LAUSR

Abstract Zonal isolation by cement barriers can be compromised in many different ways. Among the most important are shrinkage of cementing slurries and contamination of slurries with non-aqueous drilling fluids (NADF) during displacement. Class F fly ash (FA) based alkali-activated materials, referred to as geopolymers, have shown better compatibility with NADFs than ordinary Portland cement (OPC) slurries. This study questioned whether the geopolymer slurries also show enhanced performance with respect to shrinkage behavior compared to OPC slurries, especially at relevant downhole temperatures and pressures. A novel testing technique was developed to measure the autogenous shrinkage of OPC and geopolymer slurries subjected to temperatures and pressures ranging up to 80 °C (175 °F) and 13.8 MPa (2000 psi). The testing demonstrated that the total autogenous shrinkage increased for OPC slurries and decreased for geopolymer slurries with increase in testing temperature from 40 °C (104 °F) to 80 °C (175 °F). In addition, an increase in testing pressure from 1.38 MPa (200 psi) to 13.8 MPa (2000 psi) resulted in a significant increase in the autogenous shrinkage for OPC slurries when tested at 40 °C (104 °F). Furthermore, it was found that the addition of zinc- and aluminum-based expansive agents was effective in mitigating OPC shrinkage. A zinc-based expansive agent was particularly effective at shrinkage mitigation for geopolymers subjected to 80 °C (175 °F) and 13.8 MPa (2000 psi) confining pressure.