Oil & Gas Geology ›› 2000, Vol. 21 ›› Issue (3): 249-251.doi: 10.11743/ogg20000313

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GEOCHEMICAL CHARACTERISTICS OF CRUDE OIL AND CORRELATION OF OIL SOURCE IN CHAGAN SAG

Lin Weidong   

  1. Northwest Institute of Geology, CNPS, Lanzhou
  • Received:1999-11-09 Online:2000-09-25 Published:2012-01-16

Abstract:

Chagan Sag is a Meso-Cenozoic fault depression.The crude oil in it is of low density,low viscosity,low sulfur content,mid paraffin and lightweight oil characterized by high saturated hydrocarbon contents(80%~90%)and rich C27 sterane.The second member of Bayingebi Formation(K1b2)and the first member of Suhongtu Formation(K1s1)of the Lower Cretaceous are potential source rocks of the sag.The ratio of ααα(20R)C27/C29 and ααα(20R)C28/C29 of crude oil and the extract from oil bearing sand is 0.39~0.75 and 0.4~0.7 respectively.The ratio of Pr/Ph and Pr/nC 17 is 0.79~0.94 and 0.83~1.34.The carbon isotopic characteristic curve of crude oil is more similar to dolomitic mudstone of K1b2 and differs from the dark grey mudstone of K1s1.Synthetical correlation shows that the crude oil is mainly derived from the second member of Bayingebi Formation(K1b2)dolomitic mudstane.

Key words: crude oil, source rock, geochemical characteristics, oil source correlation, chagan sag

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