This study defines the areas and stratigraphic horizons of basin-centered gas, and aquifer boundaries within the Greater Green River Basin in southwestern Wyoming and northwestern Colorado. A better understanding of the settings, mechanisms, and controls of the distribution of Paleozoic- to Tertiary-aged reservoirs, aquifers, and hydrocarbons has been developed through the definition of a coherent hydrogeologic framework. Extensions of known plays and new exploration fairways have been outlined. The top of tested gas has been mapped, and can be used to plan the drilling of exploration and step-out development wells and to determine more certain costs for economic evaluations. Water salinity maps are provided for each map unit, and can be used to determine formation water resistivity and therefore, more accurate values for water saturation. This will improve reserve estimates and reduce the uncertainty in an economic evaluation of an area or prospect. A section on the theory of underpressuring and overpressuring and the formation of a basin-centered gas system is provided so that some of the risks of exploration in tight gas systems can be better understood. Specific objectives of the study were to:

• Define a coherent hydrodynamic framework by identifying major play types, regional aquifers, recharge / discharge areas, and areas of abnormal pressure.
• Define boundaries of conventional and unconventional play types as they relate to basin geology, structure and tectonics, source rocks and maturation.
• Identify zones and areas of potential stratigraphic traps.
• Identify potential fairways and extensions of existing play types.
• Identify new conceptual play types with specific hydrodynamic signatures.
• Apply regional hydrodynamics (meteoric recharge points, water chemistry, zones of biogenic activity) for CBM and shallow gas resource assessment.