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FLOW & LEVEL CONTROL A FLOWMETER REVOLUTION


complexities or a host of other reasons. With this in mind, oil & gas operators are now increasingly utilising multiphase flow meters to reduce costs, increase efficiencies and minimise downtime. The validation of MPFMs in situ is critical to


maintain end-user confidence in the flow measurement reported from the device. Yet there is little information and standardised procedures for performing this. So how does an end-user validate their


multiphase meter? Well, the common practice for validating a topside or subsea MPFM prior to installation is via a Factory Acceptance Test (FAT) at a multiphase flow laboratory. These acceptance tests are often referred to as a ‘calibration’ and are typically agreed between the end-user and the multiphase flow meter manufacturer. In terms of in situ validation, a subsea or


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Dr Chris Mills, senior consultant engineer at TÜV SÜD National Engineering Laboratory, discusses the development of multiphase flow meters for the oil & gas industry


there is growing need for the real-time monitoring of exceptionally complex multiphase flow in a variety of locations and applications. Even remote and inaccessible applications such as subsea require continuous online measurement of multiphase flow. The process conditions can vary significantly, and extreme temperatures and pressures can be prevalent along with varying water liquid ratios, gas volume fractions and solids content. Providing accurate flow measurement of


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the various components can prove challenging and requires specialist technology such as Multiphase and Wet Gas Flow Meters. Oil & gas field operators are currently utilising such meters to reduce costs and increase efficiencies, for production optimisation, allocation and some fiscal measurement applications. In simple terms, all multiphase flow meters


can be split into two measurement practices. The first is the determination of ‘Bulk or Total Flowrate/Velocity’. The second is ‘Phase Fraction Measurement’ which concerns the determination of the Gas Volume Fraction (GVF) and Water Liquid Ratio (WLR) of the


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ccurately measuring a multiphase flow mixture of oil, water and gas in field conditions is a major challenge and


multiphase flow. These multiphase flow meters are not the


only option available for oil & gas operators. Historically, multiphase oil, water and gas mixtures have been measured via the use of a test separator. These three phase separators allow ‘well tests’ to be completed and generally offer superior stability and measurement confidence in comparison to multiphase flow meters (MPFMs). However,


in situ is critical to maintain end-user confidence in the flow measurement reported from the device


“ 1 JULY/AUGUST 2022 | PROCESS & CONTROL The validation of MPFMs


topside MPFM can be compared with a test separator to provide validation of the meter performance. As mentioned earlier, these test separators aren’t always available. Another option is for the MPFM to be compared with another MPFM. Again, this might not be a viable option depending upon the installation. In some circumstances, the production might be wholly subsea with no test separator to provide a validation of the production data. Furthermore, the subsea production could be part of a tie-back system to another development, potentially owned and operated by a different oil & gas operator. This further highlights the importance of accurate measurements and in situ verification of measurement devices. The challenge for the oil and gas industry is


to take the process of verification from the laboratory and move it to the ‘in situ’ location. In essence, a verification of flow meter performance that accounts for the real-world influences and allows users to have ongoing confidence in the measurements. One method of achieving this is through measurement diagnostics where the measurement instruments themselves provide an indication of the quality of their measurement as well as a measured value. This MPFM validation/verification analysis is


these advantages come with the price of higher capital and operational costs, as well as less flexibility to the complex field architectures encountered within today’s subsea environments. Furthermore, a test separator might not be available to a particular asset due to space limitations, capital or operational costs, remote location, installation


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not a novel concept and the majority of MPFM manufacturers offer software that performs either a health check on the sensors or can be used along with a supervisory system to ensure it is within acceptable limits. This system ensures that the data is within permissible ranges and alerts the user if it deviates outside an acceptable tolerance. However, the uptake and use of these diagnostics and validation techniques have not quite reached mass usage. There are numerous techniques that can be deployed for the determination of the bulk


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