叠合盆地构造活动枢纽部位形成及其控油气原理——以塔里木盆地为例

The Formation of Structural Pivot and Its Controlling on the Accumulation and Distribution of Oil and Gas in the Superimposed Basin:An Example from the Tarim Basin

叠合盆地所经历的多期升降运动以及周缘的造山作用,形成了一些构造活动的枢纽部位,其特点是有构造活动但又相对稳定。枢纽的形成与隆起、斜坡的形成有密切的关系,根据古隆起与枢纽带的发育关系,把枢纽带分为两类,残余-活动古隆起型枢纽带(塔北、塔东、巴楚型)和稳定古隆起型(塔中型)枢纽带。枢纽带具有有利的油气成藏条件,相对凹陷而言,构造活动枢纽部位处在比较高的部位,正是油气运移的指向区;而相对于翘起的高部位来说,构造活动枢纽部位又处在相对较低的部位,极有利于油气藏的保存。碳酸盐岩层系的构造活动枢纽部位主要发育潜山风化壳孔洞型、裂缝型储层,多发育复式油气聚集。通过精细的构造演化的恢复和沉积厚度、剥蚀厚度等的计算,可以识别枢纽带,研究枢纽带对叠合盆地的油气勘探寻找有利钻探目标具有重要的意义。

Superimposed basin which had experienced multi-stage elevating and mountain-making movements, yielded some tectonic active pivot characterized by tectonic activity but remained relatively stable. The formation of the pivot is closely related to the evolution of uplift and slopes. In the light of the development correlation between the pivot and the paleo-uplift, pivot can be divided into two types： residual-active paleo-uplift pivot （e. g. Tadong and Bachu uplift） and stable paleo-uplifl pivot （Tazhong uplift）. The pivot is a favorable condition for hydrocarbon accumulation. Compared with the depression, the structural pivot positions are the pointing areas of petroleum migration because that is higher than the sags as the source of oil and gas. Alternatively, they are also the favorable positions of petroleum preservation relative to the high parts of the warps that are easily eroded. Buried-hill weathering crust cavity and cracks under unconformity boundary are the main reservoir in the pivot belt, and also have strueture-lithologic trap in the overlying strata. The pivot belt formed a complex petroleum accumulation region if hydrocarbon accumulated in the traps. At present, the pivot belt can be identified by recovery of delicate structural evolution and calculation of sedimentation or denudation thickness. Hence, the detailed study of the pivot belt in the superimposed basin is a key to explore oil and gas.