Development of High-Resolution Axial Flux Leakage Casing-Inspection Tools

Abstract Well casing and tubing integrity is a very important component in the safe operations of oil and gas wells in the US. To maintain safe operating conditions through out the life of a well, operators must periodically determine the integrity of the downhole well tubulars. Historically, casing inspection data has been acquired with downhole wireline technology, and predominately with magnetic flux leakage (MFL) inspection tools. Limitations in available electronics, however, have meant that MFL logging tools have thus far been commercially available only in low-resolution configurations. Although proven to be highly robust and effective in downhole inspection applications, all low-resolution MFL instruments incorporate measurement and analysis techniques that limit their ability to precisely resolve defect geometry in all circumstances. Baker Atlas is in the development of high resolution MFL logging instruments based on hall sensors and other improvements in the magnetic, electronic and mechanical configuration of the inspection system. From an industry survey, a set of requirements for a series of high resolution MFL logging instruments was established. A high resolution MFL instrument design program was then undertaken, incorporating magnetic finite element analysis, mechanical design and electronics design to meet the defined applications. A bench prototype device was used to acquire characterization data in a laboratory environment. The resulting axial flux leakage inspection data was then analyzed to determine the instruments basic defect detection thresholds and sensitivity to changes in defect length, width and depth. Finally, an operational field test device was used in field applications to verify operational performance of the inspection system. This paper will review the development process and outline expected benefits of the tubular inspection system. These developments of high-resolution MFL logging instruments are intended to produce a more accurate determination of defect geometry, which will provide operators with improved data for casing integrity management.