渤南洼陷沙四上亚段碳酸盐岩成藏条件与勘探潜力

Hydrocarbon accumulation conditions and prospecting potentials of carbonate rocks in the Upper E of Bonan Sag

林会喜 彭苏萍 杜文风 孔祥星

Lin Huixi Peng Suping Du Wenfeng Kong Xiangxing

渤南洼陷古近系沙河街组四段上亚段发育了大面积的湖相碳酸盐岩,而由灰岩、泥灰岩、灰泥岩或膏泥岩不等厚互层沉积形成了渤南洼陷一套重要的碳酸盐岩烃源岩。该套烃源岩厚度为20～100 m,厚度中心分别在垦西、义东地区。烃源岩的有机质类型主要为腐泥型,是一套类型好、高丰度的优质烃源岩。烃源岩有机质的生烃期较同层系泥岩生烃期早,在为0.6%左右达到生烃高峰。原油以高C/C升藿烷比值、高丰度的4-甲基甾烷、高含硫量为标志性特征。油气经历了东营组末至馆陶组,馆陶组末至明化镇组两期成藏过程。沙河街组四段上亚段碳酸盐岩、扇三角洲及砂岩滩坝等形成的各类圈闭,以及与深洼陷带油源能够侧向对接的沙河街组四段下亚段是未来的有利勘探方向。

A lacustrine carbonate sequence composed of limestone,marl,lime mudstone and gypsiferous mudstone is developed widely in the upper E (the 4 member of the Paleogene Shahejie Fm) and acts as important source rocks in Bonan Sag of northern Huanghe Delta.The source rocks are 20 m to100 m thick with the maximum thickness at Kenxi and Yidong.Rich in sapropel-type organic matters,the rocks are of excellent quality.The source rocks generated hydrocarbon earilier than that of mudstone at the same sequence and reached hydrocarbon generation peak when is about 0.6%.The crude samples show a feature of high homohopane (C/C) ratio and high abundance of 4-methylsterane and sulfur content.There were two important stages for oil accumulation:the end of E to N and the end of N to N.It is suggested that the carbonates of the upper E,the fan-delta and beach-bar sandstoneas well as the lower E in juxtaposition the oil source rocks in the deep sag,be considered favorable exploration targets.

10.11743/ogg20130203