**6. Role of nanomaterials in HPWBMs**

Nanomaterials are synthesized substances with a size ranging from 1 to 100 nanometers (nm) and are therefore used in very small dimensions. These materials have numerous applications in various fields, including automotive, electronics, pharmaceuticals, etc. In recent years their applications were also observed in the petroleum industry in different areas. In drilling fluids, nanomaterials have been used for borehole stability, filtrate loss reduction, and enhancing the rheology of mud blends. Such materials are characterized by an extremely high surface area to volume ratio due to their nano-sized particles. Nanoparticles offer enormous characteristics to reduce frictional resistance between drilling pipes and side holes and optimize torque and drag due to their extraordinarily thin and fine structure. Furthermore, NPs have broad drilling capabilities in high pressure and high temperature (HPHT) environments due to their wider surface area [11, 12].

Numerous nanomaterials, including graphene oxide, graphene nanoplatelets, titanium oxide, aluminum oxide, cupric oxide, CNT, multi-walled carbon nanotube (MWCNT) nanosilica, clay, metals, and carbon-based NPs, have been used to enhance the performance of WBMs. It was observed that the mud containing nanoparticles possesses enhanced physical and chemical properties, which enhances its efficiency. Graphene nanoparticles were found to be an excellent binding agent because these can develop a compact, impermeable, and thinner mud cake. This allows nano-pores to be physically plugged, limiting filtrate losses. As a result, using the graphene family improves wellbore stability [13].

Additionally, nanoparticles have been introduced as lubricants to minimize friction between the wellbore and the drill string, lowering the risk of a stuck pipe. **Figure 2** shows how nanoparticles have a higher surface area than macroparticles of the same volume.

In water-based mud systems, polymers nanoparticles such as TiO2/PAM nanocomposite depicted reduced filtrate loss volume and filter cake thickness while enhancing the formulated mud's rheology [14]. Likewise, SiO2/acrylic nanocomposites showed improved thermal stability [15]. Numerous studies have concluded that the synthesized composites showed improvements in rheology and lubricity while a reduction was observed in the filtrate loss. Some of the common nanoparticles with potential applications in drilling fluids are summarized in **Table 1**.

#### **Figure 2.**

*Comparison of nanoparticles surface area with bulk material.*


#### **Table 1.**

*Nanoparticle applications in drilling muds.*
