中国东部古近系洪水-漫湖沉积特征——以济阳坳陷南部为例

PALEOGENE SEDIMENTARY CHARACTERISTICS OF FLOOD-OVERLAKE IN THE EAST CHINA——AN EXAMPLE IN SOUTH OF JIYANG DEPRESSION

利用钻井取心、薄片鉴定、粒度分析、古生物鉴定、测井解释及扫描电镜分析等资料和手段,对济阳坳陷南部古近系孔一段到沙四段底部沉积特征进行研究。结果表明,济阳坳陷在孔一段到沙四段沉积早期处于湖盆裂陷初期,沉积作用明显受季节性洪水注入影响,在东营、惠民两凹陷形成洪水-漫湖沉积体系。其主要岩性特征为:岩石类型以反映氧化环境的浅色碎屑岩类为主,成熟度较低,粒度分布和沉积构造反映其兼具重力流和牵引流的沉积特点,植物碎屑贫乏而生物扰动构造丰富且具周期性,砂体呈环带状分布。该沉积体系分为洪水水道末端、泥坪、砂坪、砂泥混合坪和漫湖风暴等5个微相和侧缘远源、近岸远源两类相层序,其中洪水水道及洪水漫湖砂坪具有较好的储气能力,是济阳坳陷深层勘探开发的新领域。

It was showed,by cores observation,grain size analysis,logging data and electron microscope observation in Jiyang Paleogene depression,that the sediment of flood-overlake was controlled by ephemeral flood because the lake was shallow and the weather was dry-half dry. The clay platform,sand platform and mixing platform formed overlake sedimentation. The rocks were light corlored terrigenous and their maturities were low. Cumulative probability plots and sedimentary structures reflected that the transportation medium was characteristic of tractive current and gravity flow synchronously,without the plant segments and with abundant bioturbation structures. There were 5 microfacies,including clay platform,sand platform,mixing platform channel and overflow-tempestites. The study showed that the overflow sediments was the favorable reservoir for gas concentration.