Predicting and Controlling the Thermal Conductivity of Portland Cement for Underground Conditions

Area of Science:

• Geothermal Energy Engineering
• Materials Science
• Construction Engineering

Background:

• Low-temperature geothermal development (<150 °C) suffers significant heat loss via wellbore cement.
• Conventional oil well cement (0.8-1.5 W/(m·K) thermal conductivity) provides inadequate insulation, impacting project economics.

Purpose of the Study:

• Investigate prediction and control strategies for concrete thermal conductivity under subsurface conditions.
• Develop high-performance insulating cement for geothermal wells.

Main Methods:

• Systematic experimental analysis of thermal conductivity factors.
• Development of a regression model for Jiahua G-grade cement.
• Incorporation of impermeable insulating additives.

Main Results:

• Thermal conductivity positively correlates with moisture, curing temperature, and age.
• Thermal conductivity negatively correlates with porosity, permeability, and water-to-cement ratio.
• Moisture content identified as the dominant factor influencing thermal conductivity.
• Tailored cement formulations achieved thermal conductivity below 0.4 W/(m·K) with preserved mechanical integrity.

Conclusions:

• Controlling internal moisture via insulating additives is key to enhancing cement insulation.
• Developed insulating cement systems minimize wellbore heat loss.
• Findings support sustainable low-temperature geothermal resource utilization.