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GCTake Your Pick: Skeptic or Proponent*
By
Bob A. Hardage1, Khaled Fouad1, and Glenn Winters2
Search and Discovery Article #40228 (2006)
Posted December 22, 2006
*Adapted from the Geophysical Corner column, prepared by the authors, in AAPG Explorer, December, 2006. Editor of Geophysical Corner is Bob A. Hardage. Managing Editor of AAPG Explorer is Vern Stefanic; Larry Nation is Communications Director.
1Bureau of Economic Geology, Austin, Texas ([email protected] )
2Fasken Oil and Ranch, Midland, Texas
Intriguing
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uGeneral commentuFigure captionsuExampleuPP and PS modes
uAmplitude
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The prospect is a carbonate Strawn play in
West Texas. Traditional P-wave At this particular prospect, the Strawn play
is stratigraphic, not structural, and traditional P-wave data were
having limited success in predicting optimal drill sites. A modest-size
3C3D
Compressional Mode vs. Converted Shear Mode Figure 1 shows time-structure maps at the reservoir level created from the PP (compressional) and PS (converted shear) modes provided by the 3C3D data. In making these maps, we depth registered the PS data to the PP data before interpreting the PS data volume. The equivalence of the structural geometry shown by these two maps suggests that the PS data processing has been done well and that the PP-to-PS depth registration is reasonably accurate across the reservoir interval. Superimposed on the maps are existing wells, both producers and non-producers, showing that there is no obvious relationship between structure and producing facies. Some producers are lower on the structure than are non-producers. Drilling targets are thus controlled by stratigraphic conditions, not by structure.
Figure 2 shows
one amplitude In contrast, PS reflection amplitude appears
to react to productive and non-productive reservoir conditions (Figure
2b). The PS data show a sinuous, high-amplitude anomaly (yellow/red)
that reasonably segregates producing wells from non-producers. This
reservoir facies is a low-porosity carbonate unit; porosity ranges from
1 to 7 percent across the prospect, and minimum productive porosity is 4
percent. Detecting the narrow porosity range between non-productive
facies (1 to 3 percent) and productive facies (4 to 7 percent) is beyond
Rather than using
In this instance, the predictive value of PS reflection amplitude was tested by drilling well AL-1, labeled on the PS map (Figure 2b). This well found the thickest reservoir facies (122 feet) of all the wells shown on the maps. In other wells, the reservoir interval ranged from 80 to 111 feet. From the standpoint of reservoir thickness,
this project supports the use of multi-component Skeptics can say that multi-component The real message is that at this prospect, the PS mode provided vital reservoir information that the PP mode could not.
This research was funded by DOE/NETL. |