地层岩性圈闭形成条件及发育模式——以珠江组地层为例

新近纪珠江口盆地发生断坳转换之后，陆架坡折带一直位于番禺低隆起南侧—白云凹陷北坡地区，珠江组作为该区的主力产气层段，具有形成地层岩性圈闭的有利条件。以三维地震资料和已钻井为基础，结合周边的部分二维测线，对研究区进行了层序地层划分和沉积相分析，认为:①古珠江流域面积广、携带陆源粗碎屑物质丰富；②多期次构造运动造成古珠江流域地表物质疏松活化；③相对规模较大的海平面下降使得古珠江三角洲一直推进到陆架坡折带附近。上述3个因素的耦合叠加为番禺低隆起南侧—白云北坡地区发育粗碎屑沉积物提供了保障，这些沉积物在陆架坡折区所具有的特殊古地貌背景的控制下，在珠江组形成2套有利的储盖组合和多种类型的沉积砂体，从而为地层岩性圈闭的发育创造了有利条件。其中强制性海退体系域陆架边缘三角洲和低位体系域斜坡扇、盆底扇形成的地层岩性圈闭最为有利，而海侵体系域和高位体系域形成地层岩性圈闭的条件相对较差。 

Formation conditions and development model of stratigraphic-lithologic traps in shelf break zone,Pearl River Mouth Basin:Zhujiang Formation as an example

The shelf break zone in the south of Panyu Low Uplift and on the northern slope of Baiyun Sag since the Pearl River Mouth Basin came into the post-rifting stage in the Neogene. As the primary gas-producing layer, the Zhujiang Formation was favorable for the formation of stratigraphic-lithologic traps. Stratigraphic and sedimentary facies analyses were made based on 2D and 3D seismic data and drilling information. (1) The paleo Pearl River featured a wide drainage area and abundant detrital material of terrigenous origin. (2) The land surface material of the paleo Pearl River flow domain became loose and activated due to multiple tectonic movements. (3) The paleo Pearl River delta prograded to the shelf break belt because of extensive sea level fall. Due to the influences of these three factors, the paleo Pearl River carried abundant coarse clastic debris to the southern area of Panyu Low Uplift and the northern slope of Baiyun Sag. This clastic debris formed two favorable reservoir-seal assemblages and many kinds of sedimentary bodies at the shelf break zone which had a special palaeogeomorphologic background, and thus provided favorable conditions to the development of stratigraphic-lithologic traps. The stratigraphic-lithologic traps located in the shelf edge delta of a forced regressive system tract and which formed in the slope fan and basin fan of a lowstand system tract are most advantageous for oil and gas accumulation. The stratigraphic-lithologic traps in the transgressive and highstand system tracts have poor conditions.