This paper presents downhole magnetic imaging defectoscopy (MID) in memory mode, its key principles, differences from other corrosion logging technologies, and some results of its application in oil wells.
The MID technology is designed to check the integrity of magnetic and non-magnetic tubing and casing strings in oil and gas wells. It can be used to detect various defects, corrosion and mechanical wear, and to assess the quality of perforations.
The MID tool contains two high-sensitivity sensors: a short generator/receiver coil and a long one with short relaxation times to analyse responses even at early times of 0.1 ms. The short coil generates a short, low-amplitude electromagnetic pulse and records a response from the first metal barrier, normally tubing, where as the long coil generates a long, high-amplitude electromagnetic pulse and records a signal travelling a much longer distance of up to 13 inches to record the total response from tubing and casing. Mathematical processing of these responses can determine the thicknesses of the first and second metal barriers.
An independent power supply allows logging to be performed on slickline, which substantially reduces operating costs and enables the use of magnetic imaging defectoscopy for well monitoring to prevent leak and corrosion related incidents and thus increase environmental safety in the field. The wide use of memory magnetic imaging defectoscopy will substantially reduce the number of well incidents and expenses for remedial jobs.
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