Study Of Environment-friendly Corrosion Inhibitor For Drill Tool In Saltwater Drilling Fluids

The corrosion of drill tool is a common problem in the drilling engineering, and it is more serious with the development of drill to higher speed and deeper well. Saltwater drilling fluid used in the exploitation of the brine well located around Hongze and Huaiyin undertaken by Jiangsu Oil Field in recent years contains much more CT and is also abundant in K⁺, Ca²⁺, SO₄²⁺ etc, so its conductivity is higher. Its temperature is too high (above 80℃), and it also contains many additives with complex elements, oxygen dissolved, so the corrosion of the drill tool is severe. It is concluded from EDS analysis on corrosion productions of G105 drill pipe in saltwater drilling fluid that the corrosion products on local drill pipe is mainly consisted of Fe₂O₃, and the corrosion of drill pipe is almost caused by the depolarization of dissolved oxygen.The corrosion environment of the drill pipe, the measures used for anti-corrosion and the studies on inhibitor used in the drilling fluid both at home and abroad at present were summarized. The effects of some main ions on the corrosion in the drilling fluid were investigated through orthogonal experiments and static coupon weight loss method in the room. The result indicates the sequence of the effect on corrosion rate is Cl^-> Mg²⁺,Ca²⁺> HCO₃^-> SO₄^2-. Cathodic corrosion process was mostly controlled by oxygen diffuse, By testing polarization curve of G105 steel in saltwater drilling fluid.Results of dynamic simulation corrosion tests show the effect factor of the drill pipe corrosion. The experiments indicates that the rate increase with the surge of temperature and Cl^- content, the decrease of pH, and pit corrosion is the main corrosion whose tendency is augmented with the increase of Cl^- content. An accelerated weathering test of immersion-dry-wet combined cycles show that the corrosion rate of the specimens decrease as the time went on, but the absolute corrosion rate is also too high which indicates the protection film is weak on the specimens' surface.Sodium molybdate, sodium tungstate, silicate and organic amine A,B are selected primarily through many experiments by lineal polarization resistance method. And then...