scholarly journals Temporal variability largely explains top-down/bottom-up difference in methane emission estimates from a natural gas production region

2018 ◽  
Vol 115 (46) ◽  
pp. 11712-11717 ◽  
Author(s):  
Timothy L. Vaughn ◽  
Clay S. Bell ◽  
Cody K. Pickering ◽  
Stefan Schwietzke ◽  
Garvin A. Heath ◽  
...  
Keyword(s):  
Natural Gas ◽  
Methane Emission ◽  
Emission Rate ◽  
Greenhouse Gas Emission ◽  
Mixed Boundary ◽  
Gas Production ◽  
Top Down ◽  
Bottom Up ◽  
Natural Gas Production ◽  
Basin Scale

This study spatially and temporally aligns top-down and bottom-up methane emission estimates for a natural gas production basin, using multiscale emission measurements and detailed activity data reporting. We show that episodic venting from manual liquid unloadings, which occur at a small fraction of natural gas well pads, drives a factor-of-two temporal variation in the basin-scale emission rate of a US dry shale gas play. The midafternoon peak emission rate aligns with the sampling time of all regional aircraft emission studies, which target well-mixed boundary layer conditions present in the afternoon. A mechanistic understanding of emission estimates derived from various methods is critical for unbiased emission verification and effective greenhouse gas emission mitigation. Our results demonstrate that direct comparison of emission estimates from methods covering widely different timescales can be misleading.

scholarly journals Quantifying methane emissions from natural gas production in northeastern Pennsylvania

2017 ◽  
Author(s):  
Zachary R. Barkley ◽  
Thomas Lauvaux ◽  
Kenneth J. Davis ◽  
Aijun Deng ◽  
Yanni Cao ◽  
...  
Keyword(s):  
Natural Gas ◽  
Confidence Interval ◽  
Mass Balance ◽  
Emission Rate ◽  
Gas Production ◽  
Optimization Approach ◽  
Emission Rates ◽  
Emission Data ◽  
Natural Gas Production ◽  
Northeastern Pennsylvania

Abstract. Natural gas infrastructure releases methane (CH4), a potent greenhouse gas, into the atmosphere. The estimated emission rate associated with the production and transportation of natural gas is uncertain, hindering our understanding of its greenhouse footprint. This study presents a new application of inverse methodology for estimating regional emission rates from natural gas production and gathering facilities in northeastern Pennsylvania. An inventory of CH4 emissions was compiled for major sources in Pennsylvania. This inventory served as input emission data for the Weather Research and Forecasting model with chemistry enabled, and atmospheric CH4 mole fraction fields were generated at 3 km resolution. Simulated atmospheric CH4 enhancements from WRF-Chem were compared to observations obtained from a three-week flight campaign in May 2015. Modelled enhancements from sources not associated with upstream natural gas processes were assumed constant and known and therefore removed from the optimization procedure, creating a set of observed enhancements from natural gas only. Simulated emission rates from unconventional production were then adjusted to minimize the mismatch between aircraft observations and model-simulated mole fractions for ten flights. To evaluate the method, an aircraft mass balance calculation was performed for four flights where conditions permitted its use. Using the model optimization approach, the weighted mean emission rate from unconventional natural gas production and gathering facilities in northeastern Pennsylvania approach is found to be 0.36 % of total gas production, with a 2σ confidence interval between 0.27–0.45 % of production. Similarly, the mean emission estimates using the aircraft mass balance approach is calculated to be 0.34 % of regional natural gas production, with a 2σ confidence interval between 0.06–0.62 % of production. These emission rates as a percent of production are lower than rates found in any other basin using a top-down methodology, and may be indicative of some characteristics of the basin that makes sources from the northeastern Marcellus region unique.

scholarly journals In Pennsylvania, Methane Emissions Higher Than EPA Estimates

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Aaron Sidder
Keyword(s):  
Natural Gas ◽  
Methane Emission ◽  
Methane Emissions ◽  
Gas Production ◽  
Coal Production ◽  
Natural Gas Production

Although methane emission estimates from underground coal production appear to be accurate, the calculated emissions from natural gas production are underreported.

scholarly journals Reconciling divergent estimates of oil and gas methane emissions

2015 ◽  
Vol 112 (51) ◽  
pp. 15597-15602 ◽  
Author(s):  
Daniel Zavala-Araiza ◽  
David R. Lyon ◽  
Ramón A. Alvarez ◽  
Kenneth J. Davis ◽  
Robert Harriss ◽  
...  
Keyword(s):  
Natural Gas ◽  
Oil And Gas ◽  
Methane Emissions ◽  
Gas Production ◽  
Climate Impacts ◽  
Source Attribution ◽  
Top Down ◽  
Bottom Up ◽  
Statistical Confidence ◽  
Relative Differences

Published estimates of methane emissions from atmospheric data (top-down approaches) exceed those from source-based inventories (bottom-up approaches), leading to conflicting claims about the climate implications of fuel switching from coal or petroleum to natural gas. Based on data from a coordinated campaign in the Barnett Shale oil and gas-producing region of Texas, we find that top-down and bottom-up estimates of both total and fossil methane emissions agree within statistical confidence intervals (relative differences are 10% for fossil methane and 0.1% for total methane). We reduced uncertainty in top-down estimates by using repeated mass balance measurements, as well as ethane as a fingerprint for source attribution. Similarly, our bottom-up estimate incorporates a more complete count of facilities than past inventories, which omitted a significant number of major sources, and more effectively accounts for the influence of large emission sources using a statistical estimator that integrates observations from multiple ground-based measurement datasets. Two percent of oil and gas facilities in the Barnett accounts for half of methane emissions at any given time, and high-emitting facilities appear to be spatiotemporally variable. Measured oil and gas methane emissions are 90% larger than estimates based on the US Environmental Protection Agency’s Greenhouse Gas Inventory and correspond to 1.5% of natural gas production. This rate of methane loss increases the 20-y climate impacts of natural gas consumed in the region by roughly 50%.

scholarly journals Satellite observations reveal extreme methane leakage from a natural gas well blowout

2019 ◽  
Vol 116 (52) ◽  
pp. 26376-26381 ◽  
Author(s):  
Sudhanshu Pandey ◽  
Ritesh Gautam ◽  
Sander Houweling ◽  
Hugo Denier van der Gon ◽  
Pankaj Sadavarte ◽  
...  
Keyword(s):  
Natural Gas ◽  
Methane Emission ◽  
Emission Rate ◽  
Greenhouse Gas Emission ◽  
Average Rate ◽  
Methane Emissions ◽  
Satellite Measurements ◽  
Gas Well ◽  
Oil And Natural Gas ◽  
Total Column

Methane emissions due to accidents in the oil and natural gas sector are very challenging to monitor, and hence are seldom considered in emission inventories and reporting. One of the main reasons is the lack of measurements during such events. Here we report the detection of large methane emissions from a gas well blowout in Ohio during February to March 2018 in the total column methane measurements from the spaceborne Tropospheric Monitoring Instrument (TROPOMI). From these data, we derive a methane emission rate of 120 ± 32 metric tons per hour. This hourly emission rate is twice that of the widely reported Aliso Canyon event in California in 2015. Assuming the detected emission represents the average rate for the 20-d blowout period, we find the total methane emission from the well blowout is comparable to one-quarter of the entire state of Ohio’s reported annual oil and natural gas methane emission, or, alternatively, a substantial fraction of the annual anthropogenic methane emissions from several European countries. Our work demonstrates the strength and effectiveness of routine satellite measurements in detecting and quantifying greenhouse gas emission from unpredictable events. In this specific case, the magnitude of a relatively unknown yet extremely large accidental leakage was revealed using measurements of TROPOMI in its routine global survey, providing quantitative assessment of associated methane emissions.

scholarly journals Quantifying methane emissions from natural gas production in north-eastern Pennsylvania

2017 ◽  
Vol 17 (22) ◽  
pp. 13941-13966 ◽  
Author(s):  
Zachary R. Barkley ◽  
Thomas Lauvaux ◽  
Kenneth J. Davis ◽  
Aijun Deng ◽  
Natasha L. Miles ◽  
...  
Keyword(s):  
Natural Gas ◽  
Confidence Interval ◽  
Mass Balance ◽  
Emission Rate ◽  
Gas Production ◽  
Optimization Approach ◽  
Emission Rates ◽  
Natural Gas Production ◽  
North Eastern ◽  
Eastern Pennsylvania

Abstract. Natural gas infrastructure releases methane (CH4), a potent greenhouse gas, into the atmosphere. The estimated emission rate associated with the production and transportation of natural gas is uncertain, hindering our understanding of its greenhouse footprint. This study presents a new application of inverse methodology for estimating regional emission rates from natural gas production and gathering facilities in north-eastern Pennsylvania. An inventory of CH4 emissions was compiled for major sources in Pennsylvania. This inventory served as input emission data for the Weather Research and Forecasting model with chemistry enabled (WRF-Chem), and atmospheric CH4 mole fraction fields were generated at 3 km resolution. Simulated atmospheric CH4 enhancements from WRF-Chem were compared to observations obtained from a 3-week flight campaign in May 2015. Modelled enhancements from sources not associated with upstream natural gas processes were assumed constant and known and therefore removed from the optimization procedure, creating a set of observed enhancements from natural gas only. Simulated emission rates from unconventional production were then adjusted to minimize the mismatch between aircraft observations and model-simulated mole fractions for 10 flights. To evaluate the method, an aircraft mass balance calculation was performed for four flights where conditions permitted its use. Using the model optimization approach, the weighted mean emission rate from unconventional natural gas production and gathering facilities in north-eastern Pennsylvania approach is found to be 0.36 % of total gas production, with a 2σ confidence interval between 0.27 and 0.45 % of production. Similarly, the mean emission estimates using the aircraft mass balance approach are calculated to be 0.40 % of regional natural gas production, with a 2σ confidence interval between 0.08 and 0.72 % of production. These emission rates as a percent of production are lower than rates found in any other basin using a top-down methodology, and may be indicative of some characteristics of the basin that make sources from the north-eastern Marcellus region unique.

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