Oil & Gas Geology ›› 2005, Vol. 26 ›› Issue (4): 480-486.doi: 10.11743/ogg20050414

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Origin of superhigh wax content oils in southern slope zone of Dongying Depression

Li Sumei1,2, Pang Xiongqi1,2, Qiu Guiqiang3, Gao Yongjin3   

  1. 1. Key Laboratory for Hydrocarbon Accumulation, Ministry of Education, Beijing;
    2. Basin & Reservoir Research Center, China University of Petroleum, Beijing;
    3. Shengli Oilfield Company Limited, SINOPEC, Dongying, Shandong
  • Received:2005-07-29 Online:2005-08-25 Published:2012-01-16

Abstract:

Oils produced from Wanggu-1 and Xinjiao-1 wells' Ordovician buried-hill reservoirs in the southern slope zone of Dongying depression are characterized by superhigh wax content(40%-60%),and the wax contents of oils produced from Tertiary Kongdian Fm reservoirs in the same area are also relatively high(28.85%-31.7%).Chemical composition analysis and oil-source rock correlation of crude oils from different layers show that the origin of Ordovician high wax content oils in the study area is different from that in the overlying Tertiary Shahejie Fm.The former are derived from the deep source,as represented by the source rocks in Kongdian Fm.The latter are mianly sourced by the 4th member of Shahejie Fm within normal oil window.Absolute quantification of biomarkers shows that the bitumen contents of source rocks and waxy hydrocarbon contents of crude oils in this area increase with increasing maturity,indicating that thermal maturity is one of the major factors controlling the formation of highly waxy oils in this area.The Kongdian Fm source rocks of limnetic facies in Dongying depression contain relatively abundant terrigenous higher plants,which is another major factor causing the high wax content oils in this area.It is believed,based on comprehensive analysis,that the relatively high maturity and abundant parent materials capable of generating waxy hydrocarbons in the source rocks(the 2nd member of Kongdian Fm) are the major causes of the formation of high waxy oils in the southern slope zone of Dongying depression.Contrary to this,the influences of gas invasion and hydrocarbon migration fractionation are insignificant.

Key words: high wax content oil, oil and gas origin, Kongidan Formation, buried hill, Dongying depression

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