ISO/TS 26762:2025

Technical
Specification
ISO/TS 26762
First edition
Design and operation of allocation
2025-04
systems used in gas productions
facilities
Conception et opération des systèmes d'allocation dans les
installations de production de gaz
Reference number
© ISO 2025
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Contents Page
Foreword .vii
Introduction .viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Fluids .2
3.2 Definitions for allocation systems .4
3.3 Streams .6
4 Allocation fundamentals . 7
4.1 Allocation definition and objective .7
4.2 Allocation and metering .7
4.3 Gas productions facilities .7
4.4 Allocation applications and cases .8
4.5 Allocation types and classification .8
4.5.1 General .8
4.5.2 Technical allocation .8
4.5.3 Contractual and fiscal allocation .9
4.6 Allocation in the value realization chain.9
4.7 Allocation boundaries and steps .11
4.8 Physical streams . 12
4.8.1 General . 12
4.8.2 Products . 12
4.8.3 Input streams . 13
4.8.4 Fluid characteristics . 13
4.8.5 Gas and liquid compositions . 13
4.9 Allocation process . 13
4.10 Gas allocation cases summary .14
4.11 Allocation methodology .14
4.12 Balance and reconciliation . . 15
4.12.1 Balance . 15
4.12.2 Reconciliation .17
4.13 Units .17
4.14 Upstream allocation example .17
4.15 Contractual gas allocation.18
4.15.1 General .18
4.15.2 Gas-allocation issues . .19
4.15.3 Measurement .19
4.15.4 Terminal products . 20
4.15.5 Pipeline capacity . 20
4.15.6 System response time . 20
4.15.7 Agreements . 20
4.15.8 Regulatory . . .21
4.15.9 Commercial issues .21
4.15.10 Time period .21
4.15.11 Forecasting .21
4.15.12 Pipeline stock . 22
4.15.13 Existing systems . 22
4.15.14 Data timing . 22
4.15.15 Data flow and reporting. 22
4.15.16 Auditing . 22
4.15.17 Fallback . 22
4.15.18 Summary . 22
5 Fluid property and parameters for allocation .23

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5.1 Fluid types . 23
5.2 Gas and liquid properties .24
5.2.1 General .24
5.2.2 Stabilized fluids .24
5.2.3 Equilibrium gas (separated gas at dew point) .24
5.2.4 Equilibrium liquid (separated liquid at bubble point) .24
5.2.5 Flash calculations for non-stabilized and wet gas flows .24
5.3 Fluid information for allocation . 25
5.3.1 Fluid compositions . 25
5.3.2 Fluid properties . . . 25
5.3.3 Allocation process factors for gas allocation . 26
5.3.4 Blending effect . 29
5.4 Use of phase behaviour/process simulation models . 29
5.4.1 Introduction . 29
5.4.2 Applications . 30
5.4.3 Process simulation model types . 30
5.4.4 Fundamentals of a process simulation model .31
5.4.5 Using process simulation models .31
5.4.6 Construction of a process simulation model .32
5.4.7 Modelling approaches . 33
5.4.8 Example of process simulation modelling for allocation: calculation of shrinkage
factors . 34
6 Measurements, sampling and analysis .36
6.1 General . 36
6.2 Flow measurements. 36
6.2.1 Single-phase liquid measurement . 36
6.2.2 Multiphase measurements .37
6.2.3 Gas measurement .37
6.2.4 Wet gas and multiphase fluids . 39
6.2.5 Indirect methods . 40
6.2.6 Virtual metering . 40
6.2.7 Measurement uncertainty . 40
6.3 Sampling .41
6.3.1 General .41
6.3.2 Single phase gas .41
6.3.3 Single-phase liquid .41
6.3.4 Wet gas sampling .41
6.3.5 Multiphase sampling .42
6.3.6 PVT sampling .42
6.3.7 Considerations on sampling points .42
6.3.8 Sampling of gas containing sulfur compounds .42
6.4 Analysis .43
6.4.1 Wet gas composition analysis .43
6.4.2 Gas chromatographic method for compositional analysis .43
6.4.3 Laser Raman spectroscopy and infrared spectroscopy method .43
6.4.4 Analysis for geochemical fingerprinting .43
6.4.5 Sulfur content analysis .43
6.4.6 Water content analysis.43
6.4.7 Analysis of gaseous water .43
6.4.8 Analysis of liquid water fraction .43
6.4.9 Water-liquid ratio for liquid . 44
6.4.10 Determination of particles content . . 44
6.4.11 Wet gas physical parameters measurement . 44
6.4.12 Density . 44
6.4.13 Compression factor . 44
6.4.14 Speed of sound . . .45
6.4.15 Calorific value .45
7 Allocation principles .45

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7.1 General .45
7.2 Allocation methods .45
7.3 Allocation units for gas allocation . 46
7.4 Proportional allocation . 46
7.4.1 General . 46
7.4.2 Pro rata based on estimations . 48
7.4.3 Component mass pro rata . 49
7.5 Allocation by by-difference . 50
7.6 Allocation by process simulation . 50
7.7 Uncertainty based allocation . .51
7.8 Geochemical fingerprinting . 53
7.9 Conversion calculation . 53
7.9.1 Mass allocation conversion into volume . 53
7.9.2 Mass allocation conversion to energy . 55
7.10 Quantity allocation . 56
7.10.1 General . 56
7.10.2 Mass-quantity allocation .57
7.10.3 Volume quantity allocation .57
7.10.4 Energy-quantity allocation .57
7.11 Allocation calculations .57
7.11.1 General .57
7.11.2 Calculations at the measurement points .57
7.11.3 Allocated field’s share . 60
7.12 Allocation methodology selection . 63
7.13 Balancing and reconciliation calculations . 64
7.13.1 General . 64
7.13.2 Reconciliation . 64
7.13.3 Balancing and reconciliation accounts . 65
8 Utility and disposed gas allocation .65
8.1 General . 65
8.2 Utility gas allocation by volume .67
8.3 Injection and sales (purchase) gas allocation . 69
8.4 Export gas and oil mass and volume .70
9 Inventory .70
10 Allocation cases and typical lay out .71
10.1 Allocation cases .71
10.1.1 General .71
10.1.2 Well allocation and well production . 72
10.1.3 Asset, field and subgroup, upstream allocation . 73
10.1.4 Pipeline, midstream allocation . 73
10.1.5 Terminal, downstream allocation . 73
10.1.6 Liquid natural gas .74
10.1.7 Carbon dioxide CO .74
10.1.8 New development tied into an existing one .74
10.1.9 New development tied into an existing transportation system. . 75
10.2 Typical allocation lay out . 75
10.2.1 Gas only. 75
10.2.2 Dry gas in, dry gas and liquid out .76
10.2.3 Wet gas combined in, dry gas and liquid out .76
10.2.4 Dry gas and liquid in; dry gas and liquid out . 77
11 Allocation uncertainty (from HM 96) .78
11.1 General . 78
11.2 Relative and absolute uncertainty . 78
11.3 Uncertainty of a calculated value -analytical solution . 78
11.4 Allocation per difference . 79
11.5 Proportional/pro rata allocation . 80
11.6 Uncertainty based allocation . . 81

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11.7 Uncertainty of a calculated value – other methods . 82
11.8 Uncertainty contributors . 82
12 Allocation systems design and integration .82
12.1 General . 82
12.2 Metering and allocation philosophy . 85
12.3 Allocation agreements . 85
12.4 Regulations . 85
12.5 Development procedure . 85
12.5.1 General . 85
12.5.2 Step 1 . 86
12.5.3 Step 2 . 87
12.5.4 Step 3 . 87
12.5.5 Step 4 . 88
13 Operation of allocation systems .88
13.1 General . 88
13.2 Input QA/QC . 90
13.3 Imbalance follow up . 90
13.4 Trending .91
13.5 Surveillance .91
13.6 Validation .91
13.6.1 General .91
13.6.2 Meter validation . 92
13.6.3 Allocation procedures and process validation . 92
13.6.4 Data validation . 93
13.6.5 Data reconciliation . 93
13.6.6 Process-model validation . 93
13.6.7 Allocation-process results validation . 93
13.6.8 Software validation . 94
13.7 Mismeasurement handling . 94
14 Audits .95
14.1 General . 95
14.2 Metering and allocation audit objectives . 95
14.3 MandA audit boundary and activity . 95
14.3.1 Installations . 95
14.3.2 Systems . 95
14.3.3 Metering and allocation activity . 96
14.4 Audit scope . 96
14.5 Audit findings . 97
14.5.1 General . 97
14.5.2 Audit exceptions . 97
14.5.3 Audit recommendations . 97
14.5.4 Audit observation . 97
14.5.5 Allocation audit checklist . 97
Annex A (informative) Exposure to loss/risk assessment .99
Bibliography .103

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