Changes

[[file:amplitude-versus-offset-avo-analysis_fig1.png|left|thumb|{{figure number|1}}Possible combinations of the acoustic and shear terms.]]

[[file:amplitude-versus-offset-avo-analysis_fig1.png|left|thumb|{{figure number|1}}Possible combinations of the acoustic and shear terms.]]

Whether or not there is an application for amplitude versus offset analysis in a given exploration setting is an often posed problem. The explorationist should ask several questions. Are the AVO phenomena that may be present large enough to overcome the various noises in the system? Are there sufficient differences between geological conditions and seismic expressions to distinguish between them?

Whether or not there is an application for [[amplitude]] versus [[offset]] analysis in a given exploration setting is an often posed problem. The explorationist should ask several questions. Are the AVO phenomena that may be present large enough to overcome the various [[noise]]s in the system? Are there sufficient differences between geological conditions and seismic expressions to distinguish between them?

[[file:amplitude-versus-offset-avo-analysis_fig2.png|thumb|{{figure number|2}}Brine sand model.]]

[[file:amplitude-versus-offset-avo-analysis_fig2.png|thumb|{{figure number|2}}Brine sand model.]]

A reflection coefficient can be thought of as consisting of the sum of two components—an acoustic term and a shear term. The acoustic term depends only on the impedance of the two layers and the angle of incidence. The shear term depends on Poisson's ratio in the two layers and also on the angle of incidence.

A reflection coefficient (see [[Displaying seismic data#Polarity|seismic polarity]]) can be thought of as consisting of the sum of two components—an acoustic term and a [[shear]] term. The acoustic term depends only on the [[impedance]] of the two layers and the [[angle of incidence]]. The shear term depends on [[Poisson's ratio]] in the two layers and also on the angle of incidence.

An AVO response not only occurs from an interface characterized by a contrast in Poisson's ratio, but also from interfaces that are entirely acoustic—that is, the measured response is more than a simple contrast in Poisson's ratio.

An AVO response not only occurs from an interface characterized by a contrast in Poisson's ratio, but also from interfaces that are entirely acoustic—that is, the measured response is more than a simple contrast in Poisson's ratio.

Feasibility modeling requires the following: (1) a depth-velocity model, (2) density and velocity trend curves, (3) [[porosity]] ranges, (4) fluid content variation, (5) Poisson's ratio trend curves, and (6) a geological description of potential reservoir and encompassing environments. [[:file:amplitude-versus-offset-avo-analysis_fig2.png|Figures 2]] and [[:file:amplitude-versus-offset-avo-analysis_fig3.png|3]] show model examples consisting of two fluid types. [[:file:amplitude-versus-offset-avo-analysis_fig2.png|Figure 2]] is a brine sand model, and [[:file:amplitude-versus-offset-avo-analysis_fig3.png|Figure 3]] is a gas sand model. The sensitivity of the seismic expression can now be studied by changing model parameters. If the model studies indicate measurable AVO responses, then AVO processing and interpretation techniques can be undertaken at an early stage in the exploration effort.

Feasibility modeling requires the following: (1) a depth-velocity model, (2) density and velocity trend curves, (3) [[porosity]] ranges, (4) fluid content variation, (5) Poisson's ratio trend curves, and (6) a geological description of potential reservoir and encompassing environments. [[:file:amplitude-versus-offset-avo-analysis_fig2.png|Figures 2]] and [[:file:amplitude-versus-offset-avo-analysis_fig3.png|3]] show model examples consisting of two fluid types. [[:file:amplitude-versus-offset-avo-analysis_fig2.png|Figure 2]] is a brine sand model, and [[:file:amplitude-versus-offset-avo-analysis_fig3.png|Figure 3]] is a gas sand model. The sensitivity of the seismic expression can now be studied by changing model parameters. If the model studies indicate measurable AVO responses, then AVO processing and interpretation techniques can be undertaken at an early stage in the exploration effort.

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==AVO data processing==

==AVO data processing==