Abstract

Large-scale lithofacies variations are often observed within subsurface depositional sequences by different seismic facies. Seismic facies are 3-dimensional units recognized visually by their amplitude, frequency, internal reflection continuity, and reflection configuration. Much terminology exists to describe combinations of these characteristics and define particular seismic facies, for example; reflection free, parallel-discontinuous, chaotic and clinoform facies. However, such characteristics can also be defined mathematically from 3D seismic data, using algorithms referred to as windowed seismic attributes.

Post-stack seismic attributes comprise 3 types :

i. Instantaneous seismic attributes

ii. Single-trace windowed seismic attributes

iii. Multi-trace windowed seismic attributes

Instantaneous attributes describe individual cells within a 3D volume and are commonly used to produce conventional horizon slices. In contrast, both single-trace and multi-trace attributes are calculated over a specified vertical and/or horizontal range (window) of seismic data, and therefore describe seismic character variations in 3D space. By using single-trace and multi-trace attributes defined by the top and base of mapped sequences or systems tracts, it is possible to image their internal seismic facies variations.