裂陷盆地断层的形成和演化——目标砂箱模拟实验与认识  

Fault Formation and Evolution in Rift Basins——Sandbox Modeling and Cognition

作　　者：童亨茂[1] 孟令箭[1] 蔡东升 吴永平 李绪深 刘明全 

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]中海石油湛江分公司,广东湛江524057 [3]中国石油大港分公司,天津300280

出　　处：《地质学报》2009年第6期759-774,共16页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40772086);CNPC油气勘探超前共性科技项目(编号07-01C-01-04)资助成果

摘　　要：断层的分布、活动和演化是裂陷盆地构造研究的核心,也是其油气勘探的关键。大量高精度的三维地震资料表明裂陷盆地内断层分布组合十分复杂,无法用经典构造地质学理论——Anderson模式作出合理的解释,现有的模式(叠加模式和斜向伸展模式等)也还没有很好地揭示裂陷盆地断层复杂性的实质和断层形成和演化的内在规律。本文以渤海湾盆地张巨河构造带和北部湾盆地涠西南凹陷两个有高精度三维地震资料覆盖、断层分布与组合十分复杂并富含油气的典型裂陷盆地区为原形,进行了目标砂箱模拟实验,再现了目标区构造的基本特征。砂箱实验所揭示裂陷盆地断裂系统的基本特征是①基底先存构造所控制的主要断层构成了盆地断裂系统的基本格架。②断层的形成与演化决定于基底先存断裂的取向、区域伸展方向及伸展量。首先形成的是有刚性边界基底先存断裂控制的断层。其次,形成的是薄弱带基底先存断裂控制的断层。继而,形成的是小型基底先存断裂控制的断层。最后,在远离基底先存构造的区域,形成与伸展方向垂直的新生断层。③伸展作用早期,断层的方位主要决定于基底先存断裂的方位。随着伸展量的增大,受伸展方向的影响越来越大,晚期形成的断层常反映区域伸展作用方向。④不协调递进伸展变形过程是导致裂陷盆地复杂断层体系的根本原因。上述砂箱模拟实验揭示的裂陷盆地在不协调性伸展作用下断层的形成与演化规律可以利用"不协调性准则"从理论上给予解释,表明在裂陷盆地中具有普遍意义。Distribution, activity and evolution of faults are the core of structure research, and also the key problems for oil and gas exploration of rift basins. A large number of high-precision 3-D seismic data revealed that the fault distribution and assemblage of rift basins are very complicated and the classic structural theory fails to give a reasonable explanation to the Anderson＇s model. The complexity and evolution and rule of faults in rift basins can not be revealed by the existing multi-phase superposition model and oblique extension model. Taken the Zhangiuhe structural belt in Bohai Bay Basin and Weixinan Sag of Beibuwan Basin as trial areas, combined with full-covering high-precision 3-D seismic data, complicated fault distribution and assemblage in two typical oil-rich rift basin regions, this research conducted objective sandbox modeling experiment, and this shows the basic structural characteristics of the study areas. The basic characteristics of fault system in rift basin revealed by sandbox modeling are. 1） The faults controlled by basement pre-existing fabric constitute the basic framework of basin fault system; 2） the fault formation and evolution are controlled by basement pre-existing fabric trend, regional extension direction and extension amount. The firstly formed faults are those controlled by rigid-border basement pre-existing fault. Then the faults controlled by weak-zone basement pre-existing fault formed. Consequently, the fault controlled by small basement pre-existing fabric formed. Finally, faults perpendicular to regional extension direction begin to form in the area far away from the basement preexisting fabric. 3） At early stage of extension, fault strike is mainly controlled by the trend oI basement pre-existing fabric. With the increasing of extension amount, the affection of extensional direction become stronger, and the faults formed in late extension stage can usually reflect regional extensional direction. 4）Uncoordinated progressive extension process is the root cause

关 键 词：不协调伸展 裂陷盆地 砂箱实验 先存断裂 “不协调性准则” 

分 类 号：P618.13[天文地球—矿床学]