Primary wave azimuthal anisotropy based fracture predicting method

Abstract

The invention provides a primary wave azimuthal anisotropy based fracture predicting method. The method comprises the steps of amplitude preservation preprocessing, azimuth angle grouping, super surface element processing, sub-azimuth velocity analyzing, pre-stack amplitude equalization processing, sub-azimuth migration imaging, seismic attribute extracting, fracture ellipse fitting, fracture development intensity predicting and the like. The step of azimuth angle grouping is carried out before the step of super surface element processing so as to ensure that azimuth angle groups are relatively consistent in variation amplitude and that trace gather data of the azimuth angle groups is relatively consistence and uniform in coverage times; dynamic correction is carried out on the anisotropy through introducing anisotropy parameters in sub-azimuth velocity analysis, far-offset data with azimuthal anisotropy characteristics being the most obvious is reserved, and the far-offset data is enabled to participate in sub-azimuth migration imaging and fracture ellipse fitting calculations. In addition, a Thiessen polygon based pre-stack amplitude equalization processing method is adopted to improve the amplitude preservation performance of migration results. The fracture predicting method provided by the invention is high in acquired fracture ellipse fitting precision, and fracture prediction results are more accurate.

Description

technical field [0001] The invention relates to the technical field of petroleum exploration, in particular to a fracture prediction method based on seismic longitudinal wave azimuth anisotropy. Background technique [0002] Fractured oil and gas reservoirs widely exist in major oil and gas fields in the world. They have the characteristics of common development and complex distribution, and account for an increasing proportion of newly added reserves. Accurate prediction of fracture development zones is the premise of evaluating fractured reservoirs, and it is also the key to improving the exploration efficiency and development level of fractured reservoirs. At present, many mature seismic detection methods for fractured reservoirs have been developed at home and abroad. Among them, a fracture prediction method based on the azimuthal anisotropy of seismic P-wave is more common. Based on the principle of P-wave azimuth anisotropy, the method extracts seismic attributes fro...

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Problems solved by technology

This will lead to low accuracy of ellipse fitting results and certain errors in fracture prediction results

[0004] 2. In the velocity analysis process, the maximum superposition energy is used as the criterion to pick up the velocity, without considering the influence of anisotropy

Once the far offset data is discarded, the accuracy of the ellipse fitting results will be reduced, resulting in a large error in the fracture prediction results

[0005] 3. In the process of pre-stack amplitude equalization based on the number of coverages, since the arithmetic mean is used to calculate the weight of each trace, the offset and azimuth information of different traces are not considered, so the amplitude preservation performance of migration imaging is low , the extracted seismic attributes are partially distorted, resulting in certain errors in the fracture prediction results

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