A new type of emulsion drilling muds is developed, i.e. reversible invertible drilling mud (RIDM). RIDM is capable to change an emulsion type on a reciprocal (eversible) basis affected by a vatiety of chemical inverters; thus it can change its processing behavior from OBM to water–base solution and vice versa. The topic of discussion is methods and approaches used for transition oil-in-water emulsion into inverted (water-in-oil) emulsion and vise versa. Application of RIDM technical process is described. Process characteristics of RIDM are specified. Changes in emulsion microstructure during phase inversion are investigated. Performance analysis of RIDM application in field conditions is given.