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Fault-dependent leak points, continuity, and charge (view source)
Revision as of 15:39, 31 January 2014
, 15:39, 31 January 2014Initial import
{{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
}}
In many basins the major control on hydrocarbon column heights is not the displacement pressure of top seals but fault-dependent leak points, the lateral continuity of seals, and charge.
==Fault-dependent leak points==
A comparison of top seal capacity determined from displacement pressures and actual hydrocarbon column heights in one African basin demonstrates that while top seals are capable of trapping more than [[depth::1000 ft]] of oil, most traps contain only a few hundred feet of oil.<ref name=ch10r68>Shea, W., T., Schwalbach, J., R., Allard, D., M., 1993, Integrated rock-log evaluation of fluvio-lacustrine seals, in Ebanks, J., Kaldi, J., Vavra, C., eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research conference, unpublished abstract.</ref> Oil column heights in this basin are controlled instead by fault-dependent leak points.<ref name=ch10r3>Allard, D., M., 1993, Fault leak controlled trap fill, rift basin examples (abs.), in Ebanks, J., Kaldi, J., Vavra, C., eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg conference, Crested Butte, Colorado, June 21–23.</ref><ref name=ch10r68 />).
Similarly, only 5–10% of the fields in the Rocky Mountains and California are thought to have hydrocarbon column heights controlled by top seal capillary properties (<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> The remaining 90–95% are controlled by some other factor, including charge, faults, and synclinal spill points.
==Seal continuity==
The lateral extent and continuity of top seals can create and destroy plays within basins. In many basins, thick, continuous, areally extensive sequences of shale or salt act as regional top seals. The Gippsland basin and North Sea are only two of numerous examples. In some basins, this regional seal is lacking or limited. In the Gulf Coast, the North Frisco City field exists because the Buckner Anhydrite, a regional seal, is missing above a local basement high. Only where the regional seal is breached are hydrocarbons able to escape from the Smackover reservoir into the overlying Lower Haynesville sands.<ref name=ch10r81>Stephenson, M., Cox, J., Jones-Fuentes, P., 1992, How 3D seismic-CAEX combination affected development of N. Frisco City field in Alabama: Oil & Gas Journal, vol. 90, no. 43, p. 127–130.</ref> Where the Buckner Anhydrite is continuous, there is no Haynesville play.
==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]]
* [[Seal thickness]]
==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
}}
In many basins the major control on hydrocarbon column heights is not the displacement pressure of top seals but fault-dependent leak points, the lateral continuity of seals, and charge.
==Fault-dependent leak points==
A comparison of top seal capacity determined from displacement pressures and actual hydrocarbon column heights in one African basin demonstrates that while top seals are capable of trapping more than [[depth::1000 ft]] of oil, most traps contain only a few hundred feet of oil.<ref name=ch10r68>Shea, W., T., Schwalbach, J., R., Allard, D., M., 1993, Integrated rock-log evaluation of fluvio-lacustrine seals, in Ebanks, J., Kaldi, J., Vavra, C., eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research conference, unpublished abstract.</ref> Oil column heights in this basin are controlled instead by fault-dependent leak points.<ref name=ch10r3>Allard, D., M., 1993, Fault leak controlled trap fill, rift basin examples (abs.), in Ebanks, J., Kaldi, J., Vavra, C., eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg conference, Crested Butte, Colorado, June 21–23.</ref><ref name=ch10r68 />).
Similarly, only 5–10% of the fields in the Rocky Mountains and California are thought to have hydrocarbon column heights controlled by top seal capillary properties (<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> The remaining 90–95% are controlled by some other factor, including charge, faults, and synclinal spill points.
==Seal continuity==
The lateral extent and continuity of top seals can create and destroy plays within basins. In many basins, thick, continuous, areally extensive sequences of shale or salt act as regional top seals. The Gippsland basin and North Sea are only two of numerous examples. In some basins, this regional seal is lacking or limited. In the Gulf Coast, the North Frisco City field exists because the Buckner Anhydrite, a regional seal, is missing above a local basement high. Only where the regional seal is breached are hydrocarbons able to escape from the Smackover reservoir into the overlying Lower Haynesville sands.<ref name=ch10r81>Stephenson, M., Cox, J., Jones-Fuentes, P., 1992, How 3D seismic-CAEX combination affected development of N. Frisco City field in Alabama: Oil & Gas Journal, vol. 90, no. 43, p. 127–130.</ref> Where the Buckner Anhydrite is continuous, there is no Haynesville play.
==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]]
* [[Seal thickness]]
==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]]