Gas quality and custody transfer
challenges for UK gas network entry of
non-conventionally sourced gases
Diane Broomhall and Martin Brown
GL Noble Denton
GL Noble Denton
GL Noble Denton are independent advisors
providing consulting, design, assurance and project
execution services, combining excellent engineering
and analytical skills with operational experience of
offshore, maritime and onshore oil and gas assets.
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GL Noble Denton:
Gas Quality and Interchangeability
GL Noble Denton's consultancy services for Gas Quality include:
> network integrity
> measurement of gas properties to meet safety and contractual obligations
> energy metering and combustion analysis
Services used by clients to:
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support planning applications
review network operations
recommend, specify and evaluate monitoring instrumentation
Rhinology practices
ensure consistent and accurate energy accounting
Training courses on variations in natural gas from different international
sources and the impact of these variations
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UK Gas Quality Compliance
Statutory:
> Gas Safety (Management) Regulations 1996
> Gas (Calculation of Thermal Energy) Regulations 1996
UK Health & Safety Executive
> Licenced Gas Transporter’s Safety Case to the HSE
Licensed Gas Transporter Policies and Procedures
Network Entry Agreement between Licensed Gas
Transporter and Gas Producer
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UK Gas Safety (Management)
Regulations 1996
Property
Range or limit
Hydrogen sulphide (H2S)
< 5 mg m-3
Total sulphur
< 50 mg m-3
Hydrogen (H2)
< 0.1 mol %
Oxygen (O2)
< 0.2 mol %
Impurities
Wobbe Number
The gas shall not contain solids or liquids
that may interfere with the integrity or
operation of the network or appliances
≥ 47.20 and ≤ 51.41 MJ m-3
ICF (Incomplete Combustion Factor)
< 0.48
SI (Sooting Index)
< 0.60
Odour
Gas below 7 barg will have a stenching
agent added to give a distinctive odour
Water and hydrocarbon dewpoints
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UK Gas Interchangeability Diagram
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UK Gas (Calculation of Thermal
Energy) Regulations
Legislates for the transfer of natural gas between producers, transporters
and customers
Ensures customers receive the thermal energy specified on their gas bill
A public gas transporter shall make determinations of calorific values of
the gas conveyed by him to premises, or to pipe-line systems operated by
other public gas transporters
Where a public gas transporter has made a CV declaration, any average
calorific value of the gas conveyed to any take off point situated in the
area in respect of which the declaration is made is not less than that
declared calorific value
Any public gas transporter contravening any provision of these
Regulations shall be guilty of an offence and liable to be fined
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Practical application of Gas (COTE)
Regulations
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Practical application of Gas (COTE)
Regulations
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Licensed UK Gas Transporter’s
Safety Case to the HSE
In order to obtain a Gas Transporter’s licence a
Safety Case must be submitted to the UK HSE
The Safety Case describes what Policies and
Procedures are in place to ensure the safe
transportation of gas
One such Procedure is a Risk Assessment for all new
gas connections
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Risk Assessment for New Gas
Connections
All UK licensed Gas Transporters have an obligation
to ensure:
> any new gas connections complies with all statutory legislation
with regard to gas quality, calorific value and flow measurement
> The safety and integrity of the gas network is not compromised
> The new gas will not affect the operation of gas customers’
appliances
> Will not impact on the health of the general public either directly
or indirectly via gas combustion products
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Risk Assessment for New Gas
Connections
To ensure the correct gas measurement provisions
are included in the new NEA, the risk assessment
considers:
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The content and characteristics of gas
Odorisation
Calorific value measurement
Volume and energy flow measurement
Volume flow measurement for network control
Wet gas control, monitoring and reporting
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Gas Distribution Network Entry
Agreement – Gas Composition
Gas Component
GS(M)R limits
Typical NEA limit
5 mg m-3 = 3.3 ppm (v)
5 mg m-3 = 3.3 ppm (v)
Total sulphur
50 mg m-3
50 mg m-3
H2
0.1 mol %
0.1 mol %
O2
0.2 mol %
0.001 to 0.2 mol %
Total inerts
GS(M)R gas
interchangeability diagram
≤ 7 mol %
and CO2 ≤ 2 mol %
Gas content
GS(M)R gas
interchangeability diagram
Suitable for Ofgem
approved instruments
Total organic halides
“impurity”
≤ 1.5 mg m-3
Radioactivity
“impurity”
≤ 5 Becquerels g-1
H2S
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Gas Distribution Network Entry
Agreement – Gas Properties
Gas Property
GS(M)R limits
Typical NEA limit
HC dewpoint
Maintain integrity of grid &
appliances
≤ -2°C up to 85 barg
H2O dewpoint
WN, ICF, SI
CV
Characteristic odour for gas
≤ 7 barg
Gas temperature
Gas pressure
≤ -10°C @ 85 barg
See GS(M)R gas interchangeability diagram
WN calculation
> Target FWACV - 0.5 MJ m-3
No component that removes gas odorant or suppresses
its impact on the human nose
—
1 to 38°C
Safe for gas appliances
Depends on back pressure
and MOP @ Delivery Point
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Potential contaminants in
non-conventionally sourced gases
Potential contaminants in non-conventionally sourced gas
Component
Biomethane
BioSNG
Coal bed
methane
Shale gas
High Inerts (CO2, N2)
H2S
Total Sulphur
O2
H2
Moisture
Siloxanes
Organic halides
Micro-organisms
Terpenes
Aldehydes & ketones
Ammonia
Volatile metals (Hg, As)
Pesticides & Pharmaceuticals
CO
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Safety consequences of
uncontrolled gas connection
Component
Safety Consequences
Corrosion
Steel
(gas network)
Copper
(domestic)
High Inerts (CO2, N2)
High CO2 + H2O
H2S
If H2O present
Combustion
Control of
industrial
Safety
processes
Leakage
detection by
public
(odour)
Total sulphur
O2
Depends of partial pressure of O2
and presence of H2O
Moisture
Siloxanes
Organic halides
Micro-organisms
If H2O present
Terpenes
Aldehydes & ketones
Ammonia
Volatile metals (Hg, As)
Pesticides &
Pharmaceuticals
CO
Liquid Hg
If H2O present
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New gas connections responsibilities
Maximum connection model
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New gas connections responsibilities
Minimum connection model
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Challenge for the UK gas networks
Educate producers of non-conventionally sourced gases:
> GS(M)R compliance is a legal requirement
> Producers assume the networks have the capacity to
accommodate non-compliant gas
> Proof of GS(M)R compliance will be required
> Detailed analysis of their raw product will reduce retro-fitted
clean-up kit
> Analytical equipment must be fit-for-purpose
> Equipment for monitoring clean-up process not necessarily good
enough for monitoring GS(M)R compliance
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In conclusion:
Gas supply to the UK has changed and will continue
to change
Connection to non-conventionally sourced gas
supplies currently limited but expected to increase
rapidly
Regulatory bodies reviewing some safety limits
Gas producers must comply with very specific NEA
that includes CV limits for billing
Current challenge is the education of gas producers
with regard to GS(M)R and Gas (COTE) Regulations
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Thank-you for your attention
Contacts details:
Diane Broomhall
Martin Brown
Technical Consultant
Senior Consultant
Gas Quality Group, Utilities
Energy Measurement & Compliance
GL Noble Denton
GL Noble Denton
Phone: +44 1509 282128
Phone: +44 1509 282468
[email protected]
[email protected]
www.gl-nobledenton.com
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Gas Quality supplies to the UK
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