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Large accumulations of high purity nitrogen gas have been found in some Williston Basin oil fields. This gas has been considered for use in oil production operations.
Estimates of nitrogen gas contained in the Minnelusa formation in Clear Creek and Charlson fields in North Dakota are presented. The estimates are based on quantitative analysis of logs from 154 wells. The log calculations were performed by Pare Oil Co., utilizing their COMLOG system.
Large accumulations of free nitrogen gas occur in many underground formations throughout the southwestern portion of the Williston basin. They have been found extensively on the Cedar Creek anticline, Montana, Nesson anticline, North Dakota, and in Billings County, N. Dak.
Economically valuable nitrogen accumulations must be of sufficient size to guarantee the amount needed and must be near the place of use. Two such sources were found in the Minnelusa formation in the Clear Creek and Charlson fields, Fig. 1, located on the Nesson anticline.
Some of the potential uses for these accumulations of nitrogen are: Reservoir pressure maintenance, nitrogen slug injection in water floods, nitrogen slug injection in miscible displacement, nitrogen gas blanketing in storage tanks, gas-lift production of oil and displacing fluid with nitrogen in well completions.
The estimation of the volume of nitrogen in the Minnelusa formation in these fields was made possible by completing the large number of logging calculations with a digital computer.
The Clear Creek field is south of the Missouri River and on the west flank of the Nesson anticline [Fig. 1]. The structure of the Minnelusa formation is a large, broad, south-plunging nose, that overlies the oil productive Madison-Mississippian reservoir. The field is 3-1/4 miles long and 3 miles wide, and contains about 5,700 acres.
The structural contours on top of the Minnelusa formation are shown in Fig. 2. Structural relief is greater than 180 ft. As shown in Fig. 3, the gross potential producing zone ranges in thickness from 230 to 360 ft.
The Charlson field extends from the Missouri River southward and lies on top of the Nesson anticline [Fig. 1].