Carbon isotopic compositions identify four petroleum types in Northern California
- Geological Survey, Menlo Park, CA (United States)
- Geological Survey, Denver, CO (United States)
- Consultant, Bakersfield, CA (United States)
- DGSI, Houston, TX (United States)
On the basis of carbon isotopic compositions of saturated and aromatic hydrocarbons in 16 oil and 6condensate samples from fields and seeps in northern California, four pertroleum types have been identified. The isotopically heaviest type is represented by oils from the Petrolia, Petaluma, and Pinole Point fields with saturated hydrocarbon (SH){delta}{sup 13}C values of -22.9{+-}0.6{per_thousand} and aromatic hydrocarbon (AH) {delta}{sup 13}C values of -22.1{+-}0.5{per_thousand}. Oil seeps in the Clear Lake area and oil samples from the Arbuckle and Bunker gas fields have SH{delta}{sup 13}C values of -26.4{+-}0.9{per_thousand} and AR{delta}{sup 13}C values of -25.1{+-}1.1{per_thousand} and represent a second petroleum type. Condensate samples from Dutch Slough, Knightsen, Lindsey Slough, and Rio Vista gas fields are considered a third type and have a whole condensate {delta}{sup 13} value of -26.2{+-}0.5{per_thousand} and AH{delta}{sup 13}C value of -27.4{+-}0.3{per_thousand}, and represent the fourth type. Volumetrically, the amount of oil and condensate recovered from these fields is small when compared to the fields in southern California. However, the petroleum potential of northern California may be underestimated because the petroleum geology is poorly understood and source rocks are poorly documented. The geographic distribution of these four petroleum types in northern California, predominately a dry-gas province, suggest that the petroleum geology is complex. For example, the Petrolia field is 180 miles northwest of the Petaluma and Pinole Point fields, and the Brentwood and Livermore oil samples are isotopically similar but come from contrasting geologic settings. Although {delta}{sup 13}C values are similar, the relationship of the condensate in the Rio Vista area to the oil samples in the Clear Lake area is unclear. Their isotopic similarity but physical dissimilarity could be due to migration or to source facies variations.
- OSTI ID:
- 75419
- Report Number(s):
- CONF-9505199-; ISSN 0149-1423; TRN: 95:003618-0023
- Journal Information:
- AAPG Bulletin, Vol. 79, Issue 4; Conference: American Association of Petroleum Geologists (AAPG) Pacific Section meeting, San Francisco, CA (United States), 3-5 May 1995; Other Information: PBD: Apr 1995
- Country of Publication:
- United States
- Language:
- English
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