An effective method of protection of oil field pipes inner surface

Abstract

Corrosion is a key factor, effecting service life of field pipelines. A review of methods of protection of circle welding seam internal surfaces and adjacent end pipe areas presented in the paper, as well as their imperfections, a technology proposed to protect them by arc building-up corrosion-resistant coating. With the elaborated technology the pipe metal does not get considerable overheating, retaining correspondent level of mechanical properties. The properly selected parameters of building-up mode provide a minimal stirring in the process of building-up and the decrease of concentration of main alloying elements (Cr and Ni) in the protective layer does not exceed 20%. To determine the minimal length of protective layer, manual arc welding and welding in protective gases atmosphere by consumable electrode were considered as possible welding methods. Simulation in the program complex SYS-WELD enabled to determine the areas subjected to critical heating, what was confirmed by the data, obtained during imitation of a circle seam in laboratory conditions at 159×8 mm short pipe. The proposed technology excludes the porosity of the built-up layer and other defects, decreasing the efficiency of pipe metal protection. Content of alloying elements was selected, for the built-up coating to be inclined to passivation and to have high resistivity against corrosion processes. Total corrosion rate at the tests in an acid solution, having hydrogen sulfide, was less than 0.1 mm/year thanks to austenite structure. The efficiency of the proposed technology was confirmed by positive results of pilot-field tests at a by-pass line under conditions of Sutorminskoje oil, gas and condensate deposit.