PETROPHYSICAL AND MICROSTRUCTURAL EVALUATION OF THE THERMAL CYCLE LOADING EFFECT ON GEOTHERMAL WELLBORE CEMENTS

Five wellbore cement designs with a range of additives and fibers were subjected to 100 thermal cycles of ΔT ~50°C at 100% relative humidity in salt brine. The experimental results show leaching of portlandite will occur from the cement irrespective of wellbore cement slurry design, which causes the porosity and hydraulic conductivity to increase and the mechanical strength to decrease. Furthermore, the study shows the presence of steel fibers can improve the mechanical properties of the cement sheath under thermal cycle loading conditions; although it would not prevent it from completely degrading as the well ages.