Commonly used brine-based completion fluids are calcium chloride, sodium chloride, and potassium chloride. Our main objective for this study is to overcome the rheological performance and density limitations of existing brine-based completion fluid for workover and completion in oil and gas reservoirs. Magnesium Bromide-based completion fluid exhibits a high-density 13.41-lb/gal, with a specific gravity of 1.61. Existing, calcium chloride, potassium chloride, and sodium chloride-based completion fluid exhibit a density of 11.64-lb/gal (specific gravity 1.39), 9.6-lb/gal, (specific gravity 1.15), and 10.02-lb/gal (specific gravity 1.20), respectively. Results suggest that a high-density and solid-free novel magnesium bromide-based completion fluid show suitable optimum rheology avoid formation damage, plugging, and eroding of tubular and completion equipment. In this study, we have investigated the rheological properties such as apparent viscosity, plastic viscosity, yield point, and gel strength 10 sec and 10 min of formulated completion fluid at the varying temperature of 84 °F (28.8 °C) to 192 °F (88.8 °C). We have found that magnesium bromide-based completion fluid shows lower apparent viscosity and plastic viscosity as compared to calcium chloride-based completion fluid. A low value of apparent viscosity is desired for the design and development of the completion fluid. [ABSTRACT FROM AUTHOR]