Guidelines for efficient improvement of accuracy in oil and gas flow measurements

摘要

The process industry has plenty of flow measurement positions for natural gas and oil. Through these positions gas and oil are delivered into inner consumption positions. This in turn requires good measurement accuracy. Indmeas has developed a calibration method based on a radiotracer transit time measurement. Our method can be flexibly used for field calibrations of flow meters in industry without disturbing the production process. In a field calibration the total flow measurement chain is calibrated and the total measurement error can often be split into components caused by different parts of the flow measurement chain. Indmeas has had accreditation for these field calibrations since 1994. Experiences from natural gas and oil flow calibrations show that the largest measurement uncertainty originates from factors outside the flow meter itself. These factors and hence also the related significant errors tend to be constant and can be removed by the first field calibration. Recalibrations are needed thereafter to control the potential slow drift in the measurement chain. Field calibrations have proved to be an effective means of improving and maintaining the total measurement accuracy in natural gas and oil measurements. The long-term stability of the mechanical meters normally used for natural gas and oil is fairly good as there is an allowance for long calibration intervals.