Volumetric estimates of seismic reflector rotation and convergence—tools for mapping rotation about faults and seismic stratigraphy

Abstract

Geometric attributes such as coherence and curvature are commonly used for mapping structural deformation and depositional environment. Coherence proves useful for identification of faults, channel edges, reef edges, and collapse features while curvature images folds, flexures, subseismic conjugate faults that appear as drag or as folds adjacent to faults, rollover anticlines, diagenetically altered fractures, karst, and differential compaction over channels. Unfortunately, these two attributes have limited value in imaging classic seismic stratigraphy features such as progradation and erosional truncation. Seismic stratigraphy refers to the analysis of the configuration and termination of seismic reflection events, packages of which are then interpreted as stratigraphic patterns. These packages are then correlated to well-known patterns such as toplap, onlap, downlap, hummocky clinoforms, and so forth, which in turn represent architectural elements of a depositional environment (Mitchum et al., 1977). By integrating these elements with well control as well as modern and paleo analogs, the interpreter produces a probability map of lithofacies. Seismic facies also thicken and thin with increasing and decreasing accommodation space. Rotation of lithologic units about faults can provide increased accommodation space or subject uplifted areas to erosion.