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U.S. Department of the Interior
U.S. Geological Survey
 
Assessment of the Mesaverde Total Petroleum System in Southwestern 
Wyoming Province: a petroleum system approach to assessing 
undiscovered oil and gas resources
Compiled PowerPoint* Slides 

by Ronald C. Johnson and Thomas M. Finn
 

USGS Open-File Report 03-472
2003
 

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ABSTRACT

      The U.S. Geological Survey, in a recent assessment of the undiscovered oil and gas resources in the Southwestern Wyoming Province using a Total Petroleum System (TPS) approach, estimated a mean of 84.6 trillion cubic feet of gas (TCFG), 131 million barrels of oil (MMBO) and 2.6 billion barrels of natural gas liquids (BBNGL) that have the potential to be added to reserves over the next 30 years.  Only a fraction of this, however, may be economically recoverable

      Of the total estimate of 84.6 TCFG, a mean of 25.78 TCFG is in continuous-type reservoirs in the Mesaverde TPS.  The Mesaverde TPS is defined as all reservoirs predominantly containing gas derived from the Mesaverde Group east of the pinchout of the Lewis Shale, which acts as a top seal separating the Mesaverde TPS from the overlying Lewis TPS. 

      Continuous-type reservoirs in the Mesaverde TPS were subdivided into the Almond Continuous Gas Assessment Unit (AU) (mean of 13.35 TCFG), Rock Springs-Ericson Continuous Gas AU (mean of 12.18 TCFG), and the Mesaverde Coalbed Gas AU (mean of 0.25 TCFG).  Geologic analysis was used to determine the favorable “sweet spots” for potential gas resources.  The Almond AU has been heavily explored at depths less than 11,000 ft, thus additions to reserves will most likely be the result of infill drilling in existing fields and the discovery of sweet spots at depths greater than 11,000 ft.  There is much uncertainty in the size of undiscovered resource in the Rock Springs-Ericson AU because potential reservoirs are only sparsely explored.  Only a small fraction of in-place coal-bed gas is considered to be recoverable because of low permeability and problems posed by produced water.

INTRODUCTION

      This presentation was given at the “Petroleum Systems and Reservoirs of Southwest Wyoming” Symposium sponsored by the Rocky Mountain Association of Geologists and the PTTC-Rocky Mountain Region on September 19, 2003, in Denver Colorado.


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