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Fault Seal Analysis in the N-97 Oil Field in Wintershall Concession C97-I, Libya
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 2nd EAGE International Conference on Fault and Top Seals - From Pore to Basin Scale 2009, Sep 2009, cp-136-00038
- ISBN: 978-90-73781-69-6
Abstract
The N-97 Oil Field is located in the western Sirte Basin, Libya. Differential fluid contact and higher aquifer pressure in the east of the field suggest sealing faults. However, the initial oil pressure is in equilibrium. There are two possible explanations: either the eastern part of the field could have a perched aquifer, or the trapping could be hydrodynamic, with east-to-west water flow and progressively lower pressures in each fault block from east to west, giving progressively deeper contacts. Physical properties of the fault rock were measured in the lab: pore size distribution, permeability and mercury injection capillary curves.These fault rock properties indicated that a single fault should not be able to support the difference in OWC. Fault seal properties have been modelled in conjunction with fault displacement indicating that a single fault hold an oil column height up to 350ft. The preferred explanation of the observed pressure differences in the aquifer is a hydrodynamic aquifer drive from East to West. Aquifer pressure drops occur at each fault resulting in a series of fault compartments with successively deeper contacts and lower aquifer pressure, but with a common oil gradient.