Utah’s conventional natural gas production is mostly concentrated within the Uinta Basin in Uintah, Grand, and Summit Counties. Tight gas sands, shale gas, and coalbed methane all contribute to Utah’s natural gas production. Natural gas is primarily used for residential purposes; however, natural gas-fired power plants have greatly increased the amount used by the electric utility sector.
Tight Gas Sands
Tight gas reservoirs are often called unconventional reservoirs because “tight” refers to the fact that the permeability of the reservoir rock is very low. Unlike conventional reservoirs, unconventional reservoirs cannot produce economic volumes of gas without first being stimulated by using special processes such as hydraulic fracturing. Tight gas reservoirs include sandstone, carbonate rocks (such as limestone), shale, and coal beds. Almost all of the natural gas produced from the Uinta Basin comes from unconventional reservoirs, especially tight gas sandstones. In Utah, the Natural Buttes field in the eastern Uinta Basin is one of the primary producers of tight gas in the state.
Schematic diagram of hydraulic fracturing in tight gas sandstone.
Shale gas reservoirs in Utah have tremendous untapped potential. Paleozoic shales in the Colorado Plateau and eastern Basin and Range Province have long been known for their potential as source rocks for hydrocarbons that have migrated into other formations, but have not been considered as in situ gas reservoirs. These include the Mississippian Manning Canyon and Delle Phosphatic shales in north-central and western Utah and the Pennsylvanian Paradox Formation in southeastern Utah. Shale beds within these formations are widespread, thick, buried deep enough to generate dry gas, and contain sufficient organic material and fractures to hold significant recoverable gas reserves.
Diagram illustrating horizontal drilling in the Cane Creek shale of the Paradox Formation. In some wells multiple laterals are drilled. The Cane Creek is often gently folded and rarely ever flat-lying. The smaller diagram shows the actual path of a horizontal lateral and the difficulty of staying within the Cane Creek reservoir target (from Utah Division of Oil, Gas and Mining well records).
Where there is coal, there is also the potential for coalbed methane resources. Although it is a less common form of natural gas, coalbed methane can be mined alongside existing coal and coalbed deposits. In contrast to a conventional gas reservoir, where gas is found inside the pores of a material, coalbed methane is found stored in a near-liquid state within the surface of the coal or in natural fractures. Geology, organic maturity, and other variables contribute to the potential for gas exploration and economic production.
Frontier Areas for Coalbed-Gas Exploration
Natural Gas Resources, Posters, and Presentations
Tight Gas Sands
Gas Production Forecasting From Tight-Gas Reservoirs: Integrating Natural Fracture Networks and Hydraulic Fractures
University of Utah research funded by Research Partnership to Secure Energy for America
Utah State University
Tight Gas Sands and Natural Fractures in the Cretaceous Mesaverde Group, Greater Natural Buttes Field, Uinta Basin, Utah
Stephanie M. Carney, Thomas C. Chidsey, Jr., Craig D. Morgan, and Michael D. Laine, Utah Geological Survey
Presented at AAPG Annual Conference, Houston, TX, April 2011
Well Core Description and Natural Fractures of the Sego and Castlegate Sandstones of the Cretaceous Mesaverde Group, Greater Natural Buttes Field, Uinta Basin, Utah
Stephanie M. Carney, Craig D. Morgan, Thomas C. Chidsey, Jr., and Michael D. Laine, Utah Geological Survey
Presented at AAPG-RMS Annual Conference, Durango, CO, June 2010