A modified high density brine for use in subterranean drilling and completion operations. The modified high density brine includes the addition of high density particle addition that can optionally be surface-modified. The resultant modified high density brine eliminates the need for toxic, corrosive, and costly ZrBr2 additions or other ionic additives to boost the density of the modified high density brine to 15-17 lbs./gallon or greater.