Oil & Gas Geology ›› 2015, Vol. 36 ›› Issue (2): 175-182.doi: 10.11743/ogg20150201

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Aromatic biomarkers and oil source of the Ordovician crude oil in the Halahatang Sag, Tarim Basin

Chang Xiangchun1, Wang Tieguan2, Tao Xiaowan3, Cheng Bin2   

  1. 1. Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals, Shandong University of Science and Technology, Qingdao, Shandong 266590, China;
    2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;
    3. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
  • Received:2014-10-03 Revised:2014-11-25 Online:2015-04-08 Published:2015-05-13

Abstract: Halahatang Sag has been one of the focuses for petroleum exploration in recent years.In order to confirm its oil source,depositional environment,thermal maturity and possible source rocks,systematic aromatic biomarkers analyses were performed on 26 oil samples from the Halahatang Sag and the Ordovician in Tahe oilfield as well as 4 potential source rock samples from the unmodified foreland region of the Tarim Basin.The results show that the Halahatang oil samples are characterized by high contents of naphthalenes and phenanthrenes,low content of biphenyl,low abundance of 1,2,5-TMN,high abundance of 1,3,6-TMN,high ratios of 4-MDBT/DBT and(2+3)-MDBT/DBT,and light carbon isotope of aromatics,which are similar to those of oil samples from the Tahe oilfield,indicating typical marine origin with contribution of lower algae and bacteria in predominance.High relative content of dibenzothiophene and low values of DBT/P and Pr/Phinfer a strong reducing depositional environment and carbonate lithology for the source rock.The equivalent vitrinite reflectances,i.e.Rc1 and Rc2,reveal a moderate to high maturity.Comparison of methyl triaromatic sterane isomeride shows that the Halahatang and Tahe oils correlate well with the Middle-Upper Ordovician source rocks,indicating a genetic affinity.

Key words: oil source, depositional environment, thermal maturity, oil-source correlation, aromatic, biomarker, crude oil, Halahatang Sag

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