--> --> ABSTRACT: Sealing Behavior of Normal Faults in Fault Block II, Wilmington Oil Field, California, by L. Y. An, I. Ershaghi, C. C. Phillips, and D. D. Clarke; #91021 (2010)
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Sealing Behavior of Normal Faults in Previous HitFaultNext Hit Block II, Wilmington Oil Field, California

AN, LINJI Y., IRAJ ERSHAGHI, CHRISTOPHER C. PHILLIPS, and  DONALD D. CLARKE

Previous HitFaultNext Hit Block II in Wilmington oil field is bounded by the Wilmington Previous HitfaultNext Hit to the west and the Cerritos Previous HitfaultNext Hit to the east. Previous HitFaultNext Hit block II is further divided by the Ford Previous HitfaultNext Hit into Previous HitFaultNext Hit Block IIA and Previous HitFaultNext Hit Block IIB. The sealing property of these boundary faults are evaluated in the Tar zone interval, a Lower Pliocene Middle Repetto formation, as part of a DOE cost-share project for vigorous reservoir characterization and subsequent steam flood. Oil-water contacts indicate that the Wilmington Previous HitfaultNext Hit slowly leaks oil near the southern end from the T2, T5 and T7 sub-subzones in Previous HitFaultNext Hit Block IIA into the same sub-subzones in Previous HitFaultNext Hit Block I. The Wilmington Previous HitfaultNext Hit also leaks oil from the T2, T5, and T7 sub-subzones in Previous HitFaultNext Hit Block I into the S sand (a wet sand immediately above Tar) in Previous HitFaultNext Hit Block IIA through a paleochannel near the crest of the Wilmington anticline. Ford Previous HitfaultNext Hit leaks oil from T2, T5 and T7 sub-subzones in Previous HitFaultNext Hit Block IIA to S sand in Previous HitFaultNext Hit Block IIB, also through the paleochannel. The northern segment of Cerritos Previous HitfaultNext Hit leaks in T1 sub-subzone and gradually becomes sealing with depth. All other portions of the boundary faults are sealing structures indicated by zigzagged lower and lateral reservoir boundaries, and lack of communication between injection and production wells across the Previous HitfaultNext Hit.

Well log examination, core analysis, sandstone analysis and Allan diagram construction indicate that juxtaposition of permeable sand against impermeable shale is not enough to explain Previous HitfaultNext Hit sealing in the studied area. All the evidence indicates that a Previous HitfaultNext Hit itself behaves like a layer of impermeable shale and such a behavior becomes stronger as Previous HitfaultNext Hit displacement increases. A gouge zone model is therefore considered to be most appropriate.

The future sealing ability of each Previous HitfaultNext Hit is predicted from Previous HitfaultNext Hit sealing strength. Previous HitFaultNext Hit sealing strength at any portion of a Previous HitfaultNext Hit is evaluated by applying two criteria: (1) If a permeable layer juxtaposes against an impermeable layer, the Previous HitfaultNext Hit seal is strong; (2) if all the other conditions are the same, a Previous HitfaultNext Hit with larger displacement has a stronger Previous HitfaultNext Hit seal than the one with smaller displacement. The strong and weak sealing portions on the Previous HitfaultNext Hit planes are directly identified on the Allan diagrams constructed for each Previous HitfaultTop

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.