The nature and distribution of fluid inclusions in the Monterey Formation in the vicinity of the Santa Maria Basin, California: Implications for petroleum migration
- Virginia Polytechnic Institute and State Univ., Blacksburg (USA)
- Geological Survey, Denver, CO (USA)
The presence of petroleum fluid inclusions is definitive evidence that oil has migrated through the rocks. By relating the paragenesis of petroleum fluid inclusions to diagenetic and structural characteristics of the rocks, the timing of oil migration relative to these events may be determined. Fluid inclusion characteristics of vein-filling minerals from several coastal outcrops in the Miocene Monterey Formation in the vicinity of the Santa Maria basin California are being studied to better understand the nature of hydrocarbon migration in this important oil province. The Monterey Formation constitutes a fracture-controlled petroleum reservoir with intercalated calcareous and fine-grained siliceous rocks serving as both the source and reservoir for oil accumulations, resulting in relatively short migration distances for Monterey oils. Many fractures in the Monterey are filled with carbonate, quartz, barite, and anhydrite. These same fractures often contain visible tar or oil and occasionally a thin layer of oil can be seen coating growth surfaces between two generations of vein-filling minerals. Evidence for migration of fluids through these fractures in the geologic past is provided by aqueous and petroleum fluid inclusions contained within vein-filling minerals. Vein-filling dolomite from Jalama Beach contains three different types of primary petroleum inclusions, indicating that oils with significantly different API gravities and compositions flowed through the fractures. Petrographic and microthermometric analyses of oil and coexisting aqueous inclusions indicate that the fracture-filling minerals precipitated from aqueous solutions of seawater salinity heated to about 100{degree}C and that oil was introduced into the fracture system episodically during mineral growth A vein from the Lion's Head area consists of early calcite and late quartz both of which contain aqueous inclusions with seawater salinity.
- OSTI ID:
- 6762240
- Report Number(s):
- CONF-900605--
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Vol. 74:5; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580000 -- Geosciences
CALIFORNIA
CENOZOIC ERA
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
GEOTHERMOMETRY
MINERAL RESOURCES
NORTH AMERICA
ORIGIN
PETROLEUM DEPOSITS
RESOURCES
SEDIMENTARY BASINS
TERTIARY PERIOD
USA