Production Chemistry Networking Event

Custody Transfer and Allocation Metering

Guidelines and Standards

Colin Lightbody

15th October 2019

Technology Manager

SGC Metering

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Topics

• What is Custody Transfer and Allocation metering?

• Who regulates this metering?

• Who writes the standards used in the regulations?

• Metering standards – crude oil metering system

• Metering standards – natural gas metering system

• Key points to take away

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Terminology

Custody Transfer and Allocation Metering

• Custody Transfer Metering

• Custody transfer occurs at any metering system

where the ownership of the fluid is being transferred

from one party to another

• Measurement uncertainty for these systems is

typically ±1% for gas systems and ± 0.25% for liquid

• Fluid volume (or mass) and fluid composition

information both essential for a fair and equitable

transaction

• Following the regulations and standards is a good way

of achieving and maintaining these low uncertainties

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Offshore Projects & Operations

• Allocation

• Several offshore operators all putting

hydrocarbons into a shared pipeline to a single

on-shore reception terminal

• Terminal operator will have metering, sampling,

and analysis at the terminal to measure the total

amount and quality of fluid entering the terminal

• Offshore operators will (or should!) have

metering, sampling and analysis on each

installation to determine their pipeline input

• Metering, sampling and analysis that is used for

helping figure out who gets what is known as

allocation metering

• Sometimes allocation metering gets quite

complex…

Terminology

Custody Transfer and Allocation Metering

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Offshore Projects & Operations

UK North Sea Forties Pipeline

St. Fergus Terminals

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The regulatory framework for North Sea Operators

Who Regulates Custody Transfer and Allocation Metering?

• For custody transfer and allocation metering

in the UK the Oil & Gas Authority (OGA) is

responsible for licensing and regulation

• The Guidance Notes for Petroleum

Measurement is the “go-to” document

• In Norway regulation is by the Norwegian

Petroleum Directorate (NPD)

• Functional and technical requirements are

defined in NORSOK I-106

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The references used by the regulators…..

What are the guidelines based on?

• Both the OGA and NPD reference standards

from many international bodies

• International Standards Organisation (ISO)

• British Standards Institute (BSI)

• Energy Institute (EI)

• American Petroleum Institute (API)

• American Gas Association (AGA)

• Norwegian Society for Oil and Gas Flow

Measurement (NFOGM)

• The European Gas Research Group (GERG)

• North Sea Flow Measurement Workshop

Papers

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One Metering System – Many Standards!

• Countless standards for a typical oil or gas metering system

• Majority not measurement or analysis related, but essential

• Skid

• Pipe and valve selection

• Welding quality

• Cable trays

• Lights

• Junction boxes

• Bolts……

• Control System and Panel

• Barriers and isolation

• Power supplies

• Cabling…….

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Primary Flow Element - Liquid Ultrasonic meter

Oil Metering Skid – Metering Standards

Liquid Ultrasonic Meter

ISO 12242:2012 Measurement of fluid flow in closed

conduits — Ultrasonic transit-time meters for liquid

ISO 5168:2005, Measurement of fluid flow — Procedures for the evaluation

of uncertainties

ISO 11631:1998, Measurement of fluid flow — Methods of specifying

flowmeter performance

ISO/IEC 17025, General requirements for the competence of testing and

calibration laboratories

ISO 80000-4:2006, Quantities and units — Part 4: Mechanics

ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to

the expression of uncertainty in measurement (GUM:1995)

ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and

general concepts and associated terms (VIM)

Each standard references

other standards

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Meter proving – turbine master meter

One Metering Skid – Many Metering Standards!

Turbine Master Metering Stream

API MPMS, Chap. 4.5, Master meter provers

API MPMS, Chap. 5.1, Metering – General considerations

API MPMS, Chap. 5.3, Measurement of Liquid Hydrocarbons by Turbine Meters

ISO 7278-1:1987

Liquid hydrocarbons — Dynamic measurement — Proving

systems for volumetric meters — Part 1: General principles

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Meter Proving – Piston Prover

One Metering Skid – Many Metering Standards!

Compact Prover

API MPMS:

Chapter 4.2 Displacement Provers

Chapter 4.6 Pulse Interpolation

Chapter 4.8 Operation of Proving Systems

Chapter 12.2 Calculation of Petroleum Quantities

Chapter 13 Statistical Aspects of Measuring and Sampling

ISO 7278-1:1987

Liquid hydrocarbons — Dynamic measurement

— Proving systems for volumetric meters —

Part 1: General principles

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Fluid mixing and sampling

One Metering Skid – Many Metering Standards!

Powered Mixer and Automatic Sampling System

API MPMS Chapter 8 Sampling

Section 2-Standard Practice for Automatic Sampling of Liquid Petroleum and

Petroleum Products

ISO 3171:1988

Petroleum liquids — Automatic pipeline

sampling

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Natural gas custody transfer metering skid – Orifice metering

Another Metering Skid – Many More Metering Standards!

Orifice Plate Metering Stream

ISO 5167-1:2003

Measurement of fluid flow by

means of pressure differential

devices inserted in circular

cross-section conduits running

full — Part 1: General principles

and requirements

ISO 5167-2:2003

Part 2: Orifice plates

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Natural gas custody transfer metering skid – gas sampling and analysis

Another Metering Skid – Many More Metering Standards!

Gas Sampling and Analysis system

ISO 6976 Natural gas — Calculation of

calorific values, density, relative density and

Wobbe indices from composition

AGA Report No. 8, Part 1,

Thermodynamic Properties of

Natural Gas and Related Gases,

DETAIL and GROSS Equations of

State

ISO 10715:1997

Natural gas — Sampling

guidelines

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• Custody transfer and allocation metering transactions are very high value

• Mistakes in design and operation can generate significant financial

exposures for operators and treasuries

• It is a very heavily regulated segment of the oil and gas industry

• Failure to adhere to the regulations is always painful for the operator

• Kicked out of pipeline sharing agreement

• Fines up to £1,000,000 (OGA)

• Removal of production license.

Key points to take away

Summary

Gas Price 2.6 $/MMBTU

Gas Energy Content 1200 BTU/SCF

Daily Gas Export Volume 50 MMSCF

Daily Gas Export Energy 60,000 MMBTU

Daily Gas Export Value 156,000 US$

Actual Metering Uncertainty 2 ± %

Required Metering Uncertainty 1 ± %

Daily financial exposure @ current uncertainty 3,120 US$

Daily financial exposure @ target uncertainty 1,560 US$

Daily financial exposure due to mis-measurement 1,560 US$

Additional annual exposure due to mis-measurement 569,400 US$

Gas Price 2.6 $/MMBTU

Gas Energy Content 1200 BTU/SCF

Daily Gas Export Volume 1000 MMSCF

Daily Gas Export Energy 1,200,000 MMBTU

Daily Gas Export Value 3,120,000 US$

Actual Metering Uncertainty 5 ± %

Required Metering Uncertainty 1 ± %

Daily financial exposure @ current uncertainty 156,000 US$

Daily financial exposure @ target uncertainty 31,200 US$

Daily financial exposure due to mis-measurement 124,800 US$

Additional annual exposure due to mis-measurement 45,552,000 US$

Natural Gas Mis-measurement Financial Exposure Calcuation

Natural Gas Mis-measurement Financial Exposure Calcuation

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What questions do you

have for me?

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