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Hydrocarbon column heights may not be related only to the displacement pressure of the top seal. Once a seal has been breached and hydrocarbons forced through the seal, theoretically the hydrocarbon column will shrink until the buoyant pressure equals the displacement pressure and the system again seals. In practice, however, hydrocarbons continue to flow through the seal until there is no longer a continuous hydrocarbon filament. Although the process is not completely understood, laboratory studies suggest that flow continues until the hydrocarbon column shrinks to half its original height.<ref name=ch10r65>Roof, J. G., 1970, Snap-off of oil droplets in water-wet pores: SPE Journal, vol. 10, no. 1, p. 85–90.</ref><ref name=ch10r67>Schowalter, T. T., 1979, [http://archives.datapages.com/data/bulletns/1977-79/data/pg/0063/0005/0700/0723.htm Mechanics of secondary hydrocarbon migration and entrapment]: AAPG Bulletin, vol. 63, no. 5, p. 723–760.</ref>

[[Hydrocarbon column]] heights may not be related only to the [[Top seal displacement pressure|displacement pressure of the top seal]]. Once a seal has been breached and [[hydrocarbon]]s forced through the seal, theoretically the hydrocarbon column will shrink until the [[Buoyancy pressure|buoyant pressure]] equals the displacement pressure and the system again seals. In practice, however, hydrocarbons continue to flow through the seal until there is no longer a continuous hydrocarbon filament. Although the process is not completely understood, laboratory studies suggest that flow continues until the hydrocarbon column shrinks to half its original height.<ref name=ch10r65>Roof, J. G., 1970, Snap-off of oil droplets in water-wet pores: SPE Journal, vol. 10, no. 1, p. 85–90.</ref><ref name=ch10r67>Schowalter, T. T., 1979, [http://archives.datapages.com/data/bulletns/1977-79/data/pg/0063/0005/0700/0723.htm Mechanics of secondary hydrocarbon migration and entrapment]: AAPG Bulletin, vol. 63, no. 5, p. 723–760.</ref>

==Most traps half full==

==Most traps half full==

==Water wet vs. oil wet==

==Water wet vs. oil wet==

Estimates of seal capacity from measured displacement pressures commonly assume the seal is water wet. Oil-wet seals may be more common than we think. Organic-rich shales, a common top seal, are probably oil wet.<ref name=ch10r15>Cuiec, L., 1987, [[Wettability]] and oil reservoirs, in Kleppe, J., Berg, E. W., Buller, A. T., Hjemeland, O., and Torsaeter, O., eds., North Sea Oil and Gas Reservoirs: London, Graham and Trotman, p. 193–207.</ref> Similarly, episodic leakage of hydrocarbons through a seal may alter the seal capacity.

Estimates of seal capacity from measured displacement pressures commonly assume the seal is [http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=water-wet water wet]. [http://www.glossary.oilfield.slb.com/en/Terms/o/oil_wet.aspx Oil-wet] seals may be more common than we think. Organic-rich shales, a common top seal, are probably oil wet.<ref name=ch10r15>Cuiec, L., 1987, [[Wettability]] and oil reservoirs, in Kleppe, J., Berg, E. W., Buller, A. T., Hjemeland, O., and Torsaeter, O., eds., North Sea Oil and Gas Reservoirs: London, Graham and Trotman, p. 193–207.</ref> Similarly, episodic leakage of hydrocarbons through a seal may alter the seal capacity.

==See also==

==See also==