Two-dimensional ground nuclear magnetic resonance inversion method based on B spline interpolation

Abstract

The invention relates to a two-dimensional ground nuclear magnetic resonance inversion method based on B spline interpolation, wherein an interpreting result obtained through array type coil semi-covering can be obtained through laying relatively small number of coils and collecting signals of several measuring points according to a B spline interpolation inversion method. The two-dimensional ground nuclear magnetic resonance inversion method is suitable for detecting non-layered non-uniform water body. The B spline interpolation method is used for performing interpolation calculation on the initial amplitude of a nuclear magnetic resonance signal, thereby enlarging a data matrix and improving correlation among data. An optimal regularization factor is searched through a dichotomy, thereby improving calculation speed. A Gauss-Newton iteration method is used for solving an inversion objective function, thereby obtaining a high-precision smooth inversion result. The two-dimensional ground nuclear magnetic resonance inversion method settles the problems of long wiring time, low detecting efficiency, unsmooth inversion result and low precision in two-dimensional ground nuclear magnetic resonance detection. The two-dimensional ground nuclear magnetic resonance inversion method can be used for high-efficiency, high-resolution and high-precision detection on underground water on conditions of fracture water, karst water, etc. The two-dimensional ground nuclear magnetic resonance inversion method has advantages of greatly improving detecting efficiency and reducing field measurement time.

Description

Technical field: [0001] The invention relates to a geophysical detection method and the inversion interpretation of data thereof, in particular to simultaneously realizing a ground nuclear magnetic resonance inversion method based on B-spline interpolation in a two-dimensional measurement mode. Background technique: [0002] Surface Nuclear Magnetic Resonance (SNMR for short) is a new geophysical method for directly detecting groundwater developed internationally in recent years. This technology of directly detecting the abundance of hydrogen nuclei in the underground medium on the ground can not only be used for water shortage The exploration and evaluation of groundwater resources in the region can also play a unique role in the detection and early warning of water sources for geological disasters such as dam leakage, mine water inrush, tunnel water gushing, and landslides caused by groundwater. However, with the wide application of SNMR technology, the demand for groundwa...

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Problems solved by technology

[0004] The harmony search algorithm based on the above invention can only solve the one-dimensional ground NMR inversion problem, the lateral resolution is low, and the inversion result is unstable; the two-dimensional inversion method combining LS-SVD and ISGD can solve the simple two-dimensional The water-bearing model is used for inversion imaging. However, for complex water-bearing bodies such as fractures and karsts in the actual detection process, this method is difficult to guarantee the inversion accuracy; the half-coverage measurement mode of the rectangular array coil improves the detection resolution compared with the square array coil. However, due to the limitation of the number of acquisition channels of the instrument system, multiple measurements are required, which has disadvantages such as time-consuming and labor-intensive, low measurement efficiency, low accuracy of inversion results, and unevenness. In addition, in order to improve the horizontal resolution, the When a coil with a short side length detects and inverts a survey line with a known length, the measurement efficiency of the half-coverage mode of the rectangular array coil will be seriously reduced

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