特低渗透率储层水驱油规律实验研究

Experimental study on waterflooding in ultra-low permeability reservoirs

为研究特低渗透率储层水驱油规律,文中选取鄂尔多斯盆地3个井区的57块岩心进行水驱油实验分析,并研究了特低渗透率条件下水驱油效率与渗透率大小、注入倍数、注水压力等参数的关系。岩心主要为特低渗透率岩心,渗透率大小为研究区长4+5储层、长6储层和长8储层渗透率范围。实验结果表明:驱油效率随着渗透率增加而提高,而且在渗透率低值阶段,驱油效率提高更快;随着注水倍数的增加,驱油效率提高,直到含水100%为止,但含水越高,增加幅度越小;在同样的水驱速度下,渗透率越大,驱油效率越高,如果水驱速度不同,采收率会产生波动,但存在一个最佳驱油速度,且渗透率越大,最佳驱油速度变大;随着注水压力增加,无水期驱油效率总体呈下降趋势,但含水期驱油效率随着注水压力增加而逐渐提高,当达到一个最佳注水压力后,驱油效率又呈下降趋势;层内非均质性越强,驱油效率越低。

In order to study the rule of waterflooding in ultra-low permeability reservoirs, 57 pieces of cores from 3 well fields in Ordos Basin are selected to carry out experiment on waterflooding, and the relations of waterflooding efficiency with permeability, water injection multiple, water injection pressure and so on are studied. The selected cores mainly are ultra-low permeability that covers with Chang 4＋5, Chang 6 and Chang 8 reservoirs. The results indicate that waterflooding efficiency increases with permeability increasing and quickly increases in lower permeability reach. It is the same situation with water injection multiple increasing, but there is lower increasing range in stage of high water-cut and no increasing until water-cut to 100%. At the same waterflooding speed, the higher the permeability is, the higher the waterflooding efficiency will be, but the waterflooding efficiency will be altering when at different waterflooding speed. There exists a best speed, and the higher the permeability is, the higher the speed is. The waterflooding efficiency generally decreases in water-free stage and increases in water-bearing stage with water injection pressure increasing and it gradually decreases when the layer gets a best pressure. The stronger the heterogeneity is, the lower the waterflooding efficiency will be.