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| Using a geology-based assessment methodology, the U.S. Geological Survey estimated a mean of 8.6 trillion
cubic feet of undiscovered natural gas, a mean of 109 million barrels of undiscovered oil, and a mean of 240 million barrels of natural gas liquids in the
Montana Thrust Belt Province of northwestern Montana. |
|
| Introduction |
| The U.S. Geological Survey (USGS) recently completed an assessment
of the undiscovered oil and gas potential of the Montana Thrust Belt
Province of northwestern Montana (fig. 1). The assessment of the Montana
Thrust Belt Province is based on the geologic elements of each Total
Petroleum System defi ned in the province, including hydrocarbon source
rocks (source-rock maturation, hydrocarbon generation and migration),
reservoir rocks (sequence stratigraphy and petrophysical properties),
and hydrocarbon traps (trap formation and timing). Using this geologic
framework, the USGS defined seven Total Petroleum Systems (TPS) and
nine Assessment Units within these Total Petroleum Systems and quantitatively
estimated the undiscovered oil and gas resources within seven of the
nine Assessment Units (table
1). |
|
| Resource Summary |
| The USGS assessed undiscovered conventional oil and gas and continuous
(unconventional) oil. The USGS estimated a mean of 8.6 trillion cubic
feet of gas (TCFG), a mean of 109 million barrels of oil (MMBO), and
a mean of 240 million barrels of total natural gas liquids (MMBNGL)
in fi ve Total Petroleum Systems. Nearly all (99 percent) of the undiscovered
gas resource is conventional, whereas about 75 percent of the undiscovered
oil resource is conventional (table
1). Of the 8.6 TCFG, about 7.7 TCFG is estimated to be in the
Paleozoic/Mesozoic Composite Total Petroleum System of the Thrust
Belt, and 0.68 TCFG is in the Central Montana Trough Paleozoic Composite
Total Petroleum System of the Helena Salient. The remainder of the
gas (about 0.28 TCFG) is associated/dissolved gas in oil accumulations
(table
1). Because the USGS assessment of natural gas is for total gas,
the conventional gas in these TPSs may contain signifi cant percentages
of gases other than hydrocarbon gases, such as carbon dioxide. The
Tertiary Lacustrine Shale Total Petroleum System is estimated to contain
a mean of about 69 MMB of conventional oil, whereas the Marias River
Shale Total Petroleum System is estimated to contain about 28 MMB
of continuous (unconventional) oil. The Bakken Formation and Jurassic/Cretaceous
Total Petroleum Systems were not quantitatively assessed in this study. |
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| For Further Information |
Supporting geologic studies of Total Petroleum Systems and Assessment
Units, and reports on the methodology used in the Montana Thrust Belt
Province assessment, are in progress.
Assessment results are available at the USGS Central Energy Team website:
http://energy.cr.usgs.gov/oilgas/noga/ |
|
Figure 1. Montana Thrust Belt Province of northwestern Montana.
| Montana Thrust Belt Assessment
Team: |
| Christopher J. Schenk (Task Leader; schenk@usgs.gov), Ronald R. Charpentier, Troy A. Cook, Thaddeus S. Dyman, Christopher D.
French, Mitchell E. Henry, Timothy R. Klett, William J. Perry, Richard M. Pollastro, and Christopher J. Potter. |
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