Enhanced and fine seismic recognition of organic reefs: a case study of the Changxing Formation, eastern Sichuan, China

Abstract

Organic reefs are developed in the Changxing Formation (Fm.) in the southeastern end of the Kaijiang-Liangping ocean trough, eastern Sichuan. Due to the ambiguous seismic reflection characteristics of organic reefs, application of organic reef recognition methods that have been successfully employed in other areas is limited in the study area, but these methods can still indicate development of favorable facies zones. Accordingly, supplemented by seismic reflection characteristics analysis, seismic attributes analysis and time-difference analysis, frequency decomposition and reconstruction interpretation technique, high-frequency uncompressing method, and dominant azimuth lightening method were optimized to be the core technologies of enhanced and fine depiction technique system of organic reefs. The technique system transforms seismic data from the time and reflection angle domain to the frequency and azimuth-offset domain; increases the differences in seismic reflection characteristics in and out of organic reefs, especially patch reefs of small volume and low recognition; enhances seismic reflection characteristics of both the outline especially the lateral boundary and interior of organic reefs; and achieves precisely depicting the boundary of organic reefs and fine recognition of the internal structure of platform margin facies reefs such as reef core, fore reef, and back reef. This technique system provides a new technical idea for organic reef recognition, has produced optimistic recognition effects in the study area, and is of certain guidance significant to the research into recognition of organic reefs with ambiguous seismic reflection characteristics.