Oil migration in a major growth fault: Structural analysis of the Pathfinder core, South Eugene Island Block 330, offshore Louisiana
- Cornell Univ., Ithaca, NY (United States). Dept. of Geological Sciences
The Pathfinder core, collected in the South Eugene Island Block 330 field, offshore Louisiana, provides an outstanding sample of structures associated with a major growth fault that abuts a giant oil field and that is thought to have acted as a conduit for hydrocarbon migration into the producing reservoirs. The fault zone in the core consists of three structural domains, each characterized by a distinct rock type, distribution of fault dips and dip azimuths, and distribution of spacing between adjacent faults and fractures. Although all of the domains contain oil-bearing sands, only faults and fractures in the deepest domain contain oil, even though the oil-barren fault domains contain numerous faults and fractures that are parallel to those containing oil in the deepest domain. The deepest domain is also distinguished from the other two domains by a greater degree of structural complexity and by a well-defined power-law distribution of fault and fracture spacings. Even though oil is present in sands throughout the core, its restriction to faults and fractures in the youngest sampled portion of the fault zone implies that oil migrated only through that part of the fault that was active during the time when oil had access to it. The absence of oil in fractures or faults in the other, probably older, fault domains indicates that the oil was never sufficiently pressured to flow up the fault zone on its own, either by hydraulic fracture or by increased permeability as a result of decreased effective stress. Instead, fluid migration along faults and fractures in the Pathfinder core was enhanced by permeability created in response to relatively far-field stresses related to minibasin subsidence.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FC22-93BC14961
- OSTI ID:
- 659097
- Journal Information:
- AAPG Bulletin, Vol. 82, Issue 9; Other Information: PBD: Sep 1998
- Country of Publication:
- United States
- Language:
- English
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