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Quantification of Methane Emissions from Marginal (Small Producing) Oil and Gas Wells
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The objective of this research is on measurement of methane emissions from marginal well sites at various basins across the United States. The goal is to collect and evaluate representative, defensible and repeatable data from marginal well sites and draw quantifiable conclusions on the extent of emissions from marginal wells across oil and gas producing regions of the United States., and to compare these results to published data available on the emissions from non-marginal wells.


GSI Environmental (GSI), Austin, TX 78759
Gas Technology Institute (GTI), Des Plaines, IL 60018
Colorado State University (CSU), Fort Collins, CO 80523
Research Partnership to Secure Energy for America (RPSEA), Houston, TX 77098


The Environmental Protection Agency (EPA) issued a final rule on June 3, 2016, to amend the New Source Performance Standards (NSPS, 40 Code of Federal Regulations Part 60, Subpart OOOOa) to reduce methane emissions from new and modified oil and natural gas facilities. These new requirements include oil wells which produce <15 barrels per day or gas wells that produce <90 MCF per day, which were not previously addressed. EPA’s decision to no longer exempt these “marginal” wells from the Leak Detection and Repair (LDAR) requirements was developed based on limited data.


EPA’s NSPS via Rule OOOOa assumes that low-producing marginal well facilities have the same type and number of equipment and episodic emissions as higher producing sites and, therefore, contribute similarly to national emissions. The costs of compliance may impact all producers but will, in particular, affect small oil and gas operators of the almost 760,000 marginal wells located throughout the United States, with an associated economic impact. This study will provide a robust, “apples-to-apples” assessment of methane emissions from marginal vs. non-marginal well sites based on the quantity and condition of equipment and components within these populations and related operational information. To accomplish this, detailed operating conditions, such as frequency, equipment type, and component counts will be analyzed in conjunction with oil and gas production data for each site, production region, and as a whole.

Accomplishments (most recent listed first)
  • In April 2022, the final project report was approved.  The overall results of this study suggest that i) marginal oil and gas production in the United States may account for approximately 1 million (±140,000) tons per year (TPY) of “every day” methane emissions, as were observed in the regional field campaigns, ii) marginal gas production accounts for an estimated 60% (±10%) of emissions from U.S. natural gas production, and iii) marginal oil production accounts for an estimated 40% (±10%) of emissions from U.S. oil production.
  • In June 2021, the field campaign concluded with 589 oil and gas production sites visited in coordination with 15 participating host operators, who in addition to direct access to perform emission screening and measurements, provided valuable activity data. Among visited sites, 524 exhibited marginal production at an average rate of 2.5 BOE per day of combined oil and natural gas. Sitewide production or throughput was nonmarginal at 65 sites (approximately 11% of the total visited), where production ranged from 15 to 2100 BOE per day. The relatively small size, low equipment counts, and ease of accessibility of most emission sources led to complete screening at all visited sites and complete measurements of most observed emissions. Besides emissions screening and measurements, detailed activity data, including major equipment counts and oil and gas production rates, were documented at each visited site.
  • In November 2020, GSI completed the initial two weeks of the second, 5-week field campaign to measure and assess methane emissions from marginal oil and gas wells. Approximately 48 sites (~100 wells) were monitored in the Piceance, Green River and Anadarko basins. The sites provided a balanced mix of oil to gas sites and marginal/non-marginal wells, as well as a broader array of infrastructure equipment. Data from this campaign will be analyzed with the data from the first field campaign completed in the Appalachian Basin in November 2019 to provide a statistically robust and defensible analysis on the extent of emissions from marginal wells across oil and gas producing regions of the U.S. 
  • In November 2019, GSI completed the first of three planned campaigns to measure and assess methane emissions from marginal oil and gas wells. In the first three weeks of this planned five-week campaign centered on operations in the Appalachian Basin, the GSI team surveyed 115 sites and made equipment counts at each of these sites. At 50 of these sites, GSI collected a total of 82 discrete emissions measurements.
    Emissions were identified using optical gas imaging (OGI) and quantified using the Bacharach Hi-Flow sampler.
    Emissions were identified using optical gas imaging (OGI) and quantified using the Bacharach Hi-Flow sampler.
  • GSI developed and submitted for review a Master Workplan outlining the technologies and protocols to be used during field campaigns. Regional Workplans specific to the three planned regional field campaigns will be developed with the first region field campaign — for the Appalachian and Illinois Basins — submitted on October 1, 2019.
  • On August 5 and 6, 2019, GSI held four meetings (two per day) with industry, state and federal agencies, and other stakeholders to present the findings of the recently completed Data Source Status Assessment (DSSA). The DSSA utilized published sources and information derived from operator surveys to identify gaps in the current understanding of emissions from marginal vs. non-marginal wells.
  • GSI held calls with the Technical Advisory Steering Committee (TASC) on April 11, 2019, and a second round of calls on April 15, 2019. The purpose of these calls and involvement of the TASC is to guide and advise on key aspects of the project work scope. The TASC will be tiered with a full committee that includes representation from industry, regulators, non-government organizations, and academia, and a sub-committee comprised of industry representatives only.
Current Status

The project is complete and the final report was produced in April 2022. 

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Performer Contribution


Contact Information

NETL – Eric Smistad ( or 281-504-2269)
GSI Environmental – Ric Bowers ( or 512-346-4474)

Additional Information