环空含气圈闭压力计算

Annular pressure buildup calculation of annular gas trap

井口多次泄压、注泡沫隔离液等操作会在井口形成气柱,环空含气会对圈闭压力产生较大的影响。文中基于传热学理论,建立了生产期间的井筒传热模型;并考虑流体热膨胀/压缩效应、井筒体积变化等因素,根据气体状态方程,建立了含气状态下环空圈闭压力的计算模型;根据实例井参数,分析了气井产量、环空气柱长度对圈闭压力的影响。结果表明:气井产量越大,环空温度越高,形成的圈闭压力也越大;环空气柱越长,圈闭压力越小;产气量为30×10~4m^3/d时,70 m气柱形成的环空圈闭压力基本与大气压持平。环空含气圈闭压力的计算研究结果可为高温高压气井圈闭压力的预测及防治提供理论支持。

The operation such as multiple pressure relief and foam separation injection can form gas column at the wellhead,and the gas column in the annular space has a great influence on the annular pressure buildup(APB).Based on heat transfer theory,the model of wellbore heat transfer during production was established.The APB calculation of annular gas trap was developed by considering the liquid expansion and compression effect,wellbore volume change,fluid thermal property and gas state equation.The influence of the gas column length on the APB was analyzed according to the actual parameters.The results show that the higher the production of gas well,the higher the temperature of the annular and APB;the greater the length of gas column,the smaller the pressure of the wellhead;when the gas well production is 30×104 m3/d and annular column is 70 m,APB is reduced to atmospheric pressure.The research on APB calculation of annular gas trap provides theoretical support for the prediction and prevention of the high pressure and high temperature gas wells.