ISO/TS 26762:2025

Design and operation of allocation systems used in gas productions facilities

This document specifies how to design and operate allocation systems for gas production facilities. It describes the most common types, principles and methods used for the allocation of gas and associated liquids. The objective is to provide an approach to current best practice in the oil and gas industry. It applies to gas and liquid allocations to be performed in production, processing, transportation, storage and terminal installations dealing with natural gas and associated liquids as well as end products like sales gas, liquefied petroleum gas (LPG), liquefied natural gas (LNG), condensate and to some extend non-hydrocarbon gases like CO2, H2. This document provides the minimum information needed to develop and implement allocation procedures and systems both for internal purposes (well allocation) and fiscal or commercial applications with different owners and stakeholders. This document can be used to develop gas and liquid processing and transportation agreements and regulatory documents as well as to conduct audit of measurement and allocation systems. It also introduces the areas of competence needed and the terminology used in the industry.

Conception et opération des systèmes d'allocation dans les installations de production de gaz

General Information

• Status: Published
• Publication Date: 20-Apr-2025
• ICS: 75.160.30 - Gaseous fuels
• Technical Committee: ISO/TC 193/SC 3 - Upstream area
• Drafting Committee: ISO/TC 193/SC 3 - Upstream area
• Current Stage: 6060 - International Standard published
• Start Date: 21-Apr-2025
• Due Date: 07-May-2025
• Completion Date: 21-Apr-2025

Relations

• Revises: ISO/TR 26762:2008 - Natural gas - Upstream area - Allocation of gas and condensate
• Effective Date: 08-Jul-2023

Overview

ISO/TS 26762:2025 - Design and operation of allocation systems used in gas production facilities provides a best-practice technical specification for designing, implementing and operating allocation systems for natural gas and associated liquids. It covers allocation of inputs and products across production, processing, transportation, storage and terminal installations - including sales gas, LPG, LNG, condensate and, to some extent, non‑hydrocarbon gases (CO2, H2). The document supplies minimum information required for internal well allocation, fiscal/commercial allocation, contractual agreements, regulatory documents and measurement/allocation audits.

Key topics and requirements

• Allocation fundamentals: definitions, objectives, types (technical vs contractual/fiscal), boundaries and stepwise allocation processes.
• Physical streams & products: classification of input streams and end products, fluid characteristics and composition considerations.
• Fluid properties & phase behavior: requirements for stabilized/equilibrium fluids, flash calculations, blending effects and use of process simulation models to support allocation (e.g., shrinkage factors).
• Measurement, sampling and analysis: flow measurement methods (single‑phase, multiphase, wet gas, indirect and virtual metering), sampling best practices, laboratory analysis and measurement uncertainty.
• Balance, reconciliation & reporting: mass/volume balance approaches, reconciliation procedures, units and timing, data flow and reporting, and auditing/fallback arrangements.
• Operational & commercial considerations: pipeline capacity, system response time, forecasting, contractual clauses, regulatory interfaces and stakeholder reporting.
• Competence & terminology: recommended areas of competence and standardized terminology for consistent implementation.

Practical applications

ISO/TS 26762:2025 is applied to:

• Develop and document allocation procedures and systems for oil & gas production and processing facilities.
• Create commercial and fiscal agreements, transportation/processing contracts and regulatory filings involving allocation rules.
• Design measurement and allocation solutions for onshore/offshore platforms, processing plants, terminals (LNG, LPG) and pipeline networks.
• Support audits of measurement systems and allocation outcomes, ensuring traceability, reconciliation and accepted uncertainty.
• Guide engineering teams in integrating process simulation and metering data to compute allocations and shrinkage.

Who should use this standard

• Upstream/downstream operators and production engineers
• Measurement and metering engineers, sampling & laboratory teams
• Commercial, regulatory and contract managers
• Consultants, auditors and technical negotiators
• Process simulation and reservoir engineers

Related guidance

Use ISO/TS 26762 alongside relevant measurement, metering and sampling standards and industry best practice documents for a complete allocation and metering governance framework.

Keywords: ISO/TS 26762:2025, allocation systems, gas production facilities, gas allocation, liquid allocation, metering, sampling, process simulation, fiscal allocation, measurement uncertainty.

Standards Content (Sample)

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
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
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

iii
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

iv
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

v
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

vi
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