1、 ISO 2015 Natural Gas Wet gas flow measurement in natural gas operations Gaz naturel Mesurage du dbit de gaz humide dans les oprations de gaz naturel TECHNICAL REPORT ISO/TR 12748 Reference number ISO/TR 12748:2015(E) First edition 2015-10-15 ISO/TR 12748:2015(E)ii ISO 2015 All rights reserved COPYR
2、IGHT PROTECTED DOCUMENT ISO 2015, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, wi
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4、so.org ISO/TR 12748:2015(E)Foreword vi Introduction vii 1 Scope . 1 2 Terms and Definitions 1 3 Symbols .10 4 Objectives of wet gas flow measurement .13 4.1 Common production scenarios 14 4.2 Production allocation .15 4.3 Flow assurance aspects 16 4.4 WGFM considerations 16 4.5 Reliability in remote
5、 WGFM installations .16 5 Flow regimes 17 5.1 Horizontal wet gas flow regimes 17 5.1.1 Stratified flow 18 5.1.2 Slug flow .18 5.1.3 Annular mist flow .18 5.2 Vertical up wet gas flow regimes 18 5.2.1 Churn flow 18 5.2.2 Annular mist flow .19 5.3 Vertical down wet gas flow regimes 19 5.4 Inclined flo
6、w.19 5.5 Examples of wet gas flow regimes 19 5.6 Flow regime maps .20 5.7 Different wet gas flow parameters21 5.8 Water in wet gas flow .21 6 Wet gas flow metering principles .22 6.1 General 22 6.2 In-Line wet gas flow meters .23 6.2.1 Single-phase gas flow meter with correction factor 23 6.2.2 Two-
7、phase wet gas flow meter .24 6.2.3 Multiphase wet gas flow meter 24 6.3 Single-phase gas differential pressure meters with wet gas flow 24 6.3.1 DP Meter design influence on wet gas over-reading .25 6.3.2 Lockhart-Martinelli parameter influence on DP meter wet gas flow over-reading .25 6.3.3 Gas to
8、liquid density ratio influence on DP meter wet gas flow over-reading 25 6.3.4 Gas densiometric Froude number influence on DP meter wet gas flow over-reading .26 6.3.5 DP meter orientation influence on DP meter wet gas flow over-reading 26 6.3.6 Influence of on DP meter wet gas flow over-reading 28 6
9、.3.7 Fluid property influence on DP meter wet gas flow over-reading.28 6.3.8 Meter size/diameter influence on DP meter wet gas flow over-reading .28 6.3.9 Applying DP meter wet gas flow correlations .28 6.4 General discussion on DP meter wet gas correlations 29 6.4.1 Wet gas flow performance charact
10、erization vs. published wet gas correlations 29 6.4.2 Horizontally-installed orifice plate meter .29 6.4.3 Horizontally-installed Venturi meter 31 6.4.4 Horizontally-installed cone meter .32 6.5 Generic two-phase wet gas meter designs .33 6.5.1 Multiple single-phase meters in series 33 6.5.2 Differe
11、ntial pressure meter classical DP/permanent pressure loss wet gas meters .35 ISO 2015 All rights reserved iii Contents Page ISO/TR 12748:2015(E)6.5.3 Fast response sensor system 36 6.6 Multiphase wet gas flow meters .37 6.6.1 Trace water metering with multiphase wet gas flow meters .38 6.6.2 Multiph
12、ase wet gas flow meter subsystems .38 6.6.3 Phase fraction device choices 39 6.6.4 Gas volume fraction vs. gas void fraction measurement 41 6.6.5 Semi-empirical multiphase flow calculation Slip model .41 6.6.6 PVT (pressure volume temperature) models 42 6.6.7 Multiphase wet gas flow meter required f
13、luid property inputs .42 6.6.8 Multiphase wet gas flow meter phase fraction measurement 42 6.6.9 Measurement of water salinity .43 6.6.10 Multiphase wet gas flow meter redundant subsystems and diagnostics.43 6.6.11 Selection of multiphase wet gas flow meter technologies 44 6.7 Wet gas flow meter per
14、formance testing 44 6.8 Virtual metering system (VMS) .45 7 DP Meter Wet Gas Correlation Practical Issues .45 7.1 DP meter wet gas flow installation issues 46 7.1.1 Liquid flow rate estimation techniques 46 7.1.2 Monitoring wet gas liquid loading with a DP meter downstream port .47 8 Design and Inst
15、allation Considerations 49 8.1 Design considerations49 8.1.1 Meter orientation and fluid flow .49 8.1.2 Meter location relative to other piping components .50 8.1.3 Use of two-phase flow rate and composition maps 50 8.1.4 Fluid sampling.52 8.1.5 Redundancy and external environmental considerations 5
16、2 8.1.6 Security .53 8.1.7 Cost and project schedule implications 54 8.2 Performance specifications .54 8.3 Wet gas flow measurement uncertainty 55 8.3.1 Uncertainty evaluation methodologies .55 8.3.2 Additional factors affecting wet gas flow measurement uncertainty .55 8.3.3 Expressing uncertainty
17、of wet gas flow rates 56 9 Testing, Verification and Calibration 56 9.1 Meter orientation .56 9.2 Comments on flow regimes and mixers .57 9.3 Installation requirements .57 9.4 Wet gas flow characterization tests Single-phase DP meter baselines 57 9.5 Wet gas flow facility operational considerations
18、.58 9.5.1 Test facility operational issues Achieving thermodynamic equilibrium .58 9.5.2 Test facility operational issues Phase flow rate stability 60 9.5.3 Test facility operational issues Witnessing of tests .61 9.6 Meter testing in a wet gas flow facility 62 10 Operational and Field Verification
19、Issues .65 10.1 Laboratory reference vs. field hydrocarbon flow composition estimates 66 10.2 Laboratory reference vs. field calibration of phase fractions 66 10.3 Comparisons of multiphase wet gas flow meter and single-phase meter requirements 66 10.3.1 The challenge of supplying multiphase wet gas
20、 flow fluid properties .66 10.3.2 Confidential slip models .67 10.4 The importance of correct fluid property predictions 67 10.4.1 The importance of gas properties when metering small liquid flow rates 70 10.4.2 Preparation for fluid property variations during meter service .71 10.4.3 Fluid property
21、 sensitivity investigation71 10.5 The benefit of an initial wet gas flow facility test . 73 10.6 Line size limitations for some multiphase meters 73 10.7 In situ wet gas flow meter verification .73 iv ISO 2015 All rights reserved ISO/TR 12748:2015(E)10.7.1 Reconciliation factors and meter output con
22、fidence 74 10.8 Operation and maintenance .74 10.8.1 System redundancy and diagnostics .74 10.8.2 Operating WGFM diagnostics 75 10.9 Miscellaneous operational issues 76 10.9.1 Wet gas flow and DP transmitters .76 10.9.2 Software and fluid property update procedures .77 10.9.3 Long term trending comp
23、arisons with test facility/factory characterization .77 11 Common Field Issues 77 11.1 Inefficient separator systems 77 11.2 Separator systems An adverse environment for single-phase meters .78 11.2.1 Separator Outlet deployment 79 11.2.2 Gas Measurement at the separator outlet .79 11.2.3 Liquid Tur
24、bine Meter 80 11.2.4 Practical limitations of wet gas flow metering with separator technology .80 11.3 Wet gas flow meter practical problems 81 11.3.1 Considerations for wet gas flow metering 81 11.3.2 The adverse effects of contamination, hydrates, scale, and salts 82 11.3.3 Theoretical, laboratory
25、 and actual wet gas flow conditions .84 11.3.4 Undisclosed WGFM calculation procedures 84 11.3.5 Differential pressure measurement and wet gas flows .85 11.3.6 Problems due to lack of long time operating experience of WGFMs .86 Annex A (informative) WGFM design checklist.87 Annex B (informative) Wet
26、 gas parameters equations .89 Bibliography .90 ISO 2015 All rights reserved v ISO/TR 12748:2015(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally c
27、arried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the wor
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29、erent approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document m
30、ay be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/pate
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32、ples in the Technical Barriers to Trade (TBT), see the following URL: Foreword Supplementary information. The committee responsible for this document is ISO/TC 193, Natural Gas, Subcommitte SC 3, Upstream Area.vi ISO 2015 All rights reserved ISO/TR 12748:2015(E) Introduction Oil and gas companies st
33、arted developing Wet Gas Flow Meters (WGFMs) and Multiphase Flow Meters (MPFMs) through extensive R&D activities in the late 1980s. During this period, WGFMs and MPFMs were typically perceived as two distinct technologies for different applications: MPFMs were designed for liquid continuous flow con
34、ditions and WGFMs were designed for gas continuous flow conditions. In recent years, however, the operating range of these two technologies has increasingly overlapped, blurring the distinction between a WGFM and MPFM. As wet gas flow is presently considered a subset of multiphase flow, a WGFM is an
35、 MPFM that specializes in gas-dominant multiphase flow conditions. In this Technical Report, such technologies will be referred to as WGFMs. There are many factors that contributed in the decision to replace a separator with a WGFM, with each application warranting careful consideration. A well-desi
36、gned and maintained separator working within an appropriate flow condition range should produce accurate flow measurements. A primary concern for oil and gas companies was to reduce costs by replacing complex and bulky test separators, as well as to further simplify the upstream infrastructure, in p
37、articular for offshore and subsea projects. WGFMs typically require lower capital 1)and operational 2)expenditures than fully equipped test separators. More savings in CapEx may be achieved by omitting dedicated test lines in satellite developments. In addition, there is a significant benefit for of
38、fshore developments, in terms of weight and space conservation, by using the much smaller footprint of WGFMs. Due to various operational problems, a conventional test separator does not continuously provide accurate and reliable well test data, giving only relevant information when the well is switc
39、hed to the test separator. With the use of WGFMs testing well production more frequently or even continuously becomes possible. WGFM developments and extensive testing over the last two decades have resulted in WGFM technology that is a viable alternative to a test separator. Modern WGFMs now offer
40、continuous well monitoring (per installation on individual wells). WGFM technology is an attractive option for multiphase wet gas flow measurement. Over the last two decades, some WGFMs have been developed from prototypes into very mature, robust, advanced, and field-proven measurement devices, incr
41、easing their application scope. Although originally intended for use mainly in reservoir and well production allocations, WGFMs have evolved into a technology that spans even fiscal product allocation. In the latter case, the output of a WGFM is used to determine money transactions between operating
42、 companies or between an operating company and a host government. This Technical Report focuses on the measurement of wet gas flow, i.e. terminology, models, and principles, and the design, implementation, testing, and operation of WGFMs. 1) Capital expenditure (CapEx) or costs for purchasing and in
43、stalling a WGFM/MPFM includes all hardware to operate the WGFM (data transmission, verification facilities, sampling arrangements, etc.) 2) Operating expenditure (OpEx) or costs to operate a WGFM/MPFM (maintenance, verification processes, sampling for fluid properties, etc.) ISO 2015 All rights rese
44、rved vii Natural Gas Wet gas flow measurement in natural gas operations 1 Scope 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 hydrocarb
45、on liquids 3)(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
46、 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. Single-phase gas flow meter with
47、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 sourc
48、e. 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. WG
49、FM: 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. 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-lin
