Method for eliminating adjacent-frequency harmonic interference in ground nuclear magnetic resonance data

A ground nuclear magnetic resonance and harmonic interference technology, which is applied in the measurement using nuclear magnetic resonance spectrum, electronic magnetic resonance/nuclear magnetic resonance detection, magnetic resonance measurement, etc. Errors in the model results, etc., to achieve the effect of improving reliability, good accuracy, and high removal efficiency

Active Publication Date: 2018-07-31
JILIN UNIV
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Problems solved by technology

In the presence of adjacent frequency harmonic noise, this method cannot also disting...

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  • Method for eliminating adjacent-frequency harmonic interference in ground nuclear magnetic resonance data
  • Method for eliminating adjacent-frequency harmonic interference in ground nuclear magnetic resonance data
  • Method for eliminating adjacent-frequency harmonic interference in ground nuclear magnetic resonance data

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[0038] In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0039] Take a group of ground NMR signals with an initial amplitude of 50nV, a relaxation time of 0.3s, a Larmor frequency of 2300Hz, and an initial phase of π / 3rad; the power frequency harmonic fundamental frequency is 50.010Hz, and the amplitude of 100 harmonics The sum and phase are randomly distributed; the data with random noise of 10nV is illustrated as an example.

[0040] see figure 1 , step 1, input ground NMR data V=[V 1 ,V 2 ,L,V K ], K is the number of sampling points, its time domain and frequency domain diagrams are shown in figure 2 (a) and figure 2 (b) Shown by the black curve. Measure the geomagnetic fi...

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Abstract

The invention belongs to the ground nuclear magnetic resonance data processing field and discloses a method for eliminating an adjacent-frequency harmonic in ground nuclear magnetic resonance data. The method comprises the following steps of inputting ground nuclear magnetic resonance measurement data, measuring an experimental-location ground magnetic field and calculating a Larmor frequency; searching a power frequency harmonic fundamental frequency, modeling a power frequency harmonic and calculating and acquiring all harmonic coefficients; and determining whether there is an adjacent frequency harmonic according to a frequency difference between a Larmor frequency and each harmonic frequency, if there is no adjacent frequency harmonic, using the harmonic fundamental frequency and the harmonic coefficients to calculate and acquire a harmonic model, and subtracting the harmonic model from measured data, and if there is the adjacent frequency harmonic, removing the power frequency harmonic outside an adjacent domain harmonic and then removing the adjacent domain harmonic based on a fitting method. In the invention, under the condition that a nuclear magnetic resonance signal is not lost, the influence of the adjacent-frequency harmonic in the power frequency harmonic on subsequent data processing and inversion is removed. Especially when the Larmor frequency of the experimental location is close to the high order harmonic of the power frequency harmonic, a ground nuclear magnetic resonance signal characteristic can be accurately extracted and inversion result accuracy is increased.

Description

technical field [0001] The invention belongs to the field of ground nuclear magnetic resonance data processing, and specifically relates to a method for eliminating adjacent frequency harmonics in ground nuclear magnetic resonance data. Background technique [0002] Surface nuclear magnetic resonance is a geophysical method to directly detect the occurrence properties of groundwater. It has the advantages of fast measurement speed, high resolution and quantitative interpretation. However, the signal obtained by the ground NMR method is very weak, and usually the intensity is only on the order of nanovolts (nV, 10 -9 V), susceptible to the interference of various environmental noises, resulting in low signal-to-noise ratio of collected data, seriously affecting the accuracy of subsequent inversion results, and restricting the application of this method in complex environments such as towns, villages, and underground engineering. [0003] Ground NMR data mainly contain three ...

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Application Information

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IPC IPC(8): G01V3/14G01R33/46
CPCG01R33/4625G01V3/14
Inventor 蒋川东王琦田宝凤易晓峰范铁虎
Owner JILIN UNIV
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