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KARADAVUT, ALPER, Colorado School of Mines, Department of Geology and Geological Engineering, Golden, CO

ABSTRACT: Flow Unit Determination in the Phosphoria Formation, Little Sand Draw Field, Big Horn Basin, Wyoming

The purpose of this research is to establish a petrophysical flow unit zonation for the Ervay reservoir interval of the Phosphoria Formation, Little Sand Draw Field, Big Horn basin, Wyoming. There are 36 wells in the field, and 19 have been cored. A lithofacies-based zonation is available from conventional core descriptions.

Of the various methods proposed to characterize carbonate reservoirs into flow units, a petrophysical method based on vertical variations of flow capacity (kh), storage capacity (phih), and pore throat size (r35) has been selected. The 19 cored wells have continuous core-plug porosity and permeability data with which to create profiles of flow capacity and storage capacity versus depth. Conventional core-plug data were supplemented with capillary pressure analysis of 25 cores. These results were used to modify the empirically-derived Winland equation for rock quality, and further refine the flow unit zonation. Porosity information was available from the well logs in the non-cored wells. The study also developed a method to predict permeability in the non-cored wells using a neural-network approach. Resultant flow units displayed on a stratigraphic flow profile were then correlated between wells using the existing sequence stratigraphic model.

The results of this research will be used by another student in an ongoing reservoir simulation. This zonation should lead to quicker and more efficient history matches, and promote more efficient interactions and exchange between engineers and geologists.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid