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Natural hydraulic fracturing example, North Sea (view source)
Revision as of 15:26, 31 January 2014
, 15:26, 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
}}
==Trap description==
A trap in the Central Graben, North Sea, appears to have been bled dry by natural hydraulic fracturing. This trap is a low-relief salt structure with a dry hole and has less-than-sufficient strain to fracture the top seal.
==Evidence==
Evidence for hydraulic fracturing and seal rupture include the following:
* A fossil oil—water contact exists at the synclinal spill point of the trap. The trap was once filled with hydrocarbon, but something happened after trap fill to bleed off hydrocarbons.
* Hydrocarbon shows exist throughout the sediment column above the reservoir. These hydrocarbons are direct evidence of a breached top seal.
* The pore pressure is close to the theoretical fracture pressure. In adjacent fields, the pore pressure is significantly less than P<sub>f</sub>.
* Cores show vertical, open extension fractures rather than the more common shear fractures found in adjacent fields. These fractures are identical to fractures produced by hydraulic fracturing.
Figure 10-44 shows that the pore pressure is close to the fracture pressure at the base of the top seal (approximately [[depth::1300 ft]]). The pore pressure is inferred from mud weight and RFT measurements (solid dots). Leak-off tests (LOT) help constrain the fracture pressure. The fracture pressure is close to the lithostatic pressure or overburden pressure.
[[file:evaluating-top-and-fault-seal_fig10-44.png|thumb|{{figure number|10-44}}. Copyright: Esso Exploration and Production, U.K.]]
==See also==
* [[Overpressure and natural hydraulic fracturing]]
* [[Natural hydraulic fracturing of top seals]]
* [[Fracture threshold in the real world]]
* [[Overpressure and hydrocarbon distribution, gulf coast]]
==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
}}
==Trap description==
A trap in the Central Graben, North Sea, appears to have been bled dry by natural hydraulic fracturing. This trap is a low-relief salt structure with a dry hole and has less-than-sufficient strain to fracture the top seal.
==Evidence==
Evidence for hydraulic fracturing and seal rupture include the following:
* A fossil oil—water contact exists at the synclinal spill point of the trap. The trap was once filled with hydrocarbon, but something happened after trap fill to bleed off hydrocarbons.
* Hydrocarbon shows exist throughout the sediment column above the reservoir. These hydrocarbons are direct evidence of a breached top seal.
* The pore pressure is close to the theoretical fracture pressure. In adjacent fields, the pore pressure is significantly less than P<sub>f</sub>.
* Cores show vertical, open extension fractures rather than the more common shear fractures found in adjacent fields. These fractures are identical to fractures produced by hydraulic fracturing.
Figure 10-44 shows that the pore pressure is close to the fracture pressure at the base of the top seal (approximately [[depth::1300 ft]]). The pore pressure is inferred from mud weight and RFT measurements (solid dots). Leak-off tests (LOT) help constrain the fracture pressure. The fracture pressure is close to the lithostatic pressure or overburden pressure.
[[file:evaluating-top-and-fault-seal_fig10-44.png|thumb|{{figure number|10-44}}. Copyright: Esso Exploration and Production, U.K.]]
==See also==
* [[Overpressure and natural hydraulic fracturing]]
* [[Natural hydraulic fracturing of top seals]]
* [[Fracture threshold in the real world]]
* [[Overpressure and hydrocarbon distribution, gulf coast]]
==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]]