凝析气藏水气交替注入数值模拟研究

A STUDY OF NUMERICAL SIMULATION OF WATER ALTERNATING GAS INJECTION FOR CONDENSATE GAS RESERVOIRS

水气交替注入 (WAG)是两种传统采油方法的综合 ,是二次采油和三次采油中颇具潜力的一种方法。由于高粘度的水趋向于在高渗层形成屏蔽 ,而使气体进入油气藏基岩层或低渗层 ,提高了气体的驱扫效率。通过层状二维剖面模型的模拟研究 ,证明了在层状凝析气藏中水气交替注入的采收率比循环注气的采收率高。根据全组分模拟器模拟结果可知 :水气比、不同的注入段塞、渗透率和残余气饱和度对凝析油采收率的影响非常明显 ;而注入次序、注入水的密度和粘度、高渗层的不同位置、相对渗透率和毛细管压力对凝析油采收率的影响较小。柯克亚凝析气藏具有保压开采的条件 ,采用水气交替注入比循环注气的凝析油采出程度高 1.90 %～ 2 .75 %。

The water alternating gas (WAG) injection is a method by combining two traditional oil producing methods—water flooding and gas flooding,which has a considerable potential in secondary and tertiary oil recovery.Because the high viscosity water tends to form a shield in high permeability formations to make the gas enter into the basement rocks or low permeability formations of oil and gas pools,the gas sweepout efficiency is raised.The recovery rate by WAG injection in stratified condensate gas reservoirs is higher than that by cyclic gas injection according to the simulation study by use of stratified 2-D sectional model.In the light of the simulation results by use of full composition simulator,it is known that the water/gas ratio,different injection slug,permeability ratio and residual gas saturation have an obvious effect on the condensate recovery;but the injection order,viscosity and density of injected water,position of high permeability zone,relative permeability and capillary pressure have less effect on condensate recovery.Kekeya condensate gas reservoir has pressure maintenance operation condition,the recovery percent of the condensate by WAG injection increasing by 1.90%～2.75% as compared with that by cyclic gas injection.