EPA-600/R-96-CSOb June 

### 1996 METHANE EMISSIONS FROM 

## TiiE NATURAL GAS INDUSTRY VOLUME2: TECHNICAL REPORT FINAL REPORT Prepared by: 

### Matthew R. Harrison

Lisa M. Campbell Theresa M. Shires R. Michael Cowgill Radian International LLC

8501 N. Mopac Blvd. P.O. Box 201088 Austin, 

### TX 78720-1088

DCN: 650-049-20-01 For GRI Project Manager: Robert A. 

### Lott GAS RESEARCH INSTITUTE

Contract No. 5091-251-2171 8600 West Bryn Mawr Avenue Chicago, IL 60631 

### and EPA Project Manager: David A. Kirchgessner U.S. ENVIRONMENTAL PROTECTION AGENCY Contract No. 68-01-0031 National Risk Management Research Laboratory Research Triangie Park, NC 27711

### 3.0 METHODS This section characterizes the natural gas industry and describes in general terms 

### the methods used to define and extrapolate err.issions for all source types or categories that comprise the industry. 3.1 

### Emission Source Characterization The first step for estimating methane emissions from the U.S. natural gas industry is to identify and characterize each emission source withinthe industry, so that all significant 

### sources are included. To fully 

### characterize the industry. 

### sources were defined by 

### equipment type, mode ofoperation, andtype ofemissions. "While this section draws a general picture ofthe industry, it is not intended to be a definitive picture ofany companyorofthe industry regarding specific operational practices and procedures. Rather, 

### it is intended to define thegeneral industry equipment practices and 

### procedures used in 1992, the base year ofthe p:-ogram, that could lead to measurable emissions ofmethane. Details that were useful for detenniningmethane emissions are contained in specific reports (see Table 2-1). 

### 3.1.1 General Industry Description The natural gas industry uses wells to produce natural gas existing in underground formations, then processes, compresses, andtrar1sports the gas to the customer. Transportation and distribution ofnatural gas involve interstate and intrastate pipeline transportation, storage, and fmally distribution ofthe gas by local distribution pipeline networks.



### 9The generally accepted segments ofthe natural gas industry are: !) 

### Production 2) Processing 3) Transmission/storage 

### 4) Distribution Each ofthese segments is shown 

### in the flow chart for the industry in Figure 3-1. Some of

### the major equipment in each segment is s:town in Table 3-1. Each segment is described in more detail in the following subsections. Thisproject set specific boundaries for eachsegment ofthe industry that specify what equipment is included in the study. The guideline used for setting the boundaries wasto include only the equipment 

### in each segmentthat is required for marketing natural gas. For example, oil productionequipment isexcluded ifitis used to produceoil and not natural gas. Similarly, gas processing equipmentassociated 

### with the fractionation ofpropane, butane, and natural gas liquids are excluded from consideration. Indistribution, all equipment up to and including the customer's meter are included. End-useremissions are not included inthis estimate. Each industry segment is described inmoredetail in the following subsections: Production Segment Description The production segment is comprised ofgas and oil wells and the surface equipment required to produce gas. The well includes the holes drilled through subsurface rock to reach the producing formation and the subsurface equipment such as casing and tubing pipe. Gas and oil surface equipment can include separators, heaters, heater-treaters, tanks, dehydrators, compressors, pumps, and pipelines. 10

### PRODUCTION

Surface Facilities

Liquids 

### PROCESSING

Liquids 

### TRANSMISSION/ STORAGE I I I I I Direct 1 Compressor

Stations Sales 1 

### DISTRIBUTION Main and Service Pipelines I I I **.-~c~~~~~~--~~~~f~~~~~** Pipelines I I I I I I I



# l-**----r-~~l~i ~_i~--~~a-~**  L-J 

## c **IH~+---4M** Storage

Underground Storage Reservoir Customer Meters 

# IIJ Compressor @ Meter Q Pressure 1>'<1 Regulator 

### Figure 3-1. Gas Industry Flow Chart

### Segment Production
Processing
Transmission Storage 

### Distribution 

### TABLE 3-1. INDUSTRY CHARACTERIZATION ·Facilities
1 

### Well Sites, 

### Central Gathering Facilities

' 

### 1

Gas Plants 

# i TransmissionPipeline Networks, 

# ICompressor Stations,
,Meter and Pressure Regulating Stations I 

### ,Underground Injection/Withdrawal 

## ' ' 

# iFacilities, and Liquefied Natural Gas 

### '(LNG) Facilities 

### ' i

### Main and Service Pipeline Networks, ' 

### :Meter and Pressure Regulating Stations 

## '

12 

# I Equipmentatthe Facility I 

### ·Wellheads, Separators, Pneumatic Devices, Chemical Injection Pumps, Dehydrators, Compressors, Heaters, Meters, 

### Pipelines Vessels, Dehydrators, 

### \Compressors, Acid Gas 

# I Removal (AGR) Units, Heaters, 1

### Pneumatic Devices

**~Vessels,** Compressors, Pipelines, 

### \Meters/Pressure Regulators, i

### Pneumatic Devices i 

### )Wellheads, Vessels, j

### Compressors, Dehydrators,

.Heaters, Pneumatic Devices ;Pipelines, Meters and Pressure 

# IRegulators, Pneumatic Devices, :CustomerMetersThe definition for gas industryproduction equipment excludes equipment associated with oil production. Also, unmarketed natural gas, such as that produced by oil wells that vent gas orthat reinject gas for gas 

### lift circulation only, are not considered part ofthe natural gas industry. Figure 3-2 shows the general equipment found in the oil and gasproduction segment, 

### as well 

### as the boundaries between gas and oil production equipment used by this study. Theboundary between oil and gas equipment shov.n 

### in Figure 3-2 affects the gas industry emissions estimate since it excludes some high emissionrate production equipment associated 

### with oil production. Anaccounting oftotalproduction segment emissions, orjust oil industry emissions, 

### 'Wi11 haveto include the oil industry equipment excluded from this study (such as some pnewnatics, some chemical injection pumps, and oil tanks). Gas Processing Segment Description Natural gas processing plants recover high value liquid products from the gas stream and maintain the quality (i.e., content and heating value) ofthe gas stream. The liquid products include natural gasoline, butane, propane, and in some cases, ethane. The products are removed by compression and cooling or by absorption. A gas plant may have fractionation towers and stabilization towers to further purify the individual components oftheproduct stream. The back end ofthe gas plant, such as the fractionation train, is excluded from the gas industry defmition since its function is to purify and market liquid products. Also, the back endofthe gas planthas negligible methane emissions since the liquids handled have little methane content. The front end ofthe gas plant often contains dehydration facilities, wet gas compression, and the absorption or compression and refrigeration process. All natural gas processing plants are considered part ofthe natural gas industry, and methane emissions from these facilities are included in this study. !3

# - 0

"' 

# - - "' 

# :: OH Wd> 

# ,--A

# r::::=t Wellhead 

# ! L__.l 

### l__J

**~** Compressor
Oil Well

**w~Jlhe•d** 

## r--------, (producing

gas}

Coal Bed Methane Well

Gas Well Wellbe•d PetrokumIndustry

,.... ---- -rCOI!lj)ft$SOf



# ------

Sa!rWattt

**T~k ~** 



## ~ Vapor Recovery

**~** Comp"'ssor Pe1rokum Industry


### Figure3-2. Gas Industry Boundaries 14

### Transmission and Storage Segment Description The transmission segment moves the natural gas from the gasplant ordirectly from field production to local distribution companies (LDCs). Gas is often transported across many states, such as from the GulfCoast to the Eastern seaboard ofthe United States. The transmission segmentconsists oflarge diameter pipeline, compressor stations, and metering facilities. All ofthese facilities and all ofthe equipmentthey contain are considered part ofthe natural gas industry. Transmission compressor stationsusually consist ofpiping manifolds, reciprocating engines orgas turbines, reciprocating orcentrifugal compressors, and generators, as shown in Figure 3-3. Dehydrators may be included but are nottypicallypresent because of upstream gas drying. Sometransmission compressor stations may also include metering facilities. Transmission companies also have metering and regulating stations (M&PR) where they exchange gas with othertransmission companies, orwherethey deliver gas to LDCs or industrial customers. These stations may contain heaters, small dehydrators, and odorant addition equipment. Most storage facilities exist to store natural gas produced during off-peak times (usually summer) so that gas can be produced and delivered during peak demand. Storage facilities are often located close to consumption centers so that cross-country transmission pipelines do not have to be sized for peak demand. Storage facilities can be below or above· ground. Above-ground facilities are liquefied natural gas (LNG) facilities that liquefY the gas by supercooling and then storingthe liquid phase methane in above ground, heavily insulated storage tanks. Below-grotmd facilities compress and store the gas (in vaporphase) in one of several fonnations: I) spent gas production fields, 2) aquifers,·or 3) salt caverns. Below-ground storage is the predominantmeans ofgas storage. 

### !5Gas from Pipeline 

### TRANSMISSION ABOVE GROUND STORAGE COMPRESSOR STATION 

# g Cooling

**~** LNG Compressors Process Tank 

## c Heaters 

# I c Gas Transmission Pipeline 

## c from Pipeline 

### BELOW GROUND STORAGE 

## c Compressor 

## c



# ~.~.~ Station
Wells



## ~ **~ ~**  Dehydrator Storage Field 

### Figure 3-3. Transmission and StorageStationsMost storage stations consist ofa compressor station that is very similar to a transmission compression station (see Figure 3-3). UndergroWld storage facilities also have storage field wells, and usually have dehydrators to remove water absorbed by the gas while Wlderground. All storage equipment is included in boundaries ofthe natural gas industry defined by 

### this project.Distribution Segment Definition The distribution segment receives highpressure gas from transmissionpipelines, reduces the pressure, and delivers the gas to residential, commercial, and industrial consumers. Tills segment includespipelines (mains and services), 

### M&PR stations and customermeters. 

### All ofthese facilities are considered to be an integral 

### part ofthe gas industry. Figure 3-4 shows a schematic ofthe distribution segmentand the equipmentthat it includes. 

### 3.1.2 OperatingMode After identifying the majorequipment (sourcetypes) in each industry segment, emissions from each source were identified by examining the operatingmodes ofthe equipment that may lead to emissions, and by associating one of

### three possible types ofemissions from the source: fugitive emissions, vented emissions, or combustion emissions. The cause ofemissions is directly related to the operating mode ofthe equipment. Since more 

### than one cause ofemissions 

### can beassociated

### with 

### aparticularpiece 

### ofequipment, it is important to identify the various operating modes in orderto identify all emissions. In general, the operating modes are:
• Start-up; • Normal operations; • Maintenance; 

### • Upsets; and • Mishaps. 

### 17