Q446. How are greenhouse gas emissions calculated for subpart W (oil and natural gas systems) facilities?
Emission Calculation MethodsA446. Under this rule, facilities will detect, as applicable, and calculate GHG emissions according to the specified quantification methods. See the table below for a summary of the calculation methodologies by source type. Where volumetric emissions are measured, mass emissions of CO2 and CH4 will be estimated based on the annual mole fraction and density of each GHG.
• The engineering calculation methods use monitored process operating parameters and either software models, engineering calculations, or emission factors.
• For emissions detection, the rule allows the use of optical gas imaging instruments, organic vapor analyzers (OVA), toxic vapor analyzers (TVA) and infrared laser beam illuminated instruments or acoustic leak detection instruments for accessible components. For inaccessible components, reporters must use an optical gas imaging instrument.
• Direct measurement involves the use of the high-volume sampler; or calibrated bagging; or rotameters, turbine meters, or other meters, as appropriate, depending on the individual component for emissions measurement.
• For the use of leaking factors, the relevant emission factors will be applied to leaking components determined by using an applicable instrument and applying leaking factors. For the use of population factors, the relevant emission factor will be applied to all components.
Source Type | Engineering | Direct | Leak Detection and Leaker Emission Factor | Equipment Count and Population |
Natural gas pneumatic device venting |
|
|
| X |
Natural gas driven pneumatic pump venting |
|
|
| X |
Well venting for liquids unloading | X | X |
|
|
Gas well venting during well completions without hydraulic fracturing | X |
|
|
|
Gas well venting during well completions with hydraulic fracturing |
| X |
|
|
Gas well venting during well workovers without hydraulic fracturing | X |
|
|
|
Gas well venting during well workovers with hydraulic fracturing |
| X |
|
|
Onshore production storage tanks | X |
|
| X |
Transmission storage tanks |
| X |
|
|
Reciprocating compressor rod packing venting |
| X |
|
|
Well testing venting and flaring | X |
|
|
|
Associated gas venting and flaring | X |
|
|
|
Dehydrator vent stacks | X |
|
| X |
EOR injection pump blowdown | X |
|
|
|
Acid gas removal vent stack | X | X |
|
|
EOR hydrocarbon liquids dissolved CO2 |
| X |
|
|
Centrifugal compressor wet seal degassing venting |
| X |
|
|
Other emissions from equipment leaks |
|
| X* | X** |
Blowdown vent stacks | X |
|
|
|
Flare stacks | X | X |
|
|
Stationary and portable combustion emissions | X | X |
|
|
Above ground meters and regulators at city gate station equipment leaks |
|
| X |
|
Below ground meter and regulator station equipment leaks |
|
|
| X |
Pipeline main equipment leaks |
|
|
| X |
Service line equipment leaks |
|
|
| X |
*Applicable to the following industry segments: Processing, Transmission Compression, Underground storage, LNG storage, LNG Import and Export, and Distribution. Sources with multiple methods indicate options for monitoring.
** Applicable to the following industry segments: Production, Underground storage, LNG storage, LNG Import and Export, and Distribution. Sources with multiple methods indicate options for monitoring.
Updated on
Source: EPA, Petroleum and Natural Gas Systems, November 2011, http://www.epa.gov/ghgreporting/documents/pdf/infosheets/PetroleumNaturalGasSystems.pdf
.
Approval / Publishing History: Version 1 Do Not Publish / Cited content requires vetting by EPA SME
Expiration : none
Relevant Subpart: W
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