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In the fall of 1981, Northwest Exploration Co. drilled the discovery well for Haybarn field. The field is located in the Wind River basin of Wyoming and produces stratigraphically trapped 43° API gravity, 80°F pour point oil and associated gas from the Paleocene upper Fort Union Formation; these rocks are thought of generally as poor exploration targets and gas-prone at best. The reservoir is an arkosic sandstone deposited along the front of a lacustrine delta system. Clays in the reservoir are almost entirely secondary. Despite the precipitation of diagenetic kaolinite and chlorite, the reservoir capacity has remained high with porosities ranging from 18 to 26% and averaging about 20%. Reservoir permeabilities average about 7 md. Transmissibility has been enhanced in some z nes by natural vertical fractures. The fractures also provide an avenue for water from lower water sands. The resistivities of the formation waters are variable, making electric log calculations difficult. The R_w of the productive sand tongue in the discovery well ranges from 0.35 ohm-meters at the top to 1.40 at the base, over a vertical distance of 75 ft (23 m). Oil production is limited to the upper, more saline portion. Both the petroleum source and the trapping mechanism for the field appear to be the lacustrine Waltman Shale. The depositional system responsible for Haybarn field is not unique. Similar oil fields remain to be found in other parts of the Wind River basin.

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