PACHT, JORY A.¹, GEORGE OTOTT², SCOTT PRIOR², and STEVE ROTH^3
1Seis Strat Services, Inc., 11111 Wilcrest Green, Ste. 203, Houston Texas
²THUMS Long Beach, P.O. Box 2900, Long Beach, CA 90801
³ARCO International Oil and Gas, 2300 West Plano Pkwy, Plano Texas 75075

Abstract: New Oil from an Old Giant: Implications from Analysis of 3D Seismic Data in the Long Beach Unit of the Wilmington Oil Field, Los Angeles Basin, California

The Wilmington Oilfield discovered in 1932, is the third largest oilfield, with almost 8.8 billion barrels of oil in place of which 2.5 billion have been produced. Over 1400 wells have been drilled in the Long Beach Unit of this field and present day production is approximately 42,000 BOPD. In 1995 a 3D survey was shot over the Long Beach Unit. Interpretation of these data suggest significant changes in structural and stratigraphic framework of the field.

Four major new faults were defined using the 3D dataset. In addition, numerous smaller faults were also delineated. Many of these show strike slip movement and very steep dips. This makes them very difficult to define using missing section on welllogs. The small strike-slip faults are imaged by offset of amplitude packages on interval amplitude maps. Large normal faults also show a major component of transverse movement. Strike-slip and oblique-slip faults exhibit classic Reidel shear and conjugate Reidel shear orientations. Some correlate with known barriers to injection or production. Strata in the Wilmington oilfield were divided into depositional sequences and systems tracts. Lower lowstand systems tract exhibit more discontinuous reflections than other intervals, which suggests greater lithologic variability. Miocene through Lower Pliocene strata were deposited longitudinally from northwest to southeast along the basin axis. In contrast Upper Pliocene strata were deposited in submarine fans oriented perpendicular to the basin axis.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas