Reservoir simulations and field unitization
| 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 |
Fault plane profiles and quantitative fault seal analysis are required for realistic reservoir simulations. Neither the seal behavior, transmissibility, permeability, nor areas of sand/sand juxtaposition are constant over the entire fault surface.
Movement of hydrocarbons
Faults can “pond” hydrocarbons and affect sweep and waterflood efficiency. Routine fault seal analysis may be required for producing residual oil accumulations missed by assuming a laterally continuous reservoir.
Fault control of pressure gradients
Faults control changing pressure gradients within a field. Hydrocarbons move in response to these pressure gradients and not necessarily in response to structural dip. Gas in the Beryl field, for example, migrated downdip during production in response to changing pressure gradients, pressure compartments, and migration pathways controlled by sealing and leaking faults.[1][2]
Fault seal behavior alteration
Faults can also leak over geologic time spans but seal during production time spans. Even a low fault-zone permeability may allow hydrocarbons to leak given a time span of 106 m.y. High production rates, however, creating pressure changes over a span of 1–10 years, will cause low-permeability fault zones to act as barriers to hydrocarbon movement. A cross-leaking fault may develop different hydrocarbon contacts and different pressures during production. Shale gouge ratio (SGR) thresholds for seal behavior may have to be calibrated separately for exploration and for reservoir simulations.
Fault seal and field unitization
Fault seal is important in field unitization. Ignoring fault seal and depending solely on reservoir parameters and estimated hydrocarbon contacts can lead to extremely unequal division of reserves. The sealing behavior of faults controls both the original distribution of hydrocarbons in a field as well as the volumes of hydrocarbons produced from individual fault compartments.
See also
References
- ↑ Knutson, C., A., Erga, R., 1991, Effect of horizontal and vertical permeability restrictions in the Beryl reservoir: Journal of Petroleum Technology, vol. 43, p. 1502–1509, DOI: 10.2118/19299-PA.
- ↑ Skerlec, G., M., 1997b, Atlas of fault seal behavior in the Gulf Coast: Franklin, Pennsylvania, SEALS International, 4356 p.
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