收稿日期: 2012-05-02
修回日期: 2012-07-31
网络出版日期: 2012-12-10
Geochemical Characteristics of the Source Rock of K Formationin the Western Sag of Bongor Basin,Chad
Received date: 2012-05-02
Revised date: 2012-07-31
Online published: 2012-12-10
Bongro盆地西部地区勘探程度低，对其含油气前景认识有限。利用西部凹陷2口探井烃源岩样品的有机地球化学分析资料，结合区域地质资料，从烃源岩生烃潜力、生烃史以及生物标志化合物特征等方面，对Bongor盆地西部凹陷下白垩统K组烃源岩地球化学特征进行综合研究。结果表明:西部凹陷K组地层暗色泥岩、页岩发育；烃源岩有机质丰度高，整体评价为好烃源岩；有机质类型好，主要为Ⅱ1型有机质； K组下部烃源岩处于成熟热演化阶段，K组上部烃源岩处于低成熟热演化阶段。生烃史模拟表明，K组下部烃源岩分别于早白垩世晚期和晚白垩世早期进入生烃门限和成熟热演化阶段，而K组上部烃源岩在地质历史时期一直没有进入成熟热演化阶段，现阶段处于低成熟阶段。烃源岩饱和烃生物标志化合物特征表明，K组烃源岩形成于半咸水—淡水、弱氧化—弱还原的湖相沉积环境，其有机质组成为典型的湖相混合型有机质特征。
曾艳涛，文志刚，宋换新 . 乍得Bongor盆地西部凹陷K组烃源岩地球化学特征研究[J]. 天然气地球科学, 2012 , 23(6) : 1121 -1126 . DOI: 10.11764/j.issn.1672-1926.2012.06.1121
The exploration degree is low of the west area in the Bongor basin and the cognition of the Petroliferous potential is limited.Based on the organic geochemistry analytical data of the source rock samples of the two exploratory wells in the Western sag and combined with regional geological information,a comprehensive study of the K Formation source rocks has been carried out spanning the aspects of hydrocarbon generation potential,hydrocarbon generation history and characteristics of biomarkers,etc..The result indicates that the dark mudstone and shale are abundant in the western sag.The organic matter abundance is high and the source rock is good.The organic type is mainly typeⅡ1which is favorable for hydrocarbon generation.For the K Formation,the lower part is mature while the upper part is low mature.The hydrocarbon generation simulations indicate that source rocks of the lower part of K Formation reached the hydrocarbon generation threshold during the late stage of early Cretaceous and maturation during the early stage of late Cretaceous.However,the upper part of K Formation has not come into mature stage during the geological time and it is still low mature at present.The characteristic of saturated hydrocarbon biomarkers indicates that the source rock of the K Formation was deposited in fresh water- semi-saline water and weak oxidizing-weak reducing lacustrine sedimentary environment.The organic matter is a mixture of lacustrine facies.
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