地质过程中的跷跷板运动及对油气成藏的影响

Seesaw Movements in Geological Process and Its Effect on Hydrocarbon Accumulation

跷跷板运动是一种地质过程中由于应力场的变化而导致同一地区在不同地质时期发生交替差异升降的运动形式。跷跷板运动对烃源岩的生排烃、储层的发育和改造、油气的运移和保存等油气成藏条件有重要的控制作用,而构造平衡带是跷跷板运动过程中处于相对稳定的地区,也是最有利于油气保存的部位。为了定量研究构造平衡带分布范围的确定方法,本文以塔里木盆地为例,用地层平均剥蚀厚度表征构造平衡带,通过统计不同目的层地层平均剥蚀厚度与探井日产量的关系发现:平均剥蚀厚度在50—250m的地区,最有利于油气藏的保存,而平均剥蚀厚度太大或太小时都对油气成藏不利。在恢复不同成藏期地层平均剥蚀厚度的基础上,识别出了不同成藏期构造平衡带的分布范围,对塔里木盆地台盆区的油气勘探具有一定的指导作用。

Seesaw movement is the alternatively differential elevation and subsidence movement that happened under different stress field in the same place during geologic history. The seesaw movement controls the multiple hydrocarbon expulsion of source rocks, the development and reconstruction of reservoir quality, the migration and preservation of hydrocarbon. The kinematic equilibrium belt is the relatively stable areas and also favorable for hydrocarbon accumulation during seesaw movements. In order to identify quantatively the boundary of kinematic equilibrium belt, in this paper, Tarim Basin is taken as an example to identify kinematic equilibrium belt using average erosion thickness. After statistic analyzing the relation between average erosion thickness and daily production of exploration wells of main target layers, it is found that the average erosion thickness between 50m and 200m is the most favorable range for hydrocarbon accumulation. When the average erosion thickness is too large or too small, it is not favorable for hydrocarbon accumulation. On the basis of recovering the average erosion thickness, the kinematic equilibrium belt of Tarim basin is identified in different hydrocarbon accumulation periods. Most of the hydrocarbon occurrence is closely related to kinematic equilibrium belt.