Changes

==Fault sealing characteristics==

==Fault sealing characteristics==

Fine grained fault rock will have a higher capillary entry pressure compared to the undeformed host rock. Brown<ref name=Brown_2003>Brown, A., 2003, [http://archives.datapages.com/data/bulletns/2003/03mar/0381/0381.HTM Capillary effects on fault-fill sealing]: AAPG Bulletin, v. 87, no. 3, p. 381–395.</ref> described how the seal behavior of water-wet fault fill defines three potential zones within a fault.

Fine grained fault rock will have a higher capillary entry pressure compared to the undeformed host rock. Brown<ref name=Brown_2003>Brown, A., 2003, [http://archives.datapages.com/data/bulletns/2003/03mar/0381/0381.HTM Capillary effects on fault-fill sealing]: AAPG Bulletin, v. 87, no. 3, p. 381–395.</ref> described how the seal behavior of water-wet fault fill defines three potential zones within a fault.

* A fault can seal because the petroleum phase has insufficient buoyancy pressure to invade and displace water from the fine grained material within the fault rock; this has been termed membrane sealing.<ref name=Watts_1987 />

* A fault can seal because the petroleum phase has insufficient [[buoyancy pressure]] to invade and displace water from the fine grained material within the fault rock; this has been termed membrane sealing.<ref name=Watts_1987 />

* Higher within the petroleum column, the buoyancy pressure can increase to the point at which the oil or gas can invade the fault rock and thus leak through it. However, the fault rock will have a very low permeability, and the rate of leakage can be trivial, even over geological time.<ref name=Heum_1996>Heum, O. R., 1996, A fluid dynamic classification of hydrocarbon entrapment: Petroleum Geoscience, v. 2, no. 2, p. 145–158.</ref> The fault can then be considered to be effectively lsquosealingrsquo by hydraulic resistance.<ref name=Watts_1987>Watts, N. L., 1987, Theoretical aspects of cap-rock and fault seals for single and two phase columns: Marine and Petroleum Geology, v. 4, no. 4, p. 274–307.</ref>

* Higher within the petroleum column, the buoyancy pressure can increase to the point at which the oil or gas can invade the fault rock and thus leak through it. However, the fault rock will have a very low permeability, and the rate of leakage can be trivial, even over geological time.<ref name=Heum_1996>Heum, O. R., 1996, A fluid dynamic classification of hydrocarbon entrapment: Petroleum Geoscience, v. 2, no. 2, p. 145–158.</ref> The fault can then be considered to be effectively lsquosealingrsquo by hydraulic resistance.<ref name=Watts_1987>Watts, N. L., 1987, Theoretical aspects of cap-rock and fault seals for single and two phase columns: Marine and Petroleum Geology, v. 4, no. 4, p. 274–307.</ref>

* Where an exceptionally thick petroleum column exists, even low-permeability fault rocks can leak at significant rates. This is the zone of fault fill seal failure.

* Where an exceptionally thick petroleum column exists, even low-permeability fault rocks can leak at significant rates. This is the zone of fault fill seal failure.