墙角型陡坡带岩性圈闭油气成藏条件研究——以渤海湾盆地石南陡坡带中段BZ3区古近系东营组为例
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摘要
BZ3区西部陡坡带位于渤海湾盆地渤中凹陷石南陡坡带中段,构造上处于石臼坨凸起与凸起倾没端相交的夹角地带,石南一号断裂和石南二号断裂在此处相交,形成由多个复杂断阶所组成的复式墙角型陡坡坡折带。通过高精度层序地层学研究认为,BZ3区东营组东二下亚段发育3个4～5级基准面旋回,每个基准面旋回的上升半旋回的下部和下降半旋回均控制了辫状河三角洲沉积的发育。根据墙角型断裂坡折的形成机制和构造演化特征分析,认为其古构造背景有利,在东二下亚段沉积时期为该区水系汇聚区,以石臼坨凸起为物源,沿边界断层下降盘发育多期辫状河三角洲,并综合地震相、地震属性和地震反演等手段刻画了砂体边界。研究表明,第1、2个基准面旋回砂体发育,且呈扇形向西南方向尖灭,形成侧向尖灭型岩性圈闭,且每期旋回形成的岩性圈闭面积较大、叠合性好。该圈闭依附于边界断层,面向渤中西次洼,背靠石臼坨凸起,烃源岩、运移和储盖组合等成藏条件优越,具有良好的勘探价值,是渤中凹陷岩性圈闭勘探比较现实的目标区之一。
The western steep slope belt of BZ3 block is located in the middle part of Shinan steep slope belt,Bozhong Sag of Bohai Bay Basin.It was formed at the joint zone of Shijiutuo Uplift and its pitching end is a complex wall-corner-type steep slope with several step-fault zones formed by two intersected faults of Shinan 1 and Shinan 2.According to the theories of high resolution sequence stratigraphy,there are three base level cycles of 4-5 th order in the lower submember of Member 2 of Dongying Formation(lower Ed2),and the upper and lower parts of the base level cycle controlled the formation of the braided fluvial delta.By analyses of formation mechanism and structural evolution of wall-corner-type steep slope,the ancient tectonic background was favorable for the water convergence in the lower Ed2,there were multi-stage braided fluvial delta deposits along the down-throw side of the boundary fault from the provenance of Shijiutuo Uplift.Then the sandbody boundary is portrayed by the seismic phase,seismic attributes and seismic inversion methods.The study result shows that the 1st and 2nd base level cycles are favorable for sandbody enrichment,which pinchout to southwest and form lithological traps.They have big trap area and good reservoir-seal conditions.Because these traps were formed attaching to the boundary fault,facing to the western subsag of Bozhong Sag and relying on the Shijiutuo Uplift,the accumulation condition is favorable,and will be the exploration targets of lithological traps in the Bozhong Sag.
The western steep slope belt of BZ3 block is located in the middle part of Shinan steep slope belt,Bozhong Sag of Bohai Bay Basin.It was formed at the joint zone of Shijiutuo Uplift and its pitching end is a complex wall-corner-type steep slope with several step-fault zones formed by two intersected faults of Shinan 1 and Shinan 2.According to the theories of high resolution sequence stratigraphy,there are three base level cycles of 4-5 th order in the lower submember of Member 2 of Dongying Formation(lower Ed2),and the upper and lower parts of the base level cycle controlled the formation of the braided fluvial delta.By analyses of formation mechanism and structural evolution of wall-corner-type steep slope,the ancient tectonic background was favorable for the water convergence in the lower Ed2,there were multi-stage braided fluvial delta deposits along the down-throw side of the boundary fault from the provenance of Shijiutuo Uplift.Then the sandbody boundary is portrayed by the seismic phase,seismic attributes and seismic inversion methods.The study result shows that the 1st and 2nd base level cycles are favorable for sandbody enrichment,which pinchout to southwest and form lithological traps.They have big trap area and good reservoir-seal conditions.Because these traps were formed attaching to the boundary fault,facing to the western subsag of Bozhong Sag and relying on the Shijiutuo Uplift,the accumulation condition is favorable,and will be the exploration targets of lithological traps in the Bozhong Sag.
引文
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李素梅,庞雄奇,邱桂强,等.2004.东营凹陷北部陡坡带隐蔽油气藏的形成与分布[J].石油与天然气地质,25(4):416-421.
王英民,金武第,刘书会,等.2003.断陷湖盆多级坡折带的成因类型、展布及其勘探意义[J].石油与天然气地质,24(3):199-203.
夏东领,林社卿,全书进,等.2007.泌阳凹陷南部陡坡带隐蔽油气藏形成条件与勘探技术[J].石油天然气学报,29(5):63-65.
徐长贵.2006.渤海古近系坡折带成因类型及其对沉积体系的控制作用[J].中国海上油气,18(6):365-370.
徐长贵,于水,林畅松,等.2008.渤海海域古近系湖盆边缘构造样式对沉积层序的控制作用[J].古地理学报,10(6):633-640.
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易士威,王元杰,钱铮.2006.二连盆地乌里雅斯太凹陷油气成藏模式及分布特征[J].石油学报,27(3):27-31.
张善文,隋凤贵,陈宝宁,等.2001.济阳凹陷下第三系陡岸沉积模式[J].沉积学报,19(2):219-223.
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