断裂带对油气运聚控制作用探讨:以塔里木台盆区阿克库勒凸起与塔中低隆为例

A discussion on the impact of fault belt on the oil migration:A case study of Akekule uplift and Tazhong uplift in Tarim Basin

将断裂带分作高渗带和低渗带,利用逾渗数学模型模拟不同渗透性断裂带油气运移特征。不管将断裂考虑为低渗带还是高渗带,断裂都对油气运移有阻挡、汇聚作用。凡是在断裂投影范围内的运移路径都汇聚为一条运移路径,也就是说,断裂控制了其投影范围内的油气运移,增强了油气运移的效率。高渗带断裂和低渗带断裂存在一定的差异性,即:油气运移路径抵达高渗带时,直接进入断裂带内部,且沿着断裂带的上缘发生运移;而油气运移抵达低渗带时,运移路径并不进入断裂带内部,而是沿着断裂带下缘外部汇聚并向上运移。进一步的研究分析表明,在多个断裂带并存的条件下,塔中隆起油气主要聚集于塔中Ⅱ号带以北,且各块体分散聚集,油气分布规律复杂。而阿克库勒地区,只要断层是油气的通道,最终油气都要在高点或封堵好的圈闭聚集。但与鼻隆大角度相交的断层具有阻挡和截流聚集的特点。

In this article, we consider that the fault belts can be divided into two types： high permeability belt and low permeability belt, and simulate the oil migration in belts by percolation model. By the simulation result, the fault belt will both cumulate and prevent the oil migration, no matter the fault is of high permeability or tow permeability. However, the oil migration pathways will converge into one pathway in the range of fault belt projection. This means the efficiency of oil migration will be enhanced. In addition, there are still some differences in oil migration between high permeabi}ity and low permeability fault belt. When the oil reaches the high permeability fault belt, the oil will enter the belt and migrate along the upper edge of the belt; but when the oil reaches low permeability fault belt, the oil cannot enter the belt and will migrate along the lower edge. Based on the simulation above, the case study simulation shows that the oil mainly converge on the fault Tazhong Ⅱl and the distribution of oil is complex. In Akekule area, the oil will finally accumulate on the top plays and the fault cut off the nose-shaped uplift preventing the oil accumulation.