Darzi, H.H.Fouji, M.Heidarabad, R.G.Aghaei, H.Hajiabadi, S.H.Bedrikovetsky, P.Mahani, H.2025-07-282025-07-282022Journal of Natural Gas Science and Engineering, 2022; 105:104707-1-104707-131875-51002212-3865https://hdl.handle.net/2440/146370Although Multi-Walled Carbon NanoTubes (MWCNTs) are found to influence the rheological behavior of drilling fluids, there are yet some controversies regarding their performance towards reducing formation damage induced by the invasion of water-based drilling fluids (WBFs). To address this important question, we synthesized novel nanocomposite materials via modifying the MWCNT via varying the proportion of carboxylated MWCNTs to PolyVinyl Alcohol (PVA). These nanocomposites were then used to make nano-based drilling-fluids (NDFs). The performance of the NDFs was evaluated by a set of rheological behavior tests, filtration experiments, and core-scale mud flow tests. To distinguish between the internal and external damages made by the drilling fluid, computed tomography (CT) scanning was performed during the mud flow tests. The best yield stress (YP) and plastic viscosity (PV) were achieved at a 1:36 proportion of carboxylated MWCNTs to PVA (named as PVCNT-3). While the bulk rheological measurements (by varying the concentration of the nanocomposites between 0 and 0.6 wt%) showed a sharp increase in both YP and PV, the filtration tests showed contrary results. Independent of the nanocomposite content, the filtrates were also completely clear, demonstrating that PVCNT-3 acts as an efficient water-clay separation filter. NDFs containing a lower amount of PVCNT-3 (0.1–0.3 wt %) showed a noticeably lower degree of formation damage and a thicker external (impermeable) filter cake as confirmed by the CT scan images taken during the mud flow tests. However, high concentration of nanocomposites was found to cause significant internal pore plugging and formation damage. The results highlight the advantage of coupling core-scale tests with in-situ imaging to unravel the types of damages induced by the mud: build-up of an impermeable mud cakes (external damage) or deep-bed filtration (internal damage). This information is very essential for building proper models which capture different types of damages induced by drilling fluids.en© 2022 Elsevier B.V. All rights reserved.PolyVinyl alcohol (PVA)-Carboxylated multiwalled; carbon NanoTubes (MWCNTs); Nano-based drilling fluid; Flow behavior analysis; Formation damage; Computed tomographyJournal article10.1016/j.jngse.2022.104707618031Bedrikovetsky, P. [0000-0002-4786-8275] [0000-0002-7100-3765] [0000-0003-2909-6731]