Abstract: The non-damaging use of relatively high density calcium halide-containing brine compositions as kill weight workover fluids in high pressure water injection wells is rendered practicable via the use of an aqueous preflush composition containing an effective amount of a scale inhibitor material. In those instances where the scale inhibitor material is relatively strongly acidic in character (such as, for example, in the case of phosphonic acid materials, and the like), remarkable improvements in the injectivity of wells treated with said acidic aqueous preflush composition has also been obtained.