STRATAL SLICING, PART II - REAL 3-D SEISMIC DATA

Three-dimensional seismic data from the Gulf of Mexico Tertiary sectio n show a close dependence of seismic events on data frequency. While s ome 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 m aximum time transgression of seismic events is at least 120 ms travelt ime on lower frequency sections. Severe interference in lower frequenc y data may produce false seismic facies characteristics and obscure th e true stratigraphic relationships This phenomenon has important impli cations for seismic interpretation, particularly for sequence stratigr aphic studies. This time transgression problem is mitigated to a large degree by the stratal slicing technique discussed in Part I of this p aper. Stratal slicing on a workstation is done by first tracking frequ ency-independent, geologic-time-equivalent reference seismic events, t hen building a stratal time model and an amplitude stratal slice volum e on the basis of linear interpolation functions between references. T he new volumes have an x-, y-coordinate system the same as the origina l data, but a z-axis of relative geologic time. Stratal slicing is a u seful new tool for basin analysis and reservoir delineation by making depositional facies mapping an easier task, especially in wedged depos itional sequences. Examples show that the common depositional facies l ike fluvial channels, deltaic systems, and submarine turbidite deposit s are often imaged from real 3-D data with relatively high lateral res olution.