ACCESS NUMBER: 31163

STUDY TITLE: The Data Quality Control and Emissions Inventories of OCS Oil and 

Gas Production Activities in the Breton Area of the Gulf of Mexico 

REPORT TITLE: Data Quality Control and Emissions Inventories of OCS Oil and Gas 

Production Activities in the Breton Area of the Gulf of Mexico 

CONTRACT NUMBER(S): 1435-01-01-CT-31163 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA(S): Gulf of Mexico within 100 kilometers of the Breton 

National Wildlife Refuge/Wilderness Area 

FISCAL YEAR(S) OF PROJECT FUNDING: 2001; 2002; 2003; 2004 

COMPLETION DATE OF REPORT: October 2004 

COST(S): FY 2001: $14,600; FY 2002: $113,550; FY 2003: $82,430; FY 2004: 

$21,611; CUMULATIVE PROJECT COST: $232,191 

PROJECT MANAGER: D. Wilson 

AFFLIATION: Eastern Research Group, Inc. 

ADDRESS: 1600 Perimeter Park Drive, Morrisville, North Carolina 27560 

PRINCIPAL INVESTIGATORS: D. Wilson, R. Billings, A. Blackard 

KEY WORDS: Air pollutant emissions inventory, Gulf of Mexico, BOADS, Breton 

National Wildlife Refuge/Wilderness Area, sulfur dioxide, nitrogen oxides 

BACKGROUND: The Breton National Wilderness Area (BNWA), part of the Breton 

National Wildlife Refuge, is classified as a Class I area under the U.S. Environmental 

Protection Agency’s (EPA’s) Prevention of Significant Deterioration (PSD) regulations. 

Under the Clean Air Act, air quality degradation is limited in Class I areas by 

establishing stringent “increment” limits for nitrogen oxides (NOx) and sulfur dioxide 

(SO2). These increments are the maximum increases in ambient pollutant 

concentrations allowed over baseline concentrations. The Minerals Management 

Service (MMS) is responsible for determining if air pollutant concentrations of NOx and 

SO2 have changed over time in the Gulf of Mexico in the vicinity of the BNWA due to 

emissions from oil and natural gas production sources. In response to this mandate, 

MMS has developed an overall strategy to deal with Outer Continental Shelf (OCS) oil 

and gas production activities that could affect the BNWA. This includes developing 

inventories of platform emissions, conducting air quality monitoring activities, and 

establishing a review process for new plans that includes close coordination with the 

Fish and Wildlife Service. 
ACCESS NUMBER: 31163

OBJECTIVES: 1- Describe and quantify emission sources in the OCS that release SO2 

and NOx within 100 km of the BNWA over the course of 12 consecutive months from 

September 1, 2000 to August 31, 2001; 2- prepare a report that summarizes the 

emissions data and describes the methodology used to generate the emissions 

inventory; 3- prepare data files for platform and non-platform emissions sources that 

can be used in air quality modeling studies; and 4- update and improve the Oracle 

computer software program used to used to develop the emission estimates. 

DESCRIPTION: The study includes all oil and gas production platforms and nonplatform sources within 100 km of the BNWA. Pollutants covered in the inventory are 

SO2 and NOx. MMS attempted to collect activity data from every active offshore oil 

production platform in the vicinity of the BNWA. Operators were provided with the 

Breton Offshore Activities Data System (BOADS) Visual Basic activity data collection 

software for compiling monthly data from August 2000 through September 2001. Nearly 

600 oil and gas production platforms submitted monthly equipment activity data files. 

The monthly activity data collected from the platform operators were then combined with 

emission factors and algorithms in the final Breton Oracle Database Management 

System (DBMS) to develop the platform emission estimates. Activity data for nonplatform sources within the vicinity of the BNWA were also collected and compiled in 

order to develop emission estimates for the same time period. For the most part, the 

emission factors used to calculate the emissions from all of the engines for these nonplatform sources were obtained from the EPA’s Office of Transportation and Air Quality. 

EPA published the emission equations along with the diesel marine vessel rule in 2002. 

The resulting emission estimates have been disaggregated to MMS lease blocks using 

Geographic Information Technology (GIS) software. 

SIGNIFICANT CONCLUSIONS: At the completion of any emissions inventory effort, 

one final, useful QA/QC check is to compare the inventory results with those from 

similar inventories. The most applicable inventory to use in a comparison is a base year 

2000 (January-December) inventory of emission sources within 100 km of the BNWA. 

For oil and gas production platforms, the primary source of NOX in both studies is 

natural gas engines. The number of natural gas engines in the two studies is similar 

(513 units in this study, 499 in the base year 2000 study). Daily NOx emissions in the 

base year 2000 inventory average 90 tons per day from natural gas engines, compared 

to an average of 40 tons per day in this inventory. Aside from the reported activity data 

for each equipment type, a review of the emission factors used in each study provides a 

good indication of why the NOX emission estimates are lower in the current study. The 

estimates in both studies were developed using EPA emission factors, but the emission 

factors have been changed for natural gas engines. On average, the NOx emission 

factors for natural gas engines are 50% lower than the factors applied in the base year 

2000 inventory. The contribution of natural gas engines to total NOx emissions 

accounts for a large portion (84%) of the emissions reported in the base year 2000 

study. The discrepancy in the SO2 emission estimates is due to the flare estimates in 

the two studies. In the base year 2000 study, 67% of the SO2 emissions are from 

flares, with an average daily value of 2 tons per day. Again, the number of units in the 
ACCESS NUMBER: 31163

two studies is similar (data reported for 45 flares in the current study, vs. 51 flares in the 

base year 2000 study). In the current study, flares account for less than 1% of total SO2

emissions, with an average daily value of 2 pounds per day. It is believed that the 

difference is due to a calculation correction in the final Breton DBMS. 

STUDY RESULTS: The inventory results indicate that OCS oil and gas production 

platform and non-platform sources emit the majority of NOx and SO2 in the vicinity of 

the BNWA. OCS platform and non-platform sources account for 80% of total NOx

emissions, and 54% of SO2 emissions. Oil and gas production platforms account for 

the majority of NOx emissions (53%). Other top-emitting NOx sources are commercial 

marine vessels (a non-OCS oil and gas production source), drilling operations, support 

vessels, and pipelaying vessels. Oil and gas production platforms account for only 15% 

of total SO2 emissions. Non-OCS oil and gas production sources emit 46% of total SO2

emissions. Commercial marine vessels, drilling operations, support vessels, and 

pipelaying vessels are the top-emitting sources in the inventory. 

Recommendations for future inventory efforts for oil and gas production platforms in the 

vicinity of the BNWA focus on the data gathering tools used. There is high uncertainty 

associated with flare emission estimates, for example. Much of the uncertainty is 

thought to be due to the interpretation of the data requested by the operators as well as 

the pre-processing steps applied prior to development of the emission estimates. Work 

is underway to improve the BOADS software for these equipment types. In addition, an 

overall improvement will be made to the software to simplify the data requested each 

month to only the equipment variables that change monthly. This will reduce data entry 

volume, processing time, and the likelihood of data entry errors. 

For non-platform sources, the estimates developed for some source categories such as 

support vessels and naval operations were based on adjustments to activity data 

gathered by MMS in 1992. The estimates would be improved by directly collecting 

activity data for the inventory base year rather than adjusting a prior year’s data set. An 

up-to-date support vessel survey could collect detailed information about vessel size, 

horsepower rating, and typical operating loads, as well as annual and seasonal activity. 

The new survey vessel inventory could be used to develop emission estimates in terms 

that can be readily applied to state-of-the-art GIS tools to spatially allocate emissions 

with greater accuracy. Although it may prove difficult, MMS may be able to solicit up-todate information on naval operations in the vicinity of the BNWA. 

STUDY PRODUCT(S): Billings, R.S. and D.L. Wilson. 2004. Data Quality Control and 

Emissions Inventories of OCS Oil and Gas Production Activities in the Breton Area of 

the Gulf of Mexico: Final Report. U.S. Dept. of the Interior, Minerals Management 

Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2004-071. 94 

pp.