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The developmental history of a basin-centered gas system (BCGS) may be viewed as four reservoir pressure cycles. As a consequence of the dynamic nature of geologic processes and the response to those processes, the phases discussed here are geologically ephemeral. [[:file:BasinCenteredGasFig1.jpg|Figure 1]] is a diagrammatic representation showing these pressure phases and the development of direct and indirect BCGSs. Meissner<ref name=Meissner_1978>Meissner, F. Fm 1978, Patterns of source-rock maturity in non-marine source rocks of some typical western interior basins in non-marine Tertiary and Upper [[Cretaceous]] source rocks and the occurrence of oil and gas in the west central U.S.:Roky Mountain Association of Geologists Continuing Education Notes, unpaginated.</ref> and 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> discussed these phase changes for gas accumulations in low-permeability reservoirs.

The developmental history of a basin-centered gas system (BCGS) may be viewed as four reservoir pressure cycles. As a consequence of the dynamic nature of geologic processes and the response to those processes, the phases discussed here are geologically ephemeral. [[:file:BasinCenteredGasFig1.jpg|Figure 1]] is a diagrammatic representation showing these pressure phases and the development of direct and indirect BCGSs. Meissner<ref name=Meissner_1978>Meissner, F. Fm 1978, Patterns of source-rock maturity in non-marine source rocks of some typical western interior basins in non-marine Tertiary and Upper Cretaceous source rocks and the occurrence of oil and gas in the west central U.S.:Roky Mountain Association of Geologists Continuing Education Notes, unpaginated.</ref> and 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> discussed these phase changes for gas accumulations in low-permeability reservoirs.

[[file:BasinCenteredGasFig1.jpg|thumb|400px|{{figure number|1}}Schematic diagram showing evolution of direct and indirect basin-centered gas systems. Evolutionary phases are shown along the side of each system.]]

[[file:BasinCenteredGasFig1.jpg|thumb|400px|{{figure number|1}}Schematic diagram showing evolution of direct and indirect basin-centered gas systems. Evolutionary phases are shown along the side of each system.]]

| colspan=5 | <div style="text-align: center;">'''NORTH AMERICA'''</div>

| colspan=5 | <div style="text-align: center;">'''NORTH AMERICA'''</div>

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| Colville basin, Alaska || High || Cretaceous || Direct ? || Popov et al.<ref name=Popovetal_2001>Popov, M. A., V. F. Nuccio, T. S. Dyman, T. A. Gognat, R. C. Johnson, J. W. Schmoker, M. S. Wilson, and C. Bartberger, 2001, Basin-centered gas systems of the U.S.:U.S. Geological Survey Open-File Report 01-135, Version 1.0, 1 CD-ROM.</ref>

| Colville basin, Alaska || High || [[Cretaceous]] || Direct ? || Popov et al.<ref name=Popovetal_2001>Popov, M. A., V. F. Nuccio, T. S. Dyman, T. A. Gognat, R. C. Johnson, J. W. Schmoker, M. S. Wilson, and C. Bartberger, 2001, Basin-centered gas systems of the U.S.:U.S. Geological Survey Open-File Report 01-135, Version 1.0, 1 CD-ROM.</ref>

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| Central Alaska basins || Low/Moderate || ? || ? || Popov et al.<ref name=Popovetal_2001 />

| Central Alaska basins || Low/Moderate || ? || ? || Popov et al.<ref name=Popovetal_2001 />