Methods and devices for determining reflection coefficient dispersion and reflection energy and identifying gas layer

Abstract

The invention discloses methods and devices for determining reflection coefficient dispersion and reflection energy and identifying a gas layer. The method for determining reflection coefficient dispersion comprises the steps: preserving amplitude of seismic data and extracting angle gather; selecting the angle gather with a proper angle according to the quality of the seismic data; determining velocity of longitudinal waves, velocity of transverse waves and density by using a prestack inversion method; determining longitudinal wave quality factors and transverse wave quality factors of a stratum; and determining the reflection coefficient dispersion. The method for determining reflection energy comprises the step of determining the coefficient of reflection energy. The method for identifying the gas layer comprises the steps: determining the reflection energy; determining a threshold value according to the situations of well drilling and well testing; and identifying the stratum, whose reflection energy is lower than the threshold value, as the gas layer. By adopting the methods, the velocity dispersion and energy change of the stratum containing gas can be accurately reflected by the reflection coefficients, the reflection energy can be accurately reflected, accordingly, the gas-bearing property of a subsurface reservoir can be judged, and the interpretation ambiguity for the identification of the gas layer is effectively reduced.

Description

technical field [0001] The invention relates to the technical field of geophysics, in particular to a method and device for determining reflection coefficient dispersion, reflected energy and identifying gas layers. Background technique [0002] The reflection coefficient varies with frequency, which is called reflection coefficient dispersion. One of the most important manifestations of seismic waves passing through all media, especially rocks, is that energy is absorbed or converted into other forms of energy such as heat, commonly referred to as attenuation. There are two forms of seismic attenuation in viscoelastic medium, one is the frequency composition and amplitude change of the pulse signal passing through the attenuation medium, and the other is the reflection coefficient changing with frequency. The former is regarded as the main response of seismic attenuation in many studies, namely absorption attenuation, while the latter is rarely noticed by researchers. If ...

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Problems solved by technology

[0007] However, for the identification of gas layers, the existing velocity dispersion formula and seismic wave energy distribution equation cannot accurately determine the change of reflected energy caused by the gas-bearing formation, which makes the identification of gas layers ambiguous.

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