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The Proposed Approach

The message in the previous section was that the standard design approach incurs compromises between the requirements of image quality and the cost of the survey (and the amount of collected data). My proposed approach Alvarez (2002b) avoids those compromises by posing the design as an optimization problem in which the requirements of image quality and the survey cost are balanced against each other within the constraint of sound acquisition logistics. Note that the compromises in the design stem from insufficient input data, or what amounts to the same thing, an inappropriate subsurface model. The implicit model of flat layers with constant velocities forces us to use the same acquisition parameters for the entire survey area. In the example described above, I ``punished'' the design because of the need to image the shallow part of the target horizon, although Figures [*] and [*] show that the target reflector is only shallow in about 10 or 20% of the survey area.

The upshot, of course, is that if we can accurately establish the correspondence between the subsurface area of the shallow reflector and the part of the surface area whose sources and receivers contribute to its image, then we could use the dense acquisition parameters in that part of the survey area and use the more standard parameters in the rest of the survey area. This is the key idea that allows us to get optimum image quality with the least acquisition effort. A similar approach can be used to locally increase the offsets for high-dipping reflectors, or to increase the azimuth coverage of a locally fractured reservoir.

I will illustrate in some detail each step of my approach with the model shown in Figures [*] and  [*].


 
next up previous print clean
Next: Building of the Model Up: Alvarez: 3-D survey design Previous: The problem with the
Stanford Exploration Project
7/8/2003