Atmospheric Emission Characterization of Marcellus Shale Natural Gas Development Sites

Goetz, J. Douglas; Floerchinger, Cody; Fortner, Edward C.; Wormhoudt, J.; Massoli, P.; Knighton, W. B.; Herndon, S. C.; Kolb, C. E.; Knipping, Eladio; Shaw, Stephanie L.; DeCarlo, P. F.

doi:10.1021/acs.est.5b00452

Cited by 52 publications

(60 citation statements)

References 35 publications

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“…reactive pollutant dispersal from elevated stacks (Sutton, 1932;Bosanquet and Pearson, 1936). As models improved, the Gaussian plume model was developed assuming that a scalar concentration has a normal distribution function (Batchelor, 1949;Hilst, 1957). Additional investigation of near-surface conditions where particles can either deposit to or reflect off the surface led to the current Gaussian plume analytical model (shown in Eq.…”

Section: Reference Techniquementioning

confidence: 99%

Quantifying uncertainties from mobile-laboratory-derived emissions of well pads using inverse Gaussian methods

Caulton

Bou‐Zeid

et al. 2018

Atmos. Chem. Phys.

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Mobile laboratory measurements provide information on the distribution of CH 4 emissions from point sources such as oil and gas wells, but uncertainties are poorly constrained or justified. Sources of uncertainty and bias in ground-based Gaussian-derived emissions estimates from a mobile platform were analyzed in a combined field and modeling study. In a field campaign where 1009 natural gas sites in Pennsylvania were sampled, a hierarchical measurement strategy was implemented with increasing complexity. Of these sites, ∼ 93 % were sampled with an average of 2 transects in < 5 min (standard sampling), ∼ 5 % were sampled with an average of 10 transects in < 15 min (replicate sampling) and ∼ 2 % were sampled with an average of 20 transects in 15-60 min. For sites sampled with 20 transects, a tower was simultaneously deployed to measure highfrequency meteorological data (intensive sampling). Five of the intensive sampling sites were modeled using large eddy simulation (LES) to reproduce CH 4 concentrations in a turbulent environment. The LES output and LES-derived emission estimates were used to compare with the results of a standard Gaussian approach. The LES and Gaussian-derived emission rates agreed within a factor of 2 in all except one case; the average difference was 25 %. A controlled release was also used to investigate sources of bias in either technique. The Gaussian method agreed with the release rate more closely than the LES, underlining the importance of inputs as sources of uncertainty for the LES. The LES was also used as a virtual experiment to determine an optimum number of repeat transects and spacing needed to produce repre-sentative statistics. Approximately 10 repeat transects spaced at least 1 min apart are required to produce statistics similar to the observed variability over the entire LES simulation period of 30 min. Sources of uncertainty from source location, wind speed, background concentration and atmospheric stability were also analyzed. The largest contribution to the total uncertainty was from atmospheric variability; this is caused by insufficient averaging of turbulent variables in the atmosphere (also known as random errors). Atmospheric variability was quantified by repeat measurements at individual sites under relatively constant conditions. Accurate quantification of atmospheric variability provides a reasonable estimate of the lower bound for emission uncertainty. The uncertainty bounds calculated for this work for sites with >50 ppb enhancements were 0.05-6.5q (where q is the emission rate) for single-transect sites and 0.5-2.7q for sites with 10+ transects. More transects allow a mean emission rate to be calculated with better precision. It is recommended that future mobile monitoring schemes quantify atmospheric variability, and attempt to minimize it, under representative conditions to accurately estimate emission uncertainty. These recommendations are general to mobile-laboratory-derived emissions from other sources that can be treated as point sources.

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Section: Reference Techniquementioning

confidence: 99%

Quantifying uncertainties from mobile-laboratory-derived emissions of well pads using inverse Gaussian methods

Caulton

Bou‐Zeid

et al. 2018

Atmos. Chem. Phys.

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“…Ethane (C 2 H 6 ) and C 2 H 6 to CH 4 ratios have been used to help identify and quantify the origin of plumes of CH 4 , with sources such as coal mines showing low C 2 H 6 -to-CH 4 ratios. However, coal seams may be penetrated in the drilling for natural gas and C 2 H 6 -to-CH 4 ratios from well sites can vary widely (Goetz et al, 2015), complicating the use of this metric (National Academies of Sciences (NAS), Engineering, and Medicine, 2018). been described in detail elsewhere (Ren, Salmon, et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Methane Emissions from the Marcellus Shale in Southwestern Pennsylvania and Northern West Virginia Based on Airborne Measurements

et al. 2019

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Natural gas production in the United States has increased rapidly over the past decade, along with concerns about methane (CH4) fugitive emissions and its climate impacts. Quantification of CH4 emissions from oil and natural gas (O&NG) operations is important for establishing scientifically sound policies for mitigating greenhouse gases. We use the aircraft mass balance approach for three flight experiments in August and September 2015 to estimate CH4 emissions from O&NG operations over the southwestern Marcellus Shale. We estimate a mean CH4 emission rate as 21.2 kg/s with 28% coming from O&NG operations. The mean CH4 emission rate from O&NG operations was estimated to be 1.1% of total NG production. The individual best‐estimate emission rates from the three flight experiments ranged from 0.78 to 1.5%, with overall limits of 0% and 3.5%. These emission rates are at the low end of other top‐down studies, but consistent with the few observational studies in the Marcellus Shale region as well as the U.S. Environmental Protection Agency CH4 inventory. A substantial source of CH4 (~70% of observed CH4 emissions) was found to contain little ethane, possibly due to coalbed CH4 emitted either directly from coal mines or from wells drilled through coalbed layers in O&NG operations. Recent regulations requiring capture of gas from the completion‐venting step of hydraulic fracturing appear to have reduced the atmospheric release of CH4. Our study suggests that for a 20‐year time scale, energy derived from the combustion of natural gas extracted from this region likely exerts a net climate benefit compared to coal.

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“…2.1. Approaches based on atmospheric transport models have been used to account for errors arising from this mislocation (Goetz et al, 2015).…”

Section: The Tracer Release Methodsmentioning

confidence: 99%

Statistical atmospheric inversion of local gas emissions by coupling the tracer release technique and local-scale transport modelling: a test case with controlled methane emissions

et al. 2017

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Abstract. This study presents a new concept for estimating the pollutant emission rates of a site and its main facilities using a series of atmospheric measurements across the pollutant plumes. This concept combines the tracer release method, local-scale atmospheric transport modelling and a statistical atmospheric inversion approach. The conversion between the controlled emission and the measured atmospheric concentrations of the released tracer across the plume places valuable constraints on the atmospheric transport. This is used to optimise the configuration of the transport model parameters and the model uncertainty statistics in the inversion system. The emission rates of all sources are then inverted to optimise the match between the concentrations simulated with the transport model and the pollutants' measured atmospheric concentrations, accounting for the transport model uncertainty. In principle, by using atmospheric transport modelling, this concept does not strongly rely on the good colocation between the tracer and pollutant sources and can be used to monitor multiple sources within a single site, unlike the classical tracer release technique. The statistical inversion framework and the use of the tracer data for the configuration of the transport and inversion modelling systems should ensure that the transport modelling errors are correctly handled in the source estimation. The potential of this new concept is evaluated with a relatively simple practical implementation based on a Gaussian plume model and a series of inversions of controlled methane point sources using acetylene as a tracer gas. The experimental conditions are chosen so that they are suitable for the use of a Gaussian plume model to simulate the atmospheric transport. In these experiments, different configurations of methane and acetylene point source locations are tested to assess the efficiency of the method in comparison to the classic tracer release technique in coping with the distances between the different methane and acetylene sources. The results from these controlled experiments demonstrate that, when the targeted and tracer gases are not well collocated, this new approach provides a better estimate of the emission rates than the tracer release technique. As an example, the relative error between the estimated and actual emission rates is reduced from 32 % with the tracer release technique to 16 % with the combined approach in the case of a tracer located 60 m upwind of a single methane source. Further studies and more complex implementations with more advanced transport models and more advanced optimisations of their configuration will be required to generalise the applicability of the approach and strengthen its robustness.

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Atmospheric Emission Characterization of Marcellus Shale Natural Gas Development Sites

Cited by 52 publications

References 35 publications

Quantifying uncertainties from mobile-laboratory-derived emissions of well pads using inverse Gaussian methods

Quantifying uncertainties from mobile-laboratory-derived emissions of well pads using inverse Gaussian methods

Methane Emissions from the Marcellus Shale in Southwestern Pennsylvania and Northern West Virginia Based on Airborne Measurements

Statistical atmospheric inversion of local gas emissions by coupling the tracer release technique and local-scale transport modelling: a test case with controlled methane emissions

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