近混相状态下油/水/烃气三相流的相对渗透率研究

Study on relative permeability of oil/water/hydrocarbon gas three-phase flow under near-mixed-phase condition

油田采出气驱效果显着,但并非所有油藏都适用.文中研究了油田采出气回注后混相状态及三相流中相对渗透率变化规律.研究结果表明:(1)地层条件下烃气驱油状态为近混相驱.烃气驱油过程中,驱替压力越高,气窜时间越晚;驱替压力小于混相压力时,驱替压力越高,阶段采收率越低;驱替压力大于混相压力时,驱替压力越高,阶段采收率越高.(2)对比油气水三相等渗透率发现,该地层条件(粉砂岩-中砂岩)烃气近混相驱油状态下,油气水三相流中‘K_(ro)>K_(rw)>K_(rg)’.(3)近混相状态下,分析油气水三相渗透率与饱和度相关性发现:注入烃气能够有效提高地层中残余油相渗透率,油相渗透率与含油饱和度存在线性相关性.当含气饱和度S_(g)>20%后,残余油渗透率几乎不受含气饱和度影响.此外,对比不同含气饱和度下油相渗透率及其饱和度变化关系发现:含气饱和度增高,油相渗透率受含油饱和度影响变大.水相渗透率与含水饱和度呈线性相关性.气相渗透率与含气饱和度线性相关性较差.(4)油相渗透率实验值与Corey模型模拟值之间平均百分比相对误差为2.43%.Corey预测模型能够有效预测地层条件下该油藏中烃气/油/水三相流中油相渗透率.

Oilfield recovery gas drive is effective,but not applicable to all reservoirs.In this paper,the mixed-phase state and relative permeability change law of three-phase flow after oilfield gas recovery and reinjection are investigated.The results show that.(1)Under the formation conditions,the hydrocarbon gas drive state is close to the mixed-phase drive.In the process of hydrocarbon gas drive,the higher the repulsion pressure,the later the gas emission;when the repulsion pressure is smaller than the mixed-phase pressure,the higher the repulsion pressure,the lower the stage recovery;when the repulsion pressure is larger than the mixed-phase pressure,the higher the repulsion pressure,the higher the stage recovery.(2)Comparing the oil-gas-water three-phase equivalence permeability,we found that‘K_(ro)>K_(rw)>K_(rg)’in the oil-gas-water three-phase flow under the hydrocarbon near-mixed-phase drive state in this formation condition(siltstone-medium sandstone).(3)The correlation between oil-gas-water three-phase permeability and saturation is found in the near-mixed-phase state:the injection of hydrocarbon gas can effectively increase the permeability of the remaining oil phase in the formation,and there is a linear correlation between the oil-phase permeability and the oil-bearing saturation.After the gas-bearing saturation S g>20%,the permeability of the remaining oil phase is almost not affected by the gas-bearing saturation.In addition,comparing the oil-phase permeability under different gas-bearing saturations with its saturation variation,it is found that the oil-phase permeability is more influenced by the gas-bearing saturation when the gas-bearing saturation increases.The water-phase permeability is linearly related to the water-bearing saturation.The linear correlation between gas-phase permeability and gas-bearing saturation is lower.(4)The average relative error percentage between the experimental values of oil-phase permeability and the simulated values of Corey model is 2.43%.the Corey prediction model can effectively predict the oil-phase permeability of the reservoir under the formation conditions with oil-gas/oil/water three-phase flow.