Top seal displacement pressure
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Predicting the occurrence of oil and gas traps |
| Chapter | Evaluating top and fault seal |
| Author | Grant M. Skerlec |
| Link | Web page |
| Store | AAPG Store |
Calculation
Displacement pressure (Pd) is the pressure necessary to force hydrocarbons into the pore space of a rock and form a continuous hydrocarbon filament.[1] Displacement pressure, which is measured in dynes/cm2, can be calculated by the following formula:
where:
- γ = interfacial tension, dynes/cm
- θ = contact angle or wettability, degrees
- R = pore throat radius, cm
Variables
The displacement pressure of a seal depends on both the physical character of the seal (pore throat radius and pore throat size distribution) and the physical character of the hydrocarbons (interfacial tension and wettability).
Wettability
The wettability, or contact angle θ, is 0° for hydrocarbon/water.[2] If the wetting phase is oil or gas rather than water, the contact angle can range from 0 to 180°. Not all rocks are water wet, and oil-wet seals may not be as rare as commonly thought.[3] Organic-rich sediments may be source, seal, and oil wet.
Interfacial tension
Hydrocarbon/brine interfacial tension values typically range from 15–72 dynes/cm.[4][1][5] Laboratory studies provide interfacial tension values for a range of gas and oil compositions.[6]
See also
- How capillary properties control seal
- Buoyancy pressure
- Hydrocarbon column: calculation of maximum height
References
- ↑ 1.0 1.1 Schowalter, T. T., 1979, Mechanics of secondary hydrocarbon migration and entrapment: AAPG Bulletin, vol. 63, no. 5, p. 723–760.
- ↑ Berg, R. R., 1975, Capillary pressure in stratigraphic traps: AAPG Bulletin, vol. 59, no. 6, p. 939–956.
- ↑ Cuiec, L., 1987, Wettability and oil reservoirs, in J. Kleppe, E. W. Berg, A. T. Buller, O. Hjemeland, and O. Torsaeter, eds., North Sea Oil and Gas Reservoirs: London, Graham and Trotman, p. 193–207.
- ↑ Vavra, C. L., J. G. Kaldi, and R. M. Sneider, 1992, Geological applications of capillary pressure: a review: AAPG Bulletin, vol. 76, no. 6, p. 840–850.
- ↑ Watts, N. L., 1987, Theoretical aspects of cap-rock and fault seals for single and two-phase hydrocarbon columns: Marine and Petroleum Geology, vol. 4, no. 4, p. 274–307, DOI: 10.1016/0264-8172(87)90008-0.
- ↑ Firoozabadi, A., and H. J. Ramey Jr., 1988, Surface tension of water-hydrocarbon systems at reservoir conditions: Journal of Canadian Petroleum Technology, vol. 27, no. 3, p. 41–48, DOI: 10.2118/88-03-03.
External links
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