## 1 Introduction
The influence of the dynamic barite sag and shear rate obtained from a rheometer and a borehole-hydraulics flow circuit on an invert-emulsion fluid (IEFs) was studied by [PERSON] et al. (2018). The results suggest that the dynamic sag tendency increases with increasing hole deviation during drilling and is usually initiated at low shear rates below 4 s\({}^{-1}\) when the inclination is between 45\({}^{\circ}\) and 60\({}^{\circ}\). Drilling fluids formulated from IEFs, rheology improver additives, and nanoparticles have been investigated. The negative effect of sagging may be more devastating in elevated wells under inclined conditions. To reduce sagging incidence in dynamic and static drilling operations, it is expedient to design drilling mud to withstand HPHT conditions. Numerous materials, including the reduction of particle size of weighting materials or a blend (ilmenite, barite, vermiculite, hematite), organophilic clay, nano silica, urea-based copolymer, and polyethylene glycol, have all been studied as sag inhibitors to prevent sagging in the drilling sector. [PERSON] et al. (2018). investigated the adoption of a barite-manganese tetroxide (Micromax) blend to mitigate barite sag challenges in IEFs under elevated conditions. A Micromax of 1.7 \(\upmu\)m was added to the IEFs as anti-sagging additives at various concentrations of 0, 15, and 30 wt% of barite. The report showed that Micromax addition enhanced IEF stability by reducing the tendency to sag. Sag was minimized at 350 \({}^{\circ}\)F in both dynamic and static settings by adding only 30 wt% of the Micromax additive. Additionally, manganese tetroxide as a sag-resistant additive was also evaluated with micro-sized hematite in a water-based fluid. The formulations had a range of anti-sagging additive/weighting agent ratios (0/100, 10/90%, 15/85%, and 20/80%). The outcomes of the dynamic and static sag setting at HPHT indicated that 20% of manganese tetroxide resolved the sagging problem with hematite and brought the sag susceptibility to an acceptable range. The investigation of vermiculite as a sag-resistant additive in water-based mud (WBM) was explored by [PERSON] et al. (2018). The addition of micronized vermiculite to WBM at different concentrations (0, 1, 2, 3, and 4 lb/bbl) was studied at an elevated temperature of 250 \({}^{\circ}\)F. The obtained results of the WBM formulated with 4 lb/bbl of vermiculite were efficient in bringing sag to the API acceptable standard. The viability of employing fly ash as a sag-resisting additive in both barite and invert-emulsion fluids was verified to safely reduce sagging in a significantly inclined well and compared with the outcomes of other existing anti-sagging materials. The settling of weight material out of the mud column was thoroughly investigated in deviated positions (30\({}^{\circ}\), 45\({}^{\circ}\), 60\({}^{\circ}\), 70\({}^{\circ}\), 80\({}^{\circ}\), and 90\({}^{\circ}\)) while testing at different temperatures (250 \({}^{\circ}\)F, 300 \({}^{\circ}\)F, 350 \({}^{\circ}\)F, and 400 \({}^{\circ}\)F). The fluid samples were also assessed while in motion by utilizing a VSST to measure the sag potential in a dynamic setting. In addition, the flow parameters of high-density water-based fluids were evaluated at elevated temperatures. [PERSON] et al. [7]. provided a comprehensive analysis of the drilling fluid design and mitigation strategies for sagging during drilling operations in challenging environments. Recent advances in the oil and gas industry are toward the development of high-pressure, high-temperature (HPHT) reservoirs, which may be accessed through deepwater wells or extended-reach wells that are more prone to the sagging phenomenon. This conundrum is yet to be fully understood and may occur unexpectedly. Regardless of ongoing research, there are no immediate universal remedies, and this may be a limiting factor in the development of geothermal reservoirs.