Geological Significance of Re-recognition on Early Reservoir Forming of Paleogene in Bonan Sag
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摘要: 传统观念认为渤南洼陷古近系具有三期成藏、晚期为主的特点。随着咸化湖盆烃源岩具有早生早排、生排烃量大的新认识的提出,利用钻井、地震及分析化验资料开展了渤南洼陷古近系早期成藏作用的重新评估。结果显示:渤南洼陷沙四上亚段发育有咸化环境下形成的烃源岩,地球化学参数表明其具有生成大量油气的能力,是早期成藏的物质基础;流体包裹体荧光颜色、均一温度共同指示出渤南洼陷罗家地区和三合村洼陷存在早期成藏,三合村洼陷古近系油气是在东营组沉积早期孤南断层断距较小时由渤南洼陷罗家地区运移而来;早期成藏作用的再认识不但使三合村洼陷古近系的油气勘探取得突破,而且构建了完整的油气成藏期次序列;早期成藏造成的岩石润湿性反转利于优势运移通道继承性发育,同时成藏过程中伴随的有机酸充注利于储集空间发育,更重要的是早期成藏作用的再次认识将会转变勘探思路、拓展勘探选区,带来了重要的地质意义和勘探启示。Abstract: It was the traditional view that Paleogene of Bonan Sag had three hydrocarbon accumulation periods and the main period was later. With the proposed new theory that source rock in saline lacustrine basin was generated and expulsed early and the quantity of generation and expulsion is various. Early reservoir forming process of Bonan Paleogene was re-evaluated using the analysis and testing data of drilling and seismic exploration. The research shows that source rock formed under saline environment is well developed in the upper part of 4th member of Shahejie Formation of Bonan sag, and geochemical parameters indicate that source rocks can generate a great number of oil and gas and that is the material basis of early reservoir forming. Fluorescent color and homogenization temperature of fluid inclusion indicate that early reservoir forming is developed in Luojia area of Bonan sag and Sanhecun sag. Oil and gas of Paleonege at Sanhecun sag was transferred from Luojia area at early sedimentary stage of Dongying group when Gunan fault throw was small. Re-recognition on early reservoir forming not only made breakthroughs in oil and gas exploration of Paleonege in Sanhecun sag, but also built complete reservoir forming period sequence. Rock wettability alternation caused by early reservoir forming helped successive development of dominant migrating pathway, organic acid filling through the process of reservoir forming helped development of the reservoir space, and, more importantly, re-recognition of early reservoir forming will help transforming the exploration strategy and expand the exploration area, which will bring significant geological and exploration implication.
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