徐深气田深层气井温度压力分布计算

Calculation of Temperature and Pressure Distribution of Deep Gas Well in Xushen Gas Field

徐深气田井深3500～4000m,地层压力30～40MPa,井底温度可达150℃,各生产井不同程度含有CO2,给井下管柱安全带来挑战。气井井筒中流体的温度和压力分布是影响井下管柱受力、变形的重要因素,准确进行温度、压力分布的计算,对气井的生产动态分析和管柱优化具有重要意义。针对徐深气田深层气井的流体性质和井身结构,根据传热学理论和质量、能量守恒原理,将井筒分成若干个节点,考虑油管、套管、水泥环及地层之间的传热性质,建立温度、压力耦合模型,并运用迭代法对模型进行求解。分析计算显示,气井产量、CO2含量、油管直径等参数对井筒温度、压力分布具有重要影响:产量越高,井筒温度下降越慢,而压力下降越快;CO2含量越高,温度下降越慢,而压力下降越快;油管直径越大,温度下降越快,压力下降越慢。实例计算表明,所建立的耦合模型简单方便,具有较高的精度,适合深层气井的温度、压力分布计算,计算结果可为气井的生产动态分析和管柱优化提供依据。

The deep volcanic gas reservoirs in Xushen gas field have special characteristics,such as 3500-4000m of well depth,30-40MPa of formation pressure,up to 150℃ of bottom hole temperature and CO2-bearing in each production well,which bring great challenge to the security of the down hole string.The distribution of the temperature and pressure of the bore hole in gas wells have a great impact on the load and deformation of the tubing.Therefore,calculating the pressure and temperature precisely is significant on the production dynamic analysis and tubing optimization of gas wells.Taking into account of the fluid properties and well structure of the deep gas wells in Xushen gas field,borehole is separated into several nodes based on heat transfer theory and momentum energy conservation principle.A coupling model of the temperature and the pressure has been built and solved with iteration method considering the heat transmissibility among oil tube,casing,cement sheath and formations.The calculation presents that the parameters of gas well production,CO2 content and oil tube′s diameter have great effect on the distribution of temperature and pressure in the borehole.More gas production,slow drop on borehole temperature and fast drop on the pressure.More CO2 content,slow drop on borehole temperature and fast drop on the pressure.Larger diameter of oil tube,fast drop on the temperature and slow drop on the pressure.The case history illustrates that the built coupling model is simple and convenient and has high precision.It fits for the calculation of the distribution of temperature and pressure in deep gas wells.The result will provide fundamental parameters for the mechanical analysis of the tubing optimization of the gas wells.