天然气输气末站计量系统误差分析及措施

为了确保天然气贸易交接计量的公平、公正,结合塔里木油田南疆天然气管网计量系统现状,分析了影响计量系统准确度的3种因素,即流体状态对气体超声波流量计的影响、调压后计量对气体超声波流量计的影响及压力波动对智能旋进流量计的影响。基于国家相关标准要求,为实现经济效益最大化,对原有计量工艺流程进行改造,设计了小流量计量工艺流程和大小流量自动切换计量流程,优化了计量仪表选型,既提高了计量系统的测量准确度,又避免了前端压力波动造成流量计准确度降低的问题。应用结果表明,优化后的计量系统可满足最小工况1.2 m^3/h天然气流量连续计量,天然气输差降低50%以上,天然气商品转换率显著提高。

Error Analysis and Countermeasure on Metering System of Gas Transmission Terminal

In order to ensure the fairness and impartiality of natural gas trade transition,and combined with the current situation of the metering system of Nanjiang Natural Gas Pipeline Network in Tarim Oilfield,three factors affecting the accuracy of metering system are analyzed,namely the influence of fluid state on the gas ultrasonic flowmeter,the influence of metering after pressure regulation on the gas ultrasonic flowmeter and the Influence of pressure fluctuation on the intelligent rotary flowmeter. Based on the requirements of relevant national standards,and in order to maximize economic benefits,the original metering process flow is reformed,the small flow metering process flow and automatic switching between large and small flow are designed and the selection of metering instruments is optimized,which not only improve the measurement accuracy of the metering system,but also avoid the problem of flowmeter accuracy reduction due to pressure fluctuation at the front end. The application result shows that the optimized metering system can meet the flow continuous metering in the minimum condition with 1.2 m3/h of natural gas,and the gas transmission difference can be reduced by more than50%,which improves the conversion rate of natural gas products remarkably.