Common Reflection Surface (CRS) Processing in Complex Geology -- An Alternative to Prestack Depth Migration?

By

Henning Trappe¹, Guido Gierse¹, Juergen Pruessmann¹

(1) TEEC, Isernhagen, Germany

 Imaging in complex geology environments faces numerous problems like rapid lateral changes, discontinuous reflectors, a high noise level, and multiple contamination. Reliable velocity models often cannot be defined, neither in time nor in depth, since primary reflections are hardly visible in the prestack data, or cannot be discriminated from multiples.

Macro-model independent imaging could represent an approach to reduce these difficulties. The Common Reflection Surface (CRS) stacking technique offers several advantages with respect to the conventional NMO/DMO processing:

-         No velocity model is required. However, available velocity information may be used as a constraint.

-         The CRS stacking parameters are automatically determined from the seismic data for each point of the stack. This local adaptation optimizes the image of strong structure and velocity changes.

-         The hyperbolic stacking surfaces extend across several CMP locations. The resulting high fold leads to a strongly increased signal-to-noise ratio.

-         The CRS method assumes subsurface reflectors that are characterized by local dip and curvature. This leads to an enhanced imaging of curved and dipping structures.

Application examples show an improved image of complex geology by the CRS method in comparison to conventional imaging. Poststack depth migration of the CRS stack produces a high-resolution depth section, that can be superior to prestack depth migration results in data environments that do not allow a reliable velocity model building.