Estimating natural gas emissions from underground pipelines using surface concentration measurements^☆

Area of Science:

• Environmental Science
• Geophysics
• Chemical Engineering

Background:

• Underground natural gas leaks pose significant environmental and safety risks.
• Accurate quantification of methane emissions from leaks is crucial for effective mitigation and risk assessment.
• Current methods for estimating underground leak rates are challenged by complex subsurface transport processes.

Purpose of the Study:

• To develop and validate a novel field-based method for estimating underground natural gas leak rates.
• To establish a relationship between underground leakage rates and measurable surface methane concentrations.
• To assess the accuracy and applicability of the proposed method across various conditions.

Main Methods:

• Conducted controlled field experiments with underground natural gas releases.
• Incorporated field parameters into a dimensionless concentration number (ε) considering soil and fluid properties.
• Utilized the TOUGH3 simulator for numerical modeling to analyze methane transport and surface profiles.
• Collected surface methane concentration data at varying distances from the source under different soil and pipeline conditions.

Main Results:

• Developed a novel method for estimating underground natural gas leak rates using surface methane concentration.
• Demonstrated that peak surface methane concentrations correlate positively with leak rates.
• Observed an exponential decrease in surface methane concentrations with distance from the leak source.
• Achieved estimation accuracy with deviations ranging from 9% to 33% compared to actual leakage rates.

Conclusions:

• The proposed method provides a viable approach for estimating underground natural gas leak rates.
• This technique can aid in prioritizing leak repairs, thereby mitigating methane emissions and enhancing safety.
• Further validation studies across diverse field conditions are warranted for broader application.