Crack Detection Method Based on Azimuthal Anisotropic Elastic Impedance

Abstract

The invention relates to an azimuthal anisotropic elastic impedance based crack detection method. With a Connolly elastic impedance equation and a Ruger equation serving as the basis, anisotropic elastic impedance and crack parameters and the dominance relation formula between crack density and crack azimuth are deduced. A set of elastic impedance based crack inversion process is established, and anisotropic parameter information is added into inversion well logging constraint. Numerical model testing is performed in the method, the inversion result is roughly identical to the theoretical value, and the inversion density shows high noise immunity. The method has the advantages that anisotropic elastic impedance can be used, the crack density and the crack azimuth are calculated simultaneously, good application effects are provided in actual data, and high practicality is provided.

Description

technical field [0001] The invention belongs to the field of petroleum exploration, and relates to a method for detecting effective fractures by using the characteristics of elastic impedance azimuth anisotropy in the comprehensive evaluation of fractured reservoirs. Background technique [0002] Fractured reservoirs account for about one-third of the world's oil and gas reserves. As oil and gas migration pathways and storage spaces, detecting fractures is of great significance for finding oil and gas reservoirs. The study of fractures is also an important part of reservoir evaluation and prediction in today's era. The elastic impedance in the seismic wave has azimuthal anisotropy in fractured reservoirs, so this property can be used to detect fractures. In 1999, Connolly first proposed the concept of elastic impedance. He used the approximate reflection coefficient proposed by Aki & Richards to derive the elastic impedance formula in isotropic media (Connolly, 1999). Res...

AI Technical Summary

Problems solved by technology

The general algorithm will take the Thomsen-type anisotropic parameter system as the solution target, which will result in more complex equations and more parameters, which can achieve certain results in numerical models, but it is difficult to solve them accurately in practical applications

More importantly, in actual production, we generally use intuitive anisotropic parameters such as fracture density and direction as the basis for predicting cracks, but the above algorithm does not establish explicit expressions for such intuitive crack parameters and elastic impedance , so it is not conducive to the actual crack prediction work

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