Exploration Vignettes in the Rocky Mountain Region

Title: Exploration Vignettes in the Rocky Mountain Region: Two Wells That Put Glenrock, Wyoming, On The Map

Author: Alexander A. McGregor

Publication: The Outcrop, July 2002, p. 14

Editors’ Note: This essay is the third in an “occasional series” of short essays gathered from the experiences of oil finders in the Rockies. Author Alex McGregor is a long-time RMAG member who is perhaps best known for his part in the discovery of Bell Creek Field in southeastern Montana.

It was the early 1950s. Texaco assigned me the job of field mapping the Casper Mountain Front with the purpose of defining faulted closures.

Glenrock was the location of a Continental Oil Company refinery that processed the oil from the Big Muddy Field. Big Muddy was a well-defined surface anticline, an early target for the drill bit. It was a significant multi-pay oil field.

While mapping the Casper Mountain Front I met Jack Steele from Chicago. He was leasing the town lots in Glenrock. I wondered why. This area was a sharply northeast plunging nose off the Big Muddy anticline. In my bi-weekly letter to management I stated that the prospect of drilling at least 2000’ lower structurally than the oil-water contact at Big Muddy was a foolhardy endeavor.

Imagine my surprise when Steele’s wildcat well flowed 4000 BOPD from the Muddy sand at about 9,000’. I felt it must be a deep-seated fault trap not evident on the surface. I questioned Jack Steele, who was then described as a liquor broker. His explanation was inadequate as he was seldom sober.

Although the industry professed little interest, Steele’s well produced nearly 1 million barrels of oil in the first year, making it a well of remarkable performance. Attracted by this success, Trigood Oil Company acquired a lease on the UPRR right-of-way that passed through the Continental Oil refinery at Glenrock. This discovery was apparently in the same genre as the Steele well and after producing 100,000 barrels of oil it caused Continental to drill two offsets north and south of the Trigood lease. In spite of their proximity to the producing well, both Continental wells reported a tight Muddy sand and insignificant production.

Truly the Steele and Trigood wells were the caliber of major discoveries. The fact that the eventual producing areas were limited did not detract from their significance. More sophisticated operators entered the fray, and major oil fields named Glenrock and South Glenrock emerged.

Eventually faulting was found to have no influence on this accumulation. The production resulted from a stratigraphic trap within the Muddy sand. This experience was repeated many times throughout the Powder River Basin.