Oil & Gas Geology ›› 2013, Vol. 34 ›› Issue (1): 27-36.doi: 10.11743/ogg20130104

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Maturity of light oil and its significance in indicating oil source in Hetianhe gas field, Tarim Basin

Cui Jingwei1,2, Wang Tieguan2, Hu Jian2, Li Meijun2   

  1. 1. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China;
    2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
  • Received:2011-09-23 Revised:2012-10-15 Online:2013-02-28 Published:2013-03-18

Abstract:

GC and GC-MS analysis was performed on compounds possibly containing information on maturity in four light oil samples selected in Hetianhe gas field.Maturity indexes including heptane index,isoheptane index,methyldiamantane index,MPI,methyldibenzothiophene(MDBTs)and Ts/(Ts+Tm) indicate that the light oil in Hetianhe gas field is at high maturation stage(gas condensate).In contrast,methylnaphthalene,C29 sterane 20S/(20S+20R) and C29 sterane ββ/(αα+ββ) suggest that the source rocks have not entered peak oil generation stage.Indexes such as light hydrocarbon show that high maturity of the light oil is consistent with its physical properties.The anomalies of naphthalenes may be the result of weak biodegradation,while the low sterane indexes may be the result of overturning at the end of evolutionary balance.Comprehensive analyses of the maturity indexes reveal that the light oil is at the end of maturation-high maturation stage.Furthermore,comparison with the typical local source rocks indicates that both the light oil and natural gas are generated by the Cambrian source rocks,a conclusion supported by oil-source correlation based on sterane and terpane.

Key words: maturity index, source rock, light oil, Hetianhe gas field, Tarim Basin

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