Click to view figures in PDF format.
The Power of
Multiple Seismic
Attributes in Revealing Geologic Understanding*
By
Walter E. Johnson1, Richard O. Louden2, Donald D. Lehman3, and Duncan L. Edwards4
Search and Discovery Article #40067 (2002)
*Adapted for online presentation from
the Geophysical Corner column in AAPG Explorer, March, 2001, entitled
“Seismic
Has Its Multiple Attributes,” and prepared by the authors. Appreciation
is expressed to the authors, to R. Randy Ray, Chairman of the AAPG Geophysical
Integration Committee, and to Larry Nation, AAPG Communications Director, for
their support of this online version.
Editor’s note: Please refer to related article, “3-D
Seismic
Data in Delineating Productive Ismay Algal Mounds in Southern Paradox
Basin, Utah,” by the same authors previously posted on Search and Discovery.
1Consulting geophysicist, Denver, Colorado.
2Consulting geologist affiliated with Thomasson Partner Associates, Denver, Colorado. 3Former exploration manager for Miller Energy, is now with VuCom Data Services in Kalamazoo, Michigan.
4Independent consulting geophysicist in Rutherfordton, N.C.
Analysis of 3-D seismic
data with
several types of
seismic
attributes can reveal geologic factors that control the
location of productive algal mound reservoirs in the Paradox Basin. Routine
seismic
mapping of the producing interval did not reveal the presence of a
regional strike-slip fault that is clearly shown using
attribute
analysis. This
previously unknown strike-slip fault controls the local stratigraphy and extends
for over 30 miles.
Although each attribute
when used
alone has some level of ambiguity, it is important to note that when a number of
attributes with different mathematical algorithms yield similar results, the
reliability of the geologic interpretation is enhanced. Several commercially
available
seismic
attributes, along with attributes generally incorporated
within most workstations, collectively have had a significant impact on the
understanding of how and where the algal mound reservoirs form, and indicate
that their stratigraphic development is often not a random act. The purpose of
this article is to demonstrate that the small cost of time and money required to
perform
attribute
analysis is far outweighed by the increased understanding of
the geologic dynamics of an area.
The ability to map more geologic detail will ultimately result in reduced risk of drilling dry holes.
uAlgal mound reservoirs in Paradox Basin
uAlgal mound reservoirs in Paradox Basin
uAlgal mound reservoirs in Paradox Basin
uAlgal mound reservoirs in Paradox Basin
uAlgal mound reservoirs in Paradox Basin
uAlgal mound reservoirs in Paradox Basin
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Click here to view sequence of Figures 3 and 4, (Hovenweep amplitude and Upper Ismay isochron maps).
Click here to view sequence of
Click here to view sequence of Figures 11 and 12. Algal Mound Reservoirs in the Paradox Basin Miller Energy, of Kalamazoo, Michigan, and its partners completed the Miller Horse Canyon 1-10 in 1998 for an initial potential of 960 barrels of oil per day and 940 MCFG/D from a depth of 5,850 feet from an algal mound reservoir. The well was featured in the 1999 EXPLORER.
Figure 1 shows the location of the Paradox Basin in the southwestern
United States, where shelf carbonate buildups within the Pennsylvanian
basin have produced oil and gas since the 1950s. Generally these
carbonate buildups are the result of algal debris from Ivanovia (these
Ivanovia algal skeletons are much the same size as cereal corn flakes).
In the 1980s it became generally known that there could be a
Figure 2, a geologic cross section through the discovery well, is a
good reference for the various geologic strata that will be mentioned
throughout this article. The well was completed in an Upper Ismay
carbonate buildup; however, the test also encountered a deeper Desert
Creek carbonate buildup that is further revealed with A Note in Figure 2 how the Hovenweep thick is located to the left of the discovery well. The isochron thickness map of the Upper Ismay (from the top of the Hovenweep to the top of the Upper Ismay) shown in Figure 4 demonstrates that there is an atoll shape of increased thickness of Upper Ismay surrounding the Hovenweep island. A series of different
An Another It is important to note
that both the wavelet classification map and the multivariate Edge detection technology
has been used in the
Figure 9 is another coherency slice that is approximately 1,500 feet
below the Upper Ismay, and again this same lineament can be mapped.
Two-D Figure 10 is an amplitude map of the top of the Akah salt, and it is believed that the dim shown in green and red is the result of salt dissolution. Note how the amplitude dim conforms with the overlying Hovenweep thick. We postulate that the fault may have been a conduit to cause dissolution of the Akah salt. A horizon slice slightly above the Akah salt has a very distinctive linear pattern that also could be the result of differential salt dissolution. As another Many workstations have
add-on packages that allow some trace processing. A horizon windowed
Note the similarity between Figures 12 and 6 . Both the cross-correlation and wiggle classification mapping techniques indicate strong potential for new drill site locations on the south side of the Hovenweep “island.” The enhanced geologic
understanding gained from the various The similar patterns that emerge by running many different techniques reinforces the interpreter’s confidence when mapping subtle geologic variations. This improved geologic understanding leads to reduced risk in both development and exploration projects.
Often |