Performance Review of Tiger Ridge and Bullhook Gas Units
Authors: Bayliff William H. 
Published: December 2007

This paper was prepared for the Rocky Mountain Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in Billings, Mont., May 15–16, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
The Tiger Ridge and Bullhook Gas Units, located in north central Montana, have been on stream over one year producing natural gas from the Eagle Sandstone Formation at approximately 1300 feet. A review of both units' performance, including reservoir parameters, performance, including reservoir parameters, development programs, completion techniques, production history and problems, and economics, production history and problems, and economics, are explained within this paper. Explanations of the current state of reserve development and necessary future drilling programs are discussed.

Introduction
The Tricentrol United States, Inc. operated Tiger Ridge and Bullhook Gas Units are in Blaine and Hill Counties of north-central Montana. The area of interest lies south of Havre, Montana, and encompasses approximately 112,000 surface acres of unitized Eagle Sandstone formation in the two units as shown in Fig. 1. The Eagle gas sand is approximately 1300 feet deep and ranges in thickness from 5 feet to over 120 feet of net gas pay, with the average approximately 30 to 40 feet.
The discovery well was the O'Neil 1–8 in the SE/NE of Section 1, T31N, R17E of Blaine County drilled during September, 1966. The well was drilled through the Eagle Sandstone at 1340 feet and found productive. This indicated the possibilities of commercial gas production in the area. production in the area. With the advent of a gas field, additional wildcat drilling began to prove the extent of the reservoir. By the spring of 1969, 75 wells were drilled testing the Eagle, both in the now existing unit boundaries and areas presently outside the boundaries. Negotiations presently outside the boundaries. Negotiations were under way to bring the gas to market with sales at a reasonable rate-of-take and a gas price to justify the large necessary price to justify the large necessary development program. The operator negotiated with one intrastate and two interstate markets and in May, 1969, a gas purchase contract was signed with Northern Natural Gas Company of Omaha. Nebraska. From May of 1969 to May of 1972, Tricentrol spent time preparing evidence, submitting testimony, and appearing at hearings with the Federal Power Commission in order that the gas could be sold to an interstate market.