Sage Creek field is located on a well developed asymmetric fold in the northern Big Horn Basin of Wyoming. This structure trends northwest-southeast parallel with the Big Horn Mountain front, through T. 57 N., R. 97-98 W., in Park and Big Horn counties. It has about 500 feet of structural closure. The field consists of one Madison well producing 20° gravity oil, and 21 Tensleep wells producing 26° gravity oil. Ultimate recovery from both zones is estimated at approximately 1½ million barrels.

The Madison pool is of small areal extent and is a simple gravity accumulation in a zone of permeability well below the top of the formation. The Tensleep pool is of a more complex nature and consists of five separate oil accumulations in zones of porosity and permeability within an otherwise dolomitic Tensleep sand. These five "bubbles of oil" are displaced down the southwest or basinward limb of the structure by hydrodynamic activity of such an extreme type that the crest of the structure is water-bearing in all Tensleep zones.

The unique features of accumulation in this field indicate the need for thoroughness and caution in the evaluation of the Tensleep formation in wildcat wells.

End_of_Article - Last_Page 1096------------