Stratal slicing, Part II: Real 3-D seismic data

Abstract

Three‐dimensional seismic data from the Gulf of Mexico Tertiary section show a close dependence of seismic events on data frequency. While some events remain frequency independent, many events exhibit different occurrences with changing frequency and, therefore, are not parallel to geologic time surfaces. In the data set we have studied, observed maximum time transgression of seismic events is at least 120 ms traveltime on lower frequency sections. Severe interference in lower frequency data may produce false seismic facies characteristics and obscure the true stratigraphic relationships. This phenomenon has important implications for seismic interpretation, particularly for sequence stratigraphic studies. This time transgression problem is mitigated to a large degree by the stratal slicing technique discussed in Part I of this paper. Stratal slicing on a workstation is done by first tracking frequency‐independent, geologic‐time‐equivalent reference seismic events, then building a stratal time model and an amplitude stratal slice volume on the basis of linear interpolation functions between references. The new volumes have an x-, y-coordinate system the same as the original data, but a z-axis of relative geologic time. Stratal slicing is a useful new tool for basin analysis and reservoir delineation by making depositional facies mapping an easier task, especially in wedged depositional sequences. Examples show that the common depositional facies like fluvial channels, deltaic systems, and submarine turbidite deposits are often imaged from real 3-D data with relatively high lateral resolution.