柴达木盆地与莺歌海盆地超压体系、油气成藏特征对比分析

Comparison of Overpressure System and Hydrocarbon Accumulation between Qaidam Basin and Yinggehai Basin

柴达木盆地和莺歌海盆地都在一定深度和区域上普遍存在异常高压现象。通过对这2个盆地沉积和构造演化、超压特征及成因和油气成藏史3个方面的对比分析,阐述了盆地演化过程中油气运聚与压力系统演化之间的相互关系。研究表明,2个盆地的沉积演化都经历了沉积物快速堆积,形成了巨厚的烃源层,并且对应于盆地超压发育的主要层位;超压体系的分布受各沉积时期沉积中心和构造作用控制明显,超压顶界面基本呈现出中间高、向盆地边缘降低以至消失的特点。油气主要富集在超压顶界面附近及其上的常压系统内,在封闭和保存条件较好的深部也具有较大潜力。超压体系为油气运移提供动力条件,并在一定地质背景下控制着油气分布,同时油气成藏过程对盆地超压系统的产生和演化也具有重要影响。

Abnormal overpressures exist widely in a certain area and depth in the basins of Qaidam basin and Yinggehai basin. Sedimentary and tectonic evolution, feature and origin of overpressure, and hydrocarbon accumulatiofi history are compared to illustrate the relationship between overpressure system and hydrocarbon accumulation in the process of basin evolution. Results show that two basins accepted the rapid deposi- tion of sediments and formed the thick source rock, which is corresponding to the main layer with overpressure system. Depocenter and tectonism at the deposition stage strictly control the distribution of overpressure, and the top interface of overpressure generally represents a trend of being higher in depocenter, gradually decreasing to basin edge, and even disappearing. Hydrocarbons occur near the interface of overpres- sure and normal pressure system,and it also has a great potential in an enclosed and well preserved deep area. Overpressures provide the force for driving hydrocarbon migration and control the distribution of reservoir in a certain background. The process of hydrocarbon accumulation can seriously influence the formation and evolution of overpressure system.