Oil & Gas Geology ›› 2005, Vol. 26 ›› Issue (4): 487-493.doi: 10.11743/ogg20050415

Previous Articles     Next Articles

Evaluation of source rocks in Kongdian Formation and analysis of oil sources in Weibei sag

Song Yitao, Lao Yongsheng, Wang Zhong   

  1. Research Institute of Geological Secience, Shengli Oilfield Co.Ltd., SINOPEC, Dongying, Shandong
  • Received:2005-08-03 Online:2005-08-25 Published:2012-01-16

Abstract:

Source rocks of various qualities,including very good(with rich organic matters),good,relatively good and relatively poor source rocks,are developed in the 2nd member of Kongdian Fm in Weibei sag.The source rocks with rich organic matters were deposited in fresh-brackish water of coastal shallow lake under humid subtropical palaeoclimate.Fossils are mainly sporopollen assemblage of angiosperm and gymnosperm,and there are also ostracoda and a few algae.The kerogens are of types , 2 and 1 and the lithologies are carbonaceous mudstone and dark grey mudstone,with TOC over 4.5% and chloroform bitumen "A" over 0.17%.Crude oils in Weibei sag can be classified as heavy oil,medium density oil and low density oil,according to their physical properties;and they can also be classified as low-mature oil and mature oil,according to the characteristics of biomarkers.Most of the low-mature oil samples have high pristane/phytane ratio,low gammacerane/C30 hopane ratio and high C29 sterane content.The heavy oil and most of the medium-density oil are of low-mature oil,and oil-to-source correlation show that they have been sourced mainly by the source rocks in the 2nd member of Kongdian Fm with rich organic matters.Low density oil and some medium density oil are of mature oil,and they have the same oil source as that of low-mature oil.

Key words: organic-rich layer, low-mature oil, mature oil, oil-to-source correlation, Weibei sag

CLC Number: