· 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 Lance–Fort Union Continuous Gas Assessment Unit (7.6 TCFG)

The Lance–Fort Union Continuous Gas AU includes areas where thermal maturity (R_o) values are 0.8 percent or greater in potential source rocks near the base of the TPS (Fox Hills Sandstone and lower Lance Formation). The AU boundary is defined by the surface (vertical) projection of the 0.8 percent isoreflectance (R_o) line estimated for the top of the Lewis Shale (Hettinger and Roberts, 2005), which underlies the Lance–Fort Union Composite TPS (Roberts, 2005). At this level of thermal maturity, gas-prone source rocks have the ability to generate and expel significant amounts of gas (Meissner, 1984; Law, 1984; Roberts and others, 2005), and for this reason the potential for gas accumulation exists throughout the entire AU (Roberts, 2005). At the time of the assessment, an estimated 110 wells are considered to have tested the AU. Given that historical exploration for continuous gas accumulations within the Lance–Fort Union Composite TPS is limited, it is unlikely that production results to date are entirely representative of the future gas potential (Roberts, 2005).

Figure 22 shows the extent of the Lance–Fort Union Continuous Gas AU, the mean estimate of undiscovered gas and gas liquids in that AU, and wells from the WOGCC that produce from units of the Lance–Fort Union Composite TPS and have a completion date of 2001 or earlier. Wells shown outside of the AU boundary, tested or produced from the Fort Union, Lance or Wasatch Formations within other AUs.

Figure 22. Wells from units of the Lance–Fort Union Composite TPS at the time of the assessment (through 2001).

Figure 23 includes the same data as figure 22, with post-2001 wells added to show how drilling of wells to units of the Lance–Fort Union Composite TPS has progressed to the spring of 2008 (WOGCC).

Figure 23. Wells that produce from units of the Lance–Fort Union Composite TPS as of spring, 2008.

Since the 2002 assessment, 2506 additional wells, mostly outside the Lance-Fort Union Continuous AU, have been completed in the units of the Lance-Fort Union Composite TPS, 25 of which are shown to have produced from or terminated in coal beds (WOGCC).