储气库井口天然气计量影响特性研究

Study on influence of natural gas metering at wellhead of gas storage

关键词:  储气库井口  高压天然气  实流比对  流量计特性

Key words:  gas storage wellhead  high pressure natural gas  real flow comparison  flowmeter characteristics

摘要:

目的 获得准确的储气库井口天然气计量影响特性,评价流量计在储气库井口计量的适应性,提高储气库井口天然气计量的准确度,以优化生产运行参数、提高天然气注采率。方法 采用实验室与储气库现场相结合的实验手段,并基于大数据统计对比分析方法,建立储气库井口流量计计量性能评价方法,研究了5个流量计的计量影响特性。结果 通过对比可知:①不同类型超声流量计在不同压力条件下计量特性不同,受超声流量计探头性能的影响,有的超声流量计经低压测试后,具备代表此流量计在一定高压范围的计量性能,但在远超过检定压力范围的情况下,其计量性能将发生变化；②差压流量计在不同压力条件下计量重复性较好。结论 ①靶式流量计对天然气中杂质要求较低,压损小,但误差高达40%,且故障率高；②针对相国寺储气库气质与现场工艺条件(主要是含水量少、凝析油少、节流阀无噪声干扰),经过天然气实流校准后,5个流量计的计量示值误差符合GB 50349-2015《气田集输设计规范》中“井口计量设施的允许偏差为±7.0%”的要求,J1槽道流量计、J2均速管流量计、J3超声流量计偏差满足±5%的偏差范围；③建议储气库井口流量计需经过天然气实流校准后使用,且运行工况流量应高于拐点流量,以保证现场注采气的计量准确性。 

Abstract:

Objective sAccurately obtain the characteristics, evaluate the adaptability of the flowmeter, and improve the measurement accuracy of natural gas at the wellhead of gas storage, so as to optimize operation parameters and improve the injection production rate of natural gas. Methods Using the experimental methods of laboratory and gas storage field, and the big data statistical comparative analysis method, the evaluation method of measurement performance of flowmeter at the wellhead of gas storage is established. And the measurement characteristics of five flowmeters are studied. Results The comparison shows that:(1) Different types of ultrasonic flowmeter have different metering characteristics under different pressure conditions, and affected by the probe performance of ultrasonic flowmeter, some ultrasonic flowmeters have the metering performance representing the flowmeter in a certain high-pressure range after low-pressure test, but their metering performance will change after far exceeding the verification pressure range; (2) The differential pressure flowmeter has good measurement repeatability under different pressure conditions. Conclusion s(1) The target flowmeter has low requirements for impurities in natural gas and small pressure loss, but the error is as high as 40% and the failure rate is high; (2) According to the gas quality and site process conditions of Xiangguosi gas storage (mainly less water content, less condensate, no noise interference of throttle valve), after the calibration of natural gas flow, The measurement indication error of the five flowmeters meets the requirement of "The allowable deviation of the wellhead metering facilities is ± 7.0%" in GB 50349-2015 Code for Design of Gas Field Gathering and Transportation, and the deviation of J1 channel flowmeter, J2 differential pressure flowmeter and J3 ultrasonic flowmeter meets the range of ±5%； (3) It is recommended that the flowmeter used at the wellhead of gas storage should be firstly calibrated by the real flow of natural gas, and the flow under operating conditions should be higher than the inflection point flow, so as to ensure the measurement accuracy of the flowmeter.