ABSTRACT

The concept of seismic stratigraphy was developed during the 1970's based on 2-D seismic technology. Utilizing reflection terminations, configurations, and external forms interpreted from multiple seismic profiles, geologists could analyze seismic facies within depositional sequence boundaries and infer regional-scale depositional environments and depositional history.

Three-dimensional seismic data provide spatially dense, high-resolution, horizontal reflection patterns for improving seismic facies analysis and make seismic sedimentology a reality. A step beyond seismic stratigraphy, seismic sedimentology is the study of depositional facies, lithology, and architecture by using the relationships between spatial reflection patterns and the morphology of depositional systems.

A major obstacle facing seismic interpreters used to be their inability to pick reservoir-scale depositional surfaces on vertical seismic profiles. This problem has been largely resolved by a technique called stratal slicing. Stratal slicing tries to pick depositional surfaces by proportionally slicing between two reference seismic events. Stratal slices from two 3-D seismic volumes in Louisiana illustrate that seismic sedimentology can significantly improve seismic facies analysis by (1) reducing ambiguity in seismic facies and lithologic interpretation; (2) increasing vertical resolution from the third-order sequence (100 m) to the reservoir (10 m) level; and (3) helping identify reservoir-scale depositional architecture.