TREMAIN, CAROL M., Colorado Geological Survey, Denver, CO, RONALD E. BROADHEAD, New Mexico Bureau of Miners and Mineral Resources, Socorro, NM, THOMAS C. CHIDSEY, JR., Utah Geological Survey, Salt Lake City, UT, MARK DOELGER, Barrow & Haun, Inc., Casper, WY, and CRAIG D. MORGAN, Utah Geological Survey, Salt Lake City, UT

ABSTRACT: Low-BTU Gas in the Rocky Mountain Region-Colorado, Wyoming, New Mexico, and Utah

There are over 100 reservoirs in Colorado, Wyoming, New Mexico, and Utah that produce or could produce low-BTU (heating value less than 900 BTU/cu ft) gas. Reservoirs range in age from Devonian to Cretaceous; reservoir lithologies include both carbonates and sandstones. Frequently, the low-BTU gas (C02, N2, and He) is a byproduct of normal hydrocarbon production.

CO2-rich gas occurs in southwest to east-central Utah, in the southeastern Paradox basin (Utah and Colorado), in the North Park basin (Colorado), in southeast Colorado and northeast New Mexico, and in the Green River and Wind River basins (Wyoming). Five fields produce nearly pure (98%) CO2. The 1990 annual CO2 production from these fields was North and South McCallum (Colorado), 1.7 bcf; McElmo (Colorado), 205 bcf; Sheep Mountain (Colorado), 70.7 bcf; and Bravo Dome (New Mexico), 119.7 bcf. Big Piney-LaBarge (Wyoming) produced 120 bcf of CO2 (at a concentration of 65%) in 1990. Most of the CO2 is used in enhanced oil recovery.

Nitrogen-rich gas is found in the southern Green River basin (Utah and Wyoming), east flank of the San Rafael uplift (Utah), northern Paradox basin (Utah), Uncompahgre uplift (Utah and Colorado), Douglas Creek arch (Colorado), Hugoton embayment (Colorado), Las Animas arch (Colorado), Permian basin (New Mexico), and Four Corners platform (New Mexico). Helium is sometimes associated with the nitrogen and in concentrations of up to 8% in New Mexico and Colorado, 2.8% in Utah, and 1% in Wyoming.

AAPG Search and Discovery Article #90993©1993 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah, September 12-15, 1993.