BS PD ISO/TR 12748:2015

BS PD ISO/TR 12748:2015 describes production flow measurement of wet natural gas streams with WGFMsin surface and subsea facilities. Wet natural gas streams are gas-dominated flows with liquids likewater and/or hydrocarbon liquids). This Technical Report definesterms/symbols, explains the various concepts, and describes best practices of wet gas flow meter designand operation. It addresses metering techniques, testing, installation, commissioning, and operationpractices such as maintenance, calibration, and verification. It also provides a theoretical backgroundof this comprehensive, challenging and still evolving measurement technology.There are four general methods in measuring wet natural gas flow. Each approach is detailed below.

• Single-phase gas flow meter with correction factor: Uses a single-phase gas flow meter (oftena conventional gas flow metering device) with a correction factor for the effect of liquid on themetering system. In these cases, the liquid flow rate required to determine the correction factor,should be estimated from an external source.
• Two-phase WGFM: The gas and liquid (both water and hydrocarbon liquid combined) flow ratesare predicted with no additional external information regarding the liquid flow rate required.This is generally known as a two-phase WGFM and will be referred to in this Technical Reportsimply as WGFM.
• WGFM: A flow meter that measures the gas and liquid flow rates, and also the gas, water andhydrocarbon liquid ratios (or "phase fractions") with no external information required regardingthe liquid flow rate.
• Phase separation/Measurement after phase separation: This traditional and conventional methodof wet gas flow metering uses a two- or three-phase separator with single-phase flow metersmeasuring the outgoing single-phase flows.

The first three of these methods, which emerged in the last two decades, may be described as in-linewet gas flow metering, i.e. wet gas flow measurement is executed with WGFMs without separatingthe gas and liquid phases. This Technical Report discusses in detail these first three methods. Severalbest practice documents have already been issued to describe, among other topics, wet gas flowmeasurement.The last method is more conventional and describes wet gas flow measurement after the gas and liquidphases have been separated. Wet gas meters can be used in multiphase flow metering systems thatutilize partial separation technologies. This method is only briefly discussed in this Technical Report.Cross References:ISO 5167-1ISO 5167-4ISO 5168ISO 10715ISO 12213 ISO 14532ISO 15970ISO/TR 26762API RP 87ASME MFC Report 19G:2008ISO/IEC 98-3:2008GUM:1995ISO 13443