Application of direct frequency synthesis method in measurement of resistivity of electromagnetic wave
A technology of frequency synthesis and electromagnetic wave, which is applied in measurement, wellbore/well components, earthwork drilling and production, etc. It can solve the problems of signal frequency accuracy, stability and poor high temperature characteristics, and achieve the effect of high resolution and small error
Inactive Publication Date: 2011-09-14
CHINA NAT OFFSHORE OIL CORP +2
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In the past, oscillator circuits and phase-locked loop circuits were often used to generate fixed-frequency signals, but the frequency accuracy, stability and high-temperature characteristics of the signals generated in this way were poor.
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[0021] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.
[0022] As we all know, in the electromagnetic wave resistivity measurement technology, several steps are involved, such as signal transmission, signal reception, frequency mixing of local oscillator signal and received signal, etc. For the measurement of electromagnetic wave resistivity, at least one transmitter and two receivers are required. The local oscillator signals of the two (or more) receivers are mixed with the signals sent by the transmitter, and then the two (or more) mixed signals are mixed. Inversion, the calculated resistivity. Therefore, two (or more) receivers must provide local oscillator signals with stable frequency to achieve frequency mixing with the signal sent by the transmitter. The more stable the local oscillator signal, the higher the accuracy, and the higher the accuracy of the signal obtained after mixing. , the resistiv...
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The invention relates to application of a direct frequency synthesis method in measurement of resistivity of electromagnetic waves, and is characterized by obtaining a local oscillator signal by using the direct frequency synthesis method in the process of resistivity measurement of the electromagnetic waves comprising the steps of transmitting a signal, receiving the signal and mixing frequencies of the local oscillator signal and the received signal. A direct digital frequency synthesis technology is applied to the resistivity measurement of the electromagnetic waves, so the high-precision, sustained and stable local oscillator frequency signal is generated by the direct digital frequency synthesis technology, and after the frequencies of the local oscillator signal and the received signal are mixed, a resistivity value of the electromagnetic waves obtained by inverse computation is small in error and high in resolution. The direct frequency synthesis method is well combined with a resistivity well test system, so the system can operate stably at 150 DEG C.
Description
technical field [0001] The invention relates to a direct digital frequency synthesis technology, specifically the application of the direct frequency synthesis method in the measurement of electromagnetic wave resistivity. The technology is applied to provide high-precision frequency for the resistivity measurement system in the logging-while-drilling system. Background technique [0002] The electromagnetic wave resistivity logging tool calculates the resistivity by measuring the amplitude and phase changes of the electromagnetic wave after it propagates in the formation. The instrument is divided into two parts: transmitter and receiver. The two receivers receive the electromagnetic waves emitted by the transmitter respectively. The resistivity instrument compares the amplitude and phase of the two electromagnetic waves received by the receiver, and uses the amplitude ratio and phase difference to invert the resistivity value. The resistivity value is the resistivity of t...
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IPC IPC(8): E21B47/00E21B49/00
Inventor 周建良石岩峰何保生潘光玮李汉兴冯泽东吴光武石峻峰靳勇武广瑷
Owner CHINA NAT OFFSHORE OIL CORP