Gas Potential of Rocky Mountain Region

John D. Haun, James A. Barlow, Jr., and Donald E. Hallinger

Major gas reserves will be discovered in six Rocky Mountain areas — Uinta-Piceance, Green River, Laramie-Hanna, Wind River, Big Horn, and Powder River basins. In the San Juan and Paradox basins, in Montana, and in other peripheral areas, the quantity of additional gas to be discovered is believed to be small. Within the six areas of primary interest, 191,000 cu mi of Cretaceous and Tertiary rocks contains 10 trillion cu ft of gas (reserves plus past production) and 90,000 cu mi of pre-Cretaceous sedimentary rocks contains only 0.3 trillion cu ft of gas. Most gas discoveries, therefore, have been made in Cretaceous-Tertiary rocks and it is probable that major potential resources will be confined largely to these rocks.

During the 10-year period 1957-1967, 1,070 gas wells were completed within the six areas; 3.5-4 trillion cu ft of reserves was added. If approximately 1,000 gas wells (plus associated dry holes) are completed within these basins during the 1967-1977 period, an additional 3.5-4 trillion cu ft should be added.

Cretaceous-Tertiary areas occupy approximately 96,200 sq mi and only 9,050 sq mi (9.4%) has at least one well per sq mi. Ten trillion cu ft of gas has been discovered by drilling wells in less than 10% of the available area, and far less than 10% of the available rock volume has been explored. If the gas originally in place is 10 times the gas thus far discovered, the ultimate potential would be 100 trillion cu ft--a maximum estimate. A minimum estimate of ultimate potential should be 25 trillion cu ft. A conservative estimate, between these limits, is 40-50 trillion cu ft to be discovered in the Rocky Mountain region.

AAPG Search and Discovery Article #91051©2012 AAPG Rocky Mountain Section Meeting, Albuquerque, New Mexico, 23-26 February 1969