Using Fumed Silica to Develop Thermal Insulation Cement for Medium-Low Temperature Geothermal Wells

Area of Science:

• Geothermal Energy Engineering
• Materials Science
• Construction Materials

Background:

• Geothermal energy development faces challenges with heat loss from high-temperature fluids in wellbores.
• Thermal insulation cement (TIC) is crucial for increasing outlet temperatures and improving energy efficiency.
• Optimizing TIC properties is essential for effective geothermal fluid heat management.

Purpose of the Study:

• To develop and optimize thermal insulation cement (TIC) for geothermal applications.
• To investigate the effects of inorganic thermal insulation materials (TIMs) and additives on cement properties.
• To achieve a TIC with reduced thermal conductivity (TC) and enhanced compressive strength (CS).

Main Methods:

• Orthogonal testing was used to screen inorganic thermal insulation materials: vitrified microbubbles (VMB), expanded perlite (EP), and fly-ash cenosphere (FAC).
• Fumed silica (FS) was incorporated to decrease TC, while a reinforcing agent (RA) and calcium hydroxide (CH) were added to improve CS.
• Fresh properties, CS, TC, hydration products, pore-size distribution, and microstructure were analyzed.

Main Results:

• A TIC formulation with a TC of 0.1905 W/(m·K) and CS of 5.85 MPa was successfully developed.
• Increasing the mass fraction of TIMs effectively reduced TC.
• Fumed silica addition increased C-S-H gel content due to pozzolanic reactions, forming the primary matrix.
• The reinforcing agent significantly improved cement fluidity and increased CS from 3.5 MPa to 5.85 MPa.

Conclusions:

• Optimizing TIM content is key to reducing thermal conductivity in TIC.
• Fumed silica enhances the C-S-H gel content, crucial for cement matrix strength.
• The developed TIC demonstrates improved thermal insulation and mechanical properties for geothermal applications.
• Reinforcing agents play a vital role in enhancing both fluidity and compressive strength of TIC.