利用CT技术的超低渗岩心油水驱替特征研究

Use of CT Technology to Investigate Water Flooding in Ultra-low Permeability Sandstone

超低渗透油藏cT扫描技术能够观察水驱油过程中不同时刻各流体饱和度在岩心中的分布，以及驱替后残余油分布。通过CT扫描技术在模拟超低渗透储层水驱油过程中，测定不同时刻岩心流体饱和度，观察岩心内部油水两相饱和度变化和分布，分析水驱特征。发现在致密且孔喉分布相对均匀及毛管压力显著的岩心中，水相饱和度前缘剖面变化十分陡峭，岩心内部水相饱和度以类似“活塞”式向前驱替。水相突破后岩心内各断面上饱和度分布不再发生较大变化，岩心出口端面不再产油，驱替相水与被驱替相油之间油水共渗区极其狭窄。对于超低渗透岩心，产生“活塞”式驱替的临界端点流度比为0．02955～0．21135。

CT scanning technology can directly observe the distributions of fluids saturation in the core at differ- ent times during the experimental displacement and the remaining oil distribution after the displacement. And it can provide the direct evidence for percolation mechanism study. CT scanning technology was used to calculate the flu- ids saturation in the ultra-low permeability cores at different times, the water-oil saturation distribution and variation inside the cores during the water-oil displacement were observed. It is found that in the relatively tight and homoge- neous cores with strong capillary pressure effect, the water-oil displacement front is fairly abrupt and the water satu- ration moves forward to the outlet end in a “traveling wave” along with the water continually injected from the inlet end. After the injecting water breaking through, the water saturation in each section didn＇ t change evidently mean- while no more oil produced. The oil-water two-phase region is extremely narrow, which is derived from CT pic- tures. For the ultra-low permeability cores, the critical end-point mobility ratio causing the “traveling” displace- ment is inthe range of O. 029 55 to O. 211 35.