Lake type controls on petroleum source facies, Junggar Basin, China

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:425466

Carroll, A R ^[1]

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1. Exxon Production Research Co., Houston, TX (United States)

Junggar Basin Upper Permian rocks may be classified according to lithology, parasequence stacking patterns, organic matter type, and molecular geochemistry as {open_quotes}underfilled{close_quotes}, {open_quotes}balanced-fell{close_quotes}, or {open_quotes}overfilled{close_quotes} lake facies. These facies, which recur in other nonmarine basins, refer to the balance between the supply of water+sediment to the lake basin and potential accomodation, and provide a useful tool for predicting source rock richness and quality. Underfilled lake facies occur when the supply of water+sediment is insufficient to fill potential accommodation, resulting in a closed basin with ephemeral lakes. Shoaling-upward parasequences 10-200 cm thick are punctuated by mudcracked intervals indicating subarial exposure. Hydrocarbon extracts contain saline-hypersaline biomarkers, and TOC values are relatively low (0.2-2.0%). Balanced-fill facies reflect an approximate balance between the supply of water+sediment and potential accomodation. Laminated mudstone parasequences 1-4 m thick predominate, but mudcracks or other evidence of subarial exposure are absent. Junggar {open_quotes}oil shales{close_quotes} commonly exceed 20% TOC; biomarker geochemistry indicates saline deposition. Overfilled lake facies occur when the supply of water+sediment exceeds potential accomodation space. Shoreline progradation, rather than lake level fluctuation, dominates parasequence development. Interbedded lithologies include fluvial sandstones, conglomerates and freshwater. Biomarker assemblages document increased fluvial influx of terrestrial organic matter. Source rock-oil correlations indicate that balanced-fill to underfilled lake facies source oils in the Karamay trend, most of the eastern Junggar fields, and the Mosuowan discovery in central Junggar. No oil accumulations have yet been linked to overfilled lake facies.

• OSTI ID: 425466
• Report Number(s): CONF-960527--
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
CHINA
EXPLORATION
HYDROCARBONS
OIL SHALE DEPOSITS
SEDIMENTARY BASINS
SOURCE ROCKS
STRATIGRAPHY