Polymer-Based Sealing Materials as Cement Alternative to Restore Wellbore Isolation

Well integrity is one of the main issues during all life cycles of the well and if any barrier element fails and compromise the integrity of well, remedial strategy may have to be performed to restore the safety and economics of the well. Cement is conventionally used as the isolation material in remedial and primary jobs. However, due to several inherent limitations in cement characteristics, such as cement shrinkage or poor cement slurry compatibility with downhole fluids, it is not always the best solution. Besides, cement slurry is a particle laden fluid which prevents it penetrating in to tight cracks/pathways to ensure isolation during remedial treatments. This project illustrates the effort to develop a customized polymer system as cement alternative addressing several challenges posed by conventional materials and experimental studies are designed to evaluate its characteristics such as rheology, injectivity and mechanical properties. Furthermore, the compatibility of these systems with drilling fluids contamination and shrinkage behaviour upon cure are evaluated. Afterward, based on the results of measurements, the limitations of each system are determined and the best formulation is optimized. The results of experiments prove that beside the appropriate rheological properties, the system provides excellent mechanical properties and much lower shrinkage rate upon cure compared to cement. The system withstands and maintains its properties after being contaminated with considerable volume of downhole fluids such as drilling fluids and hydrocarbons and mechanical properties such as compressive strength is not much affected by contamination. The unique characteristics of customized sealing system as cement alternative could provide benefits to industry by solving several current challenges in achieving secure isolation. Particularly due its ability to penetrate in to tight cracks, this system affords an effective method to mitigate sustained casing pressure or as a remedial solution for casing leakages which cannot be achieved easily by conventional methods.