ABSTRACT

Pitchfork field is on a surface anticline located on the western flank of the Big Horn basin approximately 45 mi southwest of Cody, Wyoming. The Tensleep Sandstone is the main producing formation, and the Phosphoria Formation contributes 15 to 20 bbl of oil per day from three dually completed wells.

Development of Pitchfork field has proceeded in three stages. Refined or new techniques of geologic evaluation were used in re-evaluation of data gathered from each previous stage. Development in the first stage, from the discovery in 1930 to 1955, was based on surface data. It was slow because of poor economics. Development in the second stage, from 1955 to 1962, was based on a search for higher structural positions. In the final stage, from 1962 to the present, wells have been drilled on the flanks of the anticline in search of unflushed “pods” of oil.

In a low-gravity, high-viscosity reservoir, it is difficult to define the oil-water contact. Because of the relatively thick oil-water transition zone and because of the abrupt stratigraphic and porosity changes within the reservoir, it was found that high water-cut wells were offset both along strike and downdip by economic procedures, some of which found almost no water.

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