Distribution of Paleogene Sedimentary Systems of the Second Member of the Dongying Formation in the Qikou Sag

Integrated study of well core,drilling,logging,3D seismic,and biological association shows that there are four sedimentary systems in the second member of the Dongying Formation in the Qikou sag:fan delta,braided delta,distal subaqueous fan,and lake systems.And the distribution of the sedimentary systems as demonstrated by the sand bodies may be concluded as follows:1) crony-like fan delta developed in steep background which was controlled by the Cangdong fault;2) braided delta developed in the Beitang area of the northern Qikou sag,and evolved into 3) distal subaqueous fan near the downthrow wall of the Changlu-Xingang fault and ladder-like sediment system was controlled by the Binhai fault,Gangxi fault and Qizhong fault;while 4) lake system was mainly controlled by the Changlu-Xingang fault,Binhai fault,Gangxi fault,Zhangdong fault and Qidong fault,within which the shallow lake system located in the Zengfutai,Wanggangzhuang and Caofeidian areas,where as the semi-deep lake system and deep lake system located in the Lvjuhe and Gaochentou areas.Based on the research,three favorable areas are proposed,i.e.,fan delta front sand in the Banqiao sag,braided delta sand in the northern Qikou sag,and distal subaqueous fan sand in the middle of the Qikou sag.