Real data implementation

After the analysis and validation of the PS-CAM operator, I apply it to a real 3-D dataset. I use two of the results from Chapter 4 to obtain the final image for the 3-D OBS dataset acquired above the Alba oil field in the North Sea. Throughout this section, I present and compare the result of two methods. The conventional method, that uses Normal Moveout plus stacking to obtain the common-azimuth data cube, followed by PS common-azimuth migration, I refer to this method as PS-NoMoRe. The proposed method, that uses the PS-AMO operator in the data regularization process, as presented in the previous chapter, followed by PS common-azimuth migration, I refer to this method as PS-AMORe.

Figure  shows the first comparison between the PS-NoMoRe result (left) and the PS-AMORe result (right). From top to bottom four depth slices at 300 m, 400 m, 500 m, 600 m, respectively. Notice how the acquisition artifacts are stronger in the PS-NoMoRe result than in the PS-AMORe result. At a depth of 600 m the acquisition artifacts are no longer present after PS-AMORe.

 

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Figure 9 Comparison for several depth slices, of the PS-NoMoRe result (left) and the PS-AMORe result (right). Note how the acquisition artifacts are healed in after the PS-AMO correction and they are gone at a shallower depth with respect to the NMO correction.

The following comparisons focus on a selected area for the final images, the depth values were changed to relative depth values and they do not provide any information on the reservoir characteristics, however, the final results and comparisons are indpendent of this modification. Figures  and  correspond to the PS-NoMoRe and the PS-AMORe results, respectively. The ovals marked as ``A'' in the inline-midpoint sections present events that are stronger in the PS-AMORe result and are not present in the PS-NoMoRe result. Note at the very top of the ovals that the reflectors are more clearly defined after PS-AMORe, as for example, right underneath the mark ``A'', inside the ovals, the reflector is completely clear in the PS-AMORe result, this same reflector is difficult to follow in the PS-NoMoRe result. This is also the case for the main event at 720 m of depth right where the inline and crossline sections intersect. The ovals marked as ``B'' also present events that are more continuous after PS-AMORe, primarily at 720 m of depth. The ovals marked as ``C'' in the depth slices shows a channel in the PS-AMORe result that is completely lost using PS-NoMoRe.

 

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Figure 10 3-D image displayed with relative depth slice at 0 m, inline section from crossline=175 m, and crossline section from inline=4650 m. This result corresponds to the PS-NoMoRe process.

 

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Figure 11 3-D image displayed with relative depth slice at 720 m, inline section from crossline=175 m, and crossline section from inline=4650 m. This result corresponds to the PS-AMORe process.

Figures  and  also compare PS-NoMoRe with PS-AMORe. I use a different inline-midpoint sections taken at crossline-midpoint location of 575 m. The conclusions from the previous comparison still holds. There are other two areas of interest for these inline-midpoint sections. The ovals marked as ``A'' shows ``wing'' features better defined using PS-AMORe. This geological feature in the top sand reflector is one of the main contributions of this dataset, since this formation has also been confirmed with development drilling Hanson et al. (1999). Additionally, the reflector marked by ovals ``B'' is restored after using PS-AMORe.

 

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Figure 12 3-D image displayed with relative depth slice at 720 m, inline section from crossline=575 m, and crossline section from inline=4650 m. This result corresponds to the PS-NoMoRe process.

 

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Figure 13 3-D image displayed with relative depth slice at 720 m, inline section from crossline=575 m, and crossline section from inline=4650 m. This result corresponds to the Ps-AMORe process.

Figures  and  also compare the results for PS-NoMoRe and PS-AMORe, respectively. The images correspond to another inline-midpoint sections for a crossline-midpoint location of 825 m. The ovals marked as ``A'' not only shows the reflectors with brighter amplitudes but also they are more continuous after PS-AMORe. Along the crossline-midpoint sections, the events are shifted laterally, because of the spatial correction of the PS-AMO operator. These events are located at the center of the crossline-midpoint sections, in the PS-AMORe result, and they are not truncated at the boundary, as it is the case for the PS-NoMoRe result. The spatial shift is more clear in the depth slices, these are taken at a new depth (350 m). Notice the areas marked by the ovals ``C'' and ``D''. The events are continuous through the crossline direction in the PS-AMORe result, whereas, the events in the PS-NoMoRe are truncated at the edges of the crossline sections.

 

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Figure 14 3-D image displayed with relative depth slice at 350 m, inline section from crossline=825 m, and crossline section from inline=4650 m. This result corresponds to the PS-NoMoRe process.

 

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Figure 15 3-D image displayed with relative depth slice at 350 m, inline section from crossline=825 m, and crossline section from inline=4650 m. This result corresponds to the Ps-AMORe process.

Figures  and  show the last comparison between the PS-NoMoRe result and the PS-AMORe result, respectively. I compare the crossline-midpoint sections that correspond to inline-midpoint location of 2150 m. The geological feature marked by ovals ``A'' is better defined in the PS-AMORe result than in the PS-NoMoRe result. At the reservoir level, the ovals marked as ``B'' and ``C'' show the reservoir with better horizontal continuity and stronger amplitudes along the crossline-midpoint section after using PS-AMORe.

 

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Figure 16 3-D image displayed with relative depth slice at 350 m, inline section from crossline=175 m, and crossline section from inline=2150 m. This result corresponds to the PS-NoMoRe process.

 

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Figure 17 3-D image displayed with relative depth slice at 350 m, inline section from crossline=175 m, and crossline section from inline=2150 m. This result corresponds to the PS-AMORe process.