BZ25-1油田沙二段储层氮气、水交替注入室内实验研究

Indoor experimental research on N_2-alternating-water injection of BZ25-1 oilfield

BZ25-1油田沙二段储层经过长期注水开发,已进入高含水开发后期,水驱采收率偏低。通过分析气水交替注入提高采收率的作用机理,在物模实验研究的基础上提出采用N2水交替注入实现BZ25-1油田沙二段储层的挖潜控水。实验结果表明,N2水交替注入采收率较单纯水驱采收率提高3.63%。受渗透率非均质性的影响,注入水主要进入高渗透层驱油,并很快从高渗透层突破且含水上升快。注N2综合采收率较水驱略低,主要是N2从高渗透层突破后,降低了低渗透层的驱油效率。N2水交替驱在一定程度上能改善流度比,降低渗透率非均质性带来的影响,增加驱油效率。

After brag-time water-flooding exploitation, BZ25-1 oilfieht has entered the later stage of high-water-cu! exploitation and the water drive recovery efficiency is rather low. Based on the analysis of the oil reenvery enhance- ment mechanism by means of water-alternating-gas injection, and physical model experiment, this paper put for- ward the method of adopting N2-alternating-water injection for achieving high-water-cut production of BZ25-1 oil- fiehl. The experimental results show that, compared with the pure water-flooding oil recovery, the oil recovery real- ized by N2-ahernating-water injection may increase by 3.63%. Due to the influence of anisotropy of permeability, the injected water mainly enters the oil layer with high permeability and quickly breaks through the oil layer with high permeability, and the water cut rises rapidly. Because the N2 reduces the oil displacement efficiency of low permeable formation when it breaks through the oil layer with high permeability, the recovery efficiency after injec- ting the N2 is lower than injecting water. N2-ahernating-water flooding can improve mobility ratio, reduce the effects of heterogeneity of the permeability and increase oil displacement efficiency.