Frequency division matched filtering method for improving offshore seismic data resolution by utilizing seismic focuses of different depths

Abstract

The invention discloses a method for improving offshore seismic data resolution by utilizing air gun seismic focuses of different depths. The method is characterized in that air guns are respectively arranged in positions of different depths to be excited, the near-field wavelet of each seismic focus is recorded, and a far-field wavelet is obtained through simulation; and because of the existence of an offshore strong wave impedance interface, trap points occur on the frequency spectrum of each far-field wavelet, the high-frequency information of air gun seismic focuses at superficial parts is rich, the low-frequency advantages of seismic focuses at deep parts are obvious, and periodic extension is formed. The spectral analysis is carried out on the far-field wavelets to determine the dominant frequency band of each wavelet, the high-frequency dominant section of the wavelet at a superficial part is kept unchanged, the far-field wavelet of the seismic focus at a deep part is expected to be output only at the low-frequency end, and a frequency division matched filter is obtained by calculation and then is applied to all seismic records acquired by the air gun seismic focuses at the superficial parts, thereby realizing the combination of advantages of wavelets of seismic focuses in two different depths, widening the frequency band of the offshore seismic data and improving the resolution.

Description

technical field [0001] The invention relates to the field of marine seismic exploration, in particular to a method for improving the resolution of marine seismic data by using airgun sources of different depths. Background technique [0002] The 21st century is the century of the ocean. Offshore oil and gas resources are extremely rich. After long-term exploration on land and shallow seas around the world, the number of major oil and gas discoveries has become less and less. Oil companies have turned their attention to the deep sea where the degree of exploration is still very low. However, the existence of ghost reflections in offshore exploration seriously restricts the improvement of resolution. The source wavelets excited at different depths will have differences in frequency bands due to the difference in ghost reflection notch points. The shallow source has rich high-frequency components, but the low-frequency end is not as good as the deep one. Therefore, it is diffic...

AI Technical Summary

Problems solved by technology

However, the existence of ghost reflections in offshore exploration seriously restricts the improvement of resolution. The source wavelets excited at different depths will have differences in frequency bands due to the difference in ghost reflection notch points. The shallow source has rich high-frequency components, but the low-frequency end is not as good as the deep one. Therefore, it is difficult to obtain seismic records with a wider frequency band from a single-depth seismic source, which seriously restricts the high-resolution exploration of offshore oil and gas.

Images