库车坳陷西段盐构造形成主控因素

Major factors controlling salt structures in western Kuqa Depression,Tarim Basin

库车坳陷西段发育丰富的盐构造,其形成机制较为复杂,在不同发育阶段具有不同的主控因素。结合库车坳陷盐岩及围岩力学参数测量结果,运用薄膜理论建立表征库车坳陷西段盐层与上覆地层相互关系的弹-塑性层模型,并利用该模型对不同阶段影响盐构造发育的主要因素进行了对比分析。在盐构造发育的早期阶段,沉积差异负载是控制盐体运动和盐构造发育的主要因素,但当盐体隆起一定幅度后,浮力的影响程度就会超过沉积差异负载作用,上覆地层受挤压应力作用而形成的褶皱作用对盐体运动的影响也会明显超过浮力作用。因此,目前影响库车坳陷西段盐构造发育的最主要因素是挤压应力,其次为浮力,沉积差异负载作用影响最小。

Salt structures are predominant in the western Kuqa Depression, and the mechanisms of salt flowage and deformation are complex and dominated by various factors during different evolution stages. Based on the mechanical properties of rock salt and overburden in the depression, an elastic-ductile bed model is established using the thin film theory to show the relationship of the rock salt and the overburden. The comparative analysis of the major factors controlling the salt flowage of different stages shows that differential loading was the major factor controlling the salt flowage and structure development in the early stage. Then, buoyancy exerted bigger influences than differential loading when salt pillows grew to a certain extent. Besides, the overburden flexural buckling resulted from compression stress played a greater role in the salt movement than buoyancy. The most important factor driving the salt flow is compression stress, followed by buoyancy and differential loading, in turn.