Study On The Common-Reflection-Surface Stack For Zero-Offset And Common-Offset In 2D Media

The common-reflection-surface(CRS) stack method developed in the end of 1990's by professor Hubral of Karlsurhe university in Germany is an entirely data-oriented seismic reflection imaging approach of zero-offset section simulation in a macro-velocity model independent way. The idea of the CRS stack method is to provide an extension of conventional zero-offset section simulateion approaches such as normal moveout (NMO)/stack and dip moveout/stack. The CRS stack method parameterizes the reflection events in the pre-stack time domain by incorporating neighboring common-mid-point (CMP) gathers directly, and the inherent redundancy of the pre-stack data is used to collect information that pertains to common reflection surfaces in depth, which can improve the signal-to-noise ratio and resolutions of seismic stacked sections. The CRS stack approach has become an important development trend of seismic data processing in difficult terrians.Two-dimensional (2D) zero-offset CRS stack and common-offset CRS stack method have been studied respectively in this paper.Firstly,2D zero-offset CRS parabolic and hyperbolic traveltime approximation for arbitrarily curved reflector segment in complex inhomogeneous media have been derived by means of paraxial ray method and geometrical approach by starting with the surface-to-surface progagator matrix and common-reflection-point trajectory. Two hypothetical eigenwaves (the normal- incidence-point and nomal wave) establish a relationship between the depth and the time domain. In contrast to conventional stacking methods, the zero-offset CRS stack uses the full multi-coverage data volume in the stacking procedure as the CRS operator is not restricted to specific gathers. Consequently, many more traces compared to conventional stacking methods contribute to the stack.Secondly, the pragmatic search strategy for 2D zero-offset CRS attributes was studied. A Riemann sphere radius was introduced into the CRS stacking attributes search to avoid causing numerical problems and some improvement was made that the efficiency of the pragmatic search strategy is enhanced by giving a threshold in coherence analysis. The flexible polyhedron search algorithm used by the implementation of the CRS stack was studied and analized, and some adaptation was made to enhance the efficency of the CRS stacking operator optimization algorithm. Consequently, an object-oriented implementation of CRS search strategy implementation has been presented to allow a generalized handling of real data and provide more powerfull and flexible features to control the range of tested CRS stacking attributes.Thirdly, an object-oriented implementation of extended zero-offset CRS atttibutes search strategy implementation has been presented to overcome some of limitations in pragmatic search strategy caused by the ambiguity in the determineation of the radii of curvature RNIP, and the efficiency of the pragmatic search strategy is preserved as far as possible so that a more complete and more physical zero-offset simulateion section is provided by the CRS stack approach.Fourthly, the calculation of CMP stacking aperture, zero-offset stacking aperture and the CRS super gather aperture was discussed respetively, and which ensures the high efficency of the implementation of CRS stack. Consequently, the ideal CRS stacked section was acheieved by means of reasonable application of suitable stacking aperture to respective steps of the CRS stacking implementation.Fifthly,2D five-parameter CO CRS parabolic and hypobolic traveltime second-order approximation equation in complex inhomogeneous media was derived by means of paraxial ray theory by introducing the CRS stack approach into common-offset (CO) stack. Compared to the real reflection response show that the CO CRS stacking operator derived fits well to the relection response over a large range and could yield stack sections of better quality with high signal-to-noise ratio.Finally, CO CRS stack processing sequence was established by referring to the implementation of ZO CRS stack. The simultaneously five-parameter search was correctly split to save enormous computation time. The CO CRS stack can yield noteworthy CO stacked section and five kinematic wave-field attributes sections, and it also has the potential to simulate sections for converted waves. This extends the idea of seismic data processing and provides a new approach for seismic coverted wave processing in difficult terrians.Applications of the CRS stack method to several synthetic and real data sets have proved that the CRS stack approach is an entirely data-oriented macro-velocity model independent seismic reflection imaging approach, and the ZO CRS stack method can handle marine and land seismic data sets, increase fold and signal-to-noise ratio of data sets and improve the imaging quality of simulated ZO sections, so the ZO CRS stack has greate developing prospects. The CO CRS stack approach can improve the quality of CO stacked sections, and the wave field attributes determined by this approach can serve for converted waves processing.