斜向挤压叠加变形的构造解析——以四川威远地区为例

Structural analysis of superimposed deformation under oblique compression:A case study of the Weiyuan area,Sichuan Province

威远地区位于四川盆地西南部,其构造主体威远背斜属于大型穹隆状背斜构造,经历了多期构造运动的叠加变形,前人对威远背斜的形成过程与机制认识存在很大争议,无法满足油气精细勘探和高效开发的需要。本文通过地震资料的构造解析,确定威远背斜主体是在基底先存构造(NE向基底古隆起)的条件下,在燕山期近NS向斜向挤压作用过程中形成的,喜山期近EW向斜向挤压作用对其构造变形也有一定的贡献。按此认识设计了砂箱模拟实验,实验结果在平面和剖面上很好地再现了威远背斜的构造特征,表明了上述认识的合理性。这些认识不仅能为威远地区油气的勘探开发提供指导,还可以为相似区域的构造形成演化机制分析提供借鉴。

The Weiyuan area is located in the southwest of the Sichuan basin.Its main structure,the Weiyuan anticline,is a large dome-shaped anticline and has experienced the superimposed deformation by multiple tectonic movements.The previous understanding of the formation process and mechanism of the Weiyuan anticline is controversial,which cannot meet the needs of fine exploration and efficient development of oil and gas.In this paper,through the structural analysis of seismic data,it is determined that the main body of the Weiyuan anticline was formed under the condition of basement pre-existing structure(NE-trending basement paleo-uplift)in the process of nearly NS oblique compression in Yanshan epoch,and the nearly NS oblique compression in Himalayan epoch also contributed to its structural deformation.According to this understanding,the sandbox modeling experiment was designed,and the experimental results well reproduced the structural characteristics of the Weiyuan anticline on the plane and profile,indicating the rationality of the above understanding.These understandings can not only guide the exploration and development of oil and gas in the Weiyuan gas field but also provide a reference for the formation and evolution mechanism analysis in similar areas.