Abstract: Field experiments of domestic and overseas studies show that WAG flooding can further improve the oil recovery by 5%~10%. It can be used as an economical and effective way to improve oil recovery in the tertiary phase.With the help of laboratory displacement experiments,improved simulated cores,and setting up the experimental control group, a new experimental idea is put forward, and the mechanism of WAG flooding for enhancing oil recovery is revealed and clarified. The experimental results show that WAG flooding can slow the gas channeling and change the unfavorable water⁃oil ratio. Injecting⁃gas enhances the exchange, diffusion and imbibition of three⁃phase molecules. After alternating injection of water and gas, water drive seals high permeability zone, gas drive sweeps tiny pores along with the effect of gravity differentiation. The displacement process is a dynamic process in which the state of water binding in pores is broken constantly, and the large pores are plugged alternately. The breakthrough effect of injection gas on fluid is weakened, and the water absorption profile is improved, which prolongs the water breakthrough time of oil well and improves the oil recovery. For the reservoir with serious heterogeneity, the dynamic plugging effect produced by alternating water injection can further improve the oil displacement effect of WAG flooding.

Key words: WAG, Mobility ratio, EOR, Mechanism of action

摘要： 国内外矿场试验表明，WAG驱可进一步提高原油采收率5%~10%，是三次采油阶段经济、有效提高采收率的驱替方式。借助室内驱替实验，利用改进的模拟岩心，通过设置实验对照组，揭示和明确了WAG驱提高采收率的作用机理。结果表明，WAG驱可减缓气窜，改变不利的水油流度比。注入气加强了三相分子之间的交换、扩散、渗吸及突破作用。水气交替注入后水驱封堵高渗带，气驱驱扫微小孔隙，并伴随重力分异效果，且驱替过程是水在孔隙中的缚存状态不断打破、不断重建的一个动态过程；注入水交替封堵大孔隙，削弱了注入气对流体的突破作用，改善了吸水剖面，延长油井见水时间，有助于提高原油采收率。对于非均质性严重的储层，交替注水产生的动态封堵可进一步提高WAG驱油效果。

关键词: WAG驱, 流度比, 提高采收率, 作用机理