· Abstract

· Acknowledgments

· Introduction—Video of Exploration and Production Through Time

· Units of Measure

· Undiscovered Oil and Gas Resources in the Southwestern Wyoming Province

· Undiscovered Gas in the Mesaverde Total Petroleum System

· The Almond Continuous Gas Assessment Unit

· The Rock Springs–Ericson Gas Assessment Unit

· Undiscovered Gas in the Mesaverde–Lance–Fort Union Composite Total Petroleum System

· The Mesaverde–Lance–Fort Union Continuous Gas Assessment Unit

· Undiscovered Gas in the Lewis Total Petroleum System

· The Lewis Continuous Gas Assessment Unit

· Undiscovered Gas in the Hilliard-Baxter-Mancos Total Petroleum System

· The Hilliard-Baxter-Mancos Continuous Gas Assessment Unit

· Undiscovered Gas in the Mowry Composite Total Petroleum System

· The Mowry Continuous Gas Assessment Unit

· Undiscovered Gas in the Lance–Fort Union Composite Total Petroleum System

· The Lance–Fort Union Continuous Gas Assessment Unit

· Reservoirs That Contain the Majority of Undiscovered Gas Resources

· Live Data and Maps

· In Summary

· References Cited

The Rock Springs–Ericson Gas Assessment Unit (12.2 TCFG)

The Rock Springs–Ericson Gas AU (AU 50370662) covers about 4.36 million acres of the deeper parts of the Mesaverde TPS. As shown below in the generalized correlation chart, this AU includes: the Rock Springs and Ericson Formations in the western part of the Washakie and Great Divide Basins, the Allen Ridge Formation and Pine Ridge Sandstone in the eastern part of the Washakie and Great Divide Basins, and the Iles and lower part of the Williams Fork Formations in the Sand Wash Basin (Johnson and others, 2005).

As described in Johnson and others (2005) the Rock Springs–Ericson Continuous Gas AU, though largely untested, contains thick sequences of reservoir rocks that were deposited in settings similar to successfully developed, basin-centered accumulations throughout the Rocky Mountains. Figure 8 shows the extent of the Rock Springs–Ericson Continuous Gas AU, the mean estimate of undiscovered gas and gas liquids in that AU, and wells from the WOGCC that have a reservoir name of Rock Springs or Ericson and a completion date of 2001 or earlier.

Figure 8. Rock Springs Formation–Ericson Sandstone wells at the time of the assessment (through 2001).

At the time of the assessment, most of the tests of this AU date to the 1970s and 1980s when our understanding of how to produce from the tight reservoirs in basin-centered accumulation was in its infancy (Johnson and others, 2005). Testing of this AU largely ceased once the productive potential of the marginal marine-bar sandstones in the Almond was recognized. Johnson and others (2005) state that these estimates assume future production for the Rock Springs–Ericson AU would be significantly greater than production from the AU thus far because most completions are more than 12 years old, and drilling and completion practices have improved significantly since these wells were completed. An analogy for the lenticular sandstone reservoirs in the Rock Springs Formation is the productive lenticular sandstones in the lower part of the Williams Fork Formation in the Piceance Basin Continuous Gas AU (Johnson and Roberts, 2003). Lenticular sandstones in both AUs were deposited in coastal plain and fluvial settings (Johnson and others, 2005). These sandstones in the Piceance Basin are currently being developed using spacing of as little as 20 acres (Johnson and others, 2005). An analogy for the marginal marine sandstones in the Rock Springs Formation is the production from similar bar sandstones in the overlying Almond Formation (Johnson and others, 2005). The large number of currently producing Almond wells within the boundaries of the Rock Springs-Ericson AU may help spur development, as these wells could be deepened to test the Rock Springs Formation and Ericson Sandstone for a fraction of the cost of a new well (Johnson and others, 2005). Figure 9 shows the same data as the map above, but additional wells have been added to show how, according to the WOGCC wells database, drilling of the Rock Springs and Allen Ridge Formations and the Ericson Sandstone has progressed to the spring of 2008.

Figure 9. Rock Springs Formation-Ericson Sandstone wells as of spring, 2008.

The WOGCC well data shows that since the 2002 assessment, 205 additional wells are reported to have been completed in the Ericson Sandstone and the Rock Springs and Allen Ridge Formations, 91 of which are shown to have produced from or terminated in coal beds.