Page 50: of Offshore Engineer Magazine (Dec/Jan 2013)

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rate, and nitrogen gas at up to 1500cu m/ hr (1.3MMcf/d), at gas volume fraction (GVF) and water cuts of 0-100%.

Both facilities are to be used for testing and development as well as perform-

Flowlines ing certifcation, factory acceptance and calibration services.

NEL determines the performance of a meter by measuring the single-phase fows to a very low uncertainty, and combining the understanding of differ- ent multiphase fow regimes at the given process conditions. Based on its UKAS

The planned high pressure multiphase test facility.

accreditation, liquid phases are measured within 1.5% uncertainty for gas under

Use of multiphase constantly varying mixtures of gas, most conditions, and within 1% for fow meters is water, oil, fuids and other material going liquid, which ensures that we can assess increasing, driven through a pipe at any one time, from multiphase fow very well and to a trace- by the need to all gas to all liquid, and anywhere in able standard, says Muir Porter, business monitor individual between. Take that to the bottom of the manager, NEL. fow streams where ocean, and there are additional complexi- The overall fscal monitoring is ties. So accurate multiphase metering “uncertainty budget” required on felds technology is taking a long time to consists of the with multiple develop, but it is getting better.” summed uncertainty ownership, and of measurement of

Phil Mark, sales and marketing director,

Multiphase upgrade where test separa- various controlled

NEL tion facilities are To create its new high-pressure multi- elements of the pro- impractical or uneconomical. Deepwater phase facility, NEL converted an existing cess, including tem- and remote facilities are also strong can- two-phase (gas/liquid) separator into a perature, pressure,

Muir Porter, didates for multiphase metering, for the gravity-based three phase separator. It physical properties, business manager,

NEL same reasons. operates with nitrogen, water, and oil and accuracy of

Developing accurate multiphase fow (Exxsol D80, a kerosene substitute), at up secondary instrumentation. meters for simultaneous measurement of to 60bar g, and typically 20°C, with a gas “It is not possible to test fowmeters commingled oil, gas and water streams volume fraction up to 100% and water under the variable conditions they will has long been a key issue for the oil and cut of 0-100%. see in the feld, but we can measure them gas industry, however. Metering inaccu- Its fow range rate is up to 1800cu m/hr under very precise conditions through racy, even when marginal, can result in for dry gas, and up to 80cu m/hr for both very careful control of the single phases,” signifcant errors when billions of barrels water and kerosene. The test section, Porter says. “We know how multiphase are involved. which can be orientated horizontally or fuid fow regimes can change according

A key issue is measurement uncer- vertically, is 18m long and 8in (200mm) to fow rate, gas volume fraction (GVF), tainty. A manufacturer can claim single- in diameter. pressure, temperature and even in-line fgure uncertainties for a multiphase The second upgrade will be on a disturbances and installation effects.” fow meter under certain conditions, but multiphase fow test facility, built around

Erosion and research independent experts, including NEL and a full-scale three phase test separator,

Det Norske Veritas (now part of DNV GL), which also provides storage for the oil NEL also has a recently opened erosive suggest 10% would be more optimistic as and water phases. Each phase is pumped fow test facility, and is involved in a a practical fgure, especially considering as a separated single-phase stream and number of joint industry projects (JIPs), the potential for fuid phase properties to measured separately before being re- from temperature and pressure effects on change by the second. combined into a multiphase fow and Coriolis fow meters to sampling needs

Where a test separator is unavailable to transported through the test loop. It can for water-in-oil. verify fow meter results, operators have be constructed in vertical, horizontal or NEL’s High Viscosity Fluids JIP limited options to verify a fow meter’s inclined piping confgurations. recently completed and resulted in the results. The current facility operates at pres- upgrade of an existing facility at NEL to

Uncertainty of a multiphase fowmeter sures of 0-15bar g, but the new facil- allow it to test viscous fuids up to 1500 can be claimed to be as low as 2.5%. “If ity, currently being designed by NEL, centistokes (cSt).

you could get 10% in service you would will increase this to up to 150bar. To date, the most appropriate technolo- be doing well,” says Richard Harvey, lead Temperatures can be 5-40°C on 1-6in. gies for viscous fow measurement have multiphase fow engineer, at NEL. “They line sizes with a 30m test section, or 10m not been defned, NEL says.

will have sweet spots, but 10-15% would when in a horizontal confguration. The JIP saw established fowmeter- be a good result.” The facility will operate with crude ing technologies (Coriolis, Venturi and “Measurement uncertainty is a big oil (API 30) at up to 145cu m/hr ultrasonic devices) evaluated across issue,” Phil Mark says. “You can have (22,000bbl/d), salt water at the same a Reynolds number (Re) range of

December 2013 | OE oedigital.com 52 050-OE1213OPipelines1_Glasgow.indd 52 11/22/13 7:27 PM