Foamed CaP Cement Enables Drilling and Cementing of Geothermal Wells: Case History

Abstract

In Southern California, the operating company successfully cemented a geothermal well using foamed calcium aluminate phosphate (CaP) cement to achieve long-term zonal isolation. The well was drilled in a highly corrosive carbon dioxide (CO2) environment. Weak formations along the wellbore required careful planning and selection of the drilling fluid and cement properties to minimize lost-circulation potential during the drilling and cementing of the well. This cementing case history describes primarily the benefits of CaP cement and discusses the performance of Portland cements to that of CaP cement.
Naturally occurring CO2 can be found in formation waters or as the result of CO2 injection processes. When CO2 comes into contact with Portland cement, it reacts with its components, deteriorating the cement matrix. This reaction, known as carbonation, over time, can cause serious damage to well tubulars and destroy zonal isolation integrity, resulting in costly remedial services or even abandonment of a well. The results presented in this work should help in the design of solutions to contain both reservoir and injected fluids in the presence of CO2.