A
wellbore fluid having an oleaginous phase and an additive for increasing the density of the
wellbore fluid. The additive comprises
solid colloidal particles coated with a dispersant during the
comminution process of forming the particles. Exemplary starting materials for the colloidal particles include commonly known weighting agents as well as mixture and combinations thereof. The dispersant in one embodiment, is selected from carboxylic acids of molecular weight of at least 150 Daltons. Alternatively, the dispersant
coating may be made of compounds including
oleic acid, polybasic fatty acids, alkylbenzene sulfonic acids,
alkane sulfonic acids, linear alpha-olefin
sulfonic acid or the
alkaline earth metal salts of any of the above acids, and phospholipids as well as mixtures and combinations of these compounds. In another embodiment the dispersant is a polyacrylate ester having an average molecular weight from about 10,000 Daltons to about 200,000 Daltons.