涠西南凹陷陡坡带流三段扇体展布特征及有利勘探方向

Distribution characteristics and favorable exploration direction of fan body of the 3^(rd)member of Liushagang formation in steep slope zone of Weixi’nan Sag

涠西南凹陷陡坡带流三段近年获重大油气发现,但其沉积演化规律及砂体展布特征尚未系统研究,制约了下步勘探进程。在新钻井基础上,利用新处理的三维地震资料,综合录测井、岩心及化验分析等资料,对陡坡带边界断裂一号断裂进行精细刻画,着重对陡坡带流三段扇三角洲沉积体系开展细致分析。结果表明:①流三段沉积时期陡坡带发育大型粗粒扇三角洲沉积体系,具有“近源快速堆积、沉积响应速度快、沉积厚度大”的特点;②一号断裂于流三段初期处于分段生长阶段,扇三角洲主要呈多个朵叶体沿坡折带“斜列入湖”;③斜向扇三角洲近物源端发育相对限制性主水道,形成的近源扇三角洲侧向尖灭+上倾物性侧封型岩性油藏是下步重点勘探方向。研究成果从根本上拓展了陡坡带的勘探思路,对涠西南凹陷的下步勘探具有重要指导意义。

Oil and gas discoveries have been made in the 3^(rd)member of Liushagang Formation in steep slope zone of Weixi’nan sag in recent years,but its sedimentary evolution and sand body distribution characteristics have not been carefully studied,which restricts the next exploration process.Based on new drilling,using newly processed 3D seismic data,comprehensive logging,core and chemical analysis data,No.1 fault at the boundary of the steep slope zone is finely characterized,and the sedimentary system of the fan delta in the 3^(rd)member is analyzed in detail.The results show that:①During the sedimentation period of the 3^(rd)member,a large coarse-grained fan delta sedimentary system developed in the steep slope zone,characterized by rapid accumulation near the source,fast sedimentary response speed,and large sedimentary thickness.②No.1 fault is in the stage of segmented growth in the early stage of the 3 rd member,and the fan delta is mainly composed of multiple leaflets that"slant into the lacustrine"along the slope break zone.③The development of relatively restrictive main channels near the source end of the oblique fan delta has formed a structure+lithologic trap with lateral pinching out and upward dipping physical side sealing in the near source fan delta,which is the next key exploration direction.The research results have expanded the exploration idea of steep slope zone,and have a good guidance for the next exploration of Weixi’nan sag.