History And Performance Of The Coldwater Oil Field, Michigan

This paper summarizes the development and performance of the Coldwater Oil field, Isabella County, Mich. Production is obtained at a depth of 3,750 ft from a dolomite reservoir, which is probably both Rogers City and Dundee. There appears to be no barrier to vertical fluid movement between the Rogers City and Dundee, and both formations are believed to have a common original oil-water contact. No wells are open to production at the level of the Dundee. The discovery of the field in 1944 was followed by the drilling of 81 producing wells and nine dry holes. By the end of 1952, the field had produced 12,763,000 bbl of oil, at which time 69 active wells were producing 3,600 B/D oil and 21,000 B/D water. The reservoir has an effective natural water drive, and bottomhole pressure has declined 75 psi from an original pressure of 1,453 psi. Oil is undersaturated at reservoir conditions with a solution GOR of 512 cu ft/bbl and a saturation pressure of 1,190 psi. Introduction Although the Coldwater field is now in its ninth year of production, it ranks seventh in cumulative recovery, and second in current daily oil production in the state. Following complete development of the field in 1946, it has consistently contributed approximately 11 per cent of Michigan's daily production. Coldwater appears to have a greater pay thickness than most fields producing from the Rogers City formation in the west central part of the Michigan basin. Except as influenced by the extent of closure and the thickness of the oil column, reservoir performance is believed to be representative of Rogers City fields in this part of the basin. For this reason, it is felt that the following presentation of factual data for the field will be of general interest.