A wide-bandwidth and azimuth seismic exploration method for offshore streamers

Abstract

The invention relates to an offshore streamer broadband wide-azimuth seismic exploration method. The offshore streamer broadband wide-azimuth seismic exploration method comprises the following steps of: establishing a three-dimensional seismic geologic model suitable for a stratigraphic structure of a target area, based on geological horizon, rock velocity and density data of the target area for previous offshore seismic exploration; optimizing the type of a wide-azimuth observation system and the aspect ratio of streamers, so as to obtain a wide-azimuth observation system type and a streamer aspect ratio that are suitable for the target area; optimizing three-dimensional curved streamer parameters, so as to obtain optimized three-dimensional curved streamer shape and streamer parameters; optimizing multi-point depth-variable random delay excitation parameters, so as to obtain excitation delay time series distribution corresponding to each synchronous source during excitation at different excitation points; in the target area, carrying out actual offshore streamer broadband wide-azimuth seismic acquisition by the three-dimensional curved streamers during multi-point depth-variable random delay excitation, so as to obtain actual acquisition mixed source shot gather records for the series of multi-point depth-variable random delay excitation.

Description

Technical field [0001] The invention relates to an offshore seismic exploration method, in particular to an offshore streamer broadband broadband azimuth seismic exploration method. Background technique [0002] Deep-water exploration is one of the important directions of offshore seismic exploration. However, due to many factors such as the rugged deep-water seabed and complex geological conditions in the middle and deep layers, the low signal-to-noise ratio and low resolution of the medium and deep seismic data acquisition are caused. To solve this problem, in addition to using specific techniques to improve the signal-to-noise ratio and resolution in seismic data processing, it is more important to obtain raw seismic data with high signal-to-noise ratio and high resolution in seismic data acquisition. The quality of marine high-resolution 3D seismic acquisition data is affected by many factors, but the most critical is the source system and the receiving system. The combinatio...

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Problems solved by technology

[0003] At present, the most widely used source system in marine seismic exploration is the airgun array, which has the advantages of low cost, clean and environmentally friendly, stable performance, high controllability, and repeatability; however, the ghost reflection of the sea surface makes the spectrum of the airgun array wavelet There is a notch, and the energy is low at the notch point, resulting in the shallower the depth of the seismic source, the high-frequency component of the excited wavelet is rich, but the low-frequency component is limited, and the deeper the depth of the source, the richer the low-frequency component of the excited wavelet , but the high-frequency components are limited

[0004] At present, the offshore receiving system usually adopts single-ship narrow azimuth single-streamer or multi-streamer operation, and the streamer is placed at the same depth, affected by the ghost reflection of the sea surface, there is a notch characteristic, which narrows the frequency band of the seismic record. The resolution of the seismic section is reduced; and the trapping effect of the streamer is different at different depths, and the streamer at different depths has different frequency information. Insufficient information, the deep streamer receives insufficient high-frequency information, and rich low-frequency information

Moreover, due to the operation of a single source, despite the multi-cable reception, the 3D seismic survey at sea is still similar to the 2D seismic survey with a wide line on land. The wide azimuth information is also not conducive to complex structural imaging and fracture reservoir description

[0005] Therefore, it is necessary to propose a set of marine seismic exploration methods that can not only realize low-frequency and high-frequency excitation, but also enable streamers to receive low-frequency and high-frequency information at the same time, and can collect wide-zimuth information required by subsurface anisotropy. Targeted solutions to the problems of narrow frequency bands and small aspect ratios of observation systems in current offshore seismic exploration methods

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