Ensuring accurate measurements by reducing measurement uncertainty through advice, metering documentation and fiscal metering audits

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Accurate measurement of gas, oil and multiphase flows is a challenge for companies along the entire hydrocarbon value chain. If all the measurements are under control, the result is a low Unaccounted-for Gas figure (UfG) indicating a low gas imbalance (< 0.1%) which is crucial for the entire gas transmission system and its economy.

In the upstream sector, allocation measurements can get complex because of unstable production processes and the wet gas or multiphase flow conditions. Operators in the midstream sector face fiscal metering challenges on a large scale due to the sheer number of their assets and the challenges of keeping these installations accurate and compliant with contract requirements. At the end of the value chain, the large gas users, such as the feedstock and petrochemical industry as well as gas-fired power plants, want to be ensured of correct billing for what is delivered. 

Metering classification scheme

DNV experts can advocate a fitting balance between the cost of a measurement installation and the total product value measured by the installation: our metering classification scheme. In this scheme, we link the financial value of the product to a recommended level of measurement uncertainty by taking into account the financial risks of measurement errors.  

For large installations, which measure substantial volumes of product, a significant financial risk is involved with the measurements. For these installations the scheme supports the application of high-accuracy equipment and also the organization and processes to ensure all hydrocarbons are measured with a fittingly low-measurement uncertainty.  

For small installations the metering classification scheme supports cost savings. At these locations less expensive equipment with a higher measurement uncertainty may be installed. This is due to the low financial risks involved with the small volumes of measured product.

Audit method accompanying the metering classification scheme

To ensure metering installations are accurate and compliant with contractual specifications, DNV has developed an audit method accompanying the classification scheme. This audit method is used by our experts to perform allocation metering audits and fiscal metering audits. Our audits can also be combined with verification measurements to support the audit findings or they can be offered as lean, remote metering audits to save cost and time. 

Dedicated gas chromatography experts

Not only the amounts, but also the varying compositions of the hydrocarbon products pose measurement challenges. Even small deviations in quantity or quality can have a severe financial impact on revenues. Maintaining correct measurements of the heating value is often regarded as the most difficult part of any measurement installation. DNV meets these challenges with dedicated gas chromatography experts who provide advice and courses on the configuration and optimization of gas chromatography.

Decades of experience with troubleshooting the operation of the national gas grids of the UK and the Netherlands and co-authoring ISO standards, such as ISO 10723 and ISO 17089, have contributed to our level of expertise, ranging from hands-on equipment configuration and optimization to high-level metering policy and metering-manual documentation. 

What we provide:

• Metering advice based on international standards, industry best practices and our metering classification scheme
• Fiscal metering audits with 3 options for execution:
  • Remotely from our offices without the need to travel 
  • On-site with an auditor present at the location
  • On-site with an auditor, combined with technician who performs verification measurements of gas flow rate, pressure, temperature and gas composition 
• Allocation system audits and reviews
• Metering documentation compliant to ISO 10012, such as metering manuals and company metering policy  
• Metering data analytics and diagnostics 
• Flow and uncertainty calculations and certification 
• ISO 17025 accredited flow meter and P/T sensor calibration 
• ISO 17025 accredited gas mixture preparation & analysis 
• Measurement of trace components (Oxygen, Radon, Sulphur) and gas characteristics measurements such as hydrocarbon and water dew points 
• Gas Chromatograph performance evaluation according to ISO 10723 
• Technology qualification scheme for flow meters
• Multiphase flow equipment testing.