineseJ. Geophys., 41 (1): 38-47 (in Chinese with English abstract). [4] Demirci, A., Grgülü, K., Durutürk, Y. S., 2004. Thermalconductivity of rocks and its variation with uniaxial and triaxial stress. International Journal of RockMechanics and Mining Sciences, 41: 1133-1138. doi: 10.1016/j.ijrmms.2004.04.010 [5] Durutürk, Y. S., 1999. The variation of thermal conductivity with pressure in rocks and the investigation of its effect in underground mines. Cumhuriyet University, Sivas, Turkey, 188. [6] Grgülü, K., 2004. Determination of relationships between thermal conductivity and material properties of rocks. Journal of University of Science and Technology, Beijing, 11: 297. [7] Hartmann, A., Rath, V., Clauser, C., 2005. Thermal conductivity from core and well log data. International Journal of Rock Mechanics and Mining Sciences, 42: 1042-1055. doi: 10.1016/j.ijrmms.2005.05.015 [8] Lee, T. C., 1989. Thermal conductivity measured with a line source between two dissimilar media equals their mean conductivity. J. Geophys. Res., 94 (B9): 12443-12447. doi: 10.1029/JB094iB09p12443 [9] zkahraman, H. T., Selver, R., Isik, E. C., 2004. Determination of the thermal conductivity of rock from P-wave velocity. International Journal of Rock Mechanics and Mining Sciences, 41: 703-708. doi: 10.1016/j.ijrmms.2004.01.002 [10] Popov, Y., Tertychnyi, V., Romushkevich, R., etal., 2003. Interrelations between thermal conductivity and other physical properties of rocks: Experimental data. PureAppl. Geophys., 160: 1137-1161. [11] Pribnow, D., Williams, C. F., Burkhardt, H., 1993. Well logderived estimates of thermal conductivity in crystalline rocks penetrated by the 4 km deep KTB Vorbohrung. Geophys. Res. Lett., 20 (12): 1155-1158. doi: 10.1029/93GL00480 [12] Prinow, D., Sass, J. H., 1995. Determination of thermal conductivity for deep boreholes. J. Geophs. Res., 100: 9981-9994. doi: 10.1029/95JB00960 [13] Sass, J. H., Lachenbruch, A. H., Moses, T. H., 1992. Heat flow from a scientific research well at Cajon Pass, California. J. Geophys. Res., 97 (B4): 5017-5030. doi: 10.1029/91JB01504 [14] Seipold, U., Raab, S., 2000. A Method to measure thermal conductivity and thermal diffusivity under pore and confining pressure. Phys. Chem. Earth., 25 (2): 183-187. [15] Shen, X. J., Yang, S. Z., Shen, J. Y., 1995. Heat flow study and analysis along the Golmud-Ejinaqi geotransect. Chinese J. Geophys., 38 (Suppl. II): 86-97 (in Chinese with English abstract). [16] Silliman, S. E., Neuzil, C. E., 1990. Borehole determination of formation thermal conductivity using a thermal pulse frominjected fluid. J. Geophys. Res., 95 (B6): 8697-8704. doi: 10.1029/JB095iB06p08697 [17] Singh, T. N., Sinha, S., Singh, V. K., 2006. Prediction of thermal conductivity of rock through physico-mechanical properties. Building and Environment (in press). [18] Williams, C. F., Anderson, R. N., Broglia, C., etal., 1988. In situinvestigations of thermal conductivity, heat production, and hydrothermal circulation in the Cajon Pass scientific drillhole, California. Geophys. Res. Lett., 15 (9): 985-988. doi: 10.1029/GL015i009p00985 [19] 迟清华, 鄢明才, 1998. 华北地台岩石放射性元素与现代大陆岩石圈热结构和温度分布. 地球物理学报, 41 (1): 38-47. doi: 10.3321/j.issn:0001-5733.1998.01.005 [20] 沈显杰, 杨淑贞, 沈继英, 1995. 格尔木-额济纳旗地学断面热流分析与研究. 地球物理学报, 38 (增Ⅱ): 86-97.