The ultimate objective for cementing a casing string is to achieve long-term integrity of the well. This can be achieved through long-term zonal isolation between the penetrated formations with appropriate mechanical properties, low permeability, and shear bond strength properties provided by the cement sheath placed in the corresponding annuli. Experiences in the Hassi-Messaoud field have shown that zonal isolation is a very complex problem for some formations such as the LD2 zone, which exhibits, in some cases, corrosive fluids and highly saline formations as well as lost circulation zones. Cementing operations are critical and the need for cementing systems capable of solving these problems is crucial.

This paper focuses on the factors that have contributed to the potential failure of the existing cement system. Stress modeling has been used to select the appropriate cement system to overcome the challenges faced by the cement sheath in this type of environment. Stress analysis calculations, combined with mechanical properties testing of the cement system, has suggested the use of a novel cementing technology. This new system has been able to solve these problems to provide flexibility, improve corrosion control, expansion properties of the set cement, reduce the chances of microannulus creation, and therefore avoid overpressurization of the annulus casing. To ensure correct cement placement in the lost circulation zones, this slurry system has been successfully combined with fibers specifically engineered for cement slurries.

This technology has been a cost-effective solution for cementing 12 1/4-in sections in the Hassi-Messaoud field and 8 1/2-in sections in the Berkaoui and Hassi-Guettar fields. Field results have proven that significant workover costs, up to USD 1 million on wells in production, can be saved with the application of this technology.

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