Turning Waste into Resource: Red Mud as a Sustainable Alternative to Class G Cement in Surface Casing Cementing.

Sustainability of well cementing operations is a growing concern due to the high carbon footprint of Class G cement production. This study investigates the feasibility of using red mud, an industrial by-product of alumina manufacturing, as a partial replacement for Class G cement in surface casing cementing. A series of laboratory experiments was conducted to evaluate the mechanical, rheological, and performance characteristics of red mud-based cement slurries. The tests included compressive strength, plastic viscosity, yield point, gel strength, 3-rpm reading, free water content, fluid loss, and thickening time. A comparison of red mud-cement blends to a conventional Class G cement slurry was also considered in this study. The results demonstrated that the incorporation of red mud in a concentration of more than 15% resulted in crack development on the outer surface of the samples with time, and also the sample with 50% red mud showed a very high plastic viscosity, which makes it unpumpable. Red mud incorporation significantly reduced the free water content while maintaining an acceptable compressive strength above the required 700 psi threshold. However, its addition lowered the yield point and gel strength, necessitating viscosifier inclusion to restore suspension capacity. The slurry with 15% red mud showed optimal performance when combined with 0.12% viscosifier, balancing pumpability, stability, and thickening time requirements. The findings highlight that red mud-based cement formulations can provide a sustainable alternative to Class G cement, reducing waste disposal challenges and environmental impact.