Fluid producing or injecting wells may be treated with a water-in-oil emulsion for the removal or inhibition of unwanted particulates, including pipe dope, asphaltenes and paraffins. In addition, such emulsions are effective in the displacement of oil base drilling muds and/or residues from such muds from wells. The emulsion may also be used to break the interfacial and/or rheological properties of oil base mud and synthetic oil base mud filter cakes, and act as a demulsifier to break the water-in-oil emulsion present in such oil base and synthetic oil base muds. The water-in-oil emulsions may optionally contain a dispersing agent as well as a surfactant.