西湖凹陷平湖斜坡带物源-坡折耦合控砂模式

Sand-controlling model of source-slope-break coupling in Pinghu Slope Belt,Xihu Sag

平湖斜坡带为西湖凹陷岩性油气藏勘探的重要区域之一。勘探开发实践证实,平湖斜坡带平湖组砂体展布复杂,控砂模式指导下的砂体刻画已成为岩性油气藏勘探突破的关键。从物源体系研究出发,结合坡折带特征分析,梳理了研究区物源坡折耦合控制下的砂体展布特征。沟谷及重矿物特征表明,研究区存在海礁隆起西部、西南部稳定物源及宝云亭凸起动态物源三大物源体系,控制了研究区储层沉积物来源;受隆起、断裂差异活动及沉积作用控制,研究区发育的断裂坡折、挠曲坡折和沉积坡折共同控制了研究区地形特征。物源体系与坡折耦合控制了沉积物从源到汇的动态过程:平湖组下段由西南物源及宝云亭凸起动态物源共同控制,发育混源堆积型控砂模式;平湖组中段由西部海礁隆起物源主控,以挠曲坡折限制的单源改造型控砂模式为主;平湖组上段由沉积坡折主控,发育缓坡过渡型控砂模式。

Pinghu Slope Belt has become one of the important fields of lithologic reservoir exploration in the Xihu Sag.Exploration and production have confirmed that the distribution of sand bodies in the Pinghu Formation is complex,and sand body characterization guided by sand-controlling model has become the key to the breakthrough of lithologic reservoir exploration.Based on the studies on the source system and slope-break zone,the distribution characteristics of sand body under the control of source and slope-break coupling in the target area were summarized in this paper.The characteristics of ravines and heavy minerals indicate that there are three source systems in the target area:the western source and southwestern source of Haijiao Uplift,and the dynamic source of Baoyunting paleo-uplift,which controlled the source of sand material in the target area.Under the control of paleo-uplift,differential activities of faults and sedimentation,three types of slope-breaks developed in the target area,namely faulted slope-breaks,flexural slope-breaks,and depositional slope-breaks,controlled jointly the topographic features of the target area.Source system and slope-break coupling controlled the dynamic process of sediment from source to sink.Under the joint control of the southwestern source and the dynamic source of Baoyunting Uplift,the development of mixed-source sand body accretion is dominant in the lower member of Pinghu Formation.Under the main control of the source of the western Haijiao Uplift,the single-source-reformation sand-controlling mode restricted by flexural slope-break is dominant in the middle member of Pinghu Formation.Under the main control of the depositional slope break,the transitional sand-controlling mode of gentle slope was developed in the upper member of Pinghu Formation.