Vibroseis frequency division simultaneous excitation method

Abstract

The invention discloses a vibroseis excitation method of seismic data acquisition. Sub scanning signals are divided into signals with intersection frequency band and signals without intersection frequency band. The encoding is carried out in an order from a low frequency band to a high frequency band. The no-intersection-frequency-band sub scanning signal arrangement matrix scanning is carried out. Each scanning sub signal of a first row in a no-intersection-frequency-band sub scanning signal matrix or a force signal corresponding to the signal and a simultaneously excited parent record are used to carry out correlation or convolution. An earthquake sub record which is excited and formed by the scanning sub signal is separated, separated earthquake sub records which are formed by a completed scanning sequence are superimposed to form a sub seismic record, and the vibroseis frequency division simultaneous excitation is completed. Under the premise of maintaining highly efficient acquisition, adjacent gun interference and harmonic interference are greatly reduced, and the daily efficiency is 50 times of that of the conventional scanning.

Description

technical field [0001] The invention belongs to the field of seismic data acquisition, and is a vibrator excitation method for high-fidelity realization of simultaneous excitation and high-efficiency acquisition in vibrator seismic exploration. Background technique [0002] In seismic exploration, vibroseis has been widely used as the main tool for generating seismic signals. The routine use of vibrators includes the following steps: First, place one or more vibrators on a shot point. Then a scanning signal is used to drive the vibrator, the source starts to vibrate, the vibration time is generally 10 to 16 seconds, and the scanning signal is usually a signal whose frequency changes with time. Then, the geophone receives and records the response data for a period of time equal to the sweep time plus a listening time. This time shall include the minimum necessary time for seismic waves to be generated, reflected from the primary target layer, and received. Finally, the sei...

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Problems solved by technology

[0003] There are several problems with the traditional source scanning: First, the correlation process will cause correlation side lobes, which will affect the accuracy of the final processed data

Second, the harmonic distortion of the source will cause harmonic noise

But listening time limits productivity

Fourth, although the combined excitation increases the intensity of the seismic signal, the high frequency of the seismic signal will be suppressed due to the height difference and response difference of each station in the combination and the combined effect.

But the separated data is not perfect, it contains the remaining energy of the impending gun

[0007] The limitations of the above-mentioned scan length coded synchronous excitation are: 1) Due to the different scan lengths, it brings difficulties to data processing

2) The energy of different scan lengths is different, and it is difficult to balance

3) Multi-group synchronous scanning, the scanning length increases and the efficiency decreases

This cannot eliminate the listening time, because the M scan records must be independent and unrelated to solve this set of linear equations, that is, as N increases, the M equations will not be independent.

If a tandem scan with no listening time is used, the reflection data from one segment will interfere with subsequent scan segments

In addition, the recorded data will not have a one-to-one relationship with the source force signal, so harmonic interference will not be properly handled

Simultaneously the number of mutually uncorrelated scans of the phase encoding used is itself very limited

[0010] The limitations of the phase-encoded synchronous excitation above are: 1) As the phase difference between adjacent scans decreases, the data is more disturbed by adjacent shots

In this method, each record needs to be correlated multiple times, and then superimposed to form separate records, which is not efficient

At the same time, due to the large distortion in the response of the seismic source to the random signal, the excitation effect is not ideal.

The limitation of distance separation synchronous scanning technology (DS3) is that it occupies a large amount of equipment

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