Temporal Variations in Methane Emissions from an Unconventional Well Site

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Energy Resources

Background:

• Quantifying methane emissions from natural gas infrastructure is crucial for climate change mitigation.
• Existing studies often use snapshot measurements, combining spatial and temporal variability.
• Temporal variability within a single site remains under-examined.

Purpose of the Study:

• To investigate the temporal variability of methane emissions from a single unconventional natural gas well site.
• To assess the accuracy of snapshot measurements versus long-term averages for methane emissions.
• To identify factors influencing methane emission fluctuations.

Main Methods:

• Conducted six direct quantification audits over 21 months at one unconventional well site.
• Utilized a full flow sampling system for precise methane mass emission quantification (±10% uncertainty).
• Correlated methane emissions with natural gas production, water production, and weather data.

Main Results:

• Observed significant temporal variation in methane emissions (86.2–4102 g/h, mean 1371 g/h).
• Produced water tanks were the largest source of emission variability (17.3–3731 g/h).
• Relative methane loss rates (0.002–0.088%, mean 0.030%) correlated strongly with historical water production.

Conclusions:

• Single-time measurements can over-predict or under-predict methane emissions by a factor of 3 or 16, respectively.
• Temporal emissions analysis is essential for accurate methane accounting from natural gas infrastructure.
• Water production is a key factor influencing methane emissions variability at well sites.