渤海湾盆地盖层对天然气富集的影响初探

The Influence of Cap Rocks on the Accumulation and Distribution of Natural Gas in the Bohai Bay Basin

根据渤海湾盆地部分天然气藏的统计资料,分析了盖层的空间展布、厚度和类型对其封闭能力和天然气分布的影响,提出了盖层临界厚度的概念。研究认为,不同地区或同一地区不同层系天然气富集程度的差异主要是由于盖层的封闭效应造成的。气藏直接盖层厚度与天然气富集程度有一定关系。对于成藏条件相似的众多天然气藏,直接盖层厚度与气柱高度及储量之间不是简单的直线关系,而是存在一个变化范围。

Based on the statistical data from a large number of gas pools of the Bohai Bay petroliferous basin, the author discusses the influence of cap rocks on the accumulation and distribution of nat ural gas and the relationship between the thickness of direct cap rocks and the height of the hy-drocarbon column of a gas pool and puts forward the concept of critic cap rock thickness. The difference in natural gas abundance in different areas or in different formations of the same area is mainly the result of the sealing effect of the cap rocks, and the height of the hydrocarbon column of a gas pool is not simply in direct proportion to the thickness of the cap rocks. Among many oil and gas pools in a given area where there are similar reservoir-forming geological conditions, the hydrocarbon column height is only in direct proportion to the minimum thickness, i. e. the critic thickness of the cap rocks, and in most cases the height of the hydrocarbon column in an oil or gas pool is much greater than the critic thickness of the cap rocks.