Improving thermal properties of G class cement used in oil, natural gas and geothermal fields by using acidic pumice

This thesis investigates the effects of natural pumice aggregate incorporation on the thermal performance of API Class G cement, commonly used in petroleum and geothermal wells. Pumice obtained from the field was classified into different particle size distributions and added to cement slurries at volumetric replacement rates of 5%, 10%, 20%, and 30%. Both fresh and hardened properties of the cement systems were evaluated through a series of experimental tests. Within the scope of the experimental studies, key engineering parameters were evaluated, including slump, density, and setting time in fresh slurry, as well as dry density, porosity, compressive strength, flexural strength, thermal conductivity, specific heat capacity, and thermal diffusivity in hardened specimens. Furthermore, the collected data were comparatively analyzed by establishing correlations among the measured properties. Results demonstrated that the inclusion of pumice increased the overall porosity of the cement matrix, leading to a significant reduction in thermal conductivity. Consequently, the thermal insulation capacity of the cement system improved. While higher pumice content caused a moderate decline in mechanical strength, all measured values remained within the limits set by API standards. Notably, mixtures containing 10% to 20% pumice exhibited an optimal balance between insulation performance and structural integrity. In conclusion, the pumice-modified Class G cement formulations developed in this study offer a promising, energy-efficient, and cost-effective alternative for cementing operations in high-temperature well environments.