Different Methods To Avoid Annular Pressure Buildup by Appropriate Engineered Sealant and Applying Best Practices (Cementing and Drilling)

摘要

Many wells that have been successfully cemented initially are showing annulus pressure buildup due to damaged cement sheath integrity by post-cementing operations/conditions. This has been a concern by many operators where wellbores may be exposed to severe conditions and/or production regimes over a period of time. Sometimes this problem can be temporarily dealt with by releasing the annulus pressure, if environmental conditions and well type will allow. However, this method of annular gas production relief is not a long-term solution to the problem. In addition, it is not always possible to reduce the annulus pressure by releasing the trapped pressure into the environment on a regular basis, even if all other conditions permit this operation. An engineered cement slurry system can save the operator from facing this situation by applying a lifetime zonal isolation remedy through the proper cement job design. Gas injection in specific areas in the United Arab Emirates is performed to help maximize the production from these development fields. This paper will discuss the process of engineering a cementing system for these gas injection wells and the development of a solution that has successfully protected wellbores in gas injection areas where high pressures are applied to the wellbore. By treating the cement under defined wellbore conditions and studying the mechanical behavior of the cement sheath, it was possible to design a cement slurry system that could withstand the high pressures applied through gas injection operations. The mechanical behavior was evaluated using three-dimensional finite element analysis that considers mechanical properties such as Young's modulus, Poisson's ratio, and tensile strength in addition to confined compressive strength. The importance of complete zonal isolation is of high order. Elastic cement designs have provided a resilient nonfoamed, or conventional,system that successfully isolated the wellbores for more than a dozen gas injection wells.