New approach to the thermal properties of carbonate rocks in geothermal reservoirs: Molecular dynamics calculation and case studies

Abstract

Carbonate rocks are one of major geothermal reservoir types around the world. Understanding the thermal properties of carbonate rocks is of significance to the assessment and utilization of deep geothermal reservoirs. Different from conventional test methods, this paper introduced a new approach, molecular dynamics calculation (MDC), to studying the thermal properties of carbonate rocks. By means of MDC, the thermal properties including specific heat, thermal conductivity and thermal diffusivity of four types of carbonate rocks including calcite, dolomite, magnesite, and smithsonite were investigated. The intrinsic relationship among the Debye temperature, elastic and thermal properties of carbonate rocks was revealed. The variations of the thermal properties with the average atom weight and temperature (300–800K) were obtained and regressed as functional formulas for applications. Further, taking carbonate rock samples from North China as an example, the specific heat and thermal conductivity were tested and compared with the MDC results based on actual lattice parameters by using X-ray diffraction method (XRD). The results showed that there was a good agreement between the test and calculation results. Finally, the thermal properties of ferroan dolomite samples were predicted. The present method can provide a promising extension tool for analyzing other crystalline rocks for geothermal applications.