International trading of natural gas is based on high-precision, traceable,and accredited fiscal flow metering systems and international pipelinetransmission infrastructures. Norwegian O&G industry is today moving towards subsea solutions for fiscal allocation metering, to replace today?stopside metering systems. Gas is traded on basis of energy flow rate. Thus,in addition to the volumetric flow rate, the energy and quality parameters(QP) of the gas need to be measured. Traditional methods used topsidecannot be used in subsea systems. An industrial solution to this challenge ismandatory and urgent.
The objective of the research project is to develop necessary scientificbasis and technology components, as a fundament to - in a follow-upindustrial project - realize traceable and accredited gas energy and qualitymeasurement by ultrasonic gas flow meters (USMs) in subsea fiscalmetering systems. The approach is based on use of the sound velocity(VOS) measurement already available in relevant USM technologies.However, no method is available today to ensure necessary traceability andaccreditation of this VOS measurement.
The work includes development of a measurement method and a laboratoryhigh-pressure VOS measurement cell for gas, as a basis to achievehigh-precision calibration of the USM?s subsea VOS measurements.Secondly, it includes further development of an already operationalVOS-to-QP algorithm to ensure - from measurements available from theUSM and the metering system - high-precision and accredited calculations ofthe energy and quality parameters under subsea gas operational conditions.
The results of the project will serve as a necessary fundament to enableaccredited and traceable subsea measurements of the USM?s VOS reading,as input to an accredited and traceable VOS-to-QP algorithm, which ?together with the already accredited USM volumetric flow measurement ?provides the gas energy flow rate with accredited fiscal accuracy.
