Treatment of drilling fluid to combat drill pipe corrosion

The rate of corrosion of drill pipe due to different drilling fluid compositions has been studied. Polymers used to formulate different fluid samples are: cellulose ethers, lignosulfonates and synthetic copolymers. Samples are stressed chemically by adding gypsum and lime and heated up to a temperature of 230°C. Both electrochemical and weight-loss techniques were used to study the corrosion rate of the steel coupons. Results have shown that drilling fluids containing cellulose ethers and lignosulfonates exhibit severe corrosion rate of the steel coupons under bottom hole conditions. However, synthetic copolymers such as, vinyl sulfonate vinyl amide and styrene sulfonate maleic acid maintain the corrosion rate of the steel coupons to an acceptable level.