海上油田多轮次自生CO_(2)泡沫调剖效果评价研究

Evaluation on multicycle profile control effect of in-situ carbon dioxide foam in offshore oilfield

目的自生CO_(2)泡沫体系在多轮次调剖中增油效果逐渐减弱,亟需分析该体系的效果递减规律。方法结合渤海油田的纵向非均质储层特征,利用大尺寸可视化平板物理模型和数值模拟模型,研究了多轮次自生CO_(2)泡沫调剖的规律,尝试了延长体系的反应时间以增加其作用距离。结果水驱仅能波及纵向非均质模型下部的高渗层,未启动上部的低渗层;自生CO_(2)泡沫调剖体系可进入高渗层形成封堵,启动低渗层,第一轮调剖提高采收率值超过10%,但是随着调剖轮次的增加,体系未能进入储层更深的位置,提高采收率值不断降低,至第4轮调剖时不足1%;高渗层的剩余油在两翼部位富集,低渗层的剩余油分布均匀。结论自生CO_(2)泡沫体系的作用距离有限,调剖轮次增加却未能作用于更深储层,延长反应时间以增加其作用距离,多轮次调剖的效果更好,采收率总提高值为3.66%。

Objective The oil-increasing effect of in-situ carbon dioxide foam was gradually weakened in multicycle profile control.It was urgent to analyze the decreasing law of the system.Methods The paper studied the law of in-situ carbon dioxide foam profile control with multiple rounds by using large scale visual plate physical model and numerical simulation model which combined with the characteristics of vertical heterogeneity in Bohai oilfield reservoir.And an attempt was made to extend the reaction time of the system to increase its action distance.Results The research showed that water flooding could only sweep the high permeability layer in the lower part of the reservoir,but it could not sweep the low permeability layer in the upper part.The in-situ carbon dioxide foam profile control system could entered the high permeability layer to form plugging and started the low permeability layer,which improved oil recovery more than 10%in the first cycle of profile control.But the system could not enter the deeper location with the profile control rounds increased.The enhanced oil recovery value constantly decreased,which was less than 1%by the fourth cycle of profile control.The remaining oil of the high permeability layer was mainly distributed in the two wings and the remaining oil of the low permeability layer was evenly distributed.Conclusions The effective distance of in-situ carbon dioxide foam system was short which was failed to work in deeper reservoir with the profile control rounds increased.The effect of multicycle profile control was better by prolonging the reaction time to increase its effective distance,which increased the total enhanced oil recovery value by 3.66%.