Biomarker analysis of Upper Permian lacustrine oil shales, Junggar basin, NW China

Conference · Tue May 01 00:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6795721

Carroll, A ^[1]

---

1. Stanford Univ., CA (USA)

Upper Permian lacustrine oil shales containing up to 34% TOC (total organic carbon) underlie approximately 50,000 km{sup 2} of the Junggar basin in western China, and appear to be the principal source of oils in the giant Karamay field in the northwestern Junggar and in several recent discoveries in other areas of the basin. The siliceous oil shales were deposited in a sediment-starved foreland basin during a period of predominantly humid climate. Previous biomarker studies of crude oils from Karamay field have documented an abundance of {beta}-carotane (which in some cases dominates the aliphatic hydrocarbon distribution) and gammacerane, suggesting a source bed deposited under hypersaline conditions. However, relatively complete outcrop exposures of finely laminated oil shales in the southern Junggar conspicuously lack evaporites, extensive dessication horizons, or other sedimentological evidence of playa lake environments. Indeed, the aliphatic hydrocarbon distribution in bitumen extracts from southern Junggar oil shales appear characteristic of freshwater to brakish water deposition of organic matter in an anoxic lake. Normal alkanes show a slight odd-over-even preference with relatively low levels of the C{sub 22}, n-alkane, pristane/phytane ratios close to unity, low {beta}-carotane and gammacerane levels, and the absence of C{sub 34}-C{sub 35} hopanes. This apparent difference in source bed depositional environments may be due to tectonic partitioning between separate depocenters of the Late Permian Junggar basin. Alternatively, hypersaline oil shale facies may be limited to deeper basinal areas, whereas upslope southern Junggar sediments record highstands in lake level or influx of fresh water from the adjacent drainage areas.

• OSTI ID: 6795721
• Report Number(s): CONF-900605-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
58 GEOSCIENCES
CHINA
OIL SHALES
GEOCHEMISTRY
STRATIGRAPHY
GEOLOGIC HISTORY
HYDROCARBONS
PERMIAN PERIOD
SEDIMENTARY BASINS
TECTONICS
ASIA
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CHEMISTRY
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOLOGY
MATERIALS
ORGANIC COMPOUNDS
PALEOZOIC ERA
040200* - Oil Shales & Tar Sands- Reserves
Geology
& Exploration
580000 - Geosciences