Changes

==Indirect type: Lower Silurian Clinton-Medina-Tuscarora, Appalachian Basin==

==Indirect type: Lower Silurian Clinton-Medina-Tuscarora, Appalachian Basin==

The Lower Silurian Clinton-Medina-Tuscarora BCGS, located in the Appalachian basin ([[:file:BasinCenteredGasFig9.jpg|Figure 7]], [[:file:BasinCenteredGasFig10.jpg|Figure 8]]), is one of the better documented examples of an indirect BCGS. Estimates of recoverable resources range from 8.0 to 30.3 tcf.<ref name=Gautieretal_1996>Gautier, D. L., G. L. Dolton, K. I Takahashi, and K. L. Varnes, eds., 1996, 1995 national assessment of United States oil and gas resources-results, methodology, and supporting data: U.S. Geological Survey Digital Data Series DDS-30, RElease 2, 1 CD-ROM.</ref><ref name=Mccormacetal_1996>McCormac, M. P., G. O. Mychkovsky, S. T. Opritza, R. A. Riley, M. E. Wolfe, G. E. Larson, and M. T. Baronoski, 1996, Play Scm: Lower Silurian Cataract/Medina Group ("Clinton") sandstone 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. 156-163.</ref> For additional discussions of the Clinton-Medina-Tuscarora, refer to investigations by Davis,<ref name=Davis_1984 />, Law and Dickinson,<ref name=Lawanddickinson_1985>Law, B. E., and W. W. Dickinson, 1985, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0069/0008/1250/1295.htm A conceptual model for the origin of abnormally pressured gas accumulations in low-permeability reservoirs]: AAPG Bulletin, v. 69, p. 1295-1304.</ref> Laughrey and Harper,<ref name=Laughreyandharper_1986>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> Zagorski,<ref name=Zagorski_1988>Zagorski, W. A., 1988, Exploration concepts and methodology for deep Medina sandstone reservoirs in northwestern Pennsylvania (abs.): AAPG Bulletin, v. 72, p. 976.</ref><ref name=Zagorski_1991>Zagorski, W. A., 1991, Model of local and regional hydrocarbon traps in the Lower Silurian Medina Sandstone Group, Cooperstown gas field, Crawford and Venango counties, Pennsylvania: M.S. thesis, University of Pittsburgh, Pennsylvania, 132 p.</ref> Law et al.,<ref name=Lawetal_1998a /> Ryder,<ref name=Ryder_1998 /> and Ryder and Zagorski.<ref name=Ryderandzagorski_2003 />

The Lower Silurian Clinton-Medina-Tuscarora BCGS, located in the Appalachian basin ([[:file:BasinCenteredGasFig9.jpg|Figure 7]], [[:file:BasinCenteredGasFig10.jpg|Figure 8]]), is one of the better documented examples of an indirect BCGS. Estimates of recoverable resources range from 8.0 to 30.3 tcf.<ref name=Gautieretal_1996>Gautier, D. L., G. L. Dolton, K. I Takahashi, and K. L. Varnes, eds., 1996, 1995 national assessment of United States oil and gas resources-results, methodology, and supporting data: U.S. Geological Survey Digital Data Series DDS-30, RElease 2, 1 CD-ROM.</ref><ref name=Mccormacetal_1996>McCormac, M. P., G. O. Mychkovsky, S. T. Opritza, R. A. Riley, M. E. Wolfe, G. E. Larson, and M. T. Baronoski, 1996, Play Scm: Lower Silurian Cataract/Medina Group ("Clinton") sandstone 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. 156-163.</ref> For additional discussions of the Clinton-Medina-Tuscarora, refer to investigations by Davis,<ref name=Davis_1984 />, Law and Dickinson,<ref name=Lawanddickinson_1985>Law, B. E., and W. W. Dickinson, 1985, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0069/0008/1250/1295.htm A conceptual model for the origin of abnormally pressured gas accumulations in low-permeability reservoirs]: AAPG Bulletin, v. 69, p. 1295-1304.</ref> Laughrey and Harper,<ref name=Laughreyandharper_1986>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> Zagorski,<ref name=Zagorski_1988>Zagorski, W. A., 1988, Exploration concepts and methodology for deep Medina sandstone reservoirs in northwestern Pennsylvania (abs.): AAPG Bulletin, v. 72, p. 976.</ref><ref name=Zagorski_1991>Zagorski, W. A., 1991, Model of local and regional hydrocarbon traps in the Lower Silurian Medina Sandstone Group, Cooperstown gas field, Crawford and Venango counties, Pennsylvania: M.S. thesis, University of Pittsburgh, Pennsylvania, 132 p.</ref> Law et al.,<ref name=Lawetal_1998a>Law, B. E., R. T. Ryder, V F. Nuccio, and R. C. Burrus, 1998a, Pressure end-members in the Lower Silurian Clinton-Medina-Tuscarora basin-centgered gas accumulation, Appalachian basin, USA, ''in'' A. Mitchel and D. Grauls, eds., Overpressures in petroleum exploration: Elf Aquitaine Memoir 22, p. 133-135.</ref> Ryder,<ref name=Ryder_1998>Ryder, T. T., 1988, Greater Green River basin, ''in'' L. L. Sloss, ed., Sedimentary cover-North America craton: The Geology of North America, v. D-2, p. 154-165.</ref> and Ryder and Zagorski.<ref name=Ryderandzagorski_2003 />

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===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 /><ref name=Drozdandcole_1994 /><ref name=Burrussandryder_1998 /><ref name=Ryderetal_1998 /> 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: AAPG Memoir 60, p. 387-398.</ref><ref name=Burrussandryder_1998 /><ref name=Ryderetal_1998 /> 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 /><ref name=Nuccioetal_1997 /><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 /><ref name=Nuccioetal_1997 /><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 />

* 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 />

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The underpressured reservoirs in the Clinton-Medina are interpreted to have undergone an earlier overpressured phase caused by the thermal transformation of oil to gas.<ref name=Lawanddickinson_1985 /><ref name=Lawandspencer_1993 /><ref name=Lawetal_1998a /><ref name=Ryderandzagorski_2003 /> Later, during a period of regional uplift accompanied by loss of gas and reservoir cooling, the overpressured, gas-bearing Clinton-Medina underwent a transition to an underpressuring phase. The overpressured, gas-bearing Tuscarora Sandstone reservoirs in central Pennsylvania are interpreted to be pressure remnants of the earlier overpressured phase in the Clinton-Medina.<ref name=Lawetal_1998a /><ref name=Ryderandzagorski_2003 />

The underpressured reservoirs in the Clinton-Medina are interpreted to have undergone an earlier overpressured phase caused by the thermal transformation of oil to gas.<ref name=Lawanddickinson_1985 /><ref name=Lawandspencer_1993 /><ref name=Lawetal_1998a /><ref name=Ryderandzagorski_2003>Ryder, R. T., and W. A. Zagorski, 2003, [http://archives.datapages.com/data/bulletns/2003/05may/0847/0847.HTM Nature, origin, and production characteristics of the Lower Silurian regional oil and gas accumulation, central Appalachian basin, United States]: AAPG Bulletin, v. 87, no. 5, p. 847-872.</ref> Later, during a period of regional uplift accompanied by loss of gas and reservoir cooling, the overpressured, gas-bearing Clinton-Medina underwent a transition to an underpressuring phase. The overpressured, gas-bearing Tuscarora Sandstone reservoirs in central Pennsylvania are interpreted to be pressure remnants of the earlier overpressured phase in the Clinton-Medina.<ref name=Lawetal_1998a /><ref name=Ryderandzagorski_2003 />

==References==

==References==