Advanced development of chemical inhibitors in water-based drilling fluids to improve shale stability: A review

Wellbore instability is a critical challenge in drilling operations, especially in shale formations where interaction with water-based drilling fluids can result in significant operational risks and increased costs. To address these issues, shale chemical inhibitors have become a crucial component in drilling fluid formulations to ensure wellbore integrity. Although several researchers have published some reviews on shale inhibitors, the latest advancements in shale chemical inhibitors over the past five years still warrant further discussion and summary. This literature review provided a comprehensive examination of wellbore instability, focusing on the patterns of instability encountered in drilling and the various shale chemical inhibitors employed to mitigate these issues. The review explored the utilization of shale inhibitors in water-based drilling fluids, and the discussion highlights the timeline evolution of these inhibitors, from traditional salts and polymers to advanced ionic liquids and deep eutectic solvents. Additionally, the mechanisms of shale chemical inhibitors are summarized to guide their application. The objective of this paper is to provide a detailed review of the development of shale chemical inhibitors in water-based drilling fluids, aiming to fully appreciate shale hydration inhibition methods and to provide insights into the selection and optimization of shale inhibitors to improve wellbore stability in challenging drilling environments.