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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Geology and
Seismic
Modeling
of an
Aneth-Type Desert Creek Mound Trend,
Paradox Basin, Southwest Colorado
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In the Paradox Basin of southwest Colorado, a major facies change from thick, porous algal dolomite to thin, tight anhydrite occurs within the Desert Creek zone of the Pannsylvanian Paradox Formation. This northwest-trending algal mound belt is subparallel to and separated from the ancestral Uncompaghre mountain front by lagoonal anhydrite and nearshore arkosic fanglomerates. Carbonate rocks attain a maximum gross thickness of 200 ft., which can include 100 ft. of reservoir quality dolomite. These rocks have an updip and abrupt eastward facies change to thin evaporites which form a regional master trap for potentially significant hydrocarbon accumulations. Reservoir parameters and trapping mechanisms are similar to Utah's Aneth Field, where oil production exceeds 340 million barrels.
The subsurface stratigraphic changes have been seismically
modeled with a microcomputer to define the extent
of each facies. The modeling
is based on sonic logs from two
wells that exhibit the end-member facies of thick, porous
dolomite versus thin, tight evaporite. An interpolation
routine creates intermediate logs between these end-members,
thereby defining the geometry of the model. The
depth model is convolved with a zero-phase wavelet of
10/20=40/60 hz, and the result is an extra
seismic
cycle
where reservoir thickness exceeds 40 ft. Updip loss of the
cycle defines the transition from reservoir dolomite to trap
anhydrite.
The modeling
demonstrates that this major facies
change can be detected at frequencies reasonably attainable
by modern
seismic
methods. Regional subsurface stratigraphic
analysis and modern
seismic
data provide an
integrated approach to hydrocarbon prospecting in the
Pennsylvanian Desert Creek zone.
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