Common-offset-vector Gathers: an Alternative to Cross-spreads For Wide-azimuth 3-D Surveys

Typical 3-D land and OBC seismic surveys are sampled finely in two spatial coordinates (e.g. receiver-x and source-y) and coarsely in the other two coordinates (receiver-y and source-x), so a simplistic discretization of the full 5-D Kirchhoff prestack migration integral leads to artifacts due to aliasing. Padhi and Holley (1997) suggested that imaging of well-sampled subsets of the data (minimal datasets) avoids the integration over the coarsely-sampled coordinates. For 3-D orthogonal acquisition geometries there are at least two types of minimal dataset that yield unaliased 1-fold images of the subsurface. A cross-spread is one type of minimal dataset (Vermeer, 1998a). A common-offset-vector (COV) gather is an alternative “basic building block” of 3-D wide-azimuth surveys. COV gathers (or volumes) are the simple extension of 2-D common-offset gathers (or sections) to orthogonal 3-D coordinates: the inline and crossline offsets are binned in such a way as to yield N 3-D volumes with a trace at each CDP, where N is the CDP fold. Traces within each COV gather share the same binned inline offset and binned crossline offset, and when they are sorted or stacked by CDP, the volume spans most of the survey area, as illustrated in Figure 1(a).