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seismic-inversion_fig1.png|{{figure number|1}}A flowchart showing the general concept behind seismic Inversion.

seismic-inversion_fig1.png|{{figure number|1}}A flowchart showing the general concept behind seismic Inversion.

seismic-inversion_fig2.png|{{figure number|2}}Band-limited inversion of several traces around a reef. The integrated sonic log from the reef well is shown as the dark trace in the central part of the figure.

seismic-inversion_fig2.png|{{figure number|2}}Band-limited inversion of several traces around a reef. The integrated sonic log from the reef well is shown as the dark trace in the central part of the figure.

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There are two main types of inversion currently being used. The first is ''band-limited inversion'', which involves directly integrating the seismic trace. Since the seismic trace lacks a low frequency velocity trend because of the band-limited wavelet, the inverted trace lacks the “excursions” seen on the original sonic log. We must therefore add in the low frequency component from the geological model. The result is a frequency band-limited version of the original sonic logs. This is shown in [[:file:seismic-inversion_fig2.png|Figure 2]] for a carbonate reef example. The heavy trace in the center is a sonic log from the producing well. The zone of interest is at 1150 msec.

There are two main types of inversion currently being used. The first is ''band-limited inversion'', which involves directly integrating the seismic trace. Since the seismic trace lacks a low frequency velocity trend because of the band-limited wavelet, the inverted trace lacks the “excursions” seen on the original sonic log. We must therefore add in the low frequency component from the geological model. The result is a frequency band-limited version of the original sonic logs. This is shown in [[:file:seismic-inversion_fig2.png|Figure 2]] for a carbonate reef example. The heavy trace in the center is a sonic log from the producing well. The zone of interest is at 1150 msec.

The second type of inversion, which is more recent than the band-limited method, involves producing a “blocky” output rather than a band-limited output. There are several methods that produce this type of output, and they are sometimes referred to as ''sparse-spike'' or ''model-based methods''. These methods work by producing a forward model that best reproduces the seismic data when converted to synthetic form (that is, when the reflection coefficients are convolved with the wavelet). This method involves starting with a simple “guess” of this model and changing this guess iteratively until the error between the model and the observed seismic data is minimized (see [[Forward modeling of seismic data]]). The results of doing such a model-based inversion are shown in [[:file:seismic-inversion_fig3.png|Figure 3]] for the same traces shown in [[:file:seismic-inversion_fig2.png|Figure 2]]. Notice that the carbonate reef is visible, and looks like the blocked version of the log.

The second type of inversion, which is more recent than the band-limited method, involves producing a “blocky” output rather than a band-limited output. There are several methods that produce this type of output, and they are sometimes referred to as ''sparse-spike'' or ''model-based methods''. These methods work by producing a forward model that best reproduces the seismic data when converted to synthetic form (that is, when the reflection coefficients are convolved with the wavelet). This method involves starting with a simple “guess” of this model and changing this guess iteratively until the error between the model and the observed seismic data is minimized (see [[Forward modeling of seismic data]]). The results of doing such a model-based inversion are shown in [[:file:seismic-inversion_fig3.png|Figure 3]] for the same traces shown in [[:file:seismic-inversion_fig2.png|Figure 2]]. Notice that the carbonate reef is visible, and looks like the blocked version of the log.