Handling the irregular geometry

The organization of 3-D multifold data on a regular grid is commonly performed by binning the data prior to stacking. This binning technique is an extension of the 2-D CMP sort method to 3-D and is suited for poststack migration and structural interpretation. In the presence of high noise levels and in areas of the survey with limited fold coverage or many missing traces, flexbinning can be applied to increase the fold. However, as noted earlier, these binning and interpolation techniques tend to ignore completely the issue of source receiver orientation and have the detrimental effect of averaging amplitudes over given areas.

We propose applying the AMO operator Biondi and Chemingui (1994a); Fomel and Biondi (1995a) to project irregular 3-D surveys with wide azimuthal coverage onto a regular midpoint-offset subsets with a common source-receiver azimuth. The resulting regular geometry lends itself handily to other processing algorithms that require regular grids. An example of an irregularly sampled subset of a 3-D wide-azimuth data is shown in Figure 2. Traces whose source-receiver offset is between 7000 and 9000 ft and azimuth between -30^o and 30^o were extracted from a true 3-D land survey and we plotted the surface locations of their common mid-points.

In the next section, we discuss the 3-D land data and its acquisition geometry. We show how we can use the real data example to generate numerical simulations and apply our technique to process a synthetic reflectivity model.

 

irregular
Figure 2 CMP geometry of a subset from a wide azimuth 3-D land survey.