注氮气采油井筒内可燃气体爆炸数值模拟

Numerical Simulation of Combustible Gas Explosions in Nitrogen Injection Wells

注气驱油过程中井筒内存在可燃气体爆炸风险,为了明确热采注氮井筒内发生可燃气体爆炸事故后果及爆炸演化规律,开展了高温高压条件下油管大长径比空间内,轻烃组分爆炸的数值模拟研究工作。研究结果表明,管内爆炸超压峰值随初始温度的升高而降低,此现象是由于升温引起管内可燃气体总量降低,升温对燃爆反应速率的增强作用被抵消,但管内爆炸超压峰值随初始压力的升高而快速增大,同时在相同的初始压力和温度下,与中部和顶部点火相比,超压的最高值出现在管内底部点火时的井口位置,且在井筒两端由于爆炸冲击波反弹使得超压迅速上升,爆炸产生的超压最高可达300 MPa以上,足以对油管和井筒等设施造成严重破坏。研究成果为注气采油井筒爆炸安全防控提供参考依据。

There are always some risks of a combustible gas explosion in a wellbore during gas injection for oil displacement.To clarify the consequences of such accidents and establish the evolution law of combustible gas explosions in thermal recovery nitrogen injection wellbores,numerical simulation was carried out for a light hydrocarbon component explosion in a wellbore space with a high length-diameter ratio under high temperature and high pressure.The results show that explosion overpressure is closely related to initial temperature and pressure.Increase in the initial temperature will lead to a decrease in the peak explosion overpressure,and increase in initial pressure will lead to an increase in the explosion peak overpressure.Under the same initial pressure and temperature,the highest explosion pressure occurs at the wellhead when ignition occurs at the well bottom.At both ends of the wellbore,overpressure increases rapidly due to the rebound of the blast shock wave,and the maximum overpressure generated by such an explosion can be more than 300 MPa,sufficient to cause serious damage to tubings,wellbores,and other facilities.These results provide reference for safety measures to prevent explosions and improve control of gas injection wells.