CGE Training Materials National Greenhouse Gas Inventories

Training Materials for National Greenhouse Gas Inventories

Consultative Group of Experts (CGE)

CGE Training MaterialsNational Greenhouse Gas Inventories

Energy Sector – Fugitive Emissions

Version 2, April 2012

2

Target Audience and Objectives of the Training Materials

These training materials are suitable for people with beginner to intermediate level knowledge of

national greenhouse gas (GHG) inventory development.

After having read this Presentation, in combination with the related documentation, the reader should:

a) Have an overview of how emissions inventories are developed for the energy sector (fugitive

emissions);

b) Have a general understanding of the methods available, as well as of the main challenges in

that particular area;

c) Be able to determine which methods suits their country’s situation best;

d) Know where to find more detailed information on the topic discussed.

These training materials have been developed primarily on the basis of methodologies

developed by the IPCC; hence the reader is always encouraged to refer to the original

documents to obtain further detailed information on a particular issue.



3

Acronyms

• IEA International Energy Agency

• ppmv Parts per million by volume

• UNSD United Nations Statistics Department



41.4

Outline of this presentation – Fugitive Emissions

• Fugitive emissions

Introduction (slide 3)

Coal mining and handling (slide 5)

Oil and natural gas systems (slide 15)

Data issues (slide 31)

References (slides 14, 33, 34)



51.5

Introduction

• Fugitive emissions: the sum of emissions from accidental discharges,

equipment leaks, filling losses, flaring, pipeline leaks, storage losses, venting and

all other direct emissions except those from fuel use

• Mainly methane (CH4)

• Entrained carbon dioxide (CO2) can be significant in some cases

• Minor nitrous oxide (N2O) emissions from flaring.



61.6

Sources of Fugitives Emissions

• Solid fuels (primarily coal) Mining, handling, processing and storage.

• Oil and natural gas systems • Exploration, production, processing, refining, transmission, storage

and distribution.



71.7

Coal Mining and Handling

Release of trapped methane during mining

In-situ methane content of coal can vary widely

Most fugitive emissions occur at the mine

Some residual emissions occur from post-mining handling / processing activities.



8Training Materials for National Greenhouse Gas Inventories


91.9

Surface vs. Underground

• Two types of coal mines – surface and underground.

• Emissions increase with mine depth:

• i.e. higher emissions for underground mines.

• Emissions also depend on the gas content of coal:

• Some gas may remain in the coal

• 60–75% gas released during mining activity.



101.10

Abandoned Mines

• Emissions may continue after the mines have stopped producing coal.

• Typically, emissions decline rapidly once deep mine coal production stops.

• In some cases, emissions by the surrounding strata may be significant and continue for years afterwards.

• Coal waste or reject piles are minor sources of emissions.

• Flooding of mines can prevent emissions.



111.11

Controlling Emissions

• Degasification wells:

• Gas conservation

• Flaring.

• Use of catalytic combustors on the outlet of ventilation systems for underground

mines.



121.12

Monitoring and Activity Data

• Methane content of exhausted ventilation air (Tier 3)

• Coal production (Tier 1 or 2)

• Imports and exports by type of coal:• Post-mining emission, likely to be minor

• Information on the depth of each mine (Tier 2).



131.13

Tier 1 and Tier 2

• Tier 1 global average emission factors.

• Tier 2 country - or basin-specific emission factors based on actual CH4 content of coal

mined.



Source: IPCC good practice guidance, page 2.70.

141.14

Tier 3: Underground Mines

• Underground mines generally must have ventilation and degasification

systems for safety reasons.

• Often there are also degasification wells around the mining area.

• Use data to estimate emissions or to develop more specific emission

factors.

• When methane recovery from degasification wells occurs before mining,

emission should be reported in the year the coal was actually extracted.



151.15

Coal Mining Data Issues…

• Initial focus can be on most “gassy” mines for Tier 3 approach, and apply Tier

1 or 2 for other mines.

• Tier 3 not likely to be feasible for surface mines or post-mining.

• Methane recovered and combusted for energy should be included in fuel

combustion emissions.

• No inventory method is provided for coal fires.

• Significant quantities of CO2 can also be released during mining.



161.16

Coal Mining Data Issues (cont.)

• Coal statistics usually include primary (hard coal and lignite) and derived

fuels (patent fuel, coke oven coke, gas coke, brown coal briquettes, coke

oven gas and blast furnace gas). Peat may also be included.

• No information is typically provided on the method of mining (i.e.

surface or underground) or the depth of the mines. A conservative

approximation is to assume that lignite coal is surface mined and bituminous

and anthracite coal is from underground mines.

• Some useful unpublished data, including mine depth, are available from

IEA upon special request.



171.17

Coal Mining References

• Coal statistics are available for most countries from:

• US Energy Information Administration (EIA) <http://www.eia.gov/>

• United Nations Statistics Department (UNSD)

< http://unstats.un.org/unsd/default.htm>

• International Energy Agency (IEA) <http://www.iea.org/>.



181.18

Oil and Natural Gas Systems

• Equipment leaks

• Process venting and flaring

• Evaporation losses (i.e. from product storage and handling, particularly where

flashing losses occur)

• Accidental releases or equipment failures.



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• Characteristics of the hydrocarbons being produced, processed or handled:

• Conventional crude oil• Heavy oil• Crude bitumen• Dry gas• Sour gas (more than 10 ppmv of hydrogen sulphide (H2S))• Associated gas

• Equipment numbers, type and age

• Industry design, operating and maintenance practices

• Local regulatory requirements and enforcement.

1.20

Emission Rates Depend On…

i.e. methane content of fuel and

leakiness of equipment



211.21

Emissions From Venting and Flaring Depend On…

• The amount of process activity

• Operating practices

• On-site utilization opportunities for methane

• Economic access to gas markets

• Local regulatory requirements and enforcement.



221.22

Accidental Releases…

• Difficult to predict

• Can be a significant contributor

• Can include:• Well blowouts• Pipeline breaks• Tanker accidents• Tank explosions• Gas migration to the surface around the outside of wells• Surface casing vent blows• Leakage from abandoned wells.



231.23

Size of the Facility

• Oil and gas systems tend to include many small facilities.

• Exceptions:• Petroleum refineries• Integrated oil sands mining and upgrading operations.

• Small facilities are likely to contribute most of the fugitive emissions.

• Less information is available for smaller facilities.



241.24

Oil-Gas Composition

Raw natural gas and crude oil contains:

• A mixture of hydrocarbons

• Various impurities including H2O, N2, argon, H2S and CO2

• Impurities are removed by processing, treating or refining.

H2S:

• Sour gas if more than 10 ppmv of H2S

• Sweet gas if less than 10 ppmv of H2S

• The concentration of H2S tends to increase with the depth of the well.



251.25

Acid Gas

• By-product of the sweetening process to remove H2S

• May contain large amounts of raw CO2

• Regardless of how processed…• Sulphur recovery unit• Flared or vented

• …the raw CO2 is released to the atmosphere.



261.26

Patterns of Emissions

• Emissions increase as you go upstream through system.

• Emissions decrease with concentration of H2S in the produced oil and

gas.



271.27

Equipment Leaks

• Tend to be continuous emitters

• Low to moderate emission rates

• All equipment leaks to some extent

• Only a few per cent of the potential sources at a site actually leak sufficiently at

any time to be in need of repair or replacement

• If less than 2% of the total potential sources leak, the facility is considered well-

maintained.



281.28

Sources of Equipment Leaks

• Valves

• Flanges and other connections

• Pumps

• Compressors

• Pressure relief devices

• Process drains

• Open-ended valves

• Pump and compressor seal system degassing vents

• Accumulator vessel vents

• Agitator seals

• Access door seals.



291.29

Trends in Equipment Leaks

• Less leakage as toxic nature of material increases

• Less leakage where gas has been odorized (thus less leaking in sour gas sections

of systems)

• More leakage where equipment is subjected to frequent thermal cycling, vibrations

or cryogenic service.



301.30

Storage Losses

• Boiling or flashing losses of methane occur from storage tanks

• Occurs at production and processing facilities where hydrocarbon liquid flows

directly from a pressure vessel where it has been in contact with natural gas.



311.31

Methodologies

• Tier 3: Requires detailed inventories of equipment, infrastructure and bottom-up emission factors.

• Tier 2: Based on a mass balance estimate of the maximum amount of methane that could be emitted:

• Only for oil systems

• Based on gas-oil ratios.

• Tier 1: Uses national oil and gas production data and aggregate emission factors.



321.32

Fugitive Emissions Data

• Poor quality and incomplete data about venting and flaring is common:• Contact industry representatives for standard practices to split venting and

flaring.

• Data about equipment leaks at minor facilities is unavailable or incomplete:• Well-site facilities• Field facilities.



331.33

Fugitive Emissions Data (cont.)

• Collecting activity data for fugitive sources is difficult and resource intensive

• There are no real shortcuts available.

• First step can be to interview experts in industry on common practices and

processes…

• …have them compare national practices with those of countries with a known

emissions profile (e.g. an Annex I country).



341.34

Venting and Flaring Data

• Flared if gas poses an odour, health or safety concern

• Otherwise vented

• Often inconsistencies in vented and flared volumes reported by companies

• Problem with some vented volumes being reported as flared.



351.35

Oil and Gas System Data Issues

• International production data are expressed on a net basis (i.e. after shrinkage, losses, reinjection, and

venting and flaring).

• Crude oil normally includes hydrocarbon liquids from oil wells and lease condensate (separator liquids)

recovered at natural gas facilities. May also include synthetic crude oil from oil sands and shale oil.

• Infrastructure data is more difficult to obtain than production statistics.



361.36

Oil and Gas System Data Issues (cont.)

• Information on the numbers and types of major facilities, types of processes

used at these facilities, numbers and types of active wells, numbers of wells

drilled, and lengths of pipeline are typically only available from national

agencies.

• Information on minor facilities (e.g. wellhead equipment, pigging stations, field

gates and pump stations) may not be available, even from oil companies.

• The only infrastructure data potentially required for the Tier 1 method are well

counts and lengths of pipeline.

• Only facility information is required for the IPCC Tier 3 method.



371.37

Oil and Gas System References

• Other methodology manuals:

• American Petroleum Institute (API) <www.api.org>• Canadian Association of Petroleum Producers (CAPP) <www.capp.ca>• Canadian Gas Association (CGA) <www.cga.ca>• Gas Technology Institute (GTI) <www.gastechnology.org>.

• Oil and gas statistics:

• US Energy Information Administration (EIA) <www.eia.doe.gov/neic/historic/hinternational.htm>

• United Nations Statistics Division (UNSD) <http://unstats.un.org/unsd/methods/inter-natlinks/sd_natstat.asp and http://unstats.un.org/unsd/databases.htm>

• International Energy Agency (IEA) <http://www.iea.org/stats/index.asp>.



381.38

Oil and Gas System References (cont.)

• Oil and Gas Journal <www.ogjresearch.com> includes:

• Some infrastructure data (number of wells, gas plant listing, major project announcements)

• Worldwide refinery, pipeline and gas processing projects

• Historical refinery, pipeline and gas processing projects

• Worldwide oil field production survey

• Worldwide refining survey

• Worldwide gas processing survey

• Enhanced oil recovery survey.



391.39

Nitrogen Oxides (NOx)

• Indirect greenhouse gases

• Fuel combustion activities are the most significant anthropogenic source of NOx

• Energy industries• Mobile sources

• Two formation mechanisms:• Fuel NOx is from the nitrogen contained in the fuel itself• Thermal NOx is from nitrogen in the air.



401.40

Carbon Monoxide (CO)

• Indirect greenhouse gas

• Majority of emissions are from motor vehicles, but also from small residential and commercial combustion

• Intermediate product of the combustion process.



411.41

Non-Methane Volatile Organic Compounds (NMVOCs)

• Indirect greenhouse gases

• Product of incomplete combustion

• Mobile sources and residential combustion, especially biomass combustion

• Low emissions for large-combustion plants.



421.42

Sulfur dioxide (SO2)

• Aerosol precursor

• May have a cooling effect on climate

• Concentration increases with burning of fossil fuels that contain

sulphur

• Closely related to the sulphur content of fuels.



43

Thank you



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CGE Training Materials National Greenhouse Gas Inventories