Prestack migrated sections

Figure shows the prestack migrated section corresponding to the survey after the first time step of waterflood. Figure shows the same for the survey after two time steps of waterflood. The dimming of the reflection events at the reservoir depths of 2 km is imaged more clearly than on the stacked sections, and the lateral and vertical resolution is better. This increase in apparent resolution results from the Fresnel zones having been collapsed to a spatial wavelength, and the diffraction tails having been correctly positioned at the diffuse edges of the water invaded zone.

Figure shows a close up of the reservoir zone prestack migrations after one and two time steps of waterflood. This plot should be compared with the stacked section counterpart in Figure . The prestack migrated images show more correct amplitude variation and lateral extent than the stacked images, as is physically intuitive.

Figure shows the difference section of the prestack migrated sections before and after one time step of water injection. This figure can be compared directly to the stacked section counterpart of Figure . Note that the diffraction tails have been collapsed, and the spatial resolution is good enough to closely match the true extent of the P impedance water invasion zone as depicted in the true model of Figures and . Figure shows the difference section of the prestack migrated sections before and after two time steps of water injection. This figure can be compared directly to the stacked section counterpart of Figure . Again, the diffractions have been correctly positioned to image the diffusive edge of the water slug, and the spatial resolution has increased from a Fresnel width down to a seismic wavelength. Note that the boundary of the migrated reflections match closely with the P and S impedance fronts in the true models of Figures and .

 

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Figure 18 Waterflood 1: migrated section.

 

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Figure 19 Waterflood 2: migrated section.

 

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Figure 20 Waterflood 1 & 2: migrated sections.

 

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Figure 21 Waterflood 1 - Base migrated difference section.

 

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Figure 22 Waterflood 2 - Base migrated difference section.