· 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

Undiscovered Oil and Gas Resources in the Southwestern Wyoming Province

Kirschbaum and others, 2002, used a geology-based assessment methodology to estimate a mean of 84.6 trillion cubic feet of undiscovered natural gas, a mean of 131 million barrels of undiscovered oil, and a mean of 2.6 billion barrels of undiscovered natural gas liquids in nine Total Petroleum Systems (TPS) in the Southwestern Wyoming Province. Nearly all (97 percent, or 82.1 TCFG) of the undiscovered gas resource is from continuous-type reservoirs and distributed in six TPSs:

1. Mowry Composite TPS (8.5 TCFG)
2. Hilliard–Baxter–Mancos TPS (11.7 TCFG)
3. Mesaverde TPS (25.8 TCFG)
4. Mesaverde–Lance–Ft. Union Composite TPS (13.7 TCFG)
5. Lewis TPS (13.5 TCFG)
6. Lance–Ft. Union Composite TPS (8.7 TCFG)

The remainder of the undiscovered gas is associated/dissolved gas in oil accumulations (0.13 TCFG) or is in conventional nonassociated gas accumulations (2.3 TCFG, Kirschbaum and others, 2002). Because the majority of the gas resources are distributed in seven assessment units (AUs) within the six TPSs listed above, this report focuses on these seven AUs:

1. Almond Continuous Gas AU of the Mesaverde TPS
2. Rock Springs–Ericson Continuous Gas AU of the Mesaverde TPS
3. Mesaverde–Lance–Fort Union Continuous Gas AU of the Mesaverde–Lance–Ft. Union Composite TPS
4. Lewis Continuous Gas AU of the Lewis TPS
5. Hilliard–Baxter–Mancos AU of the Hilliard–Baxter–Mancos TPS
6. Mowry Continuous Gas AU of the Mowry Composite TPS
7. Lance–Fort Union Continuous Gas AU of the Lance–Fort Union Composite TPS

The 2002 USGS assessment of undiscovered resources focused on the Southwestern Wyoming Province of Wyoming, Colorado, and Utah (fig. 2). This report is focused on the area defined by the WLCI boundary. In 2003, another assessment was completed west of the Southwestern Wyoming Province, in the Wyoming Thrust Belt Province. The estimates of undiscovered gas resources in the Wyoming Thrust Belt Province are minor compared to the gas resources in the seven AUs, and for that reason, are not included in this report. Assessment values discussed in this report are within the WLCI of southwestern Wyoming but also include portions of northwestern Colorado and a small portion of northeastern Utah.  For instance, the Mancos portion of the Hilliard–Baxter–Mancos TPS, represents the Mancos Shale in the Sand Wash Basin of Colorado. Even though these assessed areas extend beyond the WLCI boundary, the data provides a good representation of the distribution, quantity, and availability of significant natural gas resources in the portion of southwestern Wyoming that is included in the WLCI.

Figure 2. Map showing boundaries of the Wyoming Landscape Conservation Initiative and the Southwestern Wyoming Province with some of the major structural features labeled. The surface geology shown in the WLCI area is from the Geologic Map of Wyoming (Green and Drouillard, 1994).

Well data used in this report were retrieved from the WOGCC in the spring of 2008. The wells shown for each of the assessment units represent those wells in the WOGCC database that report reservoir names of the stratigraphic intervals (formations and groups) included in that particular AU. Because these formations and groups extend beyond individual assessment units, the wells shown also extend beyond a particular assessment unit and, therefore, some of the wells belong to adjacent continuous and (or) conventional AUs. The purpose of showing these wells is: (1) to indicate exploration and production activity in a particular stratigraphic interval, (2) to show what was known at the time of the 2002 USGS assessment of undiscovered resources, and (3) to show where exploration and production has occurred since the assessment. Because the well information shown with each AU is formation specific and not AU specific, individual wells can be shown with more than one AU. This report has attempted to summarize the geologic aspects of the oil and gas development using information from the detailed geologic studies described in U.S. Geological Survey Southwestern Wyoming Province Assessment Team, 2005.