Improved durability of Saudi Class G oil-well cement sheath in CO₂ rich environments using olive waste

The physical properties of the oil-well cement, especially its strength and permeability, are changing significantly after reacting with CO₂-saturated brine which will alter the cement hydration products. In this study, the effect of incorporating the olive waste into Saudi Class G oil-well cement formulation subjected to CO₂ sequestration conditions at 130 °C and 10 MPa on the cement permeability, carbonation depth, compressive and tensile strength, and microstructural changes during 20 days of carbonation was evaluated. The results obtained showed that the addition of 0.1% by weight of cement (BWOC) of the olive waste to the cement enhanced the cement resistance to the carbonation process and decrease the carbonation depth from 1469 μm for the base cement to 1269 μm after 20 days of carbonation. Incorporating 0.1% BWOC of the olive waste into the cement slurry also maintained the original cement permeability of 14.3% less than that for the base cement, while the permeability of the cement samples with 0.1% BWOC olive waste after 20 days of carbonation is 33.9% lower than the base cement permeability. The permeability reduction is the main mechanism responsible for the enhancement of carbonation resistance for the olive waste-based cement. The ability of the olive waste to delay calcium leaching is attributed to the decrease in the permeability of the sample with 0.1% BWOC of olive waste.