Crack fluid type identifying method based on longitudinal wave frequency depending on amplitude versus offset (AVO) and azimuth

Abstract

The invention relates to a crack fluid type identifying method based on longitudinal wave frequency depending on amplitude versus offset (AVO) and azimuth. Earthquake anisotropism is related to frequency, and when crack media are filled with different kinds of fluid, difference exists between anisotropism intensity and the earthquake frequency changing gradient. According to the method, frequency information is introduced into an AVO and azimuth inversion theory of elastic media, and the inversion theory is expanded to the field of viscoelasticity, namely AVO and azimuth depending on frequency. By solving the formula of the AVO and azimuth depending on frequency, a longitudinal wave anisotropism frequency dispersion item is obtained. The method has the advantages that the application effect of practical data shows that longitudinal wave anisotropism frequency dispersion can be used for identifying the type of fluid in a crack, meanwhile, the method is good in water identifying effect, and the method can be used for practical data and can identify the type of fluid in a crack on an area where the anisotropism degree is high.

Description

technical field [0001] The invention belongs to the field of petroleum exploration and relates to a method for identifying fracture fluid types in the comprehensive evaluation of fractured reservoirs. Background technique [0002] AVO (Amplitude Versus Offset, variation of amplitude with offset) technology is used to study the variation characteristics of the seismic reflection amplitude with the distance between the shot point and the receiver, that is, the offset (or incident angle) to explore the reflection coefficient response with the shot. Then, the lithological characteristics and physical parameters of the overlying and underlying medium of the reflection interface can be determined. The azimuth AVO can also be expressed by AVOZ (Amplitude Versus Offset and Azimuth), that is, the seismic reflection amplitude not only changes with the offset, but also changes with the azimuth. Azimuth AVO technology is one of the commonly used crack detection technologies in the indu...

AI Technical Summary

Problems solved by technology

At present, there is some research on how to predict the fluid type in fractures, but it is not mature enough

For example, Shaw and Sen (2006) derived the relationship between P-wave azimuth AVO and fracture compliance, using the compliance parameter ratio E N / E T As an indicator factor for fracture fluid identification, but not applied to actual data; Sun et al. (2012) analyzed the isotropic gradient B in Ruger's formula based on forward modeling results ani and the anisotropic gradient term B iso Intersection is used to identify fracture fluid types, but this method is greatly affected by human factors in the intersection analysis results, and it is difficult to distinguish oil from water; in addition, Qian et al. (2007), Chapman and Liu (2004) based on Chapman (2003) et al. According to the effective medium theory, it is found that when the fracture is saturated with water, the frequency-dependent shear wave splitting is very different from that of saturated oil and gas, as shown in figure 1 shown, but in reality, the acquisition of shear wave data is expensive, and the processing cost is several to ten times that of longitudinal wave data.

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