Pipeline Insulation Quality Estimation with Superficial Electromagnetic Methods

Estimation of insulation quality from the earth surface with the help of magnetic and electrical measurements is important task for pipeline industry. Pipelines are under operation in underground conditions during tens of years and periodical inspection should be performed. Some pipes can't be inspected from inside, only superficial inspection is possible. Pipeline inspection works with very long profiles and in the same time needs high resolution. In DC electrical methods only electrical signals are measured while in AC electromagnetic methods mainly magnetic field measurements are used. In Mexican Petroleum Institute new technology of pipeline characterization named Surface Electromagnetic (SEM) Technology for Pipeline Inspection was developed based on the approximation of a metallic pipeline by heterogeneous transmission line with variable distributed parameters. Developed field operations and interpretation procedure allow us quantitative determination of insulation resistance and uncoated area rate evaluated on both magnetic field and electrical field data. Magnetic and electrical observations have different measurement time (magnetic survey is about an order faster) and different spatial resolution to insulation damage. Their integration is quite reasonable and provides complete pipeline characterization because includes reconnaissance survey and detailed study of anomalous zones. The examples presented demonstrate the efficiency of the SEM technology.