Method for detecting digital acoustic head waves

Abstract

The invention belongs to the field of acoustic logging, specifically relates to a method for detecting digital acoustic head waves. The existing method for detecting acoustic head waves is a threshold method which is characterized in that a fixed threshold value Vs is determined by an algorithm or inputted by an operator, therefore, in the method, the determination of the threshold value limits the correctness in detecting the head wave. The method for detecting digital acoustic head waves comprises the following steps: 1) initializing; 2) selecting the Tf and Ts of appropriate wave trains; 3) limiting the time detection range of the head wave of each wave train; 4) calculating the threshold value Vs of the head wave of each wave train; 5) detecting the time T1 of the head wave of each wave train; 6) fitting the time line of the head wave of each wave train by using the least square method, then reversely reasoning the theoretical times of the head waves, and comparing the obtained times; 7) searching samples Td with a threshold value less than the threshold value Vs from the head wave of each wave train; and 8) searching the largest sample as the position of the head wave between T and Td. The acoustic head waves detected by using the method provided by the invention are high in accuracy.

Description

technical field [0001] The invention belongs to the field of acoustic logging, and in particular relates to a digital acoustic first wave detection method. Background technique [0002] The current detection method for the first acoustic wave is generally the threshold method. A fixed threshold value Vs is determined by an algorithm, or the threshold value Vs is input by the operator. When the first value Vm greater than the threshold value Vs is reached, the wave where Vm is located is considered to be the first wave (see figure 1 ). Digital sound waves generally have multiple waveforms, and each waveform detects its own first wave one by one according to this method, which is used as a reference for calculating travel. [0003] In this method, the determination of the threshold limits the accuracy of detecting the first wave, and the amplitude of the first wave varies greatly in the stratum with large changes. wave; if the baseline interference is large, the baseline in...

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Problems solved by technology

[0003] In this method, the determination of the threshold limits the accuracy of detecting the first wave, and the amplitude of the first wave varies greatly in the stratum with large changes. wave; if the baseline disturbance is large, the baseline disturbance may be regarded as the first wave

And each waveform detects the first wave separately. When one or more waveforms are wrong, the corresponding first wave is also detected incorrectly. These provide wrong first wave references for the calculation of travel, resulting in errors in the calculation of travel time.

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