Changes

===General characteristics of the Greater Green River basin BCGS===

===General characteristics of the Greater Green River basin BCGS===

* Area: 19,700 mi² (51,000 km²)

* Area: 19,700 mi² (51,000 km²)

* Source rocks: Upper Cretaceous and lower Tertiary coal beds and carbonaceous shales in the Fort Union, Lance, Almond, and Rock Springs formations. Organic matter is largely gas-prone type III kerogen<ref name=Law_1984 /> with additional contribution from thermally cracked oils sourced from sapropelic coal beds.<ref name=Garciagonzalesetal_1993a /><ref name=Garciagonzalesetal_1993b /><ref name=Macgowanetal_1993 /><ref name=Surdametal_1997>Surdam, R. C., Z. S. Jiao, and H. P. Heasler, 1997, [http://archives.datapages.com/data/specpubs/mem67/ch12/ch12.htm Anomalously pressured gas compartments in Cretaceous rocks of the Laramide basins of Wyoming: A new class of hydrocarbon accumulation], ''in'' R. C. Surdam, ed., Seals, traps, and the petroleum system: AAPG Memoir 67, p. 199-222.</ref>

* Source rocks: Upper Cretaceous and lower Tertiary coal beds and carbonaceous shales in the Fort Union, Lance, Almond, and Rock Springs formations. Organic matter is largely gas-prone type III [[kerogen]]<ref name=Law_1984 /> with additional contribution from thermally cracked oils sourced from sapropelic coal beds.<ref name=Garciagonzalesetal_1993a /><ref name=Garciagonzalesetal_1993b /><ref name=Macgowanetal_1993 /><ref name=Surdametal_1997>Surdam, R. C., Z. S. Jiao, and H. P. Heasler, 1997, [http://archives.datapages.com/data/specpubs/mem67/ch12/ch12.htm Anomalously pressured gas compartments in Cretaceous rocks of the Laramide basins of Wyoming: A new class of hydrocarbon accumulation], ''in'' R. C. Surdam, ed., Seals, traps, and the petroleum system: AAPG Memoir 67, p. 199-222.</ref>

* Generation-expulsion-migration: late Eocene-late Oligocene (40-25 Ma)

* Generation-expulsion-migration: late Eocene-late Oligocene (40-25 Ma)

* Reservoir rocks: Cretaceous to lower Tertiary sandstones. Multiple, stacked reservoirs occur in rock intervals as thick as 14,000 ft (4267 m) ([[:file:BasinCenteredGasFig6.jpg|Figure 3]]). Individual reservoirs range in thickness from 15 to 125 ft (4.6-38 m). Gas reservoirs are saturated and contain water at irreducible levels. The gas-bearing interval does not commonly contain interbedded, water-bearing reservoirs.

* Reservoir rocks: Cretaceous to lower Tertiary sandstones. Multiple, stacked reservoirs occur in rock intervals as thick as 14,000 ft (4267 m) ([[:file:BasinCenteredGasFig6.jpg|Figure 3]]). Individual reservoirs range in thickness from 15 to 125 ft (4.6-38 m). Gas reservoirs are saturated and contain water at irreducible levels. The gas-bearing interval does not commonly contain interbedded, water-bearing reservoirs.

* Environments of deposition: mainly fluvial dominated and, to a lesser degree, marginal marine deltaic and barrier bar

* Environments of deposition: mainly fluvial dominated and, to a lesser degree, marginal marine deltaic and barrier bar

* Reservoir pressure: overpressured, with gradients ranging from 0.5 to 0.9 psi/ft ([[:file:BasinCenteredGasFig7.jpg|Figure 4]], [[:file:BasinCenteredGasFig8.jpg|Figure 5]])<ref name=Lawetal_1979 /><ref name=Lawetal_1980 /><ref name=Mcpeek_1981 /><ref name=Davis_1984 /><ref name=Law_1984 /><ref name=Spencer_1987>Spencer, C. W., 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0004/0350/0368.htm Hydrocarbon generation as a mechanism for overpressuring in Rocky Mountain region]: AAPG Bulletin, v. 71, p. 368-388.</ref><ref name=Spencer_1989b /><ref name=Surdametal_1997 />  

* Reservoir pressure: overpressured, with gradients ranging from 0.5 to 0.9 psi/ft ([[:file:BasinCenteredGasFig7.jpg|Figure 4]], [[:file:BasinCenteredGasFig8.jpg|Figure 5]])<ref name=Lawetal_1979 /><ref name=Lawetal_1980 /><ref name=Mcpeek_1981 /><ref name=Davis_1984 /><ref name=Law_1984 /><ref name=Spencer_1987>Spencer, C. W., 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0004/0350/0368.htm Hydrocarbon generation as a mechanism for overpressuring in Rocky Mountain region]: AAPG Bulletin, v. 71, p. 368-388.</ref><ref name=Spencer_1989b /><ref name=Surdametal_1997 />  

* Seals: Regional seals are capillary pressure seals. Locally, structural and stratigraphic seals are important.   

* Seals: Regional seals are [[capillary pressure]] seals. Locally, structural and stratigraphic seals are important.   

* Gas accumulations: downdip from normally pressured, water-bearing reservoirs ([[:file:BasinCenteredGasFig2.jpg|Figure 6]]);<ref name=Law_1984 /><ref name=Spencer_1985>Spencer, C. W., 1985, Geologic aspects of tight gas reservoirs in the Rock Mountain region: Journal of Petroleum Geology, p. 1308-1314.</ref> lacks a downdip water contact.<ref name=Law_1984 /> The level of thermal maturity at top of accumulation ranges from 0.7 to 0.9% R_o<ref name=Law_1984 /> ([[:file:BasinCenteredGasFig7.jpg|Figure 4]], [[:file:BasinCenteredGasFig8.jpg|Figure 5]]), commonly 0.8% R_o.<ref name=Law_1984 />  

* Gas accumulations: downdip from normally pressured, water-bearing reservoirs ([[:file:BasinCenteredGasFig2.jpg|Figure 6]]);<ref name=Law_1984 /><ref name=Spencer_1985>Spencer, C. W., 1985, Geologic aspects of tight gas reservoirs in the Rock Mountain region: Journal of Petroleum Geology, p. 1308-1314.</ref> lacks a downdip water contact.<ref name=Law_1984 /> The level of thermal maturity at top of accumulation ranges from 0.7 to 0.9% R_o<ref name=Law_1984 /> ([[:file:BasinCenteredGasFig7.jpg|Figure 4]], [[:file:BasinCenteredGasFig8.jpg|Figure 5]]), commonly 0.8% R_o.<ref name=Law_1984 />  

* Depth to accumulation: ranges from 8000 to 11,500 ft (2438-3505 m)  

* Depth to accumulation: ranges from 8000 to 11,500 ft (2438-3505 m)  

===General characteristics of the Lower Silurian Clinton-Medina-Tuscarora, Appalachian Basin BCGS===

===General characteristics of the Lower Silurian Clinton-Medina-Tuscarora, Appalachian Basin BCGS===

* Area: Clinton-Medina part is 45,000 mi² (116,550 km²); Tuscarora part is 30,000 mi² (77,700 km²).

* Area: Clinton-Medina part is 45,000 mi² (116,550 km²); Tuscarora part is 30,000 mi² (77,700 km²).

* Source rock: Ordovician Utica Shale.<ref name=Coleetal_1987>Cole, G. A., R. J. Drozd, R. A. Sedivy and H. I. Helpern, 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0007/0750/0788.htm Organic geochemistry and source-rock correlations, Paleozoic of Ohio]: AAPG Bulletin, v. 71, p. 788-809.</ref><ref name=Drozdandcole_1994>Drozd, R. J., and G. A. Cole, 1994, [http://archives.datapages.com/data/specpubs/methodo2/data/a077/a077/0001/0350/0387.htm Point Pleasant-Brassfield petroleum system, Appalachian basin, USA], ''in'' L. B. Magoon and W. G. Dow, eds., The petroleum system-from source to trap: AAPG Memoir 60, p. 387-398.</ref><ref name=Burrussandryder_1998>Burruss, R. C., and R. T. Ryder, 1998, Composition of crude oil and natural gas produced from 10 wells in the Lower Silurian "Clinton" sands, Trumbull County, Ohio: U.S. Geological Survey Open-file Report 98-799, 50 p.</ref><ref name=Ryderetal_1998>Ryder, R. T., R. C. Burruss, and J. R. Hatch, 1998, [http://archives.datapages.com/data/bulletns/1998/03mar/0412/0412.htm Black shale source rocks and oil generation in Cambrian and Ordovician of the central Appalachian basin, USA]: AAPG Bulletin, v. 82, p. 412-441.</ref> The Utica Shale contains type II kerogen and is thermally overmature (>1.3% R_o).

* Source rock: Ordovician Utica Shale.<ref name=Coleetal_1987>Cole, G. A., R. J. Drozd, R. A. Sedivy and H. I. Helpern, 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0007/0750/0788.htm Organic geochemistry and source-rock correlations, Paleozoic of Ohio]: AAPG Bulletin, v. 71, p. 788-809.</ref><ref name=Drozdandcole_1994>Drozd, R. J., and G. A. Cole, 1994, [http://archives.datapages.com/data/specpubs/methodo2/data/a077/a077/0001/0350/0387.htm Point Pleasant-Brassfield petroleum system, Appalachian basin, USA], ''in'' L. B. Magoon and W. G. Dow, eds., The petroleum system-from source to trap: [http://store.aapg.org/detail.aspx?id=1022 AAPG Memoir 60], p. 387-398.</ref><ref name=Burrussandryder_1998>Burruss, R. C., and R. T. Ryder, 1998, Composition of crude oil and natural gas produced from 10 wells in the Lower Silurian "Clinton" sands, Trumbull County, Ohio: U.S. Geological Survey Open-file Report 98-799, 50 p.</ref><ref name=Ryderetal_1998>Ryder, R. T., R. C. Burruss, and J. R. Hatch, 1998, [http://archives.datapages.com/data/bulletns/1998/03mar/0412/0412.htm Black shale source rocks and oil generation in Cambrian and Ordovician of the central Appalachian basin, USA]: AAPG Bulletin, v. 82, p. 412-441.</ref> The Utica Shale contains type II kerogen and is thermally overmature (>1.3% R_o).

* Generation-migration-accumulation: Late Devonian-Early Mississippian (370-320 Ma)<ref name=Drozdandcole_1994 /><ref name=Laughreyandharper_1996>Laughrey, C. D., and J. A. Harper, 1996, Play Obe: Upper Ordovician Bald Eagle Formation fractured play, ''in'' J. B. Roen and B. J. Walker, eds., The atlas of major Appalachian gas plays: West Virginia Geological and Economic Survey Publication V-25, p. 164-167.</ref><ref name=Nuccioetal_1997>Nuccio, V. F., C. J. Wandrey, R. T. Ryder, and A. G. Harris, 1997, Thermal maturity and petroleum generation of Middle Ordovician black shale source rocks, central Appalachian basin-controls on oil and gas in Lower Silurian low permeability sandstone reservoirs (abs.): AAPG Bulletin v. 81, p. 1560.</ref><ref name=Ryderetal_1998 /><ref name=Ryderandzagorski_2003 />  

* Generation-migration-accumulation: Late Devonian-Early Mississippian (370-320 Ma)<ref name=Drozdandcole_1994 /><ref name=Laughreyandharper_1996>Laughrey, C. D., and J. A. Harper, 1996, Play Obe: Upper Ordovician Bald Eagle Formation fractured play, ''in'' J. B. Roen and B. J. Walker, eds., The atlas of major Appalachian gas plays: West Virginia Geological and Economic Survey Publication V-25, p. 164-167.</ref><ref name=Nuccioetal_1997>Nuccio, V. F., C. J. Wandrey, R. T. Ryder, and A. G. Harris, 1997, Thermal maturity and petroleum generation of Middle Ordovician black shale source rocks, central Appalachian basin-controls on oil and gas in Lower Silurian low permeability sandstone reservoirs (abs.): AAPG Bulletin v. 81, p. 1560.</ref><ref name=Ryderetal_1998 /><ref name=Ryderandzagorski_2003 />  

* Reservoir rocks: Lower Silurian Clinton-Medina in eastern Ohio and western Pennsylvania and Tuscarora Sandstone in central Pennsylvania. The reservoir interval ranges in thickness from 100 to 600 ft (30-183 m).<ref name=Ryderandzagorski_2003 /> The thermal maturity of the reservoir ranges from 1.1 to 2.0% R_o.<ref name=Wandreyetal_1997>Wandrey, C. J., R. T. Ryder, V. F. Nuccio, and K. L. Aggen, 1997, The areal extent of continuous type gas accumulations in Lower Silurian Clinton sands and Medina Group sandstones of the Appalachian basin and environments affeted by their developments: U.S. Geological Survey Open-File Report 97-272, 12 p.</ref>

* Reservoir rocks: Lower Silurian Clinton-Medina in eastern Ohio and western Pennsylvania and Tuscarora Sandstone in central Pennsylvania. The reservoir interval ranges in thickness from 100 to 600 ft (30-183 m).<ref name=Ryderandzagorski_2003 /> The thermal maturity of the reservoir ranges from 1.1 to 2.0% R_o.<ref name=Wandreyetal_1997>Wandrey, C. J., R. T. Ryder, V. F. Nuccio, and K. L. Aggen, 1997, The areal extent of continuous type gas accumulations in Lower Silurian Clinton sands and Medina Group sandstones of the Appalachian basin and environments affeted by their developments: U.S. Geological Survey Open-File Report 97-272, 12 p.</ref>