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What was assessed
The U.S. Geological Survey assessed the conventional and continuous (unconventional) gas in the Late Cretaceous Mesaverde Group (Santonian to Campanian) and Lance Formation (Maastrichtian) of the Southwestern Wyoming Province, in Wyoming, Utah and Colorado. They belong to the Cretaceous–Cenozoic Composite Total Petroleum System, in the western half of the province.
Figure 1. The three assessment units in the Southwestern Wyoming Province. USGS.
The province is bounded by the Wyoming salient of the Sevier orogenic belt on the west, Laramide uplifts on the north and south, and the edge of the Lewis Shale on the east. Much of the petroleum system's production comes from the Pinedale Anticline and Jonah field.
The rocks
The system is mostly gas-prone: four Upper Cretaceous formations of river, delta and some shoreline sediments, laid down roughly at right angles to the southwest–northeast shore of the Western Interior Seaway. From oldest to youngest they are the Rock Springs Formation, Ericson Sandstone and Almond Formation of the Mesaverde Group, and the Lance Formation.
- Source rock: thermally mature coal beds in the Rock Springs Formation, with modeled vitrinite reflectance (Ro) above 0.8%. Coals in the younger formations are probably too immature (Ro below 0.8%) to contribute.
- Reservoirs: sandstones of the Mesaverde Group and river sandstones of the Lance — with its better porosity, permeability and thickness, the Lance is the main producer for the system and the whole province.
Assessment units
The USGS last assessed this system in 2005, with four units; this time it defined three:
| Unit | Type | Defined by |
|---|---|---|
| Mesaverde-Lance Conventional Gas | conventional; the largest; normally pressured, may have gas–water contacts | Sevier and Laramide uplifts and where the rocks pinch out |
| Mesaverde-Lance Continuous Gas | continuous; overpressured, no gas–water contacts | the same edges on three sides; on the west, the 0.8% Ro line in the Rock Springs Formation |
| Mesaverde-Lance Jonah Pinedale Continuous Gas | continuous; overpressured | the faults and relief of the Pinedale Anticline and Jonah field, and the extent of drilling |
Results
The mean totals, fully risked, are 4,652 billion cubic feet of gas (4.7 trillion), with an F95–F5 range of 1,189 to 9,150 billion, and 158 million barrels of natural gas liquids, range 41 to 313 million. (F95 is a 95 percent chance of at least that amount; F5 a 5 percent chance.)
| Unit | Mean gas (billion cubic feet) | Mean natural gas liquids (million barrels) |
|---|---|---|
| Mesaverde-Lance Conventional Gas (probability 0.9) | 26 | 1 |
| Mesaverde-Lance Jonah Pinedale Continuous Gas | 1,101 | 37 |
| Mesaverde-Lance Continuous Gas | 3,525 | 120 |
Results are also on the USGS Energy Resources Program website.
Sources
Based on Cretaceous–Cenozoic Composite Total Petroleum System Assessment Team (Jenny H. Lagesse and others), "Assessment of undiscovered conventional and continuous gas resources in the Mesaverde Group and Lance Formation in the Southwestern Wyoming Province, 2025," U.S. Geological Survey Fact Sheet 2025–3048; a work of the United States government in the public domain. It cites DuBois (2014), Finn and others (2005), Roehler (1990), Law (1984), Law and Spencer (2014), Rudolph and others (2015) and Kovach and others (2003). The fact sheet's table of input data is left out.
Licens: CC0 1.0 (allmän egendom) · Bearbetat efter pubs.usgs.gov
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