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{{publication
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Evaluating top and fault seal
| frompg = 10-1
| topg = 10-94
| author = Grant M. Skerlec
| link = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
==How thick is necessary?==
There is no simple relationship between seal thickness and the height of the hydrocarbon column. Seals can be extremely thin—less than [[length::1 m]] thick that seal individual hydrocarbon accumulations. There are also examples of traps with thick shale seals that are dry. This difficulty in establishing a relationship between seal thickness and column is especially true since many hydrocarbon columns are controlled by fault-related spill points that are independent of top seal thickness.
==Seal thickness studies==
Data compiled from fields in California and the Rocky Mountains show no relationship between seal thickness and hydrocarbon column height.<ref name=ch10r98>Zieglar, D., M., 1992, Hydrocarbon columns, [[buoyancy pressure]]s, and seal efficiency: comparisons of oil and gas accumulations in California and the Rocky Mountain area: AAPG Bulletin, vol. 76, no. 4, p. 501–508.</ref> Nonetheless, some workers have suggested a correlation between seal thickness and seal capacity.<ref name=ch10r58>Nederlof, M., N., Mohler, H., P., 1981, Quantitative investigation of trapping effect of unfaulted caprock: AAPG Bulletin, vol. 65, no. 6, p. 964.</ref><ref name=ch10r75>Slujik, D., Nederlof, M., H., 1984, Worldwide geological experience as a systematic basis for prospect appraisal, in Demaison, G., Murris, R., J., eds., Petroleum Geochemistry and Basin Evaluation: AAPG Memoir 35, p. 15–26.</ref>
==Seal continuity and fracturing==
Seal thickness is not an independent variable. Thin seals have a higher probability of being laterally discontinuous, of being fractured completely, or of having local variations in fracture intensity or pore throat diameter that provide a leakage pathway. Similarly, thick seals have a higher probability of being laterally continuous, having fractures terminate within the seal, and having at least one shale lamina with a high displacement pressure.
==See also==
* [[Seal capacity]]
* [[Seal capacity of different rock types]]
* [[Variation in seal capacity with depth and hydrocarbon phase]]
* [[Seal capacity and two-phase hydrocarbon columns]]
* [[Fault-dependent leak points, continuity, and charge]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Evaluating top and fault seal]]
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Evaluating top and fault seal
| frompg = 10-1
| topg = 10-94
| author = Grant M. Skerlec
| link = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
==How thick is necessary?==
There is no simple relationship between seal thickness and the height of the hydrocarbon column. Seals can be extremely thin—less than [[length::1 m]] thick that seal individual hydrocarbon accumulations. There are also examples of traps with thick shale seals that are dry. This difficulty in establishing a relationship between seal thickness and column is especially true since many hydrocarbon columns are controlled by fault-related spill points that are independent of top seal thickness.
==Seal thickness studies==
Data compiled from fields in California and the Rocky Mountains show no relationship between seal thickness and hydrocarbon column height.<ref name=ch10r98>Zieglar, D., M., 1992, Hydrocarbon columns, [[buoyancy pressure]]s, and seal efficiency: comparisons of oil and gas accumulations in California and the Rocky Mountain area: AAPG Bulletin, vol. 76, no. 4, p. 501–508.</ref> Nonetheless, some workers have suggested a correlation between seal thickness and seal capacity.<ref name=ch10r58>Nederlof, M., N., Mohler, H., P., 1981, Quantitative investigation of trapping effect of unfaulted caprock: AAPG Bulletin, vol. 65, no. 6, p. 964.</ref><ref name=ch10r75>Slujik, D., Nederlof, M., H., 1984, Worldwide geological experience as a systematic basis for prospect appraisal, in Demaison, G., Murris, R., J., eds., Petroleum Geochemistry and Basin Evaluation: AAPG Memoir 35, p. 15–26.</ref>
==Seal continuity and fracturing==
Seal thickness is not an independent variable. Thin seals have a higher probability of being laterally discontinuous, of being fractured completely, or of having local variations in fracture intensity or pore throat diameter that provide a leakage pathway. Similarly, thick seals have a higher probability of being laterally continuous, having fractures terminate within the seal, and having at least one shale lamina with a high displacement pressure.
==See also==
* [[Seal capacity]]
* [[Seal capacity of different rock types]]
* [[Variation in seal capacity with depth and hydrocarbon phase]]
* [[Seal capacity and two-phase hydrocarbon columns]]
* [[Fault-dependent leak points, continuity, and charge]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Evaluating top and fault seal]]