Applications of the common‐reflection‐surface stack

Abstract

The simulation of a zero-offset stack section from multicoverage seismic reflection data for 2-D media is a widely used seismic reflection imaging method that reduces the amount of data and enhances the signal-to-noise ratio. The aim of the common-reflection-surface stack is not only to provide a well-simulated zero-offset stack section but also to determine certain attributes of hypothetical wavefronts at the surface useful for a subsequent inversion. The main advantage of the common-reflection-surface stack is the use of analytical formulae that describe the kinematic reflection moveout response for inhomogeneous media with curved interfaces. These moveout formulae are valid for arbitrary shotreceiver pairs with respect to a common reference point and do not depend on the macro velocity model. An analytic reflection response that fits best to an actual reflection event in the multicoverage data set is determined by coherency analysis. We applied the common-reflection-surface stack to various synthetic and real data sets. For synthetic data sets, i. e. for a given model, data-derived as well as model-derived (forward calculated) wavefront attributes were computed. This enables us to verify the wavefront attributes determined by the commonreflection-surface stack exposing a wide agreement with the expected results. For real data sets we compare conventional stacking results and the common-reflection-surface stack.

Modelling of the Neves Corvo Area

“…A standard processing sequence with Pre-Stack Time Migration (PSTM) and post-stack migration, and a second processing sequence with the common-reflection surface method (CRS; Mann et al 1999) also coupled with PSTM and post-stack migration. All processing sequences included geometry introduction (crooked line geometry for lines 3, 4, 5 and 6), trace editing, first break and bottom muting, refraction statics computations (weathering zone velocity of 1 km/s and replacement velocity of 4-5 km/s) and conversion to flat datum, FK filter, spherical divergence correction, spiking deconvolution (zero phase with 240 ms operator length), bandpass frequency filtering (8-12-70-80 Hz), automatic gain control (AGC, 500 ms window length), two iterations of velocity analysis and residual statics calculations and, finally, the normal moveout (NMO) correction.…”

CRS seismic data imaging system: a case study for basib reevaluation

“…In order to satisfy the paraxial ray theory, a central ray of information has to be established, and in this case it is taken the ZO ray between the observation point and the normal incidence point (normal ray), and only primary events are taken into account. The central ray satisfies Snell's law across the interfaces, and the wavefront curvatures of the NIP-wave and N-wave change according to the refraction and transmission laws of curvature, nicely described in Hubral & Krey (1980) and used by Mann (2002).…”

“…An attractive application was proposed by Mann (2002), where the apex of the appropriate diffraction response also provides an approximation of the image location of a Kirchhoff time migration. Due to the symmetry axis, this applies to the ZO plane h = 0, where ∂t D (x m , h = 0)/∂ x m = 0 yields the apex location:…”

Sensitivity, Resolution and Ambiguity of the CRS Stack Operator

“…The CRS stack operator describes the impulsive traveltime for curved reflectors based on the paraxial ray theory, and takes into account only primary reflection trajectories (Mann, 2002). The paraxial ray theory is based on Taylor series that handles general smooth functions of many variables.…”

“…Among the specific aims of the present study are: (1) to analyze the sensitivity of the CRS hyperbolic stack operator to its parameters; and (2) to compare the results of the parameter sensitivities with the strategy for the CRS attribute search as described by Muller (1999) and Mann (2002).…”