Investigation of consolidation/thermal insulation property and mechanism of casing cement in the heat-insulating section of geothermal production well

Abstract

ABSTRACT In the process of geothermal exploitation, heat loss often occurs in the heat-insulating section of the production well, resulting in a decrease in heat extraction efficiency. However, there have been few studies on thermal insulation cement for geothermal well, lacking complete engineering application properties evaluation. In view of this, a new type of thermal insulation composite cement was successfully developed by incorporating thermal insulation filler (Hollow glass beads, HGB), heat stabilizing material (SiO2) and additives. The engineering application properties were evaluated using standardized methods, and the results demonstrated excellent rheology and stability of the cement slurry. The 14d compressive strength of the cement stone reached 21.24 MPa, and the thermal conductivity remained stable at 0.1535 W/(m·K). Finally, the consolidation/thermal insulation mechanism of the material was investigated. Analysis showed that the secondary hydration of SiO2 could generate more C-S-H, and additives could regulate the hydration reaction of slurry. The excellent thermal insulation property of material was derived from interface lattice scattering, the low thermal conductivity of HGB, and the gas heat-conduction recession within HGB. The study results provide a new idea to solve the problem of heat loss of geothermal production well from the perspective of material development.