Pressure and temperature changes during the life of the well could cause some Casing-Casing annulus (CCA) pressure leaks in the annulus between 13 3/8" and 9 5/8" casings, and 13 3/8" and 18 5/8" casings. Such failures in wellbore isolation prevent us from taking full potential of our high performance wells, Al-Yami et al. 2018.
Different solutions have been presented in past to achieve long term well integrity, however this paper works on the postulate that long-term zonal isolation can only be provided by a competent annular seal which can be achieved with improved cement bonding and a cement system which withstand sheath stresses due to well operations. Solution provided in this paper includes process of improved slurry system's design, execution and evaluation for offshore operations.
To overcome these problems, self-healing cement system and durable cement systems were developed to ensure well integrity during the life of the well, providing competent annular pressure seal. Unlike conventional cement systems, self-healing system expands after setting, improving cement bonding and sealing micro annuli that can cause unwanted gas migration. Due to its improved mechanical properties and low Young's modulus it can withstand cement sheath stresses well operations. For formation where hydrocarbons are not present to trigger the self-healing mechanism, the durable cement system is the solution to use. It has suitable components to optimize its mechanical properties to withstand pressure and temperature cycling.
Under most failure conditions, tensile strength of a cement has a greater impact on its failure as compared to the cement's compressive strength. Consequently, increasing tensile strength of a cement is higher priority than increasing its relative compressive strength. This can be achieved by using additives such as latex, polyvinyl alcohol or fibers or simply by increasing cement flexibility Al-Yami et al. 2018. The objective of this paper is to highlight new designs and applications for self-healing cement system and durable cement.