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South Ellwood Field, Santa Barbara Channel, California: Is a Normal Fault Always Normal?

K. I. Christiensen, M. D. Wracher, and S. Horner
Venoco, Inc, Santa Barbara, CA

The South Ellwood Field, discovered in 1964, has produced 60 MMBO and 50 BCFG (1/31/2000), primarily from the Miocene Monterey Formation. Reinterpretation of a reprocessed 3D over the South Ellwood field has lead to the definition of a previously unknown east-west trending fault which forms the northern boundary of the producing field. This fault has apparent down to the north normal throw, in contrast to the extensive reverse and thrust faults found elsewhere in the field and area. The fault intersects the seafloor at the prolific La Goleta and Holly Seeps, and is apparently a conduit for massive fluid flow.

Analysis of this fault suggests its origin was as a reverse fault which has subsequently been rotated into apparent normal throw. This deformational history has impact on trap formation, fracturing, and fluid flow in the field. This interpretation and implied history also has implication for regional structural deformation in the Santa Barbara Channel.

AAPG Search and Discovery Article #90904©2001 AAPG Pacific Section Meeting, Universal City, California