Oil Source Analysis of Two Paleogene OilSystems in Jiangling Depression

Key words: 
• oil system /
• geochemical property of oil /
• hydrocarbon source rock /
• Jiangling Depression

Abstract: This paper dealt with that oils from tow Paleogene oil systems in Jiangling Depression have greatlydifferent geochemical properties due to different source matter and different maturities of two sets of hy-drocarbon source rocks. In the first oil system, the principal souce sequence is ranging from the middleand lower parts and the upper partor the mudstone, barrier in the formation, it is of medium to goodsource rock and has generated relatively abundant hydrocarbons. Studies showed that in different areasor zones this oil system has two different oil souse models, i. e. oueis, the system itself alone; the other isthe system with allochthonous source. Oil migration distance may he as far as over 10 km. The source models and migration distance arebasically responsible for the distribution of Xingouzui. Formation and Jingsha Formation oil reservoirs.In the second oil system,source rocks in Qianjiang Formation, though being shallowly buried less than2000 m(Ro<0.5%),had been found to haven high abundance of organic matter in the 3rd and 4th mem-hers of Qianjiang Formation. kerogens are of Typel and Typel S, having the potential to generate im-mature oil inshould he paidearly stage of transformation, soas to constitute oil reservoirs in situ.Properattentiont should be paid to them in exploration.