A High Thermal Conductivity Cement for Geothermal Exploitation Application

In geothermal reservoir exploitation, the thermal conductivity of casing cement material is a key parameter that may affect the heat exchange and utilization efficiency of geothermal reservoirs. Based on a systematic approach of theoretical analysis, experimental research and microscopic analysis, this paper presents graphite composite cement (GC) with high thermal conductivity for potential application in geothermal reservoir exploitation. The GC consists of ordinary Portland cement (P.O 42.5), natural flake graphite, water-reducing agent (GB), early strength agent (CaCl2) and defoamer (HB-03). The physical properties of the GC, such as fluidity, pumpability, setting time, compressive strength and thermal conductivity, were obtained by carefully prepared laboratory tests that met our expectation. Finally, X-ray diffractometry and environmental scanning electron microscopy were used to analyze the micro-characteristics for an interpreted thermal conduction mechanism of GC. The results of analyses show that the formation of thermal conductivity network of natural flake graphite in cement is a key to improve thermal conductivity. The research results provide a new solution to the problems of low thermal energy extraction efficiency and poor cementing quality of geothermal reservoirs.