Adrian C. Badescu and Hongliu Zeng1
As in many mature Gulf of Mexico fields, significant reserve potential exists in Starfak and Tiger Shoal fields, offshore Louisiana, owing to structural and stratigraphic heterogeneities. Forty potential gas and oil reservoirs occur in a regressive Miocene succession, and 3-D seismic data are being used to identify untapped reserves through careful correlation between seismic attributes (SA) and reservoir properties obtained from well-log data. The study utilized a comprehensive data base (352 mi2 of 3-D seismic, 150 wells, 99 sidewall core analyses, and paleontologic and engineering data), and a detailed sequence-stratigraphic framework provides the basis for correlation and zonation.
Current work is focused on accurately characterizing reservoir-bounding sequence-stratigraphic surfaces and the strata they encompass. Fourth-order maximum flooding surfaces (MFS) were mapped from both seismic and well-log data. Incision at the sequence boundaries (SB) is poorly resolved on seismic. Therefore, SB's were mapped by (1) parallel slicing below the MFS's, (2) utilizing an acoustic impedance cube, and (3) constructing a series of amplitude stratal slices. The third approach offered many advantages. For example, thickness resolution is much improved (4ms TWT), and the SB's were mapped on the basis of geomorphology (e.g., channel-like features) depicted on the stratal slices. The result is an accurate 3-D representation of valley-fill geobodies that is suitable for geologic modeling. Research is continuing to improve the stratal-slice mapping method and to correlate reservoir properties to SA's.
1Bureau of Economic Geology, The University of Texas at Austin, University Station Box X, Austin, Texas 78713