珠江口盆地文昌凹陷陆相坡折带类型及其控砂作用

Types and Sand Control Effect of Terrestrial Slope Breaks of Wenchang Sag inside the Pearl River Mouth Basin

珠江口盆地文昌凹陷多幕构造演化与复杂构造变形形成了极具特色的坡折类型.以构造沉积学、层序地层学为理论基础,结合钻井及三维地震资料,在文昌凹陷识别出4类6种陆相坡折带,并分析各类坡折带对砂体的控制作用.断裂坡折带分布于凹陷南部陡坡带,可进一步划分为单断式盆缘断裂坡折带、多级盆缘断裂坡折带及帚状盆缘断裂坡折带,控制着扇三角洲、滑塌扇及湖底扇砂体的分布;挠曲坡折带、沉积坡折带及侵蚀坡折带分布于凹陷北部缓坡带,控制着下切水道充填砂体、三角洲砂体及小型湖底扇砂体的分布,缓坡坡折带上发育的小型断裂调整并改造沉积物充填方向与沉积体系的分布.坡折带控制下的砂体是非构造圈闭发育的有利部位,勘探潜力巨大.

The distinctive types of slope breaks of Wenchang Sag inside the Pearl River Mouth Basin are formed by a series of tectonic evolution and complex structural deformation.Based on the theory from Tectonic Sedimentology and Sequence Stratigraphy,we identified four main terrestrial slope breaks types and analyzed the sand control effect caused by these types,with the combination of drilling data and three-dimensional seismic data.Fault slope break zones are distributed in the steep slope of South Wenchang Sag.This type of breaks can be further divided into mono-faulted,multistage,and brush basinmarginal fault slope breaks.The sand body distribution of fan delta,slump fan,sublacustrine fan are controlled by these breaks.Flexure,depositional and erosional slope breaks distributed inside the gentle slope of North Wenchang Sag.The sand body distribution of incise channel,delta and small sublacustrine fan are controlled by them.Besides,the small scale faults developed in the glacis slope breaks could adjust and transform the filling direction of sediments and the distribution of sedimentary systems.In addition,those sand bodies controlled by slope breaks are favorable positions for forming non-structural trap.In a word,they have huge potential for exploration.