| Summary: | The occurrence of shale swelling during water-based drilling operations poses substantial challenges to the stability of shale formations. Clay layer expansion is the primary cause of shale swelling, which results from interactions between clay minerals and drilling fluid components. The degree of expansion is determined by variables such as clay composition, ion exchange processes, osmotic pressure, ionic strength, temperature, and pressure. Therefore, this study explores various shale swelling inhibitors and meticulously investigates the underlying mechanisms. The effectiveness of conventional inhibitors, such as potassium chloride (KCl), ammonium chloride (NH4Cl), and amine-based inhibitors, is well-established. However, it is important to note that these inhibitors do have certain limitations. Hence, the present work investigates a range of environmentally friendly inhibitors, including graphene oxide, ionic liquids, deep eutectic solvents, nanoparticles, nanocomposites, and biosurfactants. Graphene oxide exhibits notable efficacy in mitigating shale swelling and producing extensive, unbroken protective coatings. Ionic liquids, represented by 1-butyl-3-methylimidazolium chloride (BMIMCl), have demonstrated enhanced inhibitory characteristics in comparison to KCl, resulting in a reduction in bentonite swelling rates by 19.38%. Furthermore, it has been observed that deep eutectic solvents (DESs), such as NADES, exhibit remarkable inhibitory characteristics, resulting in a 49.1-62.8% reduction in the rate of swelling in clay samples. Nanocomposites, which involve the integration of single-walled carbon nanotubes (SWCNTs) and polyvinylpyrrolidone (PVP), have demonstrated successful mitigation of shale swelling and regulation of fluid loss. Moreover, biosurfactants such as chitosan-grafted l-arginine, flaxseed protein (FP), and flaxseed mucilage (FM), have exhibited potential as shale inhibitors that are both biodegradable and environmentally friendly. These findings contribute to ongoing efforts to improve the environmental sustainability of drilling operations and adhere to rigorous environmental protection standards. Nevertheless, more investigation, refinement, and practical application analysis are needed before they can be widely used. © 2024, Malaysian Society of Analytical Sciences. All rights reserved.
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