Wellbore fluids may include an oleaginous continuous phase; a non-oleaginous discontinuous phase; and an emulsifier stabilizing the non-oleaginous discontinuous phase in the oleaginous continuous phase, wherein the emulsifier is the product of a reaction between an alkyl cyclic anhydride and a polar reactant, wherein the polar reactant is one or more selected from a group containing alkyl amine, alkanolamine, and polyamine. Methods may include drilling a wellbore with an oil-based mud, wherein the oil-based mud is an invert emulsion containing an emulsifier stabilizing the invert emulsion, wherein the emulsifier is the product of a reaction between an alkyl cyclic anhydride and a polar reactant, wherein the polar reactant is one or more selected from the group of alkyl amine, alkanolamine, and polyamine.