THE GEOMETRICAL CHARACTERISTICS AND FORMATION MECHANISM OF POLYGONAL FAULTS IN DEEP-WATER BASIN
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摘要: 多边形断层是指一种在平面上呈多边形具有微小断距的张性断层系。自1994年被提出以来, 已有十余年的研究历史, 并在世界50多个被动大陆边缘盆地中被识别出来。研究多边形断层需要高精度的3D地震资料。我们根据琼东南盆地3D地震资料并利用相干切片技术, 首次在琼东南盆地南部发现了多边形断层, 并对其进行了初步研究。多边形断层的成因机制是前期多边形断层研究的重点, 许多学者认为深水沉积物早期压实脱水体积收缩形成的; 也有学者认为重力扩展控制断裂的发育。岩石物性、成岩作用及构造应力是影响多边形断层发育的重要因素。多边形断层对深水盆地的油气储集体的性质和分布; 以及油气、天然气水合物的运移和聚集有着重要的意义。Abstract: Polygonal fault system is a tensional fault system with small throws.Because of their polygonal shape on plan, they are named polygonal faults.They have been studied for more than ten years since they were defined in North Sea in 1994, and from then on, they have been recognized in more than fifty passive basins worldwide.Research on polygonal fault needs high-resolution 3D seismic data, so, until now no research on polygonal fault has been made in China.The mechanism of polygonal fault is the focus of preliminary studies.Many experts think that the volumetric contraction induced by syneresis during the early-stage compaction of fine sedimentation is the mechanism for the development of polygonal fault systems.Many polygonal faults formed in continental slope, so some scholars believe that gravitational spreading is the mechanism for the polygonal fault formation.Polygonal faults affect the attributes and distribution of deep-water hydrocarbon reservoir which provide pathway for fluid, so they are important for migration and accumulation of hydrocarbon and gas hydrate.
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Key words:
- polygonal fault /
- syneresis /
- gravitational spreading /
- channel sandstone /
- deep-water basin
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图 1 多边形断层的平面和剖面特征
左图:加拿大Sable次盆地发育在1.25~ 1.5 TWT (Sec)层段内的多边形断裂[5]; 右图:英国北海盆地中部地区多边形断层的时间倾角属性剖面[7]
Figure 1. Planimetric and sectional characteristics of polygonal faults
Left:Formation of polygonal faults is confined between 1.25 and 1.5 TWT (S), Canadian Sable Subbasin; Right:Time-dip attribute map images the geometrical characteristics of polygonal faults, Central North Sea Basin.
图 2 澳大利亚Eromanga盆地及琼东南盆地多边形断层特征
上图:澳大利亚Eromanga盆地多边形断层剖面图(500ms TWT) [25]; 下图:琼东南盆地3024ms (TWT)处多边形断层的时间相干切片图
Figure 2. Characteristics of polygonal faults in Eromanga Basin of Australia and Qiongdongnan Basin of South China Sea
Top:The seismic section of polygonal faults of Eromanga Basin, Australia (500ms TWT); Bottom :The time coherent slices of 3024ms(TWT)in Qiongdongnan Basin, South China Sea.
图 4 塑性模拟物之上的横向断层, 纵向断层及多边形断层
(据Victor & Moretti, 2006[14], 略有改动)
Figure 4. Perpendicular boundary faults, parallel boundary faults and polygonal faults above ductile analog material
图 5 颗粒大小及矿物成分对多边形断层形成的影响
(据Dewhurst & Cartwright, 1999a[8], 略有改动)
Figure 5. Influences of grain degree and mineral composition on formation of polygonal faults
图 6 东北Rockall盆地被动褶皱与多边形断层的关系
(据Hansen & Cartwright, 2006[17])
Figure 6. Relationship between forced folds and polygonal faults
图 7 构造应力对多边形断层的影响
(据Hansen & Shimeldb, 2004[5])
Figure 7. Influence of tectonic stress on polygonal faults
表 1 多边形断层主要形态特征统计表
Table 1. Statistics of major morphological features of polygonal faults
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