A far-field electromagnetic eddy current logging tool and its calibration method for quantitative interpretation

Abstract

The invention discloses a remote-field electromagnetic eddy current logging instrument and a quantitative interpretation calibration method thereof. The quantitative interpretation calibration method is that the instrument is stopped at a well section with a complete casing-pipe well; the thickness D of the casing-pipe well at the complete well section is input first after the instrument is electrified to work; after acquiring the parameter D, a single-chip microcomputer controller of the instrument calculates a proportionality factor, then a single-chip microcomputer of the instrument emits a square signal which continuously varies from 5 to 43Hz; after being varied along with the casing-pipe well, the square signal is received by a receiving coil of the instrument and then processed by a circuit and finally fed into the controller; the controller performs a phase comparison between the received signal and the emitted signal, and therefore, the influence of the parameters (sigma, micron, d) on the interpreted casing-pipe wall thickness can be removed, and as a result, the quantitative interpretation for the remote-field electromagnetic eddy current logging instrument is achieved, and meanwhile, the measurement sensitivity of the instrument can be greatly improved.

Description

technical field [0001] The invention belongs to the technical field of downhole casing well logging tools, in particular to a far-field electromagnetic eddy current logging tool and a calibration method for quantitative interpretation thereof. Background technique [0002] In the field of petroleum development, when the oilfield development enters the middle and late stages, the downhole casing will be damaged to varying degrees due to the corrosion of hydrogen sulfide and carbon dioxide, as well as the action of formation stress, high temperature and high pressure. According to the requirements of oilfield development, the casing should be monitored regularly after working in the downhole for more than 20 years. When it is found that the casing wall is damaged by more than 50%, it should be repaired in time. Otherwise, when the casing wall is damaged and there are fractures or perforations, it will not only be difficult to repair, but also likely to cause the oil well to b...

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Problems solved by technology

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art, and provide a far-field electromagnetic eddy current logging tool and a calibration method for its quantitative interpretation. The problem of the influence of the rate μ avoids the error caused by the bushing material, batch, service life and other factors on the measurement results

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