Reservoir Study of the Roosevelt Pool, Utah

Abstract

The Roosevelt pool in the Uintah basin of North-eastern Utah produces a high pour-point, high paraffin content crude oil from limestones and sand stringers in the Green River formation at a depth of about 10,000 ft. Due to the low matrix permeability of the rock the productivity of the wells was found to depend upon fracture development. Total production to March 1, 1957, from nine wells was 1,669,000 bbl and current capacity production from six wells is 450 BOPD with 440 BWPD. Production to date has been as a result of fluid expansion coupled with some water encroachment. Introduction and Geology The discovery of oil in the Green River formation at Roosevelt by the completion of the Roosevelt Unit No. 1 in June, 1949, marked the first production in the Uintah basin from reservoirs of Tertiary age. This well was completed for a flowing potential of 1,633 bbl of oil and no water at a depth of 9,350 ft. Following the Roosevelt discovery, a number of other pools were discovered in the area, including Duchesne, Red Wash, Flat Mesa and Walker Hollow. At the top of this page is a map of the Uintah basin, which is a structural, topographic and sedimentary basin in Northeastern Utah covering an area of approximately 8,000 sq miles. On this map A marks the Roosevelt pool; B Duchesne pool; C Red Wash-Walker Hollow pool; D Gusher No. 1; E Bluebell Unit No. 1; F Flat Mesa pool; and G County pool. All commercial oil production at Roosevelt has been obtained from the "D" zone of the Basal Green River. The Green River is a 4,000-ft section of well-bedded oil shales, marlstones, thin dolomites, limestones, and sandstones. The "D" zone is encountered in the lower 1,500 ft of the section with production from this interval being dependent upon a combination of structure, stratigraphy, and fracture development. The Roosevelt pool is located on a broad northwest-southeast trending nose, approximately 7 miles south of the Uintah basin synclinal axis. Fig. 1 presents a structure map of the area and Fig. 2 is cross section of the pool constructed from radioactivity logs. An extensive coring and testing program was followed at many wells in an effort to correlate and identify the pay zones. As shown by the cross section, two main intervals of production totalling approximately 125 ft in gross thickness have been observed, of which the upper has been the more important.