This new approach to oil and gas well bore cementing goes beyond maximising compressive strength. The FlexSTONE advanced flexible cementing slurry can be adapted to match dynamic conditions of pressure, temperature and formation stress over the life of the well.

FlexSTONE cementing technology has been successfully used in Gulf of Mexico and North Sea wells and on projects in Algeria, Canada, Oman and wells throughout the United States, said its developer, Schlumberger Oilfield Services.

According to Roger Keese, business development manager, cementing, for Schlumberger, the FlexSTONE cement system provides both flexibility and expansion of the set cement. Traditionally, compressive strength was the only mechanical property of set cement considered for oil and gas well cement systems, and the degree of zonal isolation could only be monitored during and immediately after logging.

By looking beyond the bond log, set cement properties can be matched from drilling to production to abandonment to ensure that problems with zonal isolation are avoided long after the logging truck has left the wellsite.

To maintain zonal isolation over the life of a well, the cement sheath around the casing must be able to adjust to changing wellbore rock properties and predicted temperature and pressure conditions. Zonal isolation is key to eliminating problems with lost production due to crossflow, surface breaching of formation fluids and gases, corrosion of casing and associated remedial repair efforts.

FlexSTONE technology uses nonmineral-based particles in an optimized distribution to produce set cement with variable mechanical properties. Using the Schlumberger SAM stress analysis model software system, the wellbore can be evaluated for future problems of zonal isolation caused by imposed stresses. With SAM software, set cement properties of this advanced slurry can be engineered to match formation properties and future well conditions.