Direct current weak signal three-level calibrating method for formation water specific resistivity logging instrument

Abstract

The invention discloses a direct current weak signal three-level calibrating method for a formation water specific resistivity logging instrument. The direct current weak signal three-level calibrating method for the formation water specific resistivity logging instrument is characterized by comprising instrument level calibrating, channel level calibrating and real-time period level calibrating;the instrument level calibrating is that a simulation box is used for calibrating a constant direct current power source of the instrument, performance of a whole analog channel and a function of a digital channel; the channel level calibrating is that a calibrating device is used for calibrating the performance of the whole analog channel and the function of the digital channel; and the real-timeperiod level calibrating is that by means of DAC, a series of fixed positive and negative voltage values are emitted according to a preset timing sequence, a calibrating relay is controlled to send signals into a measuring channel, by means of amplification and treatment of n different pre-amplification channels and multichannel gating switch and smoothing, and collecting is carried out through ADC according to a preset timing sequence. By means of the direct current weak signal three-level calibrating method for the formation water specific resistivity logging instrument, the accuracy of signal measuring and collecting of the formation water specific resistivity logging instrument is improved, and the adaptivity of the instrument to different well conditions is also improved.

Description

technical field [0001] The invention belongs to the technical field of petroleum well logging, and in particular relates to a three-level calibration method for DC weak signals of a formation water resistivity logging instrument, which is used for daily maintenance and detection of the instrument and real-time compensation of the instrument during the well logging process. Background technique [0002] In the field of domestic logging instruments, most self-emission logging instruments emit AC sine wave signals, while formation water resistivity logging instruments emit DC signals. The weak AC signal can be easily restored to the original measurement signal after amplification, filtering, acquisition and processing. At present, the AC signal in the logging instrument can realize the effective resolution and measurement acquisition of 100nV level or even smaller signals, while the weak DC signal is limited. Due to the power noise of the downhole system, the ground noise of th...

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Problems solved by technology

[0003] The purpose of the present invention is to provide a three-level calibration method for DC weak signals of the formation water resistivity logging instrument, so as to overcome the weak and small DC signal and the vulnerability of the logging signal fluctuations in the logging process of the existing formation water resistivity logging instrument The shortcoming of influence, the present invention improves formation water resistivity logging tool for the accuracy of signal measurement acquisition, plays a key role for the accurate measurement of formation water resistivity logging tool signal, also improves the automaticity of different well conditions of instrument adaptability

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