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    渤海湾盆地长堤走滑断裂带断层活动与组合样式分段差异

    Segmented difference in fault activities and combination pattern of strike-slip fault zones in Changdi area, Bohai Bay Basin

    • 摘要: 渤海湾盆地长堤走滑断裂带属于郯庐走滑断裂带东侧的派生构造带,含油气资源丰富。在沙河街组沉积时期,该断裂带经历了伸展、走滑多期叠合改造,其断裂分段活动的动力学机制及其对油气差异富集的控制模式尚未得到系统揭示。基于三维地震、钻井及岩心录井等资料,利用地震断层与层位解释、地震属性分析、断层生长指数等方法,研究了长堤走滑断裂带沙河街组沉积时期的断层性质、活动历史、组合特征及其分段性差异,以深化大型走滑断裂带背景下伴生走滑断裂分段发育特征和油气富集规律认识。研究发现,长堤走滑断裂带共识别出主断层张扭断裂组、主断层压扭断裂组、差异伸展走滑断裂组等共7组断层,剖面上组合为顺向断阶式、逆向断阶式、Y字型与反Y字型、地垒式、地堑式以及俯冲逆断层式共6种构造样式,平面上可分为分支尾端、尾端、压扭叠接区、张扭叠接区、主位移区共5段。其中,南部分支尾端断裂活动性较弱,表现为拉张性质的马尾构造,北部尾端应力释放,二者断面封堵性差,导致油气逸散;压扭叠接区断裂活动性较强,发育花状构造,断面下缓上陡,封堵性好有利于油气聚集;张扭叠接区发育脆性共轭断层和反向断阶构造;主位移段由走向相反的张扭、压扭段形成复合S型,断裂活动性最强,压扭段断面封堵性强,利于油气成藏,而张扭段沟通性强,利于油气运移,发育雁列式断层和俯冲逆断层构造。

       

      Abstract: The strike-slip fault zone in Changdi area, Bohai Bay Basin belongs to the derivative structural zone on the east side of Tanlu strike-slip fault zone, which is rich in oil and gas resources. During the sedimentary period of Shahejie Formation, the fault zone underwent a multi-stage superimposed transformation of extension and strike-slip. The dynamic mechanism of fault segment activities and its control mode for differential accumulation of oil and gas have not been systematically revealed. Three-dimensional (3D) seismic data, drilling data, and core logging data were analyzed, and seismic fault and horizon interpretation, seismic attribute analysis, fault growth index, and other methods were employed to study the fault properties, activity history, combination characteristics, and segmented differences of strike-slip fault zones in Changdi area during the sedimentary period of Shahejie Formation, so as to deepen the understanding of the segmented development characteristics and oil and gas accumulation rule of the associated strike-slip faults in the background of large strike-slip fault zones. According to the research, seven fault groups including the tension-torsion fault group of the main fault, compression-torsion fault group of the main fault, and differential extensional strike-slip fault group were identified in the strike-slip fault zones in Changdi area, and six structural styles including forward fault-step group, reverse fault-step group, Y-shaped and anti-Y-shaped fault group, horst type, graben type, and subduction reverse fault group were observed in the section. On the plane, it could be divided into five sections: branch tail end, tail end, compression-torsion overlapping area, tension-torsion overlapping area, and main displacement area. Among them, the fault activity of the southern branch tail was weak, which was manifested as the tensile horsetail structure, and the stress release was concentrated on the northern branch tail. The poor sealing property of the two sections leads to oil and gas escape. The compression-torsion overlapping area had strong fault activity, flower-like structure, gentle lower section and steep upper section, and good sealing properties, which are conducive to oil and gas accumulation. Brittle conjugate faults and reverse fault-step structures were developed in the tension-torsion overlapping area. The main displacement area was S-shaped due to the opposite tension-torsion and compression-torsion sections, with the strongest fault activity and strong section sealing in the compression-torsion section, which was conducive to oil and gas accumulation, while the tension-torsion section had strong communication, which was conducive to oil and gas migration, and with echelon faults and subduction reverse faults developed.

       

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