注汽井氮气隔热效果数学物理模拟研究

Mathematical and physical modeling of heat insulation by injecting nitrogen in steam injection wells

为评价注汽井油套环空充填氮气的隔热效果和确定环空注氮气隔热工艺的技术条件,建立了隔热油管、油套环空充氮气隔热井筒传热物理模型和数学模型,通过物理模拟现场不同注汽参数,监测井筒模型不同半径处径向温度场分布,结合井筒传热数值模拟计算,从不同侧面评价现场注蒸汽井油套环空充氮气的隔热效果、影响因素和适用范围。研究结果表明,在油套环空不发生窜流的前提下,环空注氮气会导致井筒径向总传热系数增加,不利于井筒隔热。当油套环空发生窜流时,只要保证注氮气压力不低于注汽压力,注汽井油套环空注氮气隔热技术就是有效和值得推广的。

In order to evaluate the effect of heat insulation and determine the technical conditions of applying nitrogen injection to the casing-tubing annulus of steam injection wells, the physical and mathematical models were set up. Through physical simulation of different field steam injection data, measurement of the temperature distribution in wellbore of different radius, combination with numerical simulation of wellbore thermal conduction, heat insulation effect and controlling factors and adapting range were evaluated from various aspects. The results show that under the condition of non-communication of casing-tubing annulus, nitrogen injection results in the rise of total heat transfer coefficient of the wellbore, and makes the heat insulation bad. When the casing-tubing annulus communicates, the technique of heat insulation by injecting nitrogen to the tubing-easing annulus of steam injection wellbore is effectual and popular-worthy by ensuring the pressure of nitrogen injection higher than that of steam injection.