Correlation of source rocks and oils in the Sespe oil field, Ventura County, California

Conference · Fri Feb 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5308901

Lillis, P G ^[1]; Clark, M S ^[2]

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1. Geological Survey, Lakewood, CO (United States)
2. Colorado School of Mines, Golden (United States)

The Sespe oil field in the central Ventura basin produces low sulfur (< 1%), intermediate gravity (23-32{degree} API) oil from Middle Eocene to Lower Miocene reservoirs in the upper plate of the San Cayetano thrust. Previous studies proposed the Eocene Cozy Dell, Matilija, and Juncal formations in the San Cayetano overthrust as the source rocks. Alternatively, the oils could be derived from the Miocene Monterey Formation in the subthrust. Gas chromatography and gas chromatography/mass spectrometry data are used to characterize and correlate the Sespe oils from comparison with bitumen extracts of the possible source rocks. The oils have pristane/phytane ratios of 1.3-1.6, bisnorhopane/hopane ratios of about 0.2, and relatively low amounts of diasteranes, oleanane, and C{sub 29} steranes. These data indicate that all of the oils belong to the same family and that variations in the API gravity are due to the degree of biodegradation. In addition, the sterane and triterpane distributions imply that the source organic matter is derived from marine phytoplankton and bacteria with a minor contribution from land plants. The Sespe oils do not correlate with the upper plate Eocene source rocks but correlate fairly well with the upper plate Eocene source rocks. Thus, a subthrust source is proposed. However, the Sespe oils have higher gravity and lower sulfur content than typical Monterey oils. The low sulfur content may result from the higher iron content, due to terrigenous input, of the Sespe field source rocks relative to other Monterey source rocks. Alternatively, the Sespe oils were expelled from the Monterey Formation at relatively high levels of thermal maturity.

• OSTI ID: 5308901
• Report Number(s): CONF-9103128--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
023000* -- Petroleum-- Properties &amp; Composition
API GRAVITY
BITUMENS
CALIFORNIA
CENOZOIC ERA
CHEMICAL ANALYSIS
CHEMISTRY
CHROMATOGRAPHY
COMPARATIVE EVALUATIONS
CORRELATIONS
DENSITY
DEVELOPED COUNTRIES
ENERGY SOURCES
EOCENE EPOCH
EVALUATION
FOSSIL FUELS
FUELS
GAS CHROMATOGRAPHY
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
MINERAL RESOURCES
MIOCENE EPOCH
NORTH AMERICA
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PETROLEUM
PETROLEUM DEPOSITS
PHYSICAL PROPERTIES
RESERVOIR ROCK
RESOURCES
SEPARATION PROCESSES
SOURCE ROCKS
TAR
TERTIARY PERIOD
USA