OneSubsea has developed a subsea ultrasonic flowmeter in collaboration with Equinor and Gassco and with support from the Norwegian Research Council under the DEMO2000 program. The primary application is subsea custody transfer metering of natural gas, but the subsea ultrasonic flowmeter can also be used to measure the flow of liquids, and of carbon dioxide for CCS applications. The enabling technology is a novel transducer packaging with metal-to-metal sealing. This eliminates the risk of degradation of O-rings and other soft materials exposed to process fluids while maintaining excellent acoustic performance. The subsea ultrasonic flowmeter is a full subsea design complying with applicable industry standards such as API 6A and API 17D and F.

Flow testing at a calibration laboratory demonstrates that the measurement performance satisfies the requirements for custody transfer metering of natural gas as specified by the Norwegian Petroleum Directorate. Other flow tests have been carried out with nitrogen, water, synthetic oil, and supercritical mixtures of carbon dioxide and nitrogen at pressures up to 400 bara. The meter has also been tested in static condition with CO2 in gas and liquid phase and in supercritical state, and with water at pressures up to 15.000 psi while operating.

The design and qualification program will be presented together with test results.