Oil-soluble well treatment agents may be slowly released into a well or a subterranean formation by use of an aqueous fluid of (i) an oil-in-water dispersion having the oil-soluble well treatment agent as a dispersed phase and (ii) a second component having an oil-soluble or water-soluble primer coated onto a portion of its surface. The amount of the oil-soluble well treatment agent in the oil-in-water dispersion is from 20 to 50 weight percent and the average particle size of the oil-soluble well treatment agent in the dispersion may be from 0.005 to 2 micrometers. The oil-in-water dispersion may further contain a water-soluble well treatment agent.