冀中坳陷陆相地层层序地层学的应用

应用层序地层学的基本概念和研究方法重新解释了冀中坳陷的下第三系地层.四个层序可从地震剖面和钻井资料中解释出来,每一层序可进一步划分成三个体系域：低水位期、水进期和高水位期.体系域的沉积或岩相的分布明显受湖水升降及构造沉降的双重作用控制,每一层序构成了水进到水退的沉积旋回.从现有的资料分析,冀中坳陷的水进期体系域可能与“海泛”或“海侵”有关,发育有较厚的暗色泥、页岩夹碳酸盐岩(包括生物碎屑灰岩)的沉积,并伴有大量的与“咸水”环境有关的微古生物,这些微古生物是形成油气的主要物质基础.而位于水进期之下的低水位期的盆底扇、斜坡扇、斜坡河道砂、水进三角洲和位于水进期之上的高水位期的水退三角洲、扇三角洲砂体是有利的储集层系.圈闭类型明显受砂体的成因类型控制.

AN APPLICATION OF SEQUENCE STRATIGRAPHY IN CONTINENTAL DEPOSIT OF JIZHONG DEPRESSION

The concept and method of sequence stratigraphy were applied to the reinterpretation of Palaeogene formation in the Jizhong depression.Having interpreted the seismic and drilling data,Palaeogene formation is divided into four sequences.Each sequence can be subdivided into three depositional system tracts:lowstand,transgression and highstand system tracts.The deposition of system tract or the distribution of lithofacies was controlled by both the water level (high or low)and the tectonic subsidence,so that each sequence consists of transgressive regressive sedimentary cycle. Having analysed the existing data,we know that the transgression system tract in Jizhong depression may be relating to "sea overflow" or "transgression",consists of thick dark mud shale layers with carbonate interbeds(including bioclastic limestone) and a great deal of microfossils relevant to a salt water environment.The microfossils were the main matter that became oil and gas.The favourable reservoirs are bottom fan,slope fan,slope channel sand body and transgressive delta in the lowstand tract beneath the transgression system tract,regressive delta and the fan delta sand body in highstand tract above transgression system tract.The trap type obviously depends on the generation type of sand body.