A method of treating a subterranean formation, the method comprising: (A) injecting down a well bore into the formation an admixture of (a) an emulsion having an internal aqueous phase comprising a water-soluble oil or gas field chemical or an aqueous dispersion of a water-dispersible oil or gas field chemical and an external oil phase comprising a liquid hydrocarbon and an oil-soluble surfactant and (b) a demulsifier comprising a solution of a surfactant having a cloud point temperature of above 40° C.; or (B) separately injecting down a well bore into the formation emulsion (a) and demulsifier (b) and generating an admixture of emulsion (a) and demulsifier (b) within the formation.