High-Performance Cement and Real-Time Temperature Sensing Enables Optimized Wellbore Cementing in CO2 Environments: Case History

Abstract

In southern California, a geothermal-development company successfully cemented a geothermal well using foamed calcium aluminate phosphate cement (CaP) to help achieve long-term zonal isolation. The well was drilled in a highly corrosive carbon dioxide (CO2) environment where naturally occurring hyper-saline brines were also present. 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 casehistory paper describes the benefits of CaP cement and real-time, downhole, distributed temperature-sensing (DTS) technologies. When CO2 comes into contact with Portland cement, it reacts with its components and may cause deterioration of the exposed cement sheath in severe conditions. This carbonation and related dissolution over time, can cause serious damage to well tubulars and possibly deteriorate zonal-isolation integrity, resulting in costly remedial services or even abandonment of a well. Real-time DTS provides an accurate wellbore temperature profile that can be used to make the necessary adjustments to the cement-slurry design before placement and after job completion to minimize wait-on-cement time, resulting in substantial cost savings. DTS also helps detect anomalies in cement placement and different cement heat-of-hydration temperatures. The results presented in this work can help improve the design of drilling and cementing solutions for long-term geothermal well construction.