Research Institute of Unconventional Petroleum Science and Technology, China University of Petroleum(Beijing)
由于致密油藏的孔喉结构复杂,开发困难,常规表面活性剂容易被岩石吸附而无法深入细小孔喉,在苛刻油藏中不能满足强化采油的使用要求,因此提高自发渗吸采收率效果不明显。本文研究并评价了一种纳米微乳液驱油剂体系,通过界面张力实验和润湿反转实验揭示了其驱油机理,通过自发渗吸实验验证了提高采收率效果。结果表明,0.3%浓度的纳米微乳液体系粒径尺寸为10 nm,界面张力为3.56 mN/m,能够将油湿石英片表面的润湿性(130°)反转为水湿表面(11°),具有良好的润湿反转能力。0.3%浓度的纳米微乳液自发渗吸采收率高达43.2%,约为水的2.5倍,提高自发渗吸采收率效果显著。纳米微乳液在致密油藏自发渗吸驱油过程中通过降低界面张力,改变润湿性提高自发渗吸采收率,其中,润湿性的改变是提高致密油藏自发渗吸采收率的主要机理。
Due to the complex pore-throat structure and difficult development of tight reservoirs, conventional surfactants are easy to be adsorbed by rocks and cannot penetrate into the fine pore throat, which cannot meet the application requirements of enhanced oil recovery in harsh reservoirs. Therefore, the effect of improving spontaneous imbibition recovery is not obvious. In this paper, a nanoparticle microemulsion oil displacement agent system was studied and evaluated. The mechanism of oil displacement was revealed by interfacial tension test and wetting inversion test. The effect of EOR was verified by spontaneous imbibition test. The results show that the nano-emulsion system with 0.3% concentration has a particle size of 10 nm and an interfacial tension of 3.56 mN/m, which can reverse the wettability of oil-wet quartz surface (130°) to water-wet surface (11°), and has a good wetting inversion ability. The spontaneous imbibition recovery rate of 0.3% nano emulsion is 43.2%, which is about 2.5 times that of water. The spontaneous imbibition recovery rate is significantly improved. Nano-microemulsion can improve spontaneous imbibition recovery by reducing interfacial tension and changing wettability in the process of oil displacement in tight oil reservoirs. Among them, the change of wettability is the main mechanism to improve spontaneous imbibition recovery in tight oil reservoirs.