ISO/TR 12748:2015
Natural Gas — Wet gas flow measurement in natural gas operations
ISO/TR 12748:2015 describes production flow measurement of wet natural gas streams with WGFMs in surface and subsea facilities. Wet natural gas streams are gas-dominated flows with liquids like water and/or hydrocarbon liquids. ISO/TR 12748:2015 defines terms/symbols, explains the various concepts, and describes best practices of wet gas flow meter design and operation. It addresses metering techniques, testing, installation, commissioning, and operation practices such as maintenance, calibration, and verification. It also provides a theoretical background of this comprehensive, challenging and still evolving measurement technology.
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Foreword
Introduction
1 Scope
2 Terms and Definitions
3 Symbols
4 Objectives of wet gas flow measurement
4.1 Common production scenarios
4.2 Production allocation
4.3 Flow assurance aspects
4.4 WGFM considerations
4.5 Reliability in remote WGFM installations
5 Flow regimes
5.1 Horizontal wet gas flow regimes
5.1.1 Stratified flow
5.1.2 Slug flow
5.1.3 Annular mist flow
5.2 Vertical up wet gas flow regimes
5.2.1 Churn flow
5.2.2 Annular mist flow
5.3 Vertical down wet gas flow regimes
5.4 Inclined flow
5.5 Examples of wet gas flow regimes
5.6 Flow regime maps
5.7 Different wet gas flow parameters
5.8 Water in wet gas flow
6 Wet gas flow metering principles
6.1 General
6.2 In-Line wet gas flow meters
6.2.1 Single-phase gas flow meter with correction factor
6.2.2 Two-phase wet gas flow meter
6.2.3 Multiphase wet gas flow meter
6.3 Single-phase gas differential pressure meters with wet gas flow
6.3.1 DP Meter design influence on wet gas over-reading
6.3.2 Lockhart-Martinelli parameter influence on DP meter wet gas flow over-reading
6.3.3 Gas to liquid density ratio influence on DP meter wet gas flow over-reading
6.3.4 Gas densiometric Froude number influence on DP meter wet gas flow over-reading
6.3.5 DP meter orientation influence on DP meter wet gas flow over-reading
6.3.6 Influence of β on DP meter wet gas flow over-reading
6.3.7 Fluid property influence on DP meter wet gas flow over-reading
6.3.8 Meter size/diameter influence on DP meter wet gas flow over-reading
6.3.9 Applying DP meter wet gas flow correlations
6.4 General discussion on DP meter wet gas correlations
6.4.1 Wet gas flow performance characterization vs. published wet gas correlations
6.4.2 Horizontally-installed orifice plate meter
6.4.3 Horizontally-installed Venturi meter
6.4.4 Horizontally-installed cone meter
6.5 Generic two-phase wet gas meter designs
6.5.1 Multiple single-phase meters in series
6.5.2 Differential pressure meter classical DP/permanent pressure loss wet gas meters
6.5.3 Fast response sensor system
6.6 Multiphase wet gas flow meters
6.6.1 Trace water metering with multiphase wet gas flow meters
6.6.2 Multiphase wet gas flow meter subsystems
6.6.3 Phase fraction device choices
6.6.4 Gas volume fraction vs. gas void fraction measurement
6.6.5 Semi-empirical multiphase flow calculation — Slip model
6.6.6 PVT (pressure volume temperature) models
6.6.7 Multiphase wet gas flow meter required fluid property inputs
6.6.8 Multiphase wet gas flow meter phase fraction measurement
6.6.9 Measurement of water salinity
6.6.10 Multiphase wet gas flow meter redundant subsystems and diagnostics
6.6.11 Selection of multiphase wet gas flow meter technologies
6.7 Wet gas flow meter performance testing
6.8 Virtual metering system (VMS)
7 DP Meter Wet Gas Correlation Practical Issues
7.1 DP meter wet gas flow installation issues
7.1.1 Liquid flow rate estimation techniques
7.1.2 Monitoring wet gas liquid loading with a DP meter downstream port
8 Design and Installation Considerations
8.1 Design considerations
8.1.1 Meter orientation and fluid flow
8.1.2 Meter location relative to other piping components
8.1.3 Use of two-phase flow rate and composition maps
8.1.4 Fluid sampling
8.1.5 Redundancy and external environmental considerations
8.1.6 Security
8.1.7 Cost and project schedule implications
8.2 Performance specifications
8.3 Wet gas flow measurement uncertainty
8.3.1 Uncertainty evaluation methodologies
8.3.2 Additional factors affecting wet gas flow measurement uncertainty
8.3.3 Expressing uncertainty of wet gas flow rates
9 Testing, Verification and Calibration
9.1 Meter orientation
9.2 Comments on flow regimes and mixers
9.3 Installation requirements
9.4 Wet gas flow characterization tests — Single-phase DP meter baselines
9.5 Wet gas flow facility operational considerations
9.5.1 Test facility operational issues — Achieving thermodynamic equilibrium
9.5.2 Test facility operational issues — Phase flow rate stability
9.5.3 Test facility operational issues — Witnessing of tests
9.6 Meter testing in a wet gas flow facility
10 Operational and Field Verification Issues
10.1 Laboratory reference vs. field hydrocarbon flow composition estimates
10.2 Laboratory reference vs. field calibration of phase fractions
10.3 Comparisons of multiphase wet gas flow meter and single-phase meter requirements
10.3.1 The challenge of supplying multiphase wet gas flow fluid properties
10.3.2 Confidential slip models
10.4 The importance of correct fluid property predictions
10.4.1 The importance of gas properties when metering small liquid flow rates
10.4.2 Preparation for fluid property variations during meter service
10.4.3 Fluid property sensitivity investigation
10.5 The benefit of an initial wet gas flow facility test
10.6 Line size limitations for some multiphase meters
10.7 In situ wet gas flow meter verification
10.7.1 Reconciliation factors and meter output confidence
10.8 Operation and maintenance
10.8.1 System redundancy and diagnostics
10.8.2 Operating WGFM diagnostics
10.9 Miscellaneous operational issues
10.9.1 Wet gas flow and DP transmitters
10.9.2 Software and fluid property update procedures
10.9.3 Long term trending comparisons with test facility/factory characterization
11 Common Field Issues
11.1 Inefficient separator systems
11.2 Separator systems — An adverse environment for single-phase meters
11.2.1 Separator Outlet deployment
11.2.2 Gas Measurement at the separator outlet
11.2.3 Liquid Turbine Meter
11.2.4 Practical limitations of wet gas flow metering with separator technology
11.3 Wet gas flow meter practical problems
11.3.1 Considerations for wet gas flow metering
11.3.2 The adverse effects of contamination, hydrates, scale, and salts
11.3.3 Theoretical, laboratory and actual wet gas flow conditions
11.3.4 Undisclosed WGFM calculation procedures
11.3.5 Differential pressure measurement and wet gas flows
11.3.6 Problems due to lack of long time operating experience of WGFMs
Annex A (informative) WGFM design checklist
Annex B (informative) Wet gas parameters equations
Bibliography
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Foreword
Introduction
1 Scope
2 Terms and Definitions
3 Symbols
4 Objectives of wet gas flow measurement
4.1 Common production scenarios
4.2 Production allocation
4.3 Flow assurance aspects
4.4 WGFM considerations
4.5 Reliability in remote WGFM installations
5 Flow regimes
5.1 Horizontal wet gas flow regimes
5.1.1 Stratified flow
5.1.2 Slug flow
5.1.3 Annular mist flow
5.2 Vertical up wet gas flow regimes
5.2.1 Churn flow
5.2.2 Annular mist flow
5.3 Vertical down wet gas flow regimes
5.4 Inclined flow
5.5 Examples of wet gas flow regimes
5.6 Flow regime maps
5.7 Different wet gas flow parameters
5.8 Water in wet gas flow
6 Wet gas flow metering principles
6.1 General
6.2 In-Line wet gas flow meters
6.2.1 Single-phase gas flow meter with correction factor
6.2.2 Two-phase wet gas flow meter
6.2.3 Multiphase wet gas flow meter
6.3 Single-phase gas differential pressure meters with wet gas flow
6.3.1 DP Meter design influence on wet gas over-reading
6.3.2 Lockhart-Martinelli parameter influence on DP meter wet gas flow over-reading
6.3.3 Gas to liquid density ratio influence on DP meter wet gas flow over-reading
6.3.4 Gas densiometric Froude number influence on DP meter wet gas flow over-reading
6.3.5 DP meter orientation influence on DP meter wet gas flow over-reading
6.3.6 Influence of β on DP meter wet gas flow over-reading
6.3.7 Fluid property influence on DP meter wet gas flow over-reading
6.3.8 Meter size/diameter influence on DP meter wet gas flow over-reading
6.3.9 Applying DP meter wet gas flow correlations
6.4 General discussion on DP meter wet gas correlations
6.4.1 Wet gas flow performance characterization vs. published wet gas correlations
6.4.2 Horizontally-installed orifice plate meter
6.4.3 Horizontally-installed Venturi meter
6.4.4 Horizontally-installed cone meter
6.5 Generic two-phase wet gas meter designs
6.5.1 Multiple single-phase meters in series
6.5.2 Differential pressure meter classical DP/permanent pressure loss wet gas meters
6.5.3 Fast response sensor system
6.6 Multiphase wet gas flow meters
6.6.1 Trace water metering with multiphase wet gas flow meters
6.6.2 Multiphase wet gas flow meter subsystems
6.6.3 Phase fraction device choices
6.6.4 Gas volume fraction vs. gas void fraction measurement
6.6.5 Semi-empirical multiphase flow calculation — Slip model
6.6.6 PVT (pressure volume temperature) models
6.6.7 Multiphase wet gas flow meter required fluid property inputs
6.6.8 Multiphase wet gas flow meter phase fraction measurement
6.6.9 Measurement of water salinity
6.6.10 Multiphase wet gas flow meter redundant subsystems and diagnostics
6.6.11 Selection of multiphase wet gas flow meter technologies
6.7 Wet gas flow meter performance testing
6.8 Virtual metering system (VMS)
7 DP Meter Wet Gas Correlation Practical Issues
7.1 DP meter wet gas flow installation issues
7.1.1 Liquid flow rate estimation techniques
7.1.2 Monitoring wet gas liquid loading with a DP meter downstream port
8 Design and Installation Considerations
8.1 Design considerations
8.1.1 Meter orientation and fluid flow
8.1.2 Meter location relative to other piping components
8.1.3 Use of two-phase flow rate and composition maps
8.1.4 Fluid sampling
8.1.5 Redundancy and external environmental considerations
8.1.6 Security
8.1.7 Cost and project schedule implications
8.2 Performance specifications
8.3 Wet gas flow measurement uncertainty
8.3.1 Uncertainty evaluation methodologies
8.3.2 Additional factors affecting wet gas flow measurement uncertainty
8.3.3 Expressing uncertainty of wet gas flow rates
9 Testing, Verification and Calibration
9.1 Meter orientation
9.2 Comments on flow regimes and mixers
9.3 Installation requirements
9.4 Wet gas flow characterization tests — Single-phase DP meter baselines
9.5 Wet gas flow facility operational considerations
9.5.1 Test facility operational issues — Achieving thermodynamic equilibrium
9.5.2 Test facility operational issues — Phase flow rate stability
9.5.3 Test facility operational issues — Witnessing of tests
9.6 Meter testing in a wet gas flow facility
10 Operational and Field Verification Issues
10.1 Laboratory reference vs. field hydrocarbon flow composition estimates
10.2 Laboratory reference vs. field calibration of phase fractions
10.3 Comparisons of multiphase wet gas flow meter and single-phase meter requirements
10.3.1 The challenge of supplying multiphase wet gas flow fluid properties
10.3.2 Confidential slip models
10.4 The importance of correct fluid property predictions
10.4.1 The importance of gas properties when metering small liquid flow rates
10.4.2 Preparation for fluid property variations during meter service
10.4.3 Fluid property sensitivity investigation
10.5 The benefit of an initial wet gas flow facility test
10.6 Line size limitations for some multiphase meters
10.7 In situ wet gas flow meter verification
10.7.1 Reconciliation factors and meter output confidence
10.8 Operation and maintenance
10.8.1 System redundancy and diagnostics
10.8.2 Operating WGFM diagnostics
10.9 Miscellaneous operational issues
10.9.1 Wet gas flow and DP transmitters
10.9.2 Software and fluid property update procedures
10.9.3 Long term trending comparisons with test facility/factory characterization
11 Common Field Issues
11.1 Inefficient separator systems
11.2 Separator systems — An adverse environment for single-phase meters
11.2.1 Separator Outlet deployment
11.2.2 Gas Measurement at the separator outlet
11.2.3 Liquid Turbine Meter
11.2.4 Practical limitations of wet gas flow metering with separator technology
11.3 Wet gas flow meter practical problems
11.3.1 Considerations for wet gas flow metering
11.3.2 The adverse effects of contamination, hydrates, scale, and salts
11.3.3 Theoretical, laboratory and actual wet gas flow conditions
11.3.4 Undisclosed WGFM calculation procedures
11.3.5 Differential pressure measurement and wet gas flows
11.3.6 Problems due to lack of long time operating experience of WGFMs
Annex A (informative) WGFM design checklist
Annex B (informative) Wet gas parameters equations
Bibliography