Large standoff magnetometry (LSM), a novel screening technology, has shown strong industry relevance in several pipeline integrity investigations. LSM is used to detect changes in the magnetic field of a pipeline due to changes in the magnetic susceptibility of steel. These changes are known as inverse magnetostriction (a.k.a. the Villari effect) and occur when a ferromagnetic material (steel) is subjected to mechanical stress, such as the presence of stress on the wall of a pipeline. Geometric anomalies (ovalities, dents, wrinkles), hoop stress, ground and slope movement, bend strain, thermal expansion, cracks, and material defects are examples of potential sources of stress that LSM can detect from aboveground.
This paper summarizes the use of LSM as a complimentary tool in several pipeline integrity assessments conducted on oil and gas pipelines, in this case, to pinpoint a lost inline inspection pig and to identify dents, cracks, buckles, slope movement, casing ends, unknown valve locations and other pipeline integrity and direct assessment applications. Ongoing development programs and lessons learnt from practical, real-life projects and validations of the technology are presented to demonstrate the effectiveness of LSM for pipeline integrity investigations.