Well Integrity Under Dynamic Stresses Using Flexible Cement Systems

As the field of well construction has advanced over the years, one feature that has remained consistent throughout is the use of Cement as a primary well barrier element. The long-lasting, impermeable nature of the cement matrix means no other material has been considered as an effective, widely-available alternate almost a century from the first cement job. What has changed however, with advancement in the the field of well integrity, is how we approach the cement job design and how certain materials can complement the role of the cement in improving hydraulic isolation. The historical cement job design only targeted a pumpable slurry reaching the desired placement interval, then the design moved to improving liquid slurry properties such as rheologies, fluid-loss and free fluid. Later, the short-term performance as the slurry transitioned through a gel phase to a set state also became an important criterion. More recently, after the renewed global focus on well integrity as learning from disasters such as Macondo, the annular cement’s role as a well barrier has become a major focal area for any well construction program. This paper presents a systematic approach in designing cement systems that promise long-term well integrity starting with the root-cause identification, simulating the effect on the cement sheath, required modification of the design, and finally the application and associated results.