多边形断层系及其研究现状

Study on polygonal fault systems

多边形断层为一类非构造断层,主要分布于深水环境下的细粒沉积物中。它的形成与沉积物的早期压实作用和流体排出作用有关。多边形断层系的识别主要通过时间切片分析和地震剖面解释等手段进行。研究表明,多边形断层系发育一般要经历3个阶段,即超压封存箱的形成、密度反转和多期水力压裂作用。对多边形断层系的研究有助于泥岩压实、油气运移、泥岩中流体活动状态以及对深水砂体分布和几何形态特征的分析等。由于我国还未发现有多边形断层系的存在,希望本文的介绍能为我国开展此类断层研究时有所帮助。

Polygonal fault is a type of non-tectonic fault distributing in deepwater fine-grained sediments. The formation of polygonal fault is associated with early compaction of sediments and fluid expulsion. The identification of polygonal fault is based on interpreting seismic profiles and their time slice. An episodic three-stage mechanism was proposed to explain the fault genesis,involving①the development of basin-wide overpressured compartments,② a density inversion between the overpressured units and the overlying seal,and ③ natural hydraulic fracturication,pressure bleed-off and resealing of the pressure compartment leading to a cycle repeat. The study on polygonal fault is helpful for analyzing compaction of muds,hydrocarbon migration,fluid flow in mudrocks and deepwater sand distribution and geometry. Since polygonal fault has not been found in our country yet,the introduction in this paper may be helpful for the study in China.