Low signal-to-noise ratio nuclear magnetic resonance echo signal processing method
A technology of echo signal and nuclear magnetic resonance, which is applied in the fields of electron magnetic resonance/nuclear magnetic resonance detection, acoustic re-radiation, electric/magnetic exploration, etc., can solve the problems of high data noise, unsatisfactory interpretation and application, etc., and achieve confidence High noise ratio, improved inversion quality and precision, and improved accuracy
Active Publication Date: 2021-03-19
CHINA UNIV OF GEOSCIENCES (BEIJING)
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At present, in actual well logging, data acquisition adopts superimposition of different phase signals. Although part of the noise is suppressed, the superimposed data still has quite high noise, which cannot meet the needs of interpretation applications.
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[0020] The specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.
[0021] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations thereof such as "includes" or "includes" and the like will be understood to include the stated elements or constituents, and not Other elements or other components are not excluded.
[0022] In order to improve the accuracy of relaxation time inversion, the inventors conducted the following analysis in the process of realizing the present invention: CMR-type nuclear magnetic resonance logging echo signals have the characteristics of wide bandwidth and weak signals, making detection more difficult. There are many echoes in the NMR logging echo data, and 1800 echoes can be measured by the CMR instrument, a...
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The invention discloses a low signal-to-noise-ratio nuclear magnetic resonance echo signal processing method, which comprises the following steps of: firstly, filtering echo signals of which the noiseamplitude is greater than a preset threshold value so as to preferably select some echo signals with higher signal-to-noise ratio from original echo signals, preferably, performing SVD filtering processing on the preferably selected echo signals, and while performing SVD filtering processing, conducting zero setting on some singular values in Hankel signal matrix elements of the constructed echosignals, reconstructing a signal matrix which is more accurate. The signal-to-noise ratio of the echo signals recovered based on the new signal matrix is higher, and when subsequent relaxation time inversion process is carried out based on the optimized echo signals, the inversion accuracy can be greatly improved.
Description
technical field [0001] The invention relates to the field of nuclear magnetic resonance logging, in particular to a method for processing nuclear magnetic resonance echo signals with a low signal-to-noise ratio. Background technique [0002] NMR logging technology can provide more abundant formation information than conventional logging methods, especially for the exploration of low-porosity, low-permeability and complex oil and gas reservoirs, which has incomparable advantages. The collection of nuclear magnetic resonance logging echo signals will inevitably be affected by equipment and downhole environmental noise. In complex formations such as igneous rocks, especially in igneous rock formations, the echo signals recorded due to poor signal and small porosity are noisy, which brings great uncertainty to the inversion work. When the signal-to-noise ratio is less than 5, direct inversion cannot obtain a reliable relaxation time T2 distribution, and the data must be filtere...
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IPC IPC(8): G01V3/32G01V3/38
CPCG01V3/32G01V3/38
Inventor 谭茂金李博王克文武宏亮李成林
Owner CHINA UNIV OF GEOSCIENCES (BEIJING)