基于正断层差异生长演化分析识别不同类型断层相关背斜圈闭——以苏北盆地高邮凹陷汉留断层为例

Differential Evolution Analysis of Normal Faultsin Identifying Different Types of Fault Related Anticline Traps:Taking Hanliu Fault in Gaoyou Sag of Subei Basin as an Example

为了明确正断层差异生长演化特征,以及断层相关圈闭成因与分布规律,本文以苏北盆地高邮凹陷内的汉留断层为例,通过断层垂直断距-距离(T-X)曲线和垂直断距-埋深(T-Z)曲线对苏北盆地高邮凹陷汉留断层运动学进行分析。得到汉留断层自W向E由Fh1、Fh2和Fh3等3个断层段组成,呈左阶斜列分布,各断层段形成时期与生长演化特征不同,表现在运动学上为相互独立的4个断层段。戴南组时期,Fh1段和Fh3段东部(Fh3b段)最先形成;三垛组时期,Fh1段存在新生的断层核与下部戴南组时期形成的断层段最初在垂向上是分离的,随着上下断层段的传播最终发生垂向连接,Fh3b段继承性活动,同时形成Fh2段和Fh3段西部(Fh3a)段。各个断层段相互作用并沿走向发生几何连接或者形成重叠带,最终形成了Fh1、Fh2和Fh3等3个断层段。断层在沿走向平面分段生长过程中,在其分段连接部位或重叠处可以形成背斜构造;同时在断层垂向分段生长过程中由于围岩流变学特征差异也可形成背斜构造,这2种不同类型的断层相关背斜构造均可构成油气富集的有利场所。

To clarify the different characteristics of normal fault growth and the mechanism and distribution of fault-related traps,this paper takes the Hanliu fault in Gaoyou sag of Subei basin as an example.The throw-distance(T-X)and throw-depth(T-Z)curves are used to analyze the kinematics of Hanliu fault zone in Gaoyou sag of Subei basin.The results reveal that three segments were identified along the Hanliu fault zone,Fh1,Fh2 and Fh3,left step arranged from west to east.However,there are differences between the formation period and growth evolution characteristics of different segments,that is,four fault segments with independent kinematics.During the period of the Dainan Formation,the Fh1 and the eastern Fh3(Fh3b)segments were the first to form.During the period of the Sanduo Formation,the Fh1 segment is initially separated from the fault section formed in the vertical direction during the deposition period of the lower south of the Dainan Formation.With the fault segments propagating upward and downward,a vertical connection eventually occurred and the Fh3b segment inherited activity.At the same time,the Fh2 and the western Fh3(Fh3a)segments were formed,and the interaction of each fault section was geometrically connected or formed overlapping zones,which eventually formed three fault segments of Fh1,Fh2 and Fh3,and the fault segments reach the present fault length.In the process of fault segmetation growing along the strike,the anticline can be formed at the position where the fault segments are connected or overlapped.At the same time,in the process of the fault vertical segmentation growing,the anticline can also be formed as the result of the difference of the rheological characteristics of surrounding rocks.These two types of fault-related anticlines can form favorable traps for oil and gas enrichment.