Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
Stratigraphic Controls on Higher-than-average Permeability Zones in Tight-gas Sands in the Piceance Basin
The Colorado School of Mines
Low permeability gas systems, or “tight gas”, account for more than 15% of the total domestic gas production and constitute the majority of unconventional energy resources currently produced in the United States. Commercial production of gas from tight-gas sandstones is primarily controlled by the distribution of regions with higher-than-average permeability, or “sweet spots”. The structural, stratigraphic and diagenetic controls on “sweet spots” are highly variable and very difficult to predict. Due to the complexity of tight-gas resources, current exploration strategies generally follow a simplistic approach that includes phases of reconnaissance, confirmation of gas and pore pressures, and delineating “sweet spots” based on the geologic context and other available information. However, a better understanding of the structural, stratigraphic and diagenetic controls on tight-gas sandstones would allow the development of more sophisticated exploration and production strategies that would improve recovery and reduce environmental impacts by drilling fewer wells. The purpose of this study is to evaluate the stratigraphic controls on the distribution and quality of tight-gas reservoirs using regional outcrop and subsurface data. This project complements a currently funded, multidisciplinary RPSEA project (“Reservoir Connectivity and Stimulated Gas Flow in Tight Sands”, Dr. Dag Nummedal), and fills an important gap in regional, outcrop-based stratigraphic analysis along the margins of the Piceance basin.
The Piceance basin, Colorado, is a hot-spot for exploration and production of natural gas from tight-gas sandstones in the Rocky Mountain region. More than 400 tcf of in-place gas is estimated to be held within tight-gas and basin-centered gas accumulations in the Piceance basin alone. However, the regional stratigraphic framework and detailed understanding of stratigraphic controls on tight-gas distribution and production in this basin are incomplete. This study evaluates stratigraphic controls on the location of “sweet spots” within the Piceance basin. Spectacular outcrops along the West, South and Eastern margins of the basin permit the construction of several regional outcrop-based sequence-stratigrpahic transects. Outcrop-based, regional stratigraphic transects will be carefully integrated with detailed reservoir characterization and modeling, fracture analysis and subsurface-based stratigraphic correlations conducted by Dr. Dag Nummedal’s team of scientists. Additional outcrop-based research in the Piceance basin will provide considerable insight into the depositional history of the basin and more detailed understanding of the local and regional stratigraphic controls on local and regional flow of gas in tight-gas sandstones. A better understanding of stratigraphic controls on tight-gas sandstones is the next step in developing more sophisticated exploration and production strategies to make recovery of these vital resources more efficient, with less environmental impact.
Principal Investigator: Dr. Jennifer Aschoff, Assistant Professor