understanding the revised subpart w regulation · • well testing venting and flaring replaced eq....

Understanding the Revised Subpart W Regulation

Greg Gasperecz, VP, EHS

Enviance, Inc.

2

Overview

Subpart W Revisions - Federal Register 12/23/11

• Definitions

• Calculation methods and Errors

Important: Significant Error in Eq. W-36 !!

• Reporting

• Calculation Tips and Techniques

• Emission Factor Tables Quick Look

3

Definitions Subpart A

Subpart W Definition of Source Category

• Clarified that “Owner” and “Operator” used in Subpart A have the

same definition as defined at 98.238 (Subpart W)

• Continuous and Intermittent Bleed Pneumatic Devices – meaning

clarified (Subpart A)

• Onshore Petroleum and Natural Gas Production (Subpart W 98.230)

Includes dehydrators and vessels on well pads or associated with a

single well pad

EOR operations that use CO2 are included

• Onshore Natural Gas Processing (Subpart W 98.230)

Recovery of separated gases not required to be part of this segment

Identifies the included processes in generic terms

25 MM scf/day threshold applies to plants that do not fractionate

4

Definitions Subpart W Definition of the Source Category

• Onshore Natural Gas Transmission Compression (Subpart W 98.230)

Defined “transmission pipeline” at 98.238 to consistent with intent at 98.230

Clarified what Transmission Compression includes

Removed term “natural gas dehydration”

• Natural Gas Distribution (Subpart W 98.230)

Replaced “city gate station” with “metering-regulating station”

Defined “metering-regulating station” at 98.238 to consistent with intent at 98.230

Defined “distribution pipeline” at 98.238 to consistent with intent at 98.230

Local Distribution Company description was made consistent with Subpart NN

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Definitions Subpart W – Specific Terms at 98.238

• “Associated with single well pad” – newly added; for consistency

with source category definition

• “Facility…Onshore Petroleum and Natural Gas Production” –

revised to reflect single well pad approach, and clarifying

• “Facility…Natural Gas Distribution” – revised to clarify all distribution

pipelines operated by an LDC in a single state are included

• “Farm taps” – revised to eliminate reference to city gate

• “Flare” – newly added; ground level or elevated; energy recovery

not required

• “Forced extraction of natural gas liquids” – newly added; describes

removal of C2+ hydrocarbons; excludes dehydration and other

water removal activities

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• “Gas well” – removed; now addressed in “sub-basin category”

definition

• “Natural gas” – newly added; includes field quality, pipeline quality

or process gas

• “Oil well” – removed; now addressed in “sub-basin category”

definition

• “Pressure groups” – newly added; used in revised calculations for

Well Venting for Liquids Unloading

• “Tubing diameter groups” – newly added; used in revised

calculations for Well Venting for Liquids Unloading

• “Sub-basin category” – Newly added; main concept in the change

from measurements at field level to sub-basin level. Note the county

overlay in this definition.

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• “Transmission-distribution (T-D) transfer station” - newly added;

defines what was previously termed custody transfer

• “Transmission pipeline” – revised; clarified to be consistent with

FERC or state rate-regulated pipelines or those covered by the

Hinshaw Exemption of 1994 Natural Gas Act

• “Horizontal well” – newly added; used in calculations for well

completions and workovers

• “Vertical well” – newly added; used in calculations for well

completions and workovers

• “Well testing venting and flaring” – newly added; defined as

occurring at the time production rate is determined; if production

rate determined upon completion, then that activity would be part of

completions and workovers.

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Calculation Methods Revisions

• 58 separate changes to calculation definitions or the terms used in the calculations

• Most are clarifications and technical improvements

• Standard Temperature = 60o F

• Emission factors changes often due to shift to STP change

Table 1A – onshore production; most new factors are lower; Pneumatic devices now different for Eastern vs. Western; Western US appears to be changed due to STP shift; Eastern changes due to new information?

Table 2 – natural gas processing; All changes due to STP

Table 3 – transmission compression; All changes due to STP

Table 4 – underground storage; All changes due to STP

Tables 5 & 6 – LNG storage and import/export; All changes due to STP

Table 7 – natural gas distribution; All changes due to STP

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Calculation Methods Revisions Significant Actions

• Pneumatic devices and pneumatic pumps

Eq. W-1 and W-2 now use Tt (Average estimated number of operational

hours); Default is 8760 hours.

Eq. W-1 and W-2 use correct factors to convert scf to CO2e

• CH4: 0.000403 metric tons CO2e per scf CH4 at 60F

• CO2: 0.00005262 metric tons CO2e per scf CO2 at 60F

• Acid gas removal - Eq. W-4A and W-4B added in place of W-4 to

clarify inlet vs. outlet measurement approaches

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• Well venting for liquids unloading - now uses the tubing diameter

and pressure group combination approach in Eq. W-7

• Gas well venting completions/workovers with hydraulic fracturing

Sub-basin category aggregation for measurements

Eq. W-10A and W-10B added in place of W-10 to reflect whether

backflow is metered

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• Gas well venting completions/workovers with hydraulic fracturing

Renamed equations and added Eq. W-11C to determine is flow is sonic

Eq. W-12 now defines FRM – the ratio of backflow rate to average

production rate

12


• Blowdown vent stacks

Applicable only to manually activated operations

Uses “unique physical volume” concept

Eq. W-14A used when Ta and Pa are same for all blowdowns

Eq. W-14B used when Ta and Pa vary for each event

• Onshore production storage tanks-

10 bpd threshold is based on annual average daily throughput

Eq. W-15 modified corrected to add factor of 1,000

Note: e-CFR does not display the factor of 1,000 in W-15

Eq. W-16 revised to reflect yearly emissions rather than hourly

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• Well testing venting and flaring

Replaced Eq. W-17 with W-17A (for oil well) and W-17B (for gas well)

• Flare stack emissions - 98.233(n)

Onshore natural gas processing plants that solely fractionate a liquid

stream use GHG mole percent in feed natural gas liquid for all streams

Tier 4 (CEMS)method allowed if CEMS is present

14


• Leak detection and leaker emission factors - 98.233(q)

Eq. W-30 A and W-30B added in place of W-30

• Use W-30A for natural gas processing, transmission compression, underground storage, and LNG storage and import/export

• Use W-30B for natural gas distribution

For underground storage and transmission compression GHGi use 0.975 for CH4 and 0.011 for CO2

For LNG storage and import/export GHGi use 1.0 for CH4 and 0 for CO2

For natural gas distribution GHGi use 1.0 for CH4 and 0.011 for CO2. CO2 value is likely a mistake, since total should not exceed 1.0

For natural gas distribution, monitoring for leaks can be done over a multiple year period, not to exceed 5 years.

Eq. W-30B is a multiple year, rolling sum (even if all monitoring done in first year)

15


• Population count and emission factors - 98.233(r)

“meter/ regulator runs” at above grade “metering-regulating stations”

term used in place of “non-custody transfer city-gate”

Eq. W-31 - underground storage and transmission compression GHGi

use 0.975 for CH4 and 0.011 for CO2

Eq. W-31 - LNG storage and import/export GHGi use 1.0 for CH4 and 0

for CO2

Eq. W-31 - natural gas distribution GHGi use 1.0 for CH4 and 0.011 for

CO2. Mistake?

Eq. W-32 now yields an emission factor with unit of measure of scf per

meter-regulator run per hour

Potential mistake in the combined use of W-30B and W-32 to produce

the emission factor in W-31 (double use of GHGi).

16


• Volumetric emissions - 98.233(t)

Set standard temperature as 60 F

Retained standard pressure as 14.7 psia

• GHG volumetric emissions - 98.233(u)

Mole fraction (Mi) should be an annual average value when measuring

Default mole fraction set at 0.95 for CH4. Note inconsistency with GHGi

values at 98.233(q)

Segment 98.233(u) 98.233(q)

TC 0.95 0.975

Und. Storage 0.95 0.975

LNGs 0.95 1.0

Distribution 0.95 1.0

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• GHG mass emissions - 98.233(v)

ρ i= Density of GHGi. Use 0.0526 kg/ft3 for CO2and N2O, and 0.0422

kg/ft3 for CH4at 60 F and 14.7 psia

DENSITY OF CH4 IS INCORRECT – CORRECT VALUE = 0.01919

kg/ft3

Caution: Eq. W-36 is applied to results from numerous other

calculations

Mr. Gasperecz,

Thank you for pointing out the conversion error in the CH4 density value defined in

Equation W-36 in 40 CFR part 98 subpart W. EPA is considering ways to address

this issue. If the EPA decides to issue guidance on this topic, it will be posted here:

http://www.epa.gov/climatechange/emissions/subpart/w.html

EPA Response to notice that Eq. W-36 value for CH4 density is incorrect

Notice and response dated January 13, 2012

http://www.epa.gov/climatechange/emissions/subpart/w.html

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• Onshore production and distribution combustion – 98.233(z)

External fuel combustion sources with a rated heat capacity equal to or

less than 5 mmBtu/hr are exempt

Internal fuel combustion that are not compressor drivers and with a

rated heat capacity equal to or less than 1 mmBtu/hr are exempt

Clarifies when to use Subpart C methods:

• Fuel is listed in Table C-1 or blend thereof

• Fuel is pipeline quality natural gas with minimum HHV of 950 Btu/scf

• Can use any tier of Subpart C

• Reporting as required in Subpart W - 98.236(c)(19)

Clarifies when to use Subpart W methods:

• Field gas, process vent gas or blend thereof, or not pipeline quality

• Use calculation method at 98.233(z)(2) – carbon content approach

• Reporting as required in Subpart W - 98.236(c)(19)

19

Reporting Significant Actions

• Reporting rollup required by equipment /component type is common

• Population emission factor reporting had a significant rollup change

Original rule required rollup by equipment type

Revision requires rollup by component type (valve, connector, etc.)

• For gas sent to a flare, report amount to unlit flare, and to lit flare.

Report emissions under the equipment source type, not at the flare.

• Unique name or ID required for:

Blowdown vents for all segments (unique blowdown volume)

Acid gas recovery units in onshore processing segment

Dehydrators in onshore processing segment

Flares in onshore processing segment

Storage vessels in transmission compression segment

20


• Well venting for liquids unloading – for each tubing diameter group

and pressure group combination in each sub-basin category, report

Count of wells vented to the atmosphere for liquids unloading

Count of plunger lifts

Whether the selected well from the tubing diameter and pressure group

combination had a plunger lift

Cumulative number of unloadings vented to the atmosphere

Average flow rate of the measured well venting in cubic feet per hour

Internal casing (or tubing) diameter, and well depth of each well in that

tubing size and pressure combination

Casing pressure in that tubing size group and pressure group

combination that does not have a plunger lift.

Tubing pressure in a tubing size group and pressure group combination

that has a plunger lift.

Annual CO2 and CH4 emissions, expressed in metric tons Coe for each

gas

21


• Reporting by sub-basin category also applied to

Workovers and completions

Storage tanks for onshore production

Enhanced oil recovery

• For each oil sub-basin category, also report best estimate of

API gravity

Gas to oil ratio

Average low pressure separator pressure

22

Calculation Tips and Techniques Use Templates to Leverage Your Work

• Templates are sets of calculations that are applicable across

facilities and (in most cases) segments

• Correspond to 40 CFR 98.233 (a) through (z)

• Advantages – Consistency, Transparency, Minimize time and data

Consistency

Quality assurance

Transparency

Speed of delivery

Reduce data entry

23

Calculation Tips and Techniques Monthly/Quarterly Estimates from Annual Results

• Why?

Corporate sustainability updates

California Cap & Trade planning and trading

• Typical Processing, TC, and Distribution source types that collect

data once per year

Pneumatic devices

Equipment leaks

Dehydrators, AGRs, Transmission Storage Tanks

Estimating monthly emissions from annual results

24

Calculation Tips and Techniques Example Template for Single Calculation (Es,i CH4)

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Calculation Tips and Techniques Example Template for Transmission Compression

Tables and Tidbits

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Emission Factor Comparison

Table 1A

Eastern US December 23, 2011 November 30, 2010

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Table 1A

Western US

December 23, 2011 November 30, 2010

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Table 2


30


Table 3


31


Table 4


32


Tables 5 & 6


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Table 7


34

Equation W-15

Incorrect in e-CFR

As of 2/7/2012

Federal Register 12/23/2011 E-CFR 2/7/2012

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Detailed Guide to Subpart W Revisions

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Exclusive Offer - Subpart W Revisions Guide

• Lists each revision and EPA’s

explanation by subject matter and

citation, including reporting

revisions

• Combines revisions to calculations,

monitoring, and reporting into

grouped sections

• Organized by equipment and

activities that are subject to rule

Contact John at 760-496-0200 x215

to receive your copy

Thank You

Greg Gasperecz, VP, EHS

Enviance, Inc.

[email protected]

understanding the revised subpart w regulation · • well testing venting and flaring replaced eq....

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