Geothermal energy is identified as one of the best alternatives to fossil fuels in global climate crisis and the effective efforts for net-zero emissions by 2050. The potential of geothermal heat is yet to be unlatched thus requiring a novel approach in all aspects of wellbore technology including cementing. Materials used require stability at high temperatures and be chemically resilient to geofluids that attack ordinary Portland cement (OPC) causing loss in mechanical strength. Recent studies have shown that adding graphene nanoplatelets (GNPs) to cement can improve properties and reduce risks from mechanical failures. GNPs effect on overall cement properties has been studied and experimental results show promising outcomes at very low concentrations (&lt;1% by weight of cement), it significantly impacts strength and stiffness of the cement. But the mechanism in adding low quantities of GNPs to cement is unclear as it can increase the cement strength and resistance to fracturing, even under high temperatures and high pressures (HTHP) conditions. In this study, the Class-H cement is hydrated with and without, GNPs dispersed in liquid and in the form of powder at 0.008% and 0.1% concentrations each to examine the influence on cement hydration. The samples are subjected to cyclic temperature loading between 20 <sup>o</sup>C and 110 <sup>o</sup>C following an 8-hour cycle for 7 and 28 days in an environmental chamber. These temperature cycles help us evaluate close to the realistic conditions where enhanced geothermal systems undergo changes over tens of thousands of times. The cement paste samples are examined to investigate graphene’s mechanism during hydration using scanning electron microscopy (SEM) and micro computed tomography (CT) for the microstructure of the cement while energy dispersive x-ray spectroscopy (EDS) and Raman spectroscopy for chemical analysis and phase identification.

Role of Graphene Nanoplatelets (GNPs) in preventing Geothermal Wellbore Cement Deterioration Subjected to Cyclic Temperature Loading

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