Charles Kerans1,
Kirt Kempter1,
Jason Rush1
(1) Bureau of Economic Geology, The University of Texas at Austin, Austin, TX
Abstract: Predictive
model for Paleokarst Reservoir heterogeneity
styles at high-frequency/composite-sequence boundaries
Paleokarst reservoirs represent
one of the most complex and poorly understood carbonate reservoir styles.
Predicting the size and distribution of paleokarst features is generally not
possible using well data, and the small impedance contrast between host and
collapse features makes seismic detection challenging. Improved prediction of
reservoir development and heterogeneity styles in paleokarst systems is
possible using outcrop data and unconformity rank on the basis of sequence
stratigraphic hierarchical setting. A threefold classification, including karst
developed at (1) high-frequency cycle boundaries, (2) high-frequency and
composite-sequence boundaries, and (3) super-sequence or 2nd-order boundaries, allows
key parameters to be emphasized. An example of a paired 3-D outcrop data set of
paleokarst features associated with high-frequency/composite-sequence
paleokarst and its reservoir equivalent with core, log, and 3-D seismic data is
presented to highlight predictive
aspects of this class of paleokarst
reservoir.
Detailed mapping of paleokarst features from Leonardian and Guadalupian (Permian) outcrops in the Guadalupe and Sierra Diablo Ranges of West Texas includes size, dimension, and distribution relative to the shelf margin. In the case of the Leonardian (Abo) paleokarst system, 63 individual sinkholes and collapsed caves were mapped and analyzed in terms of timing of collapse and porosity evolution. A strong correlation between extent of karst profile and shelf-margin position is demonstrated. Application of this coastal paleokarst model to Kingdom Abo field of similar age in the subsurface of the Permian Basin allows delineation of the zone of paleokarst and helps explain the high variability in performance of producer wells.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana