Journal of Petroleum Science and Engineering 221 (2023) 111312 Available online 14 December 2022 0920-4105/© 2022 Elsevier B.V. All rights reserved. Effect of CeVO 4 /Al 2 O 3 /rGO nanocomposite on rheological properties and thermal conductivity of water-based drilling fuid Nahid Kalhori a , Mehdi Mousavi-Kamazani a, * , Faramarz Hormozi b a Department of Nanotechnology, Faculty of New Sciences and Technologies, Semnan University, Semnan, Iran b Department of Chemical, Petroleum, and Gas Engineering, Semnan University, Semnan, Iran A R T I C L E INFO Keywords: Drilling fuid CeVO 4 /Al 2 O 3 /rGO Nanocomposite Rheology Thermal conductivity ABSTRACT In this research, in order to improve the rheological properties and thermal conductivity of the drilling fuid, CeVO 4 /Al 2 O 3 /rGO nanocomposite was synthesized by one-step hydrothermal method for the frst time. In addition to controlling the growth of Al 2 O 3 , CeO 2 , and CeVO 4 nanoparticles, hydrazine reduces graphene oxide (GO) to reduced graphene oxide (rGO) and enables one-step synthesis. The effect of nanoparticles (NPs) with concentrations of 0.01, 0.03, 0.05, 0.1, and 0.5 wt% on water-based drilling fuid was determined. In all samples, the shear thinning behavior of mud-containing nanoparticles was maintained at different shear rates. After adding 0.5 wt% of CeVO 4 /Al 2 O 3 /rGO nanocomposite, there was only 6 ml of lost circulation. By using CeVO 4 / Al 2 O 3 nanocomposite, the plastic viscosity (PV) was tripled by increasing the concentration from 0.01 to 0.5 wt% so that PV for CeVO 4 /Al 2 O 3 nanofuid with a concentration of 0.5 wt% increased to 12 cP. Thermal conductivity and gel strength in all samples were signifcantly improved, especially in the presence of Al 2 O 3 nanoparticles. Thermal conductivity for liquid containing 0.5 wt% Al 2 O 3 at 80 ◦ C increased from 0.60 to 0.81 W/mK. In general, nanoparticles in concentrations less than 0.5 wt% Bentonite-WBMs (water-based muds) can improve rheological properties, fltration, and thermal conductivity. 1. Introduction Drilling fuid has been used in oil and gas well drilling since the early 1900s. At that time, the most common use of drilling fuids was to remove the cuttings and move them to the top of the hole. A successful drilling operation depends heavily on the effectiveness and performance of the drilling fuid in use (Vryzas and Kelessidis, 2017; Karakosta et al., 2021). With the development of this industry, the design and tools of drilling fuids have changed in terms of safety and economics to a satisfactory level for wellbore. Drilling fuid with suitable properties is an important factor in the success and completion of drilling operations because a large part of the cost depends on the formulation of mud (K¨ ok and Bal, 2019). Drilling fuids are complex fuids composed of several additives. Most of the problems that arise when drilling a hole are directly or indirectly related to mud (Saboori et al., 2019). Circulating fuid is usually a liquid, but sometimes a gas or air can also be used as a drilling fuid. If liquid, it is often a mixture of water, although oil or diesel is also used (Karakosta et al., 2021). In general, drilling fuid is a mixture of liquids, solids, and chemicals, and the formulation of this mud depends on temperature and, pressure conditions (Aftab et al., 2017; Ridha et al., 2018). Recently nanoparticles have been widely recommended for improving the properties of drilling fuids. Nano- particle additives have been explored as an alternative to polymer-based additives. Nanoparticles are considered excellent candidates for intelli- gent drilling fuid formulation due to their unique physical and chemical properties, very small size (<100 nm), and the large surface-to-volume ratio (Chegenizadeh et al., 2016; Katende et al., 2019). In different sources, various applications of nanomaterials in drilling muds, espe- cially control of mud fltrate volume, viscosity control, minimization of differential pipe adhesion, and production at high temperature and pressure conditions, and increasing shale stability have been reported (Aftab et al., 2017; Rafati et al., 2018; Sajjadian et al., 2020). Adalatfar et al. performed rheological tests on samples containing 0, 0.5 and 1 wt % of ZnTiO 3 nanoparticles in the presence of 0, 2, and 4 wt% of KCl salt at 25 ◦ C and 90 ◦ C. Adding 1 wt% of ZnTiO 3 nanoparticles, in the presence of 2% and 4% of salt, can increase the viscosity of water-based mud by 34.88% and 37.73% at 25 ◦ C and 32.16% and 30.76% at 90 ◦ C. Filtration test on the optimal sample, adding 1 wt% of ZnTiO 3 nano- particles to the mud reduced the volume of fuid loss by 7.7%. Herschel-Bulkley and Power-Law models predicted the rheological behavior of mud containing mud nanoparticles (Edalatfar et al., 2021). * Corresponding author. E-mail address: M.Mousavi@semnan.ac.ir (M. Mousavi-Kamazani). Contents lists available at ScienceDirect Journal of Petroleum Science and Engineering journal homepage: www.elsevier.com/locate/petrol https://doi.org/10.1016/j.petrol.2022.111312 Received 19 August 2022; Received in revised form 7 November 2022; Accepted 1 December 2022