Enhancing the gel transition time and right-angle-set property of oil well cement slurries by incorporating CSA cement and gypsum

Abstract

© 2019, International Petroleum Technology Conference This study aims to design and evaluate a well cement slurry as an alternative to the standard API 'G' slurry for utilization in plugging and abandonment (P&A) of oil and gas wells. OWC slurries are formulated with Portland API 'G' cement as the base material, along with calcium sulfoaluminate (CSA) cement, gypsum and chemical additives. The slurries are experimentally tested using API standard procedures to determine gel transition time and right-angle-set (RAS) tendency at a temperature of 50 °C and pressures up to 34.5 MPa (5000 psi). The hydration characteristics of CSA cement can be utilized to control the gel development behaviour of a well cement slurry in order to minimize fluid or gas migration. Formation of ettringite greatly influences early age gelation. The potential to enhance gel strength development of an OWC slurry with CSA cement is presented whereby the gel transition time decreases with higher dosages of CSA cement. Thickening time studies to investigate the RAS tendency of the designed cement slurries are presented.