Synthesis of Ultralight Cement Using Solid Waste Fly Ash Cenosphere for Low-Fracture Gradient Formation with Reduced Shrinkage

Abstract

The significant generation of fly ash from coal fired thermal power plants tends to cause air pollution and health hazards. The cenospheres that are a component of fly ash are spherical in shape, light density, and particle size ranges from 100 to 400 μm. Therefore, for the effective utilization of this solid waste, in this study, an ultralight cement slurry will be prepared for low-fracture gradient formation by the incorporation of varying doses of fly ash cenospheres (FAC). The cement sheath often shrinks, which instigates fluid migration across the isolated zones. Therefore, for additional shrinkage compensation, dead burned magnesia (DBM) combined with FAC will be added to the cement slurry. The morphology of the cenospheres in the cement sheath will be observed using a scanning electron microscope (SEM). The water contact angle of 108.3° revealed that the cement sheath is hydrophobic. Moreover, the consistency test revealed that when 30% cenosphere was incorporated into the cement slurry it exhibited a consistency of 30 Bearden units of consistency (Bc) after 2 h, which resulted in better pumpability under downhole conditions. Furthermore, expansion studies will be conducted on the prepared cement slurry under permeable and impermeable conditions. In addition, the rheological properties and compressive strength of the cement slurries will be investigated. The prepared cement slurry exhibited a specific gravity of approximately 0.9 along with a compressive strength of approximately 24 MPa, which is acceptable for its application in oil well cement. Therefore, the solid waste cenosphere and DBM could provide a sustainable solution in oil well cementing for low-fracture gradient formation with improved zonal isolation.