Insights into the application of surfactants and nanomaterials as shale inhibitors for water-based drilling fluid: A review

Abstract Water-based drilling fluids (WBDFs), a more environment-friendly candidate than oil-based are widely used for drilling oil and gas wells. However, wellbore instability due to active clay minerals in the shales is considered a major problem faced by the WBDFs due to swelling and hydration. Several types of shale inhibitors have been proposed by researchers to help combat the menace posed by these active clay minerals during drilling operations. The purpose of this study is to investigate the application of surfactants and nanomaterials as additives to WBDFs and anti-swelling agents for drilling operations. An overview of the experimental procedures and conclusions conducted from studies to evaluate the performance of these materials ranging from types, characterization techniques, limitations, inhibition mechanisms are presented. A summary of key findings has also been reported as well as the challenges and prospects. Based on the review, we found hydrogen bond, clay surface coating, and ionic bond to be the major inhibition mechanisms. We recommend potential studies to investigate the application of vermiculate clay minerals to effectively understand the behavior of this material as shale inhibitors as compared to the commonly used montmorillonite (MMT) in the industry. Similarly, the response time of clay-bearing formation when exposed to WBDFs was suggested for future studies. Other biological extracts containing saponin molecules with fewer environmental footprints are highly recommended as shale inhibitors. Lastly, a comparative cost analysis should be encouraged for future studies interested in proposing new shale inhibitors.