APPLICATION OF ZERO OFFSET 2D CRS-STACK METHOD FOR LOW FOLD DATA: SYNTHETIC AND REAL DATA EXAMPLES

摘要

Conventional seismic stack has difficulties in imaging complex subsurface structure. This could lead to produce bad seismic section, especially if the coverage of seismic data is low. Several methods have been introduced in the past years aiming to increase image quality of reflection seismic data. One of those methods is Zero Offset CRS-stack method. In this study, ZO CRS-stack method is applied to synthetic and real data examples. The effectiveness and advantages of this method is tested and compared with the results obtained from conventional stack method. As has been already known, velocity analysis is a processing step that should be done carefully in the conventional stacking method. In contrary, the CRS-stack method does not need velocity function to obtain a stack section. Only estimation of near surface velocity model is needed. The ZO CRS-stack method depends on three stacking operators, namely emergence angle, radius of NIP-waves and radius of normal waves. Velocity model is then estimated from the automatic CMP-stack. Since the stacking operator is determined from full coverage data, this method can map the reflectors in a better way, and the S/N-ratio is better than the results of conventional one, especially if the subsurface structure is complex. Several attributes are then produced as by-products, which can be used as interpretation tools. A synthetic study has been done to test the reliable of this method for complex subsurface models. After that, this method is tested to re-process a marine seismic dataset that has low fold coverage. The results of synthetic and real datashow significant improvement in the quality of stacking sections, although the coverage of data is low. Since the acquisition was carried out near the subduction zone, the geological condition is very complex. The result of conventional method unfortunately does not show continuous reflection events. In contrary, the result of ZO CRS-stack method shows better subsurface image, in which the reflectors are more continuous and the content of non-coherent noises is now decreased.