Fault seal behavior
| 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 |
Understanding fault seal behavior in existing fields is a prerequisite for predicting seal behavior in untested prospects. Empirical studies have established patterns of seal behavior, identified seal-leak thresholds for quantitative analysis of a fault seal, provided real analogs for prospect assessment, and demonstrated how important fault seal behavior is in controlling hydrocarbon accumulations.[1][2][3][4][5]
Fault seal behavior is analyzed on the basis of the following:
- Hydrocarbon contacts
- Fault-dependent leak points
- Pressure data
Types of behavior
The two basic types of fault seal behavior are (1) cross sealing or cross leaking and (2) dip sealing or dip leaking. Cross seal and leak refers to the lateral communication across the fault between juxtaposed sands. Dip seal and leak refers to the vertical communication along the fault between stacked sands.
The type of seal behavior is important in controlling the type of fault-dependent leak points. Fault-dependent leak points limit the volume of trapped hydrocarbons. The ability to identify these fault-dependent leak points is a fundamental tool for prospect assessment.
Finite seal capacity
Faults may have some finite seal capacity. A fault might support the pressure exerted by a 50-m hydrocarbon column yet leak if the column increases to length::51 m.[1]
Caveat
A fault does not simply seal or leak; many variations exist:
- A fault can seal at one point and leak at another.
- A fault can juxtapose many individual reservoirs, and each fault-reservoir intersection can seal or leak independently.
- A fault can seal on one side and leak on the other.
- A fault can seal oil but leak gas.
- A fault can be sealing to some finite column of hydrocarbon but leaking to a larger column.
- A fault can change seal behavior during migration and fill as well as during production. Seal behavior is time dependent.
See also
- Cross-leaking faults
- Cross-sealing faults
- Dip-sealing faults
- Dip-leaking faults
- Percent fill: controlling factors
References
- ↑ 1.0 1.1 Chong, K. P., P. M. Hoyt, J. W. Smith, and B. Y. Paulsen, 1980, Effects of strain rate on oil shale fracturing: International Journal of Rock Mechanics, vol. 17, no. 1, p. 35–43., 10., 1016/0148-9062(80)90004-2 Cite error: Invalid
<ref>tag; name "ch10r13" defined multiple times with different content - ↑ Skerlec, G. M., 1990, SEALS: A short course for risking top seal and fault seal: Franklin, Pennsylvania, SEALS International, 600 p.
- ↑ Skerlec, G. M., 1997a, Atlas of fault seal behavior in the North Sea/Norwegian Sea: Franklin, Pennsylvania, SEALS International, 3948 p.
- ↑ Skerlec, G. M., 1997b, Atlas of fault seal behavior in the Gulf Coast: Franklin, Pennsylvania, SEALS International, 4356 p.
- ↑ Yielding, G., B. Freeman, and D. T. Needham, 1997, Quantitative fault seal prediction: AAPG Bulletin, vol. 81, no. 6, p. 897–917.
External links
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