Array lateral logger autonomous focusing circuit and control method

Abstract

The invention discloses an array lateral logger autonomous focusing circuit and a control method. A potential difference signal of a main monitoring electrode M0 and a main monitoring electrode M1 inan array lateral logger is measured, and the potential difference signal comprises a mixed sine wave signal with different frequencies; differential amplification, blocking filtering and band-pass amplification processing are carried out on the potential difference signal; the processed potential difference signal is converted into a current signal, the current signal is loaded to a main electrodeA0, the current signal flows into the main electrode A0, and a new potential difference signal between the main monitoring electrode M0 and the main monitoring electrode M1 is formed after attenuation; the processes are repeated, so that the continuously attenuated potential difference signals are generated between the main monitoring electrode M0 and the main monitoring electrode M1, autonomousfocusing of the main electrode current is realized, and the measurement precision and the dynamic range of the instrument are improved.

Description

technical field [0001] The invention belongs to the field of oil and gas exploration well logging, and relates to an array lateral logging instrument autonomous focusing circuit and a control method. Background technique [0002] The array laterolog tool has high vertical resolution, and can measure the apparent resistivity curves of 5 formations at different radial depths, clearly describing the change of the resistivity from the wellbore to the original formation, providing a more reliable tool for accurately identifying oil and gas layers. data of. [0003] At present, the current of the main electrode of the array lateral logging tool used in the oil field mostly uses the numerical synthesis focusing method, that is, software focusing, that is, according to the principle of non-focusing resistivity logging, each current is measured separately, and the downhole main control microprocessor In the process, the size of the transmitted signal is determined through relevant m...

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Problems solved by technology

In this method, the main monitoring circuit adopts an open-loop method, and the hardware implementation is simple, but the residual signal ΔV of the main monitoring electrodes M0 and M1 momib Contains a variety of frequencies and has a large dynamic range, making accurate detection extremely difficult, thus affecting the measurement accuracy of the instrument

Especially when the salt mud drilling fluid invades the formation, the ratio of formation to mud resistivity is very large R t / R m >10000, also known as high-contrast strata, the main electrode current focusing coefficient increases, the measured value of shallow and medium lateral apparent resistivity is generally low due to the influence of mud, and the deep lateral apparent resistivity may be disordered due to the influence of high resistivity surrounding rock. Resulting in inaccurate measurement of formation resistivity

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