The common focal point and common reflection surface methodologies: subsets or complements?

The common focal point (CFP) method and the common reflection surface (CRS) stack method are compared. The CRS method is a fast, highly automated procedure that provides high S/N ratio simulation of zero-offset (ZO) images by combining, per image point, the reflection energy of an arc segment that is tangential to the reflector. It uses smooth parametrized two-way stacking operators, based on a data-driven triplet of attributes in 2D (eight parameters in 3D). As a spin-off, the attributes can be used for several applications, such as the determination of the geometrical spreading factor, multiple prediction, and tomographic inversion into a smooth background velocity model. The CFP method aims at decomposing two-way seismic reflection data into two full-aperture one-way propagation operators. By applying an iterative updating procedure in a half-migrated domain, it provides non-smooth focusing operators for prestack imaging using only the energy from one focal point at the reflector. The data-driven operators inhibit all propagation effects of the overburden. The CFP method provides several spin-offs, amongst which is the CFP matrix related to one focal point, which displays the reflection amplitudes as measured at the surface for each source-receiver pair. The CFP matrix can be used to determine the specular reflection source-receiver pairs and the Fresnel zone at the surface for reflection in one single focal point. Other spin-offs are the prediction of internal multiples, the determination of reflectivity effects, velocity-independent redatuming and tomographic inversion to obtain a velocity-depth model. The CFP method is less fast and less automated than the CRS method. From a pointwise comparison of features it is concluded that one method is not a subset of the other, but that both methods can be regarded as being to some extent complementary.