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A 3D NMR Prestack Inversion Method Based on Multi-frequency Off-Resonance Excitation

A resonance excitation and nuclear magnetic resonance technology, which is used in electrical/magnetic exploration, re-radiation of sound waves, instruments, etc. It can solve problems such as no mature technical solutions, and achieve good vertical resolution and anti-noise characteristics. high degree of effect

Active Publication Date: 2018-05-15
SHANDONG UNIV
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Problems solved by technology

[0004] However, in practical applications, there is no mature technical solution for the technical problem of how to simultaneously utilize the advantages of complex FID signals and off-resonance excitation conditions in inversion resolution

Method used

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  • A 3D NMR Prestack Inversion Method Based on Multi-frequency Off-Resonance Excitation
  • A 3D NMR Prestack Inversion Method Based on Multi-frequency Off-Resonance Excitation
  • A 3D NMR Prestack Inversion Method Based on Multi-frequency Off-Resonance Excitation

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Embodiment Construction

[0036] The present invention is described in detail below in conjunction with accompanying drawing:

[0037] The invention discloses a three-dimensional nuclear magnetic resonance prestack inversion method based on multi-frequency off-resonance excitation. The method is based on multi-channel nuclear magnetic resonance response signals under resonance excitation and multi-frequency off-resonance excitation. Three-dimensional complex signal inversion is performed on the response signal; after inversion, the results in each channel are correlated and superimposed to finally obtain the local water content parameter m(r,T 2 * ). like figure 1 As shown, the specific steps are:

[0038] (1) Electrical analysis first, combined with existing geological data and electrical exploration methods, to divide the electrical structure of the underground medium and the three-dimensional distribution of conductivity (resistivity);

[0039] (2) Determine a resonant response signal channel an...

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Abstract

The invention discloses a three-dimensional nuclear magnetic resonance pre-stack inversion method based on multi-frequency-offset resonance excitation. The method includes: dividing a measuring area into an underground medium electrical structure and a conductivity three-dimensional distribution characteristic; determining the excitation frequency of a resonance response signal channel and the Larmor frequency thereof, and accordingly determining the frequency offset between the excitation frequencies of FID signals of other multiple channels and the determined Larmor frequency; extracting the real component and the quadrature component of the FID signals in each channel, and calculating corresponding phases; establishing a forward model in each channel in the off-resonance excitation condition, and calculating a response kernel function of the corresponding FID signals; establishing an inversion target function and an inversion equation in each channel, and performing three-dimensional complex signal inversion on the FID signals in each channel; and performing superposition processing on inversion results obtained in the channels. According to the method, the advantages of a plurality of FID signals and the off-resonance excitation condition in the inversion resolution can be simultaneously taken.

Description

technical field [0001] The invention relates to the field of applied geophysics, in particular to a three-dimensional nuclear magnetic resonance pre-stack inversion method based on multi-frequency offset resonance excitation. Background technique [0002] NMR detection is a non-invasive electromagnetic detection method that directly and quantitatively identifies the water content, permeability characteristics and pore structure of underground media by observing the free attenuation signal generated by the macroscopic magnetic moment of hydrogen protons in water after being excited by an artificial radio frequency magnetic field. . At present, nuclear magnetic resonance detection has been widely used in many exploration, engineering and scientific experiment fields such as groundwater exploration, oil well logging, landslide detection and rock sample detection. The condition for NMR to generate resonance is that the excitation frequency of the artificial radio frequency magn...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V3/38
CPCG01V3/38
Inventor 李术才范克睿李貅刘斌戚志鹏聂利超刘文韬刘征宇李尧
Owner SHANDONG UNIV
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