山东惠民凹陷中央隆起带古近系沙河街组层序地层特征及控制因素研究

结合山东惠民凹陷中央隆起带古近系层序地层学研究,依据层序中湖平面变化特点和相应的沉积物特征,提出了构造运动和气候是本区层序地层发育的主要控制因素。中央隆起带古近系沙河街组二、三、四亚段可划分为 3种层序类型,即断陷初期型、强断陷期型和断陷后期型层序。由于构造运动导致湖岸线向盆地方向退缩,产生下降体系域,本次研究采用了体系域的四分法,即一个完整层序由低位、湖侵、高位和下降四个体系域组成,并且层序界面位于湖平面最大下降的位置,介于下降域和低位域之间。断陷初期红色地层层序,受气候因素控制明显,既不同于冲积地层层序,也不同于正常湖相地层层序,在层序演化上有其独特的特点。受构造作用和沉积物补给条件的影响,研究区发育三种沉积密集段,不同类型的沉积密集段在层序中所处位置不同,控制着不同的烃源岩厚度和油气资源储量。

The Sequence Stratigraphy Characteristics and Controlling Factors of the Shahejie Formation of the Central Uplift Belt in Paleogene in Huimin Depression, Shandong Province

The sequence stratigraphy studies of the Shahejie Formation in the central uplift belt of Huimin depression of Shandong province indicate that tectonic movement and climate are dominant controlling factors to sequence development. The 2, 3and 4 submembers of Shahejie Formation can be divided into three types of stratigraphic sequence, i.e. the stratigraphic sequence in primary rifting stage, the stratigraphic sequence in violent rifting stage and the stratigraphic sequence in the later rifting stage. The sequence stratigraphy indicates that it is more suitable to divide a sequence into four system tracts in the lacusstrine basin including lowstand system tract (LTS), lake transgressive system tract (TST), highstand system tract (HST) and falling stage tract (FST). According to characteristics of lake level change and its corresponding sediments, the sequence boundary is located between the LST and FST. The red beds stratigraphic sequence is mainly controlled by the climate and has unique characteristics in sequence evolution, which is different from the alluvial fan stratigraphic sequence and also different from the normal lake facies stratigraphic sequence. Influenced by tectonic movement and sediment supply, three kinds of stratigraphic sequence in this region form three kinds of condensed sections, which located in different section of each sequence. The different condensed section will influence the abundance of source rock and resources, and every condensed section controls the distribution and thickness of the source rock.