Converted-wave imaging technology and application for complex structures

Abstract

Throughout the early years of the 21st century, multi-component seismic surveying has developed rapidly with larger capacity recording systems and digital three-component sensors. These technologies capture the seismic wavefield more completely than conventional P-wave surveys and allow extra information to be obtained from a converted-wave or ‘PS’ image. However, converted-wave seismic data is much more challenging to acquire and process than conventional P-wave data. Most existing multi-component surveys to date have been deployed in areas with geologically simple structures. This paper presents a case study of a 250 km2 3D three-component seismic survey located in an area with complex structures and faults. The complexity of the converted-wave data obtained in this survey has rarely been seen before, bringing huge technology challenges to the processing and interpretation. After several early failures, an extremely good image of the converted-wave has been obtained by combining a variety of processing algorithms. The structural features seen remain consistent with that of the P-wave image, providing a good foundation for subsequent inversion and reservoir analysis. This article describes the main techniques used, focusing in particular on three of the most challenging steps: converted-wave statics, anisotropy correction, and pre-stack time migration. We hope that this workflow will provide a technical guide, or reference for multi-component seismic data processing for complex structures.