Methods of detecting and measuring fugitive methane emissions from elements of the gas transmission infrastructure – the results of GERG project Detection and Measurement of Fugitive Emissions of Natural Gas from the Transmission Systems

Abstract

The article presents the results of the project carried out by GAZ-SYSTEM in cooperation with 5 other European gas Transmission System Operators (TSO) – ENAGAS, Fluxys, Gasunie, Snam and GRTgaz. The objective of the project was to investigate and identify the most useful devices for detecting and measuring methane emissions from infrastructure components typical for the TSO. The market analysis showed that methane detectors utilizing different principles of operation are available, but there are much fewer devices for measuring emission rates. 5 devices were selected for tests: 3 exclusively for detection based on the D-1 (semiconductor sensor), D-2 (infrared optical gas detection system), D-3(laser technology) principle of operation, and 2 devices that also enable emissions measurement – P-1 (ultrasound imaging) and P-2 (quantitative optical gas imaging). Laboratory tests were carried out in March 2020 at the Enagás’ Metrological & Innovation Center (M&I); according to the approved program, methane leaks were generated from deliberately unsealed valves, flanges, threaded and open-ended pipe connections. Field tests were carried out at the measuring gas station near the M&I. The main purpose of the research was to verify the accuracy of the selected measuring instruments. It was carried out at different flowrate and various methane concentrations in the gas escaping from the components. Ease of use of the devices, their speed and range of operation were assessed. The results showed both the advantages and limitations of each device, and they clearly indicated that the assessment of methane emissions from gas transmission infrastructure components requires the use of at least two different devices. The results indicate that sniffer devices, characterized by the fact that the probe must be placed in the vicinity of the source of emission, give results similar to the FID Detector, most commonly used in Leak Detection and Repair (LDAR) programs, but can be used in a wider range of methane concentrations. D-3 has a fast response time and a wide measuring range, but their unit of measurement i.e. ppm-m prevents the conversion of the results into methane concentration without additional measurements of the distance between the leak and the device. The P-1 and P-2 allow to measure the emissions in real time, while the measurement errors for both devices are comparable, ranging from about 70% to 100%.