Studies on the formation and migration of colloidal iron sulfide in porous media were carried out using consolidated artificial alumina-kaolin cores sintered at 1500 degrees C. The artificial alumina-kaolin cores were imbibed with a solution containing thioacetamide and ferrous ions and heated at 80 degrees C to obtain the formation of FeS particles. Scanning electron micrographs showed particles less than 1 mu m in diameter and aggregates of different sizes covering the surface of the porous media. Core flooding experiments showed that the migration of the fine FeS particles reduced the permeability of core and the injection of surfactant solutions at constant salinity restored the original permeability after the production of the redispersed iron sulfide particles, in some cases.