昌潍坳陷潍北凹陷孔二段优质烃源岩成因与分布

摘要

昌潍坳陷潍北凹陷烃源岩分布在孔二段（即始新统孔店组二段），包括暗色泥岩、灰质泥岩和油页岩3种类型，前人对灰质泥岩和油页岩的生烃贡献未进行深入研究。利用有机地球化学方法结合热模拟实验对潍北凹陷各种类型烃源岩品质进行分析，研究表明油页岩和灰质泥岩有机质丰度较高、干酪根类型主要为Ⅰ型和Ⅱ1型，为优质烃源岩；暗色泥岩有机质类型和丰度较差，基本为无效烃源岩。优质烃源岩集中分布在孔二上亚段下部和孔二中亚段上部的油页岩和灰质泥岩中，平面上分布在瓦城断阶带东部和灶户鼻状构造带，与已发现油气藏具有良好的对应性。古生物学标志、古盐度及古氧相分析表明孔二段烃源岩形成于内陆咸化湖泊沉积环境。郯庐断裂带左—右旋转换期构造活动强度较弱和晚古新世到早始新世期间发生的大陆分离事件造成的温暖湿润气候促成了优质烃源岩的发育。%The hydrocarbon source rocks of the Weibei Sag,Changwei Depression,Shandong,are distributed in the Second Member of Kongdian Formation,Eocene,include dark mudstone,calcareous mudstone and oil shale.There have been a few studies on hydrocarbon generation of calcareous mudstone and oil shale before.The aim of this paper is to review the characteristic and distribution of different types of hydrocarbon source rocks.The study is conducted at organic geoehemistry combined thermal simulation experiment,and the result shows that high abundance of organic matter in oil shale and calcareous mudstone,which kerogen are mainly typeⅠand typeⅡ1, are high-quality hydrocarbon source rocks.Dark mudstone generally are invalid hydrocarbon source rocks.The high-quality hydrocarbon source rocks longitudinally concentrated on the upper and middle of the Second Member of Kongdian Formation,laterally distributed in Zaohu and eastern part of the Wacheng fault zone.Ancient sedimentary environment is analyzed by paleontological marks,paleosalinity and paleoxygenation facies,reveals that high-quality hydrocarbon source rocks of the Second Member of Kongdian Formation formed in the inland saline lakes environment.The cause of high-quality hydrocarbon source rocks are the weak intensity of tectonic activity of Tanlu (Tancheng—Lujiang)fault zone during the conversion period from left-slip to right-slip and the warm and humid climate aroused by the mainland separation incidents occurred in the Late paleocene to Early Eocene.