A comprehensive review of in-service pipeline repair methods with a focus on axial strain capacity

Pipelines provide a reliable, cost-effective transport method for oil and gas products. However, their integrity can be threatened by defects and geohazards, making in-service repair methods crucial for maintaining safety, ensuring continuous operation, and supporting long-term sustainability. This review evaluates different in-service pipeline repair methods focusing on axial strain capacity. Repair is crucial for pipeline integrity in geohazard-prone regions where ground movements, such as landslides and subsidence, can induce significant axial strain. The review provides an in-depth analysis of these repair methods' design functionality and real-world applications while discussing their challenges and recent advancements. A comparative assessment of repair methods based on defect coverage, ease of execution, flexibility, and cost-effectiveness is included to select the most suitable repair techniques. Additionally, the review identifies current challenges in improving axial strain capacity and underscores the importance of future research. Further studies are required to optimize sleeve geometry and weld configurations, improve installation practices, and investigate the long-term behavior and interfacial bonding of grout and filler materials, as these factors are critical to enhance axial and hoop strain capacities and improve the pipeline's overall resilience and longevity.