气井井筒温度、压力与积液综合预测模型

气井积液是产水气藏开发设计和气井生产管理面临的重要问题,但目前对气井流动机理与携液预测还存在争议。从气液两相流的基本流动机理出发,建立了考虑液滴变形和井斜影响下气井井筒的流型、温度、压力与携液综合预测模型,并用实际井数据对模型进行了验证。结果表明,所建模型可用于直井、斜井和水平井的产水气井井筒温度压力预测,预测误差小于5%;在环雾状流动情况下,井筒内液体以液滴和液膜的形式被完全带出井口,不会出现井筒积液;对常规垂直气井,利用井口数据便能判断气井积液情况,Turner模型计算气井携液临界值较实际值偏大,李闽模型计算结果明显偏小,建议采用彭朝阳模型计算气井携液临界值;对斜井和水平井,则需要同时考虑液滴变形和井斜的影响,水平井近水平段携液临界流速和流量明显较垂直井段小,而造斜井段携液临界流速和临界流量随井斜角的增大先增大后减小,在井斜角为30°~60°之间达到最大值,因此造斜井段是气井积液判断的重点部位。

A comprehensive prediction model of wellbore temperature,pressure and accumulated liquid for gas wells

Accumulated fluid in gas well is a key issue confronted in development design of water-producing gas pools and production management of gas wells, but at present, there are controversies on flow mechanism and water carrying prediction in gas wells. From the basic flow mechanism of two-phase flow of gas and liquid, a comprehensive prediction model was built to predict the flow pattern, temperature, pressure and water-carrying in gas wells, and this model was verified using actual well data. The result shows that the model so built can be used to predict the wellbore temperature and pressure of water-producing vertical wells, deviated wells and horizontal wells, and the prediction error is less than 5%. Under condition of annular mist flow, the fluid in the wellbore is carried out of the wellhead completely in the forms of liquid drop and membrane, so no wellbore water shall be accumulated; for conventional vertical gas wells, the wellhead data can be used to determine the accumulated fluid in gas wells; the critical value of liquid carrying in gas wells calculated by Turner model is larger than the actual value, and that calculated by Li Min model is on the small side. So it is suggested that Peng Chaoyang Model be used to calculate the liquid-carrying critical value in gas wells. For deviated wells and horizontal wells, the effects of drop deformation and hole deviation should both be considered. The liquid-carrying critical flow velocity and flowrate in horizontal section in horizontal wells is obviously smaller than that in vertical wells, while the liquid-carrying critical flow velocity and flowrate in angle buildup section first increases with the hole drift angle, but then decreases, reaching the peak when hole drift angle is between 30°and 60°, so angle buildup section is a key place for determination of accumulated fluid in gas wells.