Major gas reserves will be discovered in the Uinta-Piceance, Green River, Laramie-Hanna, Wind River, Big Horn, and Powder River basins in the Rocky Mountain region. In the San Juan and Paradox basins, and in Montana and 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 contain 10 trillion cu ft of gas (reserves plus past production) and 90,000 cu mi of pre-Cretaceous sedimentary rocks contain less than 1 trillion cu ft of gas. Most gas discoveries, therefore, have been in the Cretaceous-Tertiary section and major potential resources probably are confined to these rocks.
During the 10-year period 1957-1966, 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 1967-1976 period, an additional 3.5-4 trillion cu ft should be added.
Cretaceous-Tertiary rocks occupy approximately 96,200 sq mi, of which only 9,050 sq mi (9.4 percent) has at least one well per square mile. Ten trillion cu ft of gas has been discovered by drilling wells in less than 10 percent of the available area. Less than 5 percent of available rock volume has been explored. If the gas originally in place were 10 times the gas discovered, the ultimate potential would be 100 trillion cu ft. The Potential Gas Committee estimate, 79 trillion cu ft of ultimately discoverable gas in Area H, is conservative.