Patent ID: 7754661

Claim:
A method for recycling a used, water-in-oil emulsion drilling mud comprising fatty acid emulsifiers or derivatives thereof, the method comprising: adding an acid to the used mud sufficient to reduce the pH of a water phase to a value less than 7 for deactivating the fatty acid emulsifiers or derivatives thereof in the drilling mud, the acid selected for having low affinity for an oil phase of the drilling mud; mixing the drilling mud with the acid for sufficient time to deactivate the fatty acid emulsifiers or derivatives thereof; separating the treated drilling mud for separating the base oil phase from the water phase and from solids, including ultra-fine solids and organoclays, contained therein, the recovered base oil phase containing at least substantially all of the deactivated fatty acid emulsifiers or derivatives thereof; and adding lime to the recovered base oil phase for reactivating the fatty acid emulsifiers or derivatives thereof contained therein for use in preparing a new drilling mud without the need to add additional fatty acid emulsifiers or derivatives thereof.