Utilization of Innovative CO2 Swelling Elastomeric Cement Integrity Sleeve as a Novel Well Integrity Enhancement Solution for Underground CO2 Storage Wells

Abstract As the world aims to mitigate the climate-changing effects of global warming, intergovernmental regulatory bodies increasingly focus on greenhouse-gas emission reduction by implementing environmental policies to phase down fossil-fuel utilization and develop sustainable energy sources as part of global energy transition efforts. While various greenhouse gasses are emitted from a wide range of natural and artificial sources, human-produced carbon dioxide (CO2) is the primary driver of climate change as it accounts for approximately 70% of global greenhouse gas emissions (Olivier et al, 2020). Efforts to reduce greenhouse gas pollution from the atmosphere have led to significant advancements in Carbon Capture and Storage (CCS) technologies, which aim to inject CO2 in underground storage wells with non-permeable formations capable of safe and permanent downhole containment. Furthermore, CCS is widely regarded as one of the most effective ways to mitigate climate change as recent studies estimate it could reduce CO2 emissions by 20% before the year 2050 (Elkatatny, 2021). The planning and execution of a comprehensive CCS well integrity strategy is considerably more complex than conventional well integrity practices commonly found in the oil and gas industry. The hydration of supercritical CO2 leads to multiple carbonation reactions producing elevated concentrations of carbonic acid (H2CO3), which can severely degrade a cement barrier in radial direction and cause longitudinal cement defects. Concurrently, cyclic pressure and temperature fluctuations during long-term CO2 injection can compromise casing-to-cement bond, causing a potential leak path through micro annuli. These factors may lead to gas migration and subsequent Sustained Annular Pressure (SAP) buildup on surface, increasing the risk of direct CO2 leakage into the atmosphere. An innovative CO2 Elastomeric Cement Integrity Sleeve (C-ECIS) has been developed specifically for the purpose of SAP prevention and well integrity optimization in CO2 storage wells. Distinctly different to a swellable packer, the C-ECIS was designed as a slip-on seal for external installation onto downhole tubulars. It is comprised of a novel swellable elastomer which utilizes CO2 as the primary swelling fluid medium for its volumetric expansion. It permanently swells and seals a casing-to-cement microannular flow path immediately upon direct exposure to gas migration within the casing-to-cement microannulus. The C-ECIS is a unique technological innovation with the potential to transform the industry's current approach to CCS well integrity planning due to its simplicity and reliability. This publication provides an in-depth overview of the technology, its qualification process, and current field implementation status.