Exploring the role of hydrophobic nanofluids in reducing shale swelling during drilling: A step towards eco-friendly and sustainable practices

This study conducts a comparative analysis between hydrophobic nanosilica (HNS) and potassium chloride (KCl), a widely used shale inhibitor, to better understand how HNS can effectively manage water and shale interactions by restricting mud filtration into the formation. Due to their small size and optimal interfacial properties, nanoparticles emerge as remarkable solutions for addressing this issue. In this work, shale samples were collected from the Kolosh Formation in the Kurdistan Region of Iraq, known for being one of the most challenging formations to drill. Investigations into the properties of drilling fluid were conducted using low pressure and low temperature (LPLT) and high pressure high temperature (HPHT) filter press, alongside analyzing rheological properties at three different temperatures (25, 50 and 75°C). In addition, the impact of the HNS on clay swelling was examined using the liner swelling meter (LSM) test, shale dispersion test (SDT) and capillary suction time (CST) test. The obtaining results revealed that the shale hydration in the drilling fluids was reduced 24.36–15.53% and the shale recovery at high temperatures was improved from 80.2% to 94% by adding 0.4 wt% HNS. Furthermore, HNS demonstrated improved clay suspension in the CST test wherein the suspension time reduced from 303 to 80 sec at the same HNS concentration. Utilizing HNS effectively reduced clay swelling in all experiments and enhanced the rheological properties of the mud, showcasing stability across a range of temperatures and significantly reducing the formation of filter cake and fluid loss. As is obvious, KCl based drilling fluids are prohibited in several parts in the word due to its negative impact on the environment and subsurface activities; thus, it can be substituted by HNS as an active shale inhibitor additive.