致密气井筒热流耦合高压气水两相温度场动态特性

Dynamic Characteristics of Thermal Field Coupled with Gas-Water Two Phase Flow in High-Pressure Tight Gas Wellbores

分析井筒气水两相管流温度的动态分布对保障致密气井连续稳定安全开采和实现智能计产具有重要意义。综合井筒流体、油管、环空、套管、水泥环和地层之间热流耦合传热,将井筒流体的焓、焦耳-汤姆逊系数、温度梯度、传热速率等热力学和两相流动力学进行统一,提出适用于致密气井筒气水两相流态温度场分布预测方法,从而通过数值模拟和井场测试更全面和准确地分析致密气井筒温度分布随产量、管径、地层温度、导热率等动态变化情况。结果表明:在气水两相流热耦合作用下,提高致密气井产量、缩小油管内径、提升地层温度和降低地温梯度会增大井筒内单位质量流体承载的热量,并有助于井筒保温和有效抑制水合物的生成,且深井处井底温度的影响较大;改变油管、环空和套管以及水泥环导热率会影响井筒传热系统的总热阻、松弛距离与无因次时间,并改变井筒整体温度的分布;与产量和地层温度相比,总传热系数对井筒温度的影响较小。

Dynamic temperature distributions of gas-water two phase flow in wellbores are essential for the continuous,stable and safe mining and intelligent metering output of tight gas wells.The thermodynamics of enthalpy,Joule-Thomson coefficient,temperature gradient and heat transfer rate and dynamics of two-phase flow were unified under coupling heat transfer between wellbore fluid,oil tubing,annulus,casing,cement sheath and rock layer.A methodology on predicting temperature field distribution was proposed for gas-water two phase flow in tight gas wellbores.The dynamic variations of wellbore temperature with production,tubing diameter,layer temperature,thermal conductivity were analyzed more comprehensively and accurately by numerical simulation and well site testing.The results show that the amount of heat carried per unit mass of fluid in wellbores increases with the enhanced flow rates and layer temperatures and the reduced tubing inner diameters and geothermal gradients.And it is beneficial for wellbore insulation and effectively inhibits hydrate formation,and bottomhole temperature plays an important role in deep wells.The thermal conductivities of cement sheath,tubing,annulus and casing can affect the total thermal resistance,relaxation distance,dimensionless time and temperature distribution of the wellbore heat transfer system.Heat transfer coefficient has less effect on wellbore temperature compared to production and layer temperature.