THE APPLICATION OF 2D COMMON-OFFSET COMMON-REFLECTION-SURFACE (CO CRS) STACK METHOD TOWARDS SYNTHETIC DATA

摘要

Improving appearance and continuity of reflection seismic data by applying Common Offset Common Reflection Surface (CO CRS) Stack method is presented in this paper. This method is based on summing up correlated events in the multi coverage data. To prove the effectiveness and advantages of this method a synthetic study is used.The CO CRS-stack method was introduced by Bergler et al (2001). This method was actually the generalisation form of Zero Offset CRS-stack, that had been discovered previously (Jaeger,1999 ; Mueller,1999 ; Mann et al, 2001). In comparison with the ZO CRS-stack, that depends on 3 (three) stacking operators, the CO CRS-stack depends on 5 (five) stacking operators, namely emerge angles of the central ray in the position of the source and the receiver (βs and Pg), and wavefront curvatures associated to the central ray that computed at the respective emergence points (K1, K2 and K3). These five parameters are related to wavefield attributes. These CO CRS stacking operators have data derived fully automatically by means of a coherency analysis. This means a velocity model of subsurface is not required to perform the stacking process. Only near-surface velocities around sources and receivers are necessary in order to calculate wavefield attributes with a geometrical meaning and to compute the search ranges for the attributes. A set of synthetic data was used to investigate the advantages of this method compared to a conventional stack.The results of the CO CRS-stack are better than the results of the conventional stack method. The undulated reflectors can be mapped more clearly and could be correlated with an increasing of the S/N ratio. Even if the fold coverage of seismic data is low, the result of the CO CRS-stack still clearlyshows undulated reflectors, whereas the conventional stack will fail to produce better images. Also, several attributes are produced as by products of this new method, which can be used as a tool for further calculations.The CO CRS stack is an alternative method that gives high quality stacked sections, as well as producing important wavefield attributes. The application of this method will increase in the future inline with the improvement in computer hardware technology.