--> Abstract: The Impact of Sequence Stratigraphy on Thermal Operations within the Upper Miocene Potter Sand, Midway-Sunset Field, Kern County, California, by W. T. Fedewa; #90992 (1993).

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FEDEWA, WILLIAM T., ARCO Oil & Gas Company, Bakersfield, CA

ABSTRACT: The Impact of Sequence Stratigraphy on Thermal Operations within the Upper Miocene Potter Sand, Midway-Sunset Field, Kern County, California

Sequence stratigraphy interpretation significantly affects prediction of heat distribution in cyclic steam and steamflood operations within the Potter sand at Midway-Sunset field, Kern County, California. Identification of shale-bounded parasequences within this 1000-ft thick oil-bearing sand results in the recognition of flow units.

Traditionally the Potter sand is considered to represent a homogeneous sequence of unconsolidated turbidite sands and gravels deposited in a restricted active-margin basin. However, core data and detailed correlation of more than 600 wells indicate that the Potter sand consists of a heterogeneous sequence of sand, gravel, and shale which was deposited along a shelf margin in a delta-front environment.

The top of the Potter sand is truncated by the Miocene-Pliocene angular unconformity and the base downlaps on the Antelope Shale. Individual shale-bounded parasequences are grouped into a series of highstand and lowstand systems tracts. The western-most highstand systems tract displays parasequences that extend from the truncation at the top of the Potter to downlap at the base of the Potter. The overlying lowstand systems tract downlaps at the base of the Potter and toplaps at a transgressive unconformity surface within the Potter. A younger highstand systems tract overlies and downlaps this unconformity surface and is in turn truncated by the angular unconformity at the top of the Potter. This highstand sequence extends eastward beyond the limits of the lowstand deposit.

Recognition of the parasequences within the Potter reservoir has impacted the design of steamflooding operations. Treating the Potter sand as a homogeneous reservoir would result in incomplete heating of the oil zones and heat loss to depleted intervals. Selectively perforating steam-injection wells into desired flow units results in optimal heat distribution and oil recovery from the Potter sand reservoir.

AAPG Search and Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach, California, May 5-7, 1993.