The Magnetic Thickness Tool Detection Method

The Magnetic Thickness Tool is designed based on the principle of Faraday's law of electromagnetic induction and the transient electromagnetic method as the theoretical foundation. It consists of two parts: the transmitting system and the receiving system. The working process is divided into three parts: transmitting, electro-magnetic induction and receiving. The transmitting current is a bipolar current pulse, which is emitted in a positive and negative intermittent manner and has the characteristics of instantaneous and planar wave fields.

The Casing Damage Detection of production wells is carried out by using the transient electromagnetic principle. The physical theoretical model of logging is an electromagnetic field problem in a multi-layer cylindrical layered medium. When the DC pulse current is turned off, a primary field is generated around it, and then the magnetic field decays, generating longitudinal eddy currents and radial loop currents in the downhole casing. As the induced current varies with time, a secondary magnetic field that decays exponentially with time is generated around it. The induced electromotive force ε is detected by the receiving coil. After the transmitting current is turned off, due to the continuous attenuation and tendency to disappear of the primary field, only the secondary induced current and magnetic field interact. Meanwhile, the propagation and attenuation rate of the secondary field is related to information such as the shape and conductivity of the bushing. When the bushing undergoes deformation, corrosion, holes, cracks or other damages, it will partially or completely cut off the path of the induced current, which will change the amplitude of the induced electromotive force, and then through the interpretation path by displaying, analyzing and processing the measured data, the loss status can be qualitatively and quantitatively determined.

1, It has a stronger detection capability.

Measuring pure secondary field information eliminates the interference of the primary field, reduces the analysis of abnormal responses to the detection object, has high resolution, and the detection capability can be directly improved by increasing the transmission power.

2, It has higher observation accuracy.

Single-pulse excitation can obtain the attenuation curve of the entire transient magnetic field containing more information. Through multiple superpositions, the signal-to-noise ratio can be significantly improved, and the observation accuracy can be enhanced.

3, It has a faster logging speed.

The downhole speed measurement is 700m/h, which improves the testing efficiency and operation timeliness.

4,It has widespread adaptability.

It adopts non-contact, continuous, and rapid logging, offering simple, reliable on-site operation and high logging efficiency.

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