Electromagnetic probe for transient electromagnetic logging instrument

Abstract

The invention belongs to the technical field of special instruments for petroleum logging construction and relates to an electromagnetic probe for a transient electromagnetic logging instrument. The electromagnetic probe is reasonable and compact in structure; the high-power launching capability of transmitting coils is enhanced, at the same time, secondary field voltage signal receiving accuracyis improved by means of comparative receiving coils; and assistance can be provided for casing damage detection and effective measurement of the formation resistivity of an open-hole well and a casedwell. According to the electromagnetic probe for the transient electromagnetic logging instrument of the invention, one set of transmitting coil system and two sets of comparative receiving coil systems are arranged in the electromagnetic probe, wherein any one set of comparative receiving coil system is composed of two receiving coils of which the winding directions are opposite to each other; and transmitting coils in the transmitting coil system and the receiving coils in the comparative receiving coil systems are coaxially wound on the same frame.

Description

technical field [0001] The invention belongs to the technical field of special instruments for petroleum well logging construction, and in particular relates to an electromagnetic probe for a transient electromagnetic well logging instrument. Background technique [0002] As a common technique to detect the quality of casing in open hole and cased hole, and extract the corresponding formation resistivity information, the transient electromagnetic method logging technology uses periodic bipolar rectangular pulse sequence as the excitation waveform. A brief direct current is applied to the transmitting coil to realize the electromagnetic conversion of the transmitting coil, thereby generating a stable magnetic field in the medium around the well. Wherein, the strength of the primary magnetic field is related to the power of the transmitting coil. According to Faraday's law of electromagnetic induction, after the transmitting coil is powered off, the primary magnetic field in ...

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Problems solved by technology

[0003] During the research process, the inventor found that, on the one hand, in order to ensure the effective measurement of the secondary field voltage signal in the later stage, it is necessary to consider increasing the high-power transmission capability of the transmitting coil. However, due to the limitation of the size of the wellbore, the diameter of the transmitting coil cannot be unlimited On the other hand, the receiving process of the secondary field voltage signal belongs to the signal receiving process of the whole frequency band, and there are electromagnetic interferences of different frequencies in nature, which will adversely affect the receiving accuracy of the receiving system, so for As far as the receiving coil is concerned, its primary design task should be to enhance the denoising ability of the signal

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