ISO/TS 21354:2020

Overview

ISO/TS 21354:2020 provides a technical specification for the measurement of multiphase fluid flow in oil & gas production systems. It establishes a common basis for classifying applications and multiphase flow meters (MPFMs) and gives guidance and recommendations for their implementation and use. The document focuses on in-line MPFMs that directly measure oil, water and gas flow rates and on partial- and full-separation MPFMs. Conventional two- or three-phase separators are excluded. Wet-gas meters are only referenced briefly (see ISO/TR 11583 and ISO/TR 12748).

Key topics and requirements

• Scope and terminology: standardized terms, symbols and subscripts for multiphase metering and metrology.
• Multiphase flow fundamentals: flow regime maps (vertical and horizontal), slip effects and classification of multiphase flows.
• Performance specification: technical descriptions, sensor/primary device specs, output formats, measuring ranges, rated and limiting conditions.
• Measurement uncertainty: evaluation methodology, influence quantities, repeatability, stability and frequency response.
• Production and MPFM envelopes: plotting production and measuring envelopes on two-phase and composition maps to guide selection and design.
• Testing, calibration and adjustment: factory acceptance testing (FAT), static and dynamic performance verification, test facilities, in‑situ testing, blind tests and reporting.
• Installation and commissioning: field installation considerations, electrical and site integration, commissioning and start‑up procedures.
• Operational verification: baseline monitoring and ongoing verification during operation.

Practical applications and users

ISO/TS 21354 is practical for:

• Oil & gas operators specifying MPFMs for well surveillance, production allocation, well testing and fiscal/non-fiscal measurement.
• Instrumentation and MPFM vendors preparing technical offers, FAT plans and performance documentation.
• Flow assurance and production engineers using flow maps and production envelopes for equipment selection and optimization.
• Metrology teams and test facilities designing calibration plans, blind tests and uncertainty assessments.
• Regulatory and commercial stakeholders interested in measurement uncertainty, custody transfer considerations and allocation metering.

Benefits

• Harmonizes terminology and specification practices for multiphase metering.
• Supports reliable selection, testing and commissioning of MPFMs.
• Helps quantify measurement uncertainty for operational and commercial decisions.

Related standards

• ISO/TR 11583 (wet‑gas metering)
• ISO/TR 12748 (wet‑gas measurement)

Keywords: multiphase flow, MPFM, multiphase meters, measurement uncertainty, factory acceptance testing, production envelope, fluid metering, well testing, multiphase flow measurement.