An aqueous well completion/workover fluid, including a surfactant, at least one salt and an alkaline material, wherein the surfactant comprises a mixture of a phosphate ester and a non ionic ethoxylated alcohol, wherein the fluid has a pH between 6 and 8, and wherein the fluid generates an interfacial tension with crude oil of less than or equal to 1 dyne/cm. The fluid is not harmful to a formation if it penetrates the formation, and further exhibits an excellent detergency which can be beneficial as well.