Crack detection method based on prestack coherence

Abstract

The invention provides a crack detection method based on prestack coherence, which belongs to the field of oil-gas field exploration. The method comprises the following steps of: firstly, processing actual prestack seismic data to obtain a prestack seismic trace gather subjected to dynamic correction; secondly, stacking separated directions and separated offset distances through utilizing the prestack direction common midpoint seismic trace gather, and obtaining separated directions and separated offset distances stacking trace gather; and carrying out covariance matrix-based coherency cube calculation on the separated directions and separated offset distances stacking trace gather obtained through stacking to obtain a crack coherency cube, carrying out crack parameter inversion calculation on the obtained crack coherency cube, and further obtaining a final crack development direction and development strength. According to the crack detection method based on prestack coherence, a coherence algorithm is introduced in the prestack seismic trace gather for the first time, and a method for recognizing faultage in a stratum with the thickness being smaller than a seismic wavelength is provided, so that the breakage or the crack in three-dimensional seismic data can be more distinct, clear and visual.

Description

technical field [0001] The invention belongs to the field of oil and gas field exploration, and specifically relates to a pre-stack coherence-based fracture detection method. Aiming at the problem of natural fractures existing in actual oil and gas field exploration, the pre-stack seismic gather data coherence technology is used to carry out fracture detection. Background technique [0002] Natural fractures play an important role in petroleum exploration because fractures exist in nearly every reservoir, rock type, and depth. Determining these fractures and identifying their orientation can help exploration scientists better understand the reservoir. Subsurface fractures vary in size. Fractures smaller than seismic magnitude below 10 meters are of great interest in reservoir characterization, and determining areas of maximum fracture density or determining the orientation of these fractures within a reservoir is of great interest to geophysicists. is an important technical...

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Problems solved by technology

[0004] At present, the method of using seismic coherence technology to identify fractures is often based on post-stack seismic data, and the main problem faced by post-stack seismic data is the lack of azimuth data. Azimuth angle, the obtained seismic coherence result is also the result of the average fracture information of all azimuths, which is no problem for the development and prediction of large underground faults or larger fractures, but for some small-scale fractures and In other words, the averaged results obliterate the azimuth direction of the fracture development

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