## 1 Introduction  
Drilling mud is known as the flowing fluid used during the drilling operation of oil and gas production. The main functions of drilling mud are to maintain the hydrostatic pressure, suspend and bring up the drilling solid cuttings to the surface, provide a lubricant and cool down the drill string and drill bit, and minimize formation damage [1; 2]. As deeper and longer wells are drilled, the engineers face greater problems and challenges. The synthesizing and preparation of drilling muds must become more complex to satisfy the various operational demands and challenges that are attributed to formation characteristics. In particular, degradation of drilling mud additives, gelation or breakdown of polymeric additives during drilling operation can affect the performance of conventional water-based muds [3]. These drilling mud additives are chemicals added to drilling mud in order to change the mud properties and composition [4]. Nonetheless, many efforts have been devoted to drilling mud formulation mainly to enhance the quality and function of drilling muds, as well as to comply with the more stringent laws on underground or marine contamination. Filtrate loss is another alarming issue during an extended-well drilling operation. It occurs in high permeability formation where the drilling mud seeps through the wall of the wellbore and invadesthe formation. The solid residue of the drilling mud will deposit a layer of mud cake on the wall of the borehole. Commonly, filtrate loss is controlled by the addition of a control additive, which are substances that can reduce the volume of the filtrate during propagation of a hydraulic fracture such as bentonite, starch, and organophililic lignite. However, bentonite degrades at high pressure-high temperature (HPHT) conditions. Based on these notions, nanoparticles are being explored to improve drilling mud formulation in which they function both as weighing agent and filtrate loss control agent. The utilization of nanoparticles is of increasing interest to the oil industry with the intention of improving the performance of water-based drilling fluids as reflected by the efforts shown in Table 1.  
It is reported the nanoparticles could improve drilling mud formulation; the main attributes are the particle size and the interaction potential with the formation, which might be due to the high availability of the active site. [PERSON] et al. [13] have reported a review on the role of drilling mud during the drilling process in oil and gas production, followed by the recent advances in the utilization of nanoparticles in a drilling fluid system. They summarized the impact of various types of nanoparticles on drilling mud performance to make the drilling operation smooth, cost effective, and efficient. [PERSON] et al. [6] investigated the effect of carbon nanotubes and found that the rheological properties of water-based drilling mud were improved. They reported that carbon nanotubes can increase the shear stress; also, the shear stress was linearly proportional to the shearing rate. This is due to the better dispersion of drilling mud with the presence of carbon nanotubes at high shear rates. Also, the viscosity and the yield points were found to be higher for carbon nanotubes-added drilling mud than those of the conventional water-based mud. This means that the lifting capacity of the carbon nanotubes-added drilling mud is increased. [PERSON] et al. [5] have experimentally investigated the effect of multi-walled carbon nanotubes and graphene nanoplatelets in water-based mud. They reported that the addition of 0.01 ppb of multi-walled carbon nanotubes and graphene nanoplatelet increased the plastic viscosity (PV) after a hot-roll of water-based mud from 21 cP to 23 cP and 25 cP, respectively. They analyzed the results and concluded that both multi-walled carbon nanotubes and graphene nanoplatelet increased the PV and reduced filtrate loss.