Abstract: Basin Center Gas in the Williston Basin

T. J. Heck, J. A. LeFever

The Williston basin is an oil-prone basin. However, in the central part of the basin some of the deeper formations are gas productive. There are only 22 pools classified as gas pools, all of which produce from the Ordovician Red River, Ordovician Winnipeg and Cambrian-Ordovician Deadwood formations. Most of the gas produced from the basin center is associated gas, and gas/oil ratios increase as the center of the basin is approached. GOR's vary from 1,000 near the flank to more than 100,000, with most presently producing wells having GOR's in the 5,000-10,000 range. Gasses typically are rich in liquids and have BTU's in excess of 1,200. One drawback is that gas produced from some of the Red River fields, Midway for example, may be very sour. H₂S content can be near 20%.

The typical gas trap in the basin center is a small, 4-way closed structure with at least some component of stratigraphic change involved. There are no known purely stratigraphic traps producing from the Red River Formation.

Through the end of June, 1992, there have been more than 206 BCF of gas sold from the basin-center fields of which 80% is from the Red River Formation and 20% from the Winnipeg-Deadwood formations. Many of the currently producing fields have yet to be fully developed, and the middle of the basin is virtually untested. We estimate the middle case undiscovered resource at more than 300 BCF.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994