Abstract: A method of removing calcium carbonate-containing oil-based filter cake from a wellbore involving contacting the calcium carbonate-containing oil-based filter cake with a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, a surfactant, and a glycol ether mutual solvent. The method is performed at a pressure of 200 to 400 psi and a temperature of 50 to 125° C. The method removes calcium carbonate-containing oil-based filter cake made of a water-in-oil emulsion, calcium carbonate, a primary emulsifier, a secondary emulsifier, a contamination treatment agent, a viscosity control agent, a filtration control agent. The method meets industry standard steel corrosion rates of less than 0.049 lb/ft2 per day. Also disclosed is a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, a surfactant, and a glycol ether mutual solvent that meets OECD 301B thresholds for ready biodegradability.

Abstract: A method of removing calcium carbonate-containing oil-based filter cake from a wellbore involving contacting the calcium carbonate-containing oil-based filter cake with a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, a surfactant, and a glycol ether mutual solvent. The method is performed at a pressure of 200 to 400 psi and a temperature of 50 to 125° C. The method removes calcium carbonate-containing oil-based filter cake made of a water-in-oil emulsion, calcium carbonate, a primary emulsifier, a secondary emulsifier, a contamination treatment agent, a viscosity control agent, a filtration control agent. The method meets industry standard steel corrosion rates of less than 0.049 lb/ft2 per day. Also disclosed is a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, a surfactant, and a glycol ether mutual solvent that meets OECD 301B thresholds for ready biodegradability.