Application Of Superficial Electromagnetic Methods For Localization And Inspection Of Oil And Gas Pipelines' Technical Condition

Abstract

Superficial non-destructive inspection of oil and gas pipelines is performed using electromagnetic methods. For that an external AC generator connects to a control post of cathodic protection potentials to pass the current in the pipe system. To obtain the current distribution, the magnetic field on the earth surface is measured. Based on the approximation of metallic pipeline by transmission line we developed the electromagnetic (EM) technology for the control of pipeline technical conditions. This EM technology includes measurements of magnetic field, voltage on several cathodic protection posts and subsoil resistivity and allows determining the distributions of current along the pipes, leakage current, leakage resistance and resistance of insulating coating. The practical studies of the technical condition of oil and gas pipelines have been realized at several places in urban areas of Mexico. For potential leveling, pipelines are frequently connected to a joint cathodic protection system using jumpers between pipes. The regional study applying the proposed EM technology characterizes the group trajectory and integral quality of the pipe insulating coating. Additionally, this technology reveals the amount of tubes including pipes out of operation and provides the individual information in each pipe about the variations of current and insulation resistance. The detailed survey in the detected anomalous zones allow estimating the positions of jumpers, and also separating the zones with damage of the pipe coating from the connection of pipes out of operation or other grounded constructions.