BSI PD ISO/TR 12748:2015:2016 Edition
$215.11
Natural Gas. Wet gas flow measurement in natural gas operations
| Published By | Publication Date | Number of Pages |
| BSI | 2016 | 104 |
This Technical Report 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 liquids3) (see 2.67 for a detailed definition). This Technical Report 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.
There are four general methods in measuring wet natural gas flow. Each approach is detailed below.
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Single-phase gas flow meter with correction factor: Uses a single-phase gas flow meter (often a conventional gas flow metering device) with a correction factor for the effect of liquid on the metering system. In these cases, the liquid flow rate required to determine the correction factor, should be estimated from an external source.
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Two-phase WGFM: The gas and liquid (both water and hydrocarbon liquid combined) flow rates are 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 Report simply as WGFM.
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WGFM: A flow meter that measures the gas and liquid flow rates, and also the gas, water and hydrocarbon liquid ratios (or “phase fractions”) with no external information required regarding the liquid flow rate.
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Phase separation/Measurement after phase separation: This traditional and conventional method of wet gas flow metering uses a two-or three-phase separator with single-phase flow meters measuring the outgoing single-phase flows.
The first three of these methods, which emerged in the last two decades, may be described as in-line wet gas flow metering, i.e. wet gas flow measurement is executed with WGFMs without separating the gas and liquid phases. This Technical Report discusses in detail these first three methods. Several best practice documents have already been issued to describe, among other topics, wet gas flow measurement[9][10][11][12].
The last method is more conventional and describes wet gas flow measurement after the gas and liquid phases have been separated. Wet gas meters can be used in multiphase flow metering systems that utilize partial separation technologies. This method is only briefly discussed in this Technical Report.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 8 | Foreword |
| 9 | Introduction |
| 10 | 1 Scope 2 Terms and Definitions |
| 19 | 3 Symbols |
| 22 | 4 Objectives of wet gas flow measurement |
| 23 | 4.1 Common production scenarios |
| 24 | 4.2 Production allocation |
| 25 | 4.3 Flow assurance aspects 4.4 WGFM considerations 4.5 Reliability in remote WGFM installations |
| 26 | 5 Flow regimes 5.1 Horizontal wet gas flow regimes |
| 27 | 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 |
| 28 | 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 |
| 29 | 5.6 Flow regime maps |
| 30 | 5.7 Different wet gas flow parameters 5.8 Water in wet gas flow |
| 31 | 6 Wet gas flow metering principles 6.1 General |
| 32 | 6.2 In-Line wet gas flow meters 6.2.1 Single-phase gas flow meter with correction factor |
| 33 | 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 |
| 34 | 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 |
| 35 | 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 |
| 37 | 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 |
| 38 | 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 |
| 40 | 6.4.3 Horizontally-installed Venturi meter |
| 41 | 6.4.4 Horizontally-installed cone meter |
| 42 | 6.5 Generic two-phase wet gas meter designs 6.5.1 Multiple single-phase meters in series |
| 44 | 6.5.2 Differential pressure meter classical DP/permanent pressure loss wet gas meters |
| 45 | 6.5.3 Fast response sensor system |
| 46 | 6.6 Multiphase wet gas flow meters |
| 47 | 6.6.1 Trace water metering with multiphase wet gas flow meters 6.6.2 Multiphase wet gas flow meter subsystems |
| 48 | 6.6.3 Phase fraction device choices |
| 50 | 6.6.4 Gas volume fraction vs. gas void fraction measurement 6.6.5 Semi-empirical multiphase flow calculation — Slip model |
| 51 | 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 |
| 52 | 6.6.9 Measurement of water salinity 6.6.10 Multiphase wet gas flow meter redundant subsystems and diagnostics |
| 53 | 6.6.11 Selection of multiphase wet gas flow meter technologies 6.7 Wet gas flow meter performance testing |
| 54 | 6.8 Virtual metering system (VMS) 7 DP Meter Wet Gas Correlation Practical Issues |
| 55 | 7.1 DP meter wet gas flow installation issues 7.1.1 Liquid flow rate estimation techniques |
| 56 | 7.1.2 Monitoring wet gas liquid loading with a DP meter downstream port |
| 58 | 8 Design and Installation Considerations 8.1 Design considerations 8.1.1 Meter orientation and fluid flow |
| 59 | 8.1.2 Meter location relative to other piping components 8.1.3 Use of two-phase flow rate and composition maps |
| 61 | 8.1.4 Fluid sampling 8.1.5 Redundancy and external environmental considerations |
| 62 | 8.1.6 Security |
| 63 | 8.1.7 Cost and project schedule implications 8.2 Performance specifications |
| 64 | 8.3 Wet gas flow measurement uncertainty 8.3.1 Uncertainty evaluation methodologies 8.3.2 Additional factors affecting wet gas flow measurement uncertainty |
| 65 | 8.3.3 Expressing uncertainty of wet gas flow rates 9 Testing, Verification and Calibration 9.1 Meter orientation |
| 66 | 9.2 Comments on flow regimes and mixers 9.3 Installation requirements 9.4 Wet gas flow characterization tests — Single-phase DP meter baselines |
| 67 | 9.5 Wet gas flow facility operational considerations 9.5.1 Test facility operational issues — Achieving thermodynamic equilibrium |
| 69 | 9.5.2 Test facility operational issues — Phase flow rate stability |
| 70 | 9.5.3 Test facility operational issues — Witnessing of tests |
| 71 | 9.6 Meter testing in a wet gas flow facility |
| 74 | 10 Operational and Field Verification Issues |
| 75 | 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 |
| 76 | 10.3.2 Confidential slip models 10.4 The importance of correct fluid property predictions |
| 79 | 10.4.1 The importance of gas properties when metering small liquid flow rates |
| 80 | 10.4.2 Preparation for fluid property variations during meter service 10.4.3 Fluid property sensitivity investigation |
| 82 | 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 |
| 83 | 10.7.1 Reconciliation factors and meter output confidence 10.8 Operation and maintenance 10.8.1 System redundancy and diagnostics |
| 84 | 10.8.2 Operating WGFM diagnostics |
| 85 | 10.9 Miscellaneous operational issues 10.9.1 Wet gas flow and DP transmitters |
| 86 | 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 |
| 87 | 11.2 Separator systems — An adverse environment for single-phase meters |
| 88 | 11.2.1 Separator Outlet deployment 11.2.2 Gas Measurement at the separator outlet |
| 89 | 11.2.3 Liquid Turbine Meter 11.2.4 Practical limitations of wet gas flow metering with separator technology |
| 90 | 11.3 Wet gas flow meter practical problems 11.3.1 Considerations for wet gas flow metering |
| 91 | 11.3.2 The adverse effects of contamination, hydrates, scale, and salts |
| 93 | 11.3.3 Theoretical, laboratory and actual wet gas flow conditions 11.3.4 Undisclosed WGFM calculation procedures |
| 94 | 11.3.5 Differential pressure measurement and wet gas flows |
| 95 | 11.3.6 Problems due to lack of long time operating experience of WGFMs |
| 96 | Annex A (informative) WGFM design checklist |
| 98 | Annex B (informative) Wet gas parameters equations |
| 99 | Bibliography |
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