Imaging dipping reflectors

On the above smooth background velocity model, I superimposed two dipping reflectors with depths of 40 m and 160 m at the left well. They both tilt 15-degree upward to produce opposite dip directions relative to the source. Figure 5(a) is the common-shot profile data generated by the same recording geometry as the above horizontal reflector case. Figure 5(b) shows data for the same common-shot profile after the direct wave has been muted. It is clear that the opposite dipping reflectors generate reflection events with different amounts of moveout. Figure 6 is the reflectivity depth image between the two wells. All parts of the upper reflector are imaged clearly, with the exception of a short segment near the right receiver well. This segment is not imaged because its reflection event is damaged by direct wave muting. The left part of the lower reflector is not imaged. Ray tracing indicates that its reflections do not propagate to the receivers in the right well.

 

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Figure 5 Crosswell common-shot profile, (a) the data without any processing, (b) after the direct wave has been muted. The opposite dipping reflectors generate reflection events with different amounts of moveout.

 

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Figure 6 Crosswell depth image generated by migrating a common-shot profile. The two dipping reflectors have opposite dips relative to the source. The upper reflector is imaged clearly. The left part of the lower reflector is not imaged because its reflections do not propagate to the receivers well.