砂岩侵入体系模拟及形成机理分析

Sand injectite simulation and formation mechanism analysis

砂岩侵入体系是一种普遍的地质现象,近些年来越来越受到地学界的重视,但对其形成机理探讨较少。作者及研究团队通过设计一套室内模拟实验装置,来简化模拟3层地层结构中砂岩侵入体系的形成和演化过程。在之前模拟实验(实验变量为顶层沉积物的厚度、进水管的结构)结果的基础上,进一步考察了地形坡度对实验结果的影响,并对砂岩侵入体系的形成机理进行了分析。实验过程中,共观察到7种不同形态不同样式的管道,并对实验过程中压力变化进行了测试。对实验结果分析认为:盖层厚度越大,压力下降的速度越慢,越不利于压力的释放;随着实验的继续进行,砂岩侵入体最终会转化为砂岩喷出体并喷出地表;不稳定的地形有利于触发疏松沉积物发生变形。实验表明,超压是砂岩侵入体发生的最重要条件之一,沉积盆地中的压实不均衡和生烃作用是可独立产生大规模超压的2种主要机制。

Soft sediment deformation is a common geological phenomenon,which has been focused on these years in the field of geosciences,but less study is on the formation mechanism of soft sediment de_formation.A set of laboratory simulation device is designed to simulate the formation and evolution of sand injectites in a simplified three layers model in this paper.On the basis of the former simulation experi_ments,which only took account of the thickness of the overlying coarse sediment layer and the configura_tion of inlet pipes,the slope angles of terrain are examined to test the influence of three main variables on the structures formed during fluidization.Also,the formation mechanism is discussed.7 different shape pipes in different types are observed and the pressures are tested during the experiments.The results show that the thicker the overlying layer is,the slower the pressure drops;the sand injectites finally will erupt out of the surface and turn out to be sand extrusions;unstable terrain is conducive to trigger the deforma_tion of soft sediments.It is showed that overpressure is one of the most important conditions.Compaction disequilibrium and hydrocarbon generation are the two main independent controlling factors of different phases for the development and evolution of overpressure in sedimentary basins.