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Production Chemistry Networking Event
Custody Transfer and Allocation Metering
Guidelines and Standards
Colin Lightbody
15th October 2019
Technology Manager
SGC Metering
2
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
3
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
4
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
5
Offshore Projects & Operations
UK North Sea Forties Pipeline
St. Fergus Terminals
6
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
7
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
8
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…….
9
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
10
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
11
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
12
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
13
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
14
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
15
• 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
16
What questions do you
have for me?
17