PRCI

Recent Results

LNG Measurement Uncertainty Analysis

Current practice for LNG measurement at terminals was characterized to identify potential sources of uncertainty.  When an LNG tanker arrives at a terminal, the quantity of LNG transferred to the terminal is determined by measuring the changes in static volume within the ship’s tanks. The LNG volume is inferred from measurements of the liquid height, along with tables of tank characteristics predetermined by a method known as “tank strapping.” Once transferred, the LNG is then regasified at the terminal before being shipped out via pipeline.

There is concern that the basis for uncertainty estimates in the energy content of the transferred LNG (typically taken as ±0.5% to ±0.6%) may underestimate the true magnitude of measurement uncertainties. Dynamic methods of liquid flow measurement, gas flow measurement, product sampling, and composition determination used elsewhere in the energy industry may reduce the measurement uncertainties at the LNG terminal as they relate to terminal balances. Measurement uncertainties for conventional meters and equipment placed into LNG service may lead to reduced lost-and-unaccounted-for (LAUF) quantities at receipt terminals.

Key Results

This report describes research to evaluate the measurement uncertainties associated with both static and dynamic methods of determining LNG volumes and energy content delivered to, processed by, and shipped from, LNG terminals. This was performed to determine whether dynamic methods are potentially more effective than existing static methods.  Another objective was to establish which methods offer the most potential for reducing custody transfer measurement uncertainty and LAUF within LNG receipt terminals. The Final Report is available for members on PRIME.

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