Methods of drilling well bores using invertible oil external-water internal drilling fluids

摘要

Methods of drilling well bores using an invertible oil external-water internal emulsion drilling fluid and then inverting the drilling fluid to a water external-oil internal emulsion are provided. The methods basically comprise the steps of contacting the oil external-water internal emulsion with an aqueous acid solution containing an anionic sulfonate surfactant for preventing aqueous acid solution-crude oil emulsions and crude oil sludging and a chemical for preventing the anionic sulfonate surfactant from reacting with the emulsifier in the oil external-water internal emulsion.