LOW-SPECIFIC-GRAVITY GEOTHERMAL WELL CEMENT SLURRY FOR USE AT HIGH TEMPERATURE

摘要

PROBLEM TO BE SOLVED: To provide a stable low-specific-gravity cement slurry suitable for cementing a geothermal well. SOLUTION: This slurry is prepared by dispersing a high-temperature-use cement composition mainly consisting of 35-65wt.% pulverized portland cement and 65-35wt.% finely powdered silicaceous admixture in water and has a specific gravity of 1.40-1.65 (desirably 1.40-1.60). In this slurry, the finely powdered silicaceous admixture comprises 10-90wt.% fine crystalline silica powder and 90-10wt.% fine amorphous silica powder, both powders having a fineness (Blaine value) of 8,500cm2 /g or above, and the fine amorphous silica powder has a fineness (BET specific surface area) of 120,000cm2 /g or above.