emission estimation technique manual for oil and gas exploration and production version 1.2

National Pollutant Inventory www.npi.gov.au

Emission Estimation Technique Manual

for Oil & Gas

Exploration & Production Version 1.2

February 2010

First published in February 1999 Version 1.2 – February 2010

NPI oil and gas production and exploration Version 1.2 – February 2010

i

ISBN: 0642550573

www.npi.gov.au

© Commonwealth of Australia 1999 to 2009

This manual may be reproduced in whole or part for study or training purposes subject to the inclusion of an acknowledgment of the source. It may be reproduced in whole or part by those involved in estimating the emissions of substances for the purpose of National Pollutant Inventory (NPI) reporting. The manual may be updated at any time. Reproduction for other purposes requires the written permission of the Department of the Environment, Water, Heritage and the Arts, GPO Box 787, Canberra, ACT 2601, e-mail [email protected], internet address www.npi.gov.au or phone 1800 657 945.

Disclaimer

The manual was prepared in conjunction with Australian states and territories according to the National Environment Protection (National Pollutant Inventory) Measure.

While reasonable efforts have been made to ensure the contents of this manual are factually correct, the Commonwealth does not accept responsibility for the accuracy or completeness of the contents and shall not be liable for any loss or damage that maybe occasioned directly or indirectly through the use of, or reliance on, the contents of this manual.


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Erratum for oil and gas exploration and production (EET) Manual

Version 1.2 – 1 February 2010 Page Outline of alteration

Throughout Removed transfers exclusion.

Page 23 Amended Worksheet 3

Page 11 Amended worksheet references

Version 1.1 – 1 June 2005

Page Outline of alteration

Throughout Provided emissions factors to only two significant figures.

Throughout Separated worksheets from tables. Worksheets are now all in Appendix 2.

Various tables

Changed the emission factors to kilograms rather than tonnes.

Throughout Removed sections that are covered in other NPI manuals. For example the combustion engines, combustion in boilers and fuel and organic liquid storage.


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EMISSION ESTIMATION TECHNIQUES FOR

OIL & GAS EXPLORATION & PRODUCTION TABLE OF CONTENTS

Disclaimer ............................................................................................................................................ i Erratum for oil and gas exploration and production (EET) Manual ...........................................ii 1. Introduction......................................................................................................................... 1 2. Process description.............................................................................................................. 2 3. Potential emissions .............................................................................................................. 4

3.1 Destinations substances are emitted to: air, water and land......................................... 4 3.1.1 Emissions to air ..................................................................................................... 4 3.1.2 Emissions to water ................................................................................................ 4 3.1.3 Emissions to land .................................................................................................. 4 3.1.4 Transfers................................................................................................................ 5

4. Emission estimation techniques (EET) ............................................................................. 6 4.1 Determining emissions from this industry sector........................................................... 6

4.1.1 Determining emissions and reporting thresholds from Produced Formation Water (PFW) ......................................................................................................... 6

4.1.2 Throughput of crude oil/gas to determine NPI reporting thresholds based on use ......................................................................................................................... 7

4.1.3 Determining emissions from use of drilling fluids ............................................... 7 4.1.4 Two methods for determining fugitive emissions of organic compounds

which are NPI substances for different equipment (e.g. valves) at facilities....... 8 4.1.5 Determining emission from flaring operations ................................................... 11 4.1.6 Determining emissions from loading crude product onto tankers ...................... 11 4.1.7 Determining emissions from venting waste gas.................................................. 12 4.1.8 Determining emissions from venting from crude oil storage tanks .................... 12 4.1.9 Determining emissions from wastewater ............................................................ 12 4.1.10 Determining emissions from spills and leaks...................................................... 12

4.2 Category 2a and 2b NPI substances – emissions from burning fuel .......................... 13 4.2.1 Fuel combustion emissions - general .................................................................. 13 4.2.2 Sulfur dioxide emissions from combustion......................................................... 13 4.2.3 Metals emissions from combustion..................................................................... 14

4.3 Category 3 substances ..................................................................................................... 14 5. Assumptions....................................................................................................................... 16

5.1 Produced Formation Water (PFW)............................................................................... 16 5.2 Storage tank emissions.................................................................................................... 16 5.3 Sources of information.................................................................................................... 16 5.4 Emission factors............................................................................................................... 16 5.5 Facility specific factors.................................................................................................... 16 5.6 Flaring .............................................................................................................................. 17 5.7 Conversion of measurement units (e.g. volume to mass)............................................. 18

6. Definitions and abbreviations .......................................................................................... 19 7. References.......................................................................................................................... 21

7.1 References cited in text ................................................................................................... 21 7.2 References not cited in text............................................................................................. 21


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Appendix 1. Examples of determining emissions using the techniques in this manual ....... 23 A1.1 Determining carbon monoxide emissions from fuel combustion................................ 23 A1.2 Determining fugitive emissions of organic compounds which are NPI

substances from different types of pipe fittings............................................................ 23 A1.3 Determining emissions of organic compounds which are NPI substances from

venting which takes place during loading crude oil onto ships................................... 25 Appendix 2. Worksheets to assist you to determine NPI reporting thresholds and

emissions ............................................................................................................................ 26


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OIL & GAS EXPLORATION & PRODUCTION LIST OF FIGURES, TABLES AND WORKSHEETS

Figure 1. Potential sources of NPI substance emissions from oil and gas production and

exploration ................................................................................................................ 3

Table 1. Organic compounds that are NPI substances contained in various products from oil and gas production based on total organic compounds emissions............................. 9

Table 2. Average emission factors for fugitive emissions from oil and gas processes.......... 10

Table 3. Definition of material moved by or through different types of equipment.............. 11

Table 4. Indicative emission factors for total nitrogen and total phosphorus emissions to determine if the NPI reporting threshold is exceeded for these substances............. 15

Table 5. Conversion of E&P Forum data to metric units....................................................... 18

Worksheet 1. Determining category 1 and 1a NPI reporting thresholds based on default substance levels contained in Produced Formation Water (PFW) ........................................... 26

Worksheet 2. Determining category 1 and 1a substance usage from crude oil/gas throughput .... 27

Worksheet 3. Determining the amount of drilling fluids emitted to the environment ................... 28

Worksheet 4. Determining fugitive emissions of Total Volatile Organic Compounds (Total VOCs) ...................................................................................................................... 29

Worksheet 5. Determining fugitive emissions of organic compounds that are NPI substances.... 30

Worksheet 6. Determining carbon monoxide (CO), oxides of nitrogen (NOx) and Total VOCs from flaring .............................................................................................................. 32

Worksheet 7. Determining emissions of carbon monoxide (CO), oxides of nitrogen (NOx) and Total VOC from power generation: diesel equipment............................................. 33

Worksheet 8. Determining emissions of PM10 and NPI substances that are organic compounds from associated gas combustion .............................................................................. 34

Worksheet 9. Determining emissions of metals that are NPI substances and fluoride from associated gas combustion ....................................................................................... 35

Worksheet 10. Determining emissions of metals that are NPI substances and fluoride from non-associated gas combustion ....................................................................................... 36

Worksheet 11. Determining for losses of Total VOCs from loading oil or gas to tankers .............. 37

Worksheet 12. Using mass balance to determine the mass of gas vented ....................................... 37

Worksheet 13. Determining emissions from venting of total organic compounds from FPSO crude oil storage tanks ....................................................................................................... 38

Worksheet 14. Determining NPI emissions from wastewater discharges ....................................... 38

Worksheet 15. Determining emissions of PM10 and NPI substances that are organic compounds from non-associated gas combustion ....................................................................... 39

Worksheet 16. Determining emissions of carbon monoxide (CO), oxides of nitrogen (NOx) and Total VOCs from combustion of gas (associated and non-associated) ................... 40

Worksheet 17. Determining total nitrogen and total phosphorus in wastewater flows ................... 41


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1. Introduction Before commencing reporting to the National Pollutant Inventory (NPI) you should refer to the NPI Guide to determine if you need to report and which substances you will need to report.

The purpose of NPI Emission Estimation Technique (EET) manuals is to assist Australian manufacturing, industrial, and service facilities to report emissions of NPI substances to the NPI. This manual and other guidance materials for NPI reporting can be found on the NPI web address (www.npi.gov.au). This manual describes the procedures and recommended approaches for determining emissions from facilities engaged in oil and gas exploration and production, both on and offshore. You may need to use other NPI manuals to complete reporting for your facility.

The separation and conditioning of hydrocarbons is included in this manual, up to the point of loading and transport of hydrocarbons to the refinery only.

Emissions from crude oil transport are included for loading of product only, and not for emissions while in transit.

The refining of crude oil and petrochemical processing sector is not included in this manual.

EET MANUAL: Oil & Gas Exploration & Production

HANDBOOK: Oil and Gas Extraction

ANZSIC CODE: 0700

This manual has been prepared in 1999 by PPK Environment & Infrastructure in conjunction with the NSW Environment Protection Authority on behalf of the Commonwealth Government.

The manual has been developed through a process of national consultation involving key industry stakeholders and State and Territory environment agencies. Particular thanks are due to the Australian Petroleum Production and Exploration Association (APPEA), and its members for their comments, advice and information.

http://www.npi.gov.au/


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2. Process description Petroleum exploration and production operations are conducted both onshore and offshore and encompass the following activities:

1. Exploration

Seismic (Note that emissions from this activity are NOT reportable under the NPI)

Exploration and appraisal drilling

Production testing

2. Production

Development drilling

Separation and processing

Storage

Loading

Associated service activities such as work boat and helicopter operations that link and support facilities and their bases. (Note that such activities conducted outside the facility’s boundary are classed as diffuse mobile sources, and emissions from such activities are NOT reportable under the NPI)

Figure 1 illustrates the potential sources of emissions of NPI substances from Oil & Gas Production and Exploration.

Figure 1. Potential sources of NPI substance emissions from oil and gas production and exploration

ONSHORE PRODUCTIONDrillingPower generationProduction TestingVenting / PurgingFlaringFugitive Emissions

OFFSHORE PRODUCTIONDrillingPower generationSeparation processProduction TestingVenting / PurgingFlaringFugitive Emissions

STORAGE / LOADINGVenting / PurgingFugitive EmissionsLoading Losses

OFFSHORE EXPLORATIONDrillingPower generationProduction TestingVenting / Purging

ONSHORE EXPLORATIONDrillingPower generationProduction TestingVenting / Purging

(Adapted from APPEA, 1997)


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3. Potential emissions The NPI Guide is on the web (under industry reporting at: www.npi.gov.au) and details how to determine if you need to report you facility’s emissions to the NPI, and which substances need to be reported. You need to report all NPI substances for which your facility exceeds an NPI reporting threshold. The NPI Guide assists you in determining which reporting thresholds are exceeded.

3.1 Destinations substances are emitted to: air, water and land

3.1.1 Emissions to air

Air emissions may be categorised as:

• Point source emissions (e.g. fuel combustion, flares) where the release is through single point sources into the atmosphere; and

• Fugitive emissions (e.g. volatilisation of vapour from open vessels, and equipment leaks such as valves and flanges).

3.1.2 Emissions to water

Emissions of substances to water can be categorised as discharges to:

• Surface waters (e.g. lakes, rivers, dams, and estuaries);

• Coastal or marine waters; and

• Stormwater.

For the NPI emissions to groundwater are considered as emissions to land, not water.

Generally, the most accurate method for determining emissions to the environment from wastewater is to use direct measurement if this information is available. If unavailable, default emission factors have been provided to assist you in meeting your reporting requirements under the NPI.

Spills to water are included when reporting to the NPI. The mass of NPI substances in unrecovered material must be included.

3.1.3 Emissions to land

Emissions of substances to land include:

• uncontained solid wastes;

• slurries;

• sediments; and

• spills and leaks.

The discharge of NPI substances to a sewer should not be reported to the NPI (See The NPI Guide for more information).

Spills to land are included when undertaking NPI reporting. The mass of NPI substances in unrecovered material must be included in reports as an emission to the environment.



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3.1.4 Transfers

Within the oil and gas exploration and production industry, transfers include:

• reinjection of Produced Formation Water (PFW) and gas;

• wastes managed by an off-site facility;

• discharges to sewer; and

• discharges to surface impoundments, such as balancing ponds and treatment plants.

While the reinjection of PFW is classed as a transfer, any NPI substances contained in production chemicals that are added to the PFW (such as scale inhibitor) must be reported as an emission. The emissions is most likely to be to land. (Decision of NPI Implementation Working Group, Meeting of 20-21 April 1998).


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4. Emission estimation techniques (EET) Emissions of NPI listed substances to air, water and land should be reported for each substance for which an NPI reporting threshold is exceeded. The NPI Guide on the web (www.npi.gov.au) provides details about reporting thresholds and the NPI substance list.

This Manual aims to provide the most effective techniques for determining emissions of NPI substances for processes specific to this industry. Other manuals provide guidance for determining emissions from other sources, such as emissions from engines, boilers and fuel storage. The absence of an EET for a substance in NPI manuals does not necessarily imply that an emission should not reported to the NPI. The obligation to report on all relevant emissions remains for substances where the reporting thresholds have been exceeded.

You are able to use emission estimation techniques that are not outlined in this document. To do this you need the consent of your State or Territory Government environment agency. For example, if your company has developed site specific emission factors, you may use these if approved by your relevant environment agency.

Usually direct measurement is the most accurate way to determine emissions and, where available, such data should be used in preference to other EETs presented in this Manual. However, additional direct measurement is not required to complete NPI reporting.

The techniques in this Manual relate mainly to the average emissions from processes. Emissions resulting from non-routine events such as spills are rarely discussed in the literature, and there is a general lack of EETs for such events. However, it is important to recognise that emissions resulting from significant operating excursions and/or accidental situations (e.g. spills) will also need to be determined. The emission resulting from a spill is the net emission, i.e. the quantity of the NPI reportable substance spilled, less the quantity recovered or consumed during clean up operations.

Total facility emissions are determined by calculating emissions from individual sources within the facility for each NPI substance to be reported, and then adding emissions from each of these sources to provide a total emission for each substance.

4.1 Determining emissions from this industry sector

This section outlines information specifically relevant to this industry sector that will assist you to determine reporting thresholds and emissions.

4.1.1 Determining emissions and reporting thresholds from Produced Formation Water (PFW)

PFW will vary between facilities and oil and gas reservoirs (refer to Section 5.1 of this Manual). However, a generic PFW composition has been developed for the purposes of reporting to the NPI. This generic composition has been developed by APPEA, in consultation with industry, by averaging PFW analyses across numerous sites from a number of companies.

The generic composition can be used by facilities as default values in the absence of facility specific data. Where facility specific data is available, this should be used in preference to the generic default values provided in Worksheet 1 from Appendix 2 of this Manual.

The use of NPI substances from PFW reinjection can be determined using Worksheet 1 from Appendix 2. In determining usage of Category 1 and 1a substances, the transfers of NPI substances calculated using Worksheet 1 will correspond to the 'use' of those substances associated with PFW. The transfers will need to be added to the use of NPI substances from other activities/sources to determine whether the 10 tonne per annum NPI reporting threshold is exceeded for a particular facility.



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You should note that the reinjection of PFW is classed as a transfer. Any NPI substances contained in production chemicals that are added to the PFW (such as scale inhibitor) must be reported as an emissions if the substance’s reporting threshold is exceeded.

4.1.2 Throughput of crude oil/gas to determine NPI reporting thresholds based on use

Crude oil consumption will vary between facilities and reservoirs. Facilities should use existing crude oil composition data to determine NPI substance ‘usage’.

The calculation to determine the contribution of crude oil to the total usage of Category 1 and 1a substances at a facility can be made using Worksheet 2 from Appendix 2. These will need to be added to other Category 1 and 1a substance usage (e.g. from PFW not re-injected) to determine total substance use for a facility.

4.1.3 Determining emissions from use of drilling fluids

The concentration of NPI substances in drilling fluids will vary according to the type and manufacturer of drilling fluid used. It is recognised that information on the composition of drilling fluids is not readily available. Therefore, information on the concentration of NPI substances in drilling fluids will need to be derived from suppliers and manufacturers.

Losses of drilling fluids, and the NPI substances they contain, may be estimated using a mass balance. The mass balance needs to take into account:

• total volume of drilling fluid used;

• down hole losses (such losses are required to be reported as releases to land); and

• volume of drilling fluid recovered.

The first step is to determine the volume of losses to the environment. The losses to the environment are likely to include down hole losses (most likely to land) and other losses (which could be to land or water). The equation to determine the loss to the environment is:

Volume lost to the environment

(Litres)

=

Total volume of fluid used

(Litres)

― Volume of fluid recovered

(Litres)

In order to estimate the emission of NPI substances to the environment the ‘Volume lost to the environment’ for each relevant NPI substance must be multiplied by the concentration of that NPI substance in the drilling fluid. Only substances that exceed an NPI reporting threshold need to be considered.

Emission of NPI substance to the environment

(kg)

=

Volume lost to the environment

(Litres)

×

Concentration of NPI substance in drilling fluid

(mg/Litre)

/

1,000,000

A Worksheet 3 from Appendix 2 can assist you with estimating the emissions of NPI substances associated with drilling fluids. You need to determine if the emissions are to air, land or water.


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The quantity of NPI substances used in drilling fluids will also need to be added to other Category 1 and 1a substance usage (for example, from PFW and crude oil/gas) to determine total usage for a facility.

4.1.4 Two methods for determining fugitive emissions of organic compounds which are NPI substances for different equipment (e.g. valves) at facilities

Process fugitive sources within the oil and gas exploration and production sectors include:

• valves;

• flanges;

• pumps;

• connectors;

• compressors; and

• drains (onshore).

For the purposes of reporting to the NPI, the use of average emission factors is recommended. Two methods of calculation are available to estimate fugitive emissions. These methods are detailed below (Note: it is likely that Method 1 will be most suitable for the majority of facilities).

Method 1

In 1995, APPEA developed a suite of generic emission factors for characterising fugitive emissions from the oil and gas exploration and production industry in Australia and this material was published in 1997.

Process fugitive emissions can be estimated using Worksheet 4 from Appendix 2. Fugitive emissions from storage tanks can also be estimated using the emission factors in Worksheet 4.

Once the fugitive emissions have been calculated, the speciation fractions in Table 1 can be applied using the Worksheet 5 from Appendix 2. Only columns ‘ETOC’, ‘SF’ and ‘ESF’ in Worksheet 5 are used when Method 1 is applied.


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Table 1. Organic compounds that are NPI substances contained in various products from oil and gas production based on total organic compounds emissions

Substance Gas Heavy Oil Light Oil Water/Oil Benzene 6.9E-04 9.4E-03 1.2E-03 1.2E-03 Ethylbenzene 3.0E-05 5.1E-04 1.6E-04 1.6E-04 n-hexane (a) 6.9E-03 7.5E-03 2.3E-02 2.3E-02 Toluene 3.8E-04 3.4E-03 1.1E-03 1.1E-03 Total VOC 1.7E-01 3.0E-02 3.0E-01 3.0E-01 Xylenes 9.0E-05 3.7E-03 3.3E-04 3.3E-04 Notes: 1. Reference: API, 1996. 2. Upper limit of n-hexane based on C6+ fraction. 3. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02

Method 2

For process fugitive emissions, average emission factors have been derived from the USEPA, 1995 and API, 1996, and are provided in Table 2. Total fugitive emissions may be calculated using Worksheet 5 from Appendix 2.

The following data is required for ‘average emission factors’ estimation calculations:

• The number of each type of component (e.g. valves, flanges, etc.) in each process unit;

• The service each component is in (e.g. gas, light liquid, heavy liquid, water/oil). The definitions in Table 3 should be used when determining the type of ‘service’ a particular piece of equipment is in, so that the appropriate emission factors are used;

• The weight fraction of Total Organic Compounds (TOC) within the stream; and.

• Hours operational (e.g. hours/year). Hours of operation should be determined for particular streams as detailed above.


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Table 2. Average emission factors for fugitive emissions from oil and gas processes

Service7 Emission Factor (kg/hr/source)2 Equipment Type Gas Heavy Oil Light Oil Water/Oil

Valves 4.5E-03 8.4E-06 2.5E-03 9.8E-05 Pump Seals 2.4E-03 NA 1.3E-02

(note 6) 2.4E-05

Others 5 8.8E-03 3.2E-05 7.5E-03 1.4E-02 Connectors 3 2.0E-04 7.5E-06 2.1E-04 1.1E-04 Flanges 3.9E-04 3.9E-07 1.1E-04 2.9E-06 Open-ended Lines 2.0E-03 1.4E-04 1.4E-03 2.5E-04 Drains (onshore) 4 3.2E-02 3.2E-02 3.2E-02 3.2E-02 Notes: 1. Reference: USEPA, 1995a & API, 1996 [both quote the same emission factors

unless otherwise indicated] 2. These factors are for total volatile organic compound emission rates (including

non-Total VOC’s, such as methane and ethane), and apply to light crude, heavy crude, gas plant, and off-shore facilities. “NA” indicates that not enough data was available to develop the indicated emission factor.

3. Defined as non-flanged connectors. 4. Source: NPI Manual for Petroleum Refining. 5. This ‘other’ category should be applied to all equipment types in heavy liquid

service that have not been specifically considered elsewhere in the table. Note, however, that some equipment types have emission factors applicable to ‘All’ service types, including the heavy liquid category. Therefore, care must be taken to ensure that these are NOT included under the ‘other’ category.

6. Applicable to agitator seals where no other data is available. 7. Water/Oil emission factors apply to water streams in oil service with a water

content greater than 50%, from the point of origin, to the point where the water content reaches 99%. For water streams with a water content greater than 99%, the emission rate is considered negligible.

8. Heavy Oil : < 20 API Gravity and Light Oil : > 20 API Gravity 9. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 =

3.5×10+02


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Table 3. Definition of material moved by or through different types of equipment

Service Type Definition Gas/vapour Material is in a gaseous state at operating conditions Light liquid Material is in a liquid state in which the sum of the concentrations of

individual constituents with a vapour pressure over 0.3 kilopascals (kPa) at 20°C, is greater than, or equal to, 20 weight percent (wt %);

Heavy liquid Material does not fall under the classifications for gas/vapour, or light liquid service

Water/Oil Water streams in oil service with a water content greater than 50%, from the point of origin to the point where the water content reaches 99%. For water streams with a water content greater than 99%, the emission rate is considered negligible.

Notes: 1. Reference: API, 1996.

The emission factors are presented on a ‘per individual source’ basis. However, the factors are most valid for estimating emissions from a population of equipment, and are not intended for use when estimating emissions from an individual piece of equipment over a short time period (e.g. several hours).

An example calculation is presented in Appendix 1. (You should note that steps used in the average emission factors approach to fugitive emissions estimation have been based on the steps detailed in the Emission Estimation Technique Manual for Petroleum Refining, and amended to suit the oil and gas exploration and production industry).

You should also note that the emission factors presented in Table 2 only apply to process fugitive emissions. Emissions from storage tanks will need to be calculated separately using methods detailed in the NPI fuel and organic liquid storage manual.

4.1.5 Determining emission from flaring and other fuel combustion operations

Emissions of NPI substances from flaring can be calculated using the emission factors provided in Worksheet 6.

Worksheets 7, 8, 9 and 10 from Appendix 2 can be applied to flaring and other fuel combustion activities, in the absence of facility specific information data to estimate emissions of metals and organics.

4.1.6 Determining emissions from loading crude product onto tankers

Emissions from the loading of crude product on to tankers can be estimated using the emission factors provided in Worksheet 11 from Appendix 2.

In the absence of other information, the speciation factors presented in Table 1 can be used to provide estimates on the composition of the emitted Total VOCs.


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4.1.7 Determining emissions from venting waste gas

The volume of waste gas vented can be calculated using a mass balance approach as detailed below:

GV = GP - (Gs + GF + GFl)

where : GV = Mass of gas vented GP = Mass of gas produced GS = Mass of gas sold/processed GF = Mass of gas lost as fugitive emissions GFl = Mass of gas flared How to determine the amount of gas vented (GV) is detailed in Worksheet 12 from Appendix 2.

In the absence of other information, the speciation factors for gas presented in Table 1 can be used to provide estimates on the composition of the emitted Total VOCs.

4.1.8 Determining emissions from venting from crude oil storage tanks

Venting from the crude oil storage tanks on an FPSO (floating production storage and offloading facility) may be estimated using the factor presented below. (This factor is derived from USEPA, (1995b), and relates to TOC losses from tankers in transit to refineries.)

TOC emissions = 0.022 kg/day/m3 of stored crude

How to determine the level of TOC emissions from crude oil storage tanks is detailed in Worksheet 13 from Appendix 2.

In the absence of other information, the speciation factors presented in Table 1 can be used to provide information on the composition of the emitted TOCs.

4.1.9 Determining emissions from wastewater

Wastewater streams are likely to be treated at a common point at onshore facilities, while offshore facilities are likely to discharge treated and untreated wastewater from a number of points. If available, existing monitoring data should be used.

Direct measurement data can be supplemented by a range of data including:

• Manufacturers’ specifications for treatment packages; and

• Material/chemical mass balance.

When considering wastewater discharges, you should consider the definition of ‘transfer’. Reporting is required for those releases that are classed as emissions or transfers.

The estimation of NPI substance emissions from wastewater discharges is detailed in Worksheet 14 from Appendix 2.

General guidance on the characterisation of process wastewater streams is provided in Emission Estimation Technique Manual for Sewage and Wastewater Treatment.

4.1.10 Determining emissions from spills and leaks

A mass balance EET can also be applied to emissions of NPI substances as a result of accidental spills and leaks.

The mass balance would require consideration of:


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• the total volume of material spilled or leaked; and

• the volume of material recovered.

The difference between these volumes would be considered to be emissions to the environment.

As with drilling fluids, the proportion of NPI substances within the material must be determined. Emissions of NPI substances to the environment could then be estimated by multiplying the volume of material lost to the environment, by the proportion of NPI substances present in the spilled material.

Information on the composition of spilled materials may be obtained from either suppliers or manufacturers (e.g. production chemicals), or through direct measurement (e.g. crude oil).

4.2 Category 2a and 2b NPI substances – emissions from burning fuel

The burning of fuel triggers reporting for some NPI substances. To determine whether Category 2a or 2b thresholds are exceeded, the total fuel burnt must be determined. This will require comparing annual and peak hourly fuel usage with the Category 2a and 2b thresholds. The NPI Guide should be referred to for more details. This manual provides guidance for determining emissions from combustion processes specific to this industry. For emissions from generic sources such as engines or boilers see the manuals that relate to these sources.

4.2.1 Fuel combustion emissions - general

Emissions of NPI substances from combustion activities can be calculated using the emission factors provided in Worksheets 7, 8, 9, 10,15 and 16 from Appendix 2.

For gas, the specific emission factors presented for the combustion of associated gas (Worksheets 8 and 9 from Appendix 2) and non-associated gas (Worksheets 10 and 15 from Appendix 2) should be used. Otherwise, you should use the general emission factors presented in Worksheet 16 from Appendix 2.

Similarly, when estimating emissions from diesel combustion, the specific emission factors provided for turbines, engines, or heaters should be used (Worksheet 7 from Appendix 2). Where specific emission factors are not provided, use the general emission factors for combustion for equipment of greater than, and less than 600 hp as appropriate (see the NPI combustion engines manual).

4.2.2 Sulfur dioxide emissions from combustion

Fuel analysis can be used to predict emissions of SO2 resulting from combustion activities (e.g. power generation, flaring etc.).

The basic equation used in fuel analysis emission calculations is the following:

Ei = Qf × substance concentration in fuel × ( MWp / EWf )

where: Ei = emissions of substance (kg/hr) Qf = rate of fuel use (kg/hr) MWp = molecular weight of substance emitted (kg/kg-mole) EWf = elemental weight of substance in fuel (kg/kg-mole)

For instance, SO2 emissions from oil combustion can be calculated based on the concentration of


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sulfur in the oil or gas. This approach assumes complete (100%) conversion of sulfur to SO2. Therefore, for every kilogram of sulfur (EW = 32) burned, two kilograms of SO2 (MW = 64) are emitted.

Emission of SO2 (kg/hr) = Fuel Usage (kg/hr) × wt % S × MWSO2

100 EWS

Where: wt % S = weight percent of sulfur (as elemental S) in the fuel.

MWSO2= 64

EWS = 32

The emissions are estimated as kg/hr and as such, should be multiplied by the number of hours of operation in a year in order to determine the annual emissions.

Hydrogen sulfide (H2S) is generally routed to flare following its stripping from the gas stream. H2S is converted to SO2 in the flaring process, and emissions may be calculated based on the efficiency of flaring conversion of H2S to SO2 (assume 100%), and the H2S content of the gas. A similar calculation to that for fuel combustion can be applied to the combustion of H2S to estimate SO2 emissions, as shown below:

Emission of SO2 = Volume of gas to be flared x wt % H2S x MWSO2

(kg/hr) (kg/hr) 100 MWH2S

where: wt % H2S = weight percent of H2S in the gas to be flared.

MWSO2 = 64

MWH2S = 34

The ‘volume of gas to be flared’ may refer to either the waste H2S gas stream, or the total volume of all gas to be flared. Whichever volumetric flow is used, it is essential that the ‘wt % H2S’ relates to that gas stream in order to ensure that emission estimations are valid.

4.2.3 Metals emissions from combustion

Where fuel analysis data is available for metals, this data can be used to estimate emissions of various NPI-listed metals in preference to the default emission factors provided in Worksheets 9 and 10 from Appendix 2.

These emissions are calculated by assuming that all metals in the fuel are emitted to air (i.e. therefore, no metals are contained in fuel ash). While this is somewhat conservative in most cases, this approach will provide a much more accurate characterisation of metals emissions than use of the default emission factors.

4.3 Category 3 substances

Category 3 substances are total nitrogen and total phosphorus. These are reportable if emissions to water of these substances exceed the following amounts:

• 15 tonnes per year of total nitrogen; and

• 3 tonnes per year of total phosphorus.

While the emission of total nitrogen and total phosphorus to water from facilities is unlikely to


15

exceed the reporting threshold, it is the responsibility of each facility to determine whether this is the case. Table 4 gives the indicative facility population likely to result in the Category 3 thresholds being exceeded if this is the only source of these substances.

Based on the West Australian Water Corporation wastewater treatment design criteria, the per person per day loading of total nitrogen and phosphorus has been calculated. This data has been applied to the NPI reporting thresholds to provide an indicative facility population that will exceed the reporting thresholds.

Table 4. Indicative emission factors for total nitrogen and total phosphorus emissions to determine if the NPI reporting threshold is exceeded for these substances

NPI substance kg per person per day Indicative facility population Total nitrogen 1.1E-02 3700

Total phosphorus 2.5E-03 3200

Notes: 1. Reference: Derived from West Australian Water Corporation wastewater treatment design

criteria. 2. Assumes:

• Annual dry weather flow of 200 litres per person per day • Total nitrogen concentration of 55 mg/L (range of 40 – 70 mg/L) • Total phosphorus concentration of 12.5 mg/L (range of 10 – 15 mg/L) • 365 days per year of N and P loading

3. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6 x 10-3 or 350 = 3.5E+02 = 3.5 x 10+02

The estimation of total nitrogen and total phosphorus from wastewater discharges is detailed in Worksheet 17 from Appendix 2.


16

5. Assumptions

5.1 Produced Formation Water (PFW)

While a generic PFW composition (developed by APPEA) is detailed in Worksheet 1 from Appendix 2, it must be recognised that this data should only be used in situations where facility specific composition data is not available.

The composition of PFW is highly oil/gas field specific, and will change over the lifetime of the oil/gas reservoir. The use of a generic PFW composition in the estimation of emissions is likely to introduce a significant uncertainty in to the calculations.

5.2 Storage tank emissions

Worksheet 4 from Appendix 2 presents Total VOC emission factors for fugitive emissions and storage tanks. These emission factors have been developed by APPEA as part of its Greenhouse Gas Inventory.

Alternative EETs are available for the characterisation of these emissions (included in the NPI Manual for Fuel & Organic Liquid Storage). The APPEA emission factors were selected as they present a simple approach to the estimation of these emissions, and have been specifically developed for the Australian oil and gas exploration and production industry.

5.3 Sources of information

A wide range of data was reviewed in the development of this Manual, and that deemed most applicable to the oil and gas exploration and production industry has been used. Generally, E&P Forum data has been used in preference to other sources, except where either no data is available, or where an alternate source, (e.g. AP42 or API), more accurately represents the environmental performance of the industry.

5.4 Emission factors

The available data on NPI substances in the literature is not uniform, with more detail being available for some substances and sources than for others.

For example, extensive data is available relating to the combustion of fuels. Factors have been taken from specific sources based on their applicability to oil and gas production and exploration. While data was not found for some NPI substances in the available literature (e.g. see shaded areas in Worksheets 8, 9 and 15 from Appendix 2), this does not mean that the substance is not emitted by the oil and gas industry. It is the responsibility of each operator to identify the NPI substances for which reporting is required and subsequently, to quantify the emissions of the relevant substances.

5.5 Facility specific factors

This manual does not take account of facility specific upgrades, cleaner technologies, or emission reduction programs employed. Where applicable, the effectiveness of upgrades and emission reduction programs should be determined, and factored into any emission estimations. The effectiveness of techniques may be determined with reference to:

• manufacturer’s specifications;

• engineering calculations; and

• facility monitoring programs.


17

The effectiveness of these emission reduction initiatives can be factored into emissions estimation by including a proportional factor based on an assumed control efficiency, as detailed below:

[1 - (ER/100)]

where: ER = overall emission reduction efficiency, %.

This would be applied to an emission factor as shown below:

Ekpy,I = [A x OpHrs] × EFi × [1 - (CEi /100)]

where : Ekpy,i = emission of pollutant i, kg/yr A = activity rate, t/hr OpHrs = operating hours, hr/yr EFi = uncontrolled emission factor of pollutant i, kg/t CEi = overall control efficiency for pollutant i, %

For processes where retro-fitting and continual improvement of emission controls have been carried out, the combined effectiveness of all emission reduction methods should be accounted for when characterising emissions for the purposes of NPI reporting. Where ‘effectiveness factors’ are used, these should be stated in all reports with the justification for their use. You should note that any modifications or changes to the default emission factors provided in this Manual require the consent of your relevant environmental authority.

5.6 Flaring

The emission factors for gas flaring presented in Section 4.2.1 assume a gas composition of 70wt% methane (CH4), 30wt% Total VOCs. However, vented gas composition varies depending on the type of facility, and emission factors should be modified using actual composition if this information is known.

Vent gas compositions, for example, include (E&P Forum, 1994):

• UK oil production platform 51wt% methane, 49wt% Total VOCs

• UK gas production platforms 92wt% methane, 8wt% Total VOCs

• Norway inventory assumed a composition of 65vol% methane, 35vol% Total VOCs


18

5.7 Conversion of measurement units (e.g. volume to mass)

For combustion, the E&P Forum expresses emission in terms of tonnes emission/tonne. These emission factors may be converted to kg/m3 where the density of the combusted material is known.

Using the assumed densities below, a conversion factor was calculated to convert the E&P Forum data to metric units (Source: E&P Forum, 1994).

Table 5. Conversion of E&P Forum data to metric units

Material Density Diesel 0.85 tonne /m3

Associated gas1 1 tonne/1000sm3

Non-associated gas1 0.8 tonne/1000sm3

Notes: 1. Associated gas is the gas produced from an oil and gas extraction operation, while non-

associated gas is the gas from a well that only produces gas. 2. sm3 is standard cubic metres.

While standard cubic metres (sm3) are referred to in the E&P documentation, it is understood that facilities generally report emission as cubic metres (m3) rather than sm3 (Source: PPK, 1998). Therefore, all sm3 units are assumed to be equal to m3 units.

Standard Cubic Metres relates to the volume of gas at ‘standard’ conditions. Generally standard conditions refer to an absolute pressure of 101.3 kPa and a temperature 273.15K. Some organisations may use a different definition of standard conditions. To convert to cubic metres site-specific characteristics must be known and applied to the calculation shown below.

VF = VS PS TF

TS PF

Where: VS = Volume at ‘standard’ conditions, sm3 PS = Standard pressure, 101.3 kPa TS = Standard temperature, 273.15 Kelvin VF = Volume at facility conditions, m3 PF = Pressure at facility conditions TF = Temperature at facility conditions

Conversion of units cited in USEPA, (1995b) documentation have used conversion factors stated in the text. However, when converting MMBtu to other units, it must be appreciated that MMBtu is equivalent to 1E+06 (1 million) Btu NOT 1E+12 (1012) Btu.


19

6. Definitions and abbreviations Reference should be made to the NEPM for the National Pollution Inventory and the NPI Guide for definition of terms used within the NPI system.

Term Explanation

API American Petroleum Institute APPEA Australian Petroleum Production and Exploration Association Associated Gas Gas produced from an oil and gas extraction operation. Non-Associated Gas Gas from a well that only produces gas. Direct Measurement Technique used to estimate emissions to the environment

through the sampling and analysis of emission streams. Emission Any release of substances to the environment, whether it is in a

pure form, or contained in other matter. Emissions may be solid, liquid, or gaseous.

EF Emissions factor. Emission Factor A number or equation that may be applied to raw data from a

facility to estimate emissions from that facility without the need for emissions sampling and analysis. This technique is most often used to estimate gaseous emissions to the environment.

EET Emission estimation technique Flaring Combustion of waste, or surplus gases via stack. Fugitive Emissions Emissions not released from a vent or stack. Inventory Means of recording usage and stores of all materials and product

held on a facility, or utilised by a process. Loading Losses Emissions resulting from the transfer of product to non-pipeline

transportation methods, such as rail, trucks, or tankers. Mass Balance Technique Estimation of emissions to the environment through the

equalisation of inputs and outputs to a particular process or facility.

PM10 Particulate matter 10 micrometers or less (an NPI substance). PAHs Polycyclic aromatic hydrocarbons (an NPI substance). Power Generation Production of power for the operation of facilities, and use in

processes. Produced Formation Water (PFW)

Water produced from the formation with the crude oil, that is separated, treated and disposed of either to surface waters, or through reinjection to the formation.

Production Testing Testing activities associated with exploration activities to determine the viability of a well.

sm3 Standard cubic metres (usually at a Standard pressure of 101.326 kPa and Standard temperature of 273.15 Kelvin)

TOC Total Organic Compounds (calculated as an intermediate step for determining emissions of organic compounds which are NPI substances)

TP Throughput Total VOCs Total Volatile Organic Compounds (an NPI substance). Venting Non-combusted emissions released from non-machinery

sources, such as the release of waste gas, or volatilisation from crude oil storage tanks


20

Term Explanation wt% Weight percent Vol% Volume percent


21

7. References

7.1 References cited in text

API (1996), Calculation Workbook for Oil and Gas Production Equipment Fugitive Emissions, API Publication 4638.

APPEA (1997), Greenhouse Gas Emissions and Action Plans from the Australian Petroleum Exploration and Production Industry 1990-1995, Report to the Greenhouse Challenge Program, 8 August 1997.

APPEA (1998), Letter from Barry Jones (APPEA) to Rory Sullivan (NSW EPA), 29 September 1998.

E&P Forum (1994), Methods for Estimating Atmospheric Emissions from E & P Operations, Report no. 2.59/197.

Emission Inventory Improvement Programme (1997), Introduction to Stationary Point Source Emission Inventory Development, Volume II, Eastern Research Group Inc.

PPK (1998), E-mail from Steve Marlborough (PPK) to Rory Sullivan (NSWEPA) re E&P Forum Data, 13 October 1998, 16.58.

USEPA (1995a), Protocol for Equipment Leak Emission Estimates, EPA -453/R-95-017.

USEPA (1995b), Compilation of Air Pollutant Emission Factors, Volume I, Fifth Edition, AP-42.

FIRE (1997), Factor Information Retrieval System (Air Chief CD ROM, Version 5.0, USEPA.

The following Emission Estimation Technique Manuals referred to in this Manual

can be obtained from your local environment agency.

• Emission Estimation Technique Handbook for Petroleum Refineries

• Emission Estimation Technique Manual for Sewage and Wastewater Treatment

• Emission Estimation Technique Manual for Fuel & Organic Liquid Storage

7.2 References not cited in text

APPEA (1994), The Findings of an Independent Scientific Review, Edited by Swan, Neff, Young, Australian Petroleum Production & Exploration Association.

API, 1993a, Estimation of Aromatic Hydrocarbon Emissions from Glycol Dehydration Units using a Process Simulation Model, DR110

API (1993b), Fugitive Hydrocarbon Emissions from Oil and Gas Production Operations, API Publication 4589

API (1995a), Emission Factors for Oil and Gas Production Operations, API Publication 4615.


22

API (1995b), Potential BTEX Emissions from the Nations Triethylene Glycol Units in Oil and Natural Gas Facilities, DR220.

BP (1997), Environmental Performance - Group Reporting Guidelines, Version 1.0.

E&P Forum (1994a), North Sea Produced Water:, Fate and Effects in the Marine Environment, Report no. 2.62/204.


23

Appendix 1. Examples of determining emissions using the techniques in this manual

This section provides example calculations for determining emissions from various sources. The section is intended to provide guidance on determining emissions from a range of sources. It must be noted that total facility emissions are determined by calculating emissions from individual sources, and then adding each of these estimates for a cumulative total.

A1.1 Determining carbon monoxide emissions from fuel combustion

A facility uses gas fired turbines and heaters.

Annual fuel usage is:

• Turbines : 8,346 tonnes of gas

• Heaters : 135 tonnes of gas

To calculate carbon monoxide emissions from combustion at the facility, the annual fuel use is multiplied by the relevant emission factor (Worksheets 7 and 16 from Appendix 2) to give the annual emission of carbon monoxide (CO) from that source:

Turbines Heaters Total combustion carbon monoxide

emissions Emission Factor [EF] (kg emissions/tonnes

throughput)

2.7

0.80

Throughput [TP]

(tonnes/year)

8,346

135

Emission = [EF] × [TP]

(kg/year)

22,534

108

23,000 kg1

Notes: 1. Because of the accuracy of the emission factors the total emission should be reported to a

precision of two significant figures only.

A1.2 Determining fugitive emissions of organic compounds which are NPI substances from different types of pipe fittings

A review of facility equipment types is carried out and an inventory developed as shown below:

Valves 1000 Open-ended lines 500 Pump Seals 600 Connectors 560 Flanges 230 Others 430 Of the 1000 valves:

500 are in gas service:


24

350 are in oil service; and

150 are in water/oil service

Of the 500 valves in gas service, it is ascertained that 100 valves are, on average, 90 percent weight TOCs and 10 percent water vapour, and it is estimated that these valves operate for 7400 hours per year.

The gas service emission factor for valves of 4.5E-03 kg/hr/source (Table 2) is applied to the calculation and emissions are estimated with the following parameters:

Source of fugitive emissions

(N) Number pieces of equipment

(WTOC) Average weight

fraction

(FA) Average emission

factor from Table 2

(ETOC) Emission rate of

TOC = (FA × WTOC × N)

(kg/year) Valves - gas service

500 0.9 4.5E-03 2.0


precision of two significant figures only.

Speciated fraction for valves - gas

service

ETOC

(kg TOC/hr)

(HRS) Hours of operation

(hr/year)

(SF) Speciation factor from

Table 1

[ESF] Speciated substance

emission = (ETOC x HRS x SF)1

(kg/year) Benzene 2.0 7400 6.9E-04 10 Ethylbenzene 2.0 7400 3.0E-05 0.4 n-hexane (a) 2.0 7400 6.9E-03 100 Toluene 2.0 7400 3.8E-04 5.6 Total VOC 2.0 7400 1.7E-01 2500 Xylenes 2.0 7400 9.0E-05 1.3 Notes: 1. Because of the accuracy of the emission factors the total emission should be reported to a

precision of two significant figures only. 2. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6 x 10-3 or 350 = 3.5E+02 = 3.5 x 10+02.

This process would be carried out for all component streams at the facility, providing a facility- wide fugitive emission estimate.


25

A1.3 Determining emissions of organic compounds which are NPI substances from venting which takes place during loading crude oil onto ships

Assuming that each year, 4,024,500 tonnes of light crude oil are loaded to ships (tankers), the total Total VOC emissions from this activity would be estimated by multiplying the volume loaded, by the emission factor from Worksheet 11.

Ship loading losses Total VOC1

Emission Factor [EF] (kg emissions/

tonnes throughput)

0.10

Throughput [TP]

(tonnes/year)

4,024,500

Emission = [EF] × [TP]

(kg/year)

400,000

Notes: 1. Because of the accuracy of the emission factors the total

emission should be reported to a precision of two significant figures only.

As highlighted in Section 4.1.7 the Total VOC emissions may be speciated using the light oil speciation factors from Table 1:

Speciation Substance

Total VOC Emission Speciation factor for light oil

Speciated emission (kg/year)

Benzene 400,000 1.2E-03 480

Ethylbenzene 400,000 1.6E-04 64

n-hexane 400,000 2.3E-02 9200

Toluene 400,000 1.1E-03 420

Xylenes 400,000 3.3E-04 130


precision of two significant figures only. 2. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02.

These emission estimates would then be added to the total facility emission of the NPI substance.


26

Appendix 2. Worksheets to assist you to determine NPI reporting thresholds and emissions Worksheet 1. Determining category 1 and 1a NPI reporting thresholds based on default substance levels contained in Produced

Formation Water (PFW)

As Benzene Cd Cu Cr (III) Ethyl-benzene

Pb (lead)

Mn Hg (mercury

)

Ni Toluene Phenol Xylenes Total VOCs

Zn

Substance Concentration [SC]2 (mg/L)

0.0010

1.0

0.0063

0.0074

0.0070

0.071

0.0066

1.7

0.0010

0.0099

1.5

3.6

0.86

0.0063

Throughput of PFW

[TP] (L/year) 2

Emission

= [SC] x [TP] / 1E+06

(kg/year)

Notes: 1. Reference: APPEA, 1998. 2. The quantity of PFW released or discharged (note that reinjection of PFW is classed as a transfer except for additives – see sections 3.1.4 and 4.1.1

for more information). 3. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02


27

Worksheet 2. Determining category 1 and 1a substance usage from crude oil/gas throughput

As Benzene Cd Cr (III) Cu Ethyl benzene

Pb (lead)

Mn Hg (mercury)

Ni Phenol Toluene Xylenes Total VOCs

Zn

Substance Concentration

[SC]2

(mg/L)

Throughput of crude oil or gas

[TP]

(L/year)

Emission = [SC] x [TP] /

1E+06

(kg/year)

Notes: 1. Reference: PPK, 1998. 2. Facilities will need to provide their own crude oil composition for each of the substances listed. It should be recognised that NPI substances other

than those listed above, may also be relevant to a facility. In determining whether or not reporting is required, it may be necessary to consider these substances (e.g. hydrogen sulfide).


28

Worksheet 3. Determining the amount of drilling fluids emitted to the environment

Volume of fluid used [VU]

(L/year)

Volume of fluid recovered

[VR]

(L/year)

Volume of fluid lost down hole

[VDH]

(L/year)

Volume of fluid emitted to the environment2

[VE] VU - (VR + VDH)

(L/year)

Concentration of NPI substance in fluid

[C]

(mg/L)

Mass of NPI substance emitted to

the environment3

[E] (VE + VDH) x C /

1E+06 (kg/year)

Notes: 1. Reference: PPK, 1998. 2. Emission to air and water 3. Note that the volume of fluid lost down hole should be reported as a discharge to land. The allocation of the volume of fluid emitted to the

environment to air, water and land will depend on the mechanisms by which the drilling fluid is lost to the environment. 4. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02


29

Worksheet 4. Determining fugitive emissions of Total Volatile Organic Compounds (Total VOCs)

General Leaks Fixed Roof Tank Floating Roof Tank Internal Floating Roof Tank

Description

Total VOC Total VOC Total VOC Total VOC

Emission Factor [EF]2

(tonnes emissions/tonnes throughput)

7.0E-06 1.1E-04 8.5E-07 7.0E-08

Throughput of all product (oil and gas)

[TP] (tonnes/year)

Emission = [EF] x [TP] x 1000 (kg/year)

Notes: 1. Reference: APPEA, 1997 2. For more information on fugitive emissions from tanks, please refer to the NPI Manual for Fuel and Organic Liquid Storage 3. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02


30

Worksheet 5. Determining fugitive emissions of organic compounds that are NPI substances

Source of fugitive emission(a)

(N) Number of pieces of

equipment

(WFTOC) Average weight

fraction

(FA) Average

emission factor from

Worksheet 4

(ETOC) Emission rate of

TOC = (FA x WTOC x N)

(HRS) Hours of operation

(SF) Speciation

fraction from Table 1

[ESF] Speciated

substance emission = (ETOC x HRS x

SF) (kg/year)

Notes: See the next page.

• ETOC = Emission rate of TOC from all sources grouped in a particular equipment type and service (kg/hr). (e.g. valves in light liquid service). For further guidance on this, see Table 2.

• WFTOC = Average weight fraction of TOC in the stream (e.g. 80% TOC and 20% water vapour gives value of 0.8). Where a TOC fraction is assumed, this information must be recorded.

NPI oil and gas production and exploration

2. The speciation to relevant NPI substances from calculated TOC emissions must be carried out for each species identified in Table 7.

• ETOC = Emission rate of TOC from all sources grouped in a particular equipment type and service (kg/hr)

• Hrs = Hours of operation in the reporting year for each type of equipment and stream

• N = number of pieces of equipment grouped in the relevant category according to:

3. See Worksheet 4 for list of equipment types, and Table 2 for definitions of the service for these items.

• FA = Applicable average emission factor for the equipment type (Worksheet 4)

Version 1.2 – February 2010

31

• ESF = Speciated Substance Emission (kg/yr)

• SF = Speciation fraction (from Table 1)

- weight fraction of TOC.

4. Abbreviations used in Worksheet 5:

1. Reference: based on API 1996.

- equipment type,

- service; and

Worksheet 5. (continued)

Notes:


32

Worksheet 6. Determining carbon monoxide (CO), oxides of nitrogen (NOx) and Total VOCs from flaring

Gas Flared (Associated & Non-associated)

Liquids/Oil Flared Parameters

CO NOx Total VOC

CO NOx Total VOC

Emission Factor1 [EF]

(kg emissions/ tonnes throughput)

8.7

1.5

15

18

3.7

3.0

Throughput [TP]

(tonnes /year)

Emission = [EF] x [TP]

(kg/year)

Notes: 1. Reference: E&P Forum 1994.


33

Worksheet 7. Determining emissions of carbon monoxide (CO), oxides of nitrogen (NOx) and Total VOC from power generation: diesel equipment

Heaters Carbon monoxide (CO) Oxides of nitrogen (NOx) Total volatile organic

compounds (Total VOCs) Emission Factor [EF] 1 (kg emissions/tonnes throughput)

0.70

3.0

0.028

Throughput [TP] (tonnes /year)

Emission = [EF] x [TP] (kg/year)

Notes: 1. Reference: E&P Forum, 1994. 2. See the combustion engines and combustion in boilers manuals for more information about determining emissions from

combustion.


34

Worksheet 8. Determining emissions of PM10 and NPI substances that are organic compounds from associated gas combustion

Acetaldehyde Benzene Formaldehyde PM10 PAH’s Toluene Xylenes Emission Factor

[EF]1 (kg emissions/

tonnes throughput)

3.4E-05 1.2E-03 0.12 5.4E-05

Throughput [TP]

(tonnes of assoc gas/year)


(kg/year)

Notes: 1. Reference: USEPA, 1995b (Adapted – see Section 5.7). 2. Abbreviations: Particulate matter 10 micrometres or less in diameter (PM10), Polycyclic aromatic hydrocarbons (PAH’s) 3. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02.


35

Worksheet 9. Determining emissions of metals that are NPI substances and fluoride from associated gas combustion

Metals Non-metals

As Be Cd Cr (VI)

Cu Pb Hg Ni Co Mn Se Zn F

Emission Factor [EF]1 (kg emissions/ tonnes throughput)

3.2E-06

1.9E-07

1.8E-05 (note 2)

1.1E-06

1.4E-06

4.3E-06

4.1E-06

3.4E-05

1.3E-06

6.1E-06

3.8E-07 (note 2)

4.6E-04

Throughput [TP] (tonnes/year)


Notes: 1. Reference: USEPA, 1995b (Adapted – see Section 5.7), except for (a), from FIRE, 1997 (Adapted – see Section 5.7). 2. It is expected that the emission factor is less than this. Use value provided if no other information is available. 3. Reference: FIRE, 1997 (Adapted – see Section 5.7) 4. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02.


36

Worksheet 10. Determining emissions of metals that are NPI substances and fluoride from non-associated gas combustion

Metals Non metals

As Be Cd Cr(VI)2 Cu Pb Hg Ni Co Mn Se Zn F Emission

Factor1 [EF] (kg emissions/

tonnes throughput)

4.0E-06

2.4E-07

2.2E-05

1.4E-06

1.7E-06

5.4E-06

5.2E-06

4.2E-05

1.7E-06

7.6E-06

4.8E-07

5.8E-04

Throughput [TP]

(tonnes/year)


(kg/year)

Notes: 1. USEPA, 1995b (Adapted – see Section 5.7). 2. FIRE, 1997 (Adapted – see Section 5.7). 3. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02.


37

Worksheet 11. Determining for losses of Total VOCs from loading oil or gas to tankers

Rail/Truck Loading Losses Ship Loading Losses Parameter Total VOC Total VOC

Emission Factor1 [EF] (kg emissions/

tonnes throughput)

0.33

0.10

Throughput [TP] (tonnes/year)


(kg/year)

Notes: 1. Reference: E&P Forum 1994.

Worksheet 12. Using mass balance to determine the mass of gas vented

Mass of Gas Produced [GP]

1

(kg/year)

Mass of Gas sold/processed

[GS]

(kg/year)

Mass of Gas lost as fugitives

[GF]

(kg/year)

Mass of Gas Flared [GFl]

(kg/year)

Mass of Gas Vented [GV]

GP - (GS + GF + GFl)

(kg/year)

Notes:

1. Gas volume can be converted to mass using the standard densities below (E&P Forum, 1994): • associated gas: 1 tonne/1000 m3 • non-associated gas: 0.8 tonne/1000 m3

[See Section 5.7 for a further discussion of this conversion.]


38

Worksheet 13. Determining emissions from venting of total organic compounds from FPSO crude oil storage tanks

Crude Oil Storage Tank

No. 1

No. of days stored

[N]

(days/year)

Volume of Crude stored

[V]

(m3)

TOC Emission Factor

[EF]

(kg/day/m3)

Mass of TOCs emitted [ETOC]

EF x V x N (kg/year)

0.022

0.022

0.022

0.022

Notes: 1. Reference: USEPA, 1995b. 2. An EPSO is a floating production storage and offloading facility. 3. TOC emissions may be estimated from individual tanks, or from facility as a whole.

Worksheet 14. Determining NPI emissions from wastewater discharges

Wastewater Discharge 2

Volume of wastewater discharged

[V] (L/year)

Concentration of NPI substance 3

[C]

(mg/L)

Mass of NPI substance emitted

[E] V x C / 1,000,000

(kg/year)

Notes: 1. Reference: PPK, 1998. 2. Emissions from wastewater can be calculated at individual discharge points, or for the facility

as a whole. 3. Concentrations are assumed to be from ‘end of pipe’ following any treatment process. 4. Where concentrations are taken prior to the treatment process, the efficiency of the treatment

process must be factored into the EET.


39

Worksheet 15. Determining emissions of PM10 and NPI substances that are organic compounds from non-associated gas combustion

Acetaldehyde Benzene Formaldehyde PM10 PAH’s Toluene Xylenes Emission Factor

[EF]1 (kg emissions/

tonnes throughput)

4.2E-05 1.5E-03 0.15 6.8E-05

Throughput [TP]

(tonnes of non-assoc gas/year)


(kg/year)

Notes: 1. Reference: USEPA, 1995b (Adapted – see Section 5.7). 2. Abbreviations: Particulate matter 10 micrometres or less in diameter (PM10), Polycyclic aromatic hydrocarbons (PAH’s) 3. Scientific notation is used e.g. 0.0026 = 2.6E-03 = 2.6×10-3 or 350 = 3.5E+02 = 3.5×10+02.


40

Worksheet 16. Determining emissions of carbon monoxide (CO), oxides of nitrogen (NOx) and Total VOCs from combustion of gas (associated and non-associated)

Turbines Engines Heaters CO NOx Total

VOC CO NOx Total

VOC CO NOx Total

VOC Emission Factor [EF]1 (kg emissions/tonnes throughput)

2.7 6.9 0.051 9.6 76 3.0 0.80 3.3 0.62

Throughput [TP] (tonnes of assoc gas/year)


Notes: 1. Reference: E&P Forum, 1994. 2. Associated gas is the gas produced from an oil and gas extraction operation, while non-associated gas is the gas from a well that only produces

gas.


41

Worksheet 17. Determining total nitrogen and total phosphorus in wastewater flows

NPI Substance

Average No. of people at the facility over

period [N]

Length of period

[D] (days)

Emission Factors

[EF] (kg/person/day)

Emission of substance [ENP]

N x D x EF (kg)

Total Nitrogen

0.0110

Total Phosphorus

0.0025

Notes: 1. Considers total nitrogen and total phosphorus emissions from the facility’s population only. 2. Derived from West Australian Water Corporation wastewater treatment facility design criteria.

emission estimation technique manual for oil and gas exploration and production version 1.2

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