LNG sampling and methods for improving measurement uncertainty

Joey Walker, EffecTech (GB)

One of the main challenges facing the LNG industry is reducing the total uncertainty of LNG energy measurements in custody transfer operations. Current best estimates of uncertainty for total LNG energy measurement fall around 0.5% under ideal conditions. However, under normal operating conditions this value can exceed 1%, far greater than typical oil and gas fiscal transactions. A 1% uncertainty for global LNG trade in 2015 (245 million tons) translates to approximately US$1.5 billion, a colossal impact considering the growing market for LNG. Many research programs have been deployed to focus on reducing this uncertainty by improving existing methods of measurement, validating new methods, and developing calibration systems that are traceable to national primary standards. Total LNG energy content is derived from volume, density and calorific value. Both density and calorific value depend on measurements of composition. Currently, LNG is vaporized into its gaseous state before measurement, a process that has surfaced many concerns over possible fractionation in sampling lines, leading to unrepresentative samples reaching the final measurement device. The application of direct measurements, such as Raman spectroscopy, offers a new approach for measuring LNG composition directly, removing the need for pre-measurement processing. This paper outlines the problems associated with LNG sampling and its impact on final measurement uncertainty, and demonstrates the application of direct methods for measuring LNG composition.


Pen Profile

Joey completed his master’s degree in Chemistry from Loughborough University UK in 2013 and grew an interest in the energy sector during his studies. Following his interests in energy, Joey started an Industry-led EngD with EffecTech and Loughborough University in October 2013 with a research project focused on LNG metrology, specifically the testing of direct measurement instrumentation using a bespoke designed cryostat. Currently, Joey is in his penultimate year of research and aims to finish in September 2017.

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