稠油油藏氮气辅助蒸汽驱室内实验

Laboratory experiment of nitrogen assisted steam flooding in heavy oil reservoir

针对稠油油藏蒸汽驱进入开发中后期高温蒸汽超覆现象严重、开发效果变差的问题,依据蒸汽驱物理模拟相似准则,利用高温高压二维比例物理模型,开展了单纯蒸汽驱和氮气辅助蒸汽驱物理模拟实验。通过实验直观分析了蒸汽超覆温度场特征,探讨了氮气对蒸汽波及效率、驱替效率和热损失的影响。实验结果表明:单纯蒸汽驱时,蒸汽波及范围主要集中在油层顶部,剩余油主要集中在油层底部,蒸汽波及效率57.3%;注氮气后,蒸汽波及范围明显扩大,蒸汽超覆现象得到抑制,蒸汽波及效率65.8%,比单纯蒸汽驱提高了8.5百分点,而驱替效率提高了1.5百分点,氮气提高波及效率是蒸汽驱增产的主要因素。氮气辅助蒸汽驱能够有效降低生产井含水率,较单纯蒸汽驱可提高采收率6.7百分点;氮气辅助蒸汽驱降低了蒸汽热损失,较单纯蒸汽驱热损失降低了1.6×10^4 J。

In order to solve the problems of high temperature steam overlap and poor development effect in heavy oil reservoir during the middle and late stage of steam flooding,the physical simulation experiments of pure steam flooding and nitrogen-assisted steam flooding were carried out by using two-dimensional proportional physical model of high temperature and high pressure based on similarity criteria.Through experiments,the characteristics of temperature field of steam overlap are analyzed,and the effects of nitrogen on sweep efficiency,displacement efficiency and heat loss of steam are discussed.The experimental results show that the steam sweep range of pure steam flooding mainly concentrates on the top of the reservoir and the remaining oil mainly concentrates on the bottom of the reservoir,with the steam sweep efficiency of 57.3%.After nitrogen injection,the scope of steam sweep is obviously enlarged and the phenomenon of steam overlap is restrained,and the sweep efficiency of steam is 65.8%.Compared with pure steam flooding,the sweep efficiency is increased by 8.5%and the displacement efficiency is increased by 1.5%.Increasing sweep efficiency of nitrogen gas is the main factor for steam flooding to increase production.Nitrogen-assisted steam flooding can effectively reduce water cut of the low-yield wells and increase oil recovery by 6.7%compared with pure steam flooding.Nitrogen-assisted steam flooding reduces the heat loss of steam,which is 1.6×10^4 J lower than that of pure steam flooding.