Laboratory core flow tests were conducted to assess the formation damage potential of brines with densities between 13.4 and 19.2 pounds per gallon (ppg). Unfavorable fluid/rock interactions are not evident. Recovery of oil permeability is slow but complete, in agreement with established displacement theories. Observed damage effects are the result of instability of the brine or incompatibility with water in the cores. The effectiveness of ZnBr2 in preventing impairment suggests acid soluble impairing materials.