Supplementary Information: Mobile Laboratory Observations of Methane Emissions in the Barnett

Transcription

1 Supplementary Information: Mobile Laboratory Observations of Methane Emissions in the Barnett Tara I. Yacovitch, Scott C. Herndon, Gabrielle Pétron, Jonathan Kofler, David Lyon, Mark S. Zahniser, Charles E. Kolb 50 Figures Pages S1 to S49 Summary This document begins with a description of the iterative forward dispersion methodology (Sections 1 2) along with an error quantification of this method using staged release data (Section 3). Then, the sorting and data quality filters used in preparing the final dataset of methane emitters is outlined (Section 4). Maps showing binned production of natural gas and oil over the study region are shown (Section 5) for comparison with Figures 2 and 3 of the manuscript. Sections 6 8 show the results from individual methane dispersion calculations for select sources outlined in Table 1 of the manuscript. Section 9 shows a dispersion calculation performed for an ethaneonly source. S1

2 1. Iterative Forward Dispersion Calculations The iterative forward dispersion method is used to estimate both the emission source location and emission magnitude using downwind plume intercepts. The seven steps below are followed and Figures S1 - S3 illustrate the procedure: 1. Determine the wind direction 2. Set a min and max allowed distance from mobile lab (for the Barnett dataset, 1 m to m) 3. Draw 50 points along the wind fetch, and along two rays at slightly different angles (+/- 4 degrees). Figure S2 shows the drive path and points. 4. Choose a Pasquill Stability Class (see below) 5. Perform a dispersion calculation a. Use an emission rate of 1 g/s b. Repeat at each selected point along the wind fetch 6. Determine the emission rate by scaling the simulation to match the magnitude of the experimental data (by taking a linear fit of Measured vs Simulated data). Figure S1 shows the measured mixing ratio (ethane in this example) and the scaled simulation. Figure S3 shows the linear fit that gives the scaling factor. 7. Determine the best source position by choosing the calculation that best fits the shape of the experimental plume data (by minimizing Chi Squared of the simulated time trace vs the measured time trace). See Figure S2 Figure S1. Time trace showing the experimental data (black trace) and best simulated data (dotted trace). The stability class used was C. S2

3 Figure S2. Map of each point in an iterative forward dispersion calculation. The mobile lab path is shown as a grey line, colorcoded by increasing ethane mixing ratio as shown in Figure S1. The central ray corresponds to the measured wind fetch, and two auxiliary rays appear at +/- 5 degrees from the wind fetch. 150 points are chosen in total. The deeper the color, the better the shape of the simulation fits the data. The bigger the circle, the higher the emission required to reproduce the magnitude of the experimental data. S3

4 Figure S3. Measured ethane mixing ratio vs simulated ethane mixing ratio for a 1 g/sec emission. The slope allows for the determination of the final emission rate of g/sec. 2. Stability Class Determination The stability class greatly affects the results of a dispersion calculation. Three methods for determining the stability class were tested: 1. Weather method using qualitative Weather Underground 2 data a. The solar elevation angle was used to estimate a base solar irradiation level (scaled to 1) b. Hourly Weather Underground weather data gives wind speed and a verbal description of cloud cover (eg. partially cloudy ), which was transformed into a scaling factor and applied to the solar irradiation c. Hourly Wunderground wind speed is used. 2. Hard-coded class D a. Class D is the most stable of the daytime stability classes. 3. Standard deviation of the horizontal wind a. The measured second-by-second wind was used to calculate the average wind vector for the transect. This average was then compared to the instantaneous wind measurements to get a standard deviation of the wind. 4. Weather method using STAR classifications and hourly Wunderground METAR data from a nearby airport The STAR program (STability ARray) is a program developed by the EPA and the National Climatic Data Center to provide meteorological data for dispersion models. 8 This program uses an objective method for determining stability parameters. This same method (Beychok s Table 20. Objective Definition of Stability Class 4 ) is used here. a. The measured second-by-second wind was used to calculate the average wind speed during the transect. S4

5 b. The solar elevation angle for the transect was determined c. The percent cloud coverage was determined from the METAR SKY descriptor, and averaged, if multiple descriptors were present d. The cloud ceiling height was determined from the METAR SKY descriptor, and averaged if multiple descriptors were present. e. Six stability classes were allowed (A to F). 3. Error Assessment in the Gaussian Dispersion Emission Estimation Methodology A 5-day dataset of staged tracer-release experiments was used to investigate the error involved in the Gaussian dispersion methodology. A staged release of multiple tracers at once (2 to 5) was set up in 3 areas near Houston in October The tracers used were nitrous oxide, acetylene, ethane, methane and propene. Release rates were logged by mass flow controllers (for nitrous oxide, acetylene and propene) or monitored intermittently for changes by manual measurement of the flow (for methane and ethane). The Aerodyne Mobile Lab, equipped with a suite of laser-based absorption spectrometers and a protontransfer mass spectrometer among other instruments, drove downwind of the staged release and acquired transects through the transported plumes. The dataset included three separate locations, with and without obstacles such as shrubs, trees and occasional small buildings. The release positions were varied within a given location, and include configurations where the tracer release positions are separated by large distances; separated by small distances; in a clear wind fetch; in the wake of a structure; in an area with vegetation; at different heights or elevations; above grass or asphalt; etc. The goal of the tracer placement was to collect a varied dataset approaching the complexities of real-world field studies. Distances downwind were dependent on road access, but varied between 0 and 3500 m. Between 2 and 5 plumes (differing trace gases) were measured during any given transect. Wind measurements were acquired using three fixed on-site sonic anemometers and a 4 th anemometer mounted to the top of the Aerodyne Mobile Lab. This dataset contains 141 separately identified plumes, each considered to be an independent replicate for the purposes of this error assessment. The Gaussian simulations of each tracer plume were conducted with the following constraints: Wind class D Fixed known release position (latitude/longitude) Fixed release height to 0 Wind bearing fixed to the vector between the maximum of the measured plume and the position of the tracer release Default use of truck-mounted anemometer for wind but manual override to on-site anemometers allowed in cases of disagreement between measurements. Since the true release rate is known for the tracer release experiment, but may be different in magnitude depending on tracer identity and the time of release, a factor error, x, was used to investigate the distribution of errors, where sim is the simulated emission magnitude (slpm) and true is the actual emission magnitude of the staged release. Factor error = sim true x=. 1 S5

6 Values of x < 1 indicate an underestimate in the true emission, while values of x > 1 indicate an overestimate of the true emission. A histogram of number of plumes vs factor error was created with these data. The data yielded a lognormal distribution that was normalized to an area of 1 and fit to the function below. f ( x) = 1 e S x 2π (ln( x) M ) 2 2S 2 2 S and M are parameters chosen such that the S=1, M=0 case simplifies to a function where log(x) has a normal distribution. The lognormal mean and variance are given respectively by: = 2 M S 2 µ l e + 3 and = e 2 2 ( e 1) 2 S + 2M S σ l. 4 The totality of the dataset (653 plumes) yielded a lognormal mean of.41 much lower than the ideal of 1. Many parameters were investigated and it was determined that eliminating data with lower wind speeds increased the lognormal mean, thus resulting in a distribution closer to the ideal. The tradeoff was a decrease in the number of sample points and an increase in the lognormal variance. A 4 m/s average wind speed cutoff was chosen, yielding a lognormal distribution containing 72 data points and with µ l = This distribution, normalized to an area under the curve of 1, is shown in Figure S4 below. Figure S4. Distribution of factor errors (histogram in red) between the simulated flow and the true released flow in the staged tracer release experiment. A fit of the distribution is shown in blue. The distribution above is used to quantify the error inherent in the Gaussian dispersion method. The fraction of the population with factor errors falling between α/2 and (1- α/2) defines a (1- α) confidence interval (α=0.05 for 95% confidence intervals). This fraction was investigated for the above distribution S6

7 by using the cumulative distribution function (CDF). The CDF below was obtained by integrating the fit shown in blue above. Figure S5. Cumulative probability function for the distribution of factor error (blue). The red lines indicate lower and upper 95% confidence bounds. The crossing points with α/2 = and (1 - α/2) = (horizontal lines) were determined graphically at and 2.99, respectively: sim 0.300< < true Rearranging the equation above, we see that 95% confidence limits on the true emission estimate can be written as sim < true < sim. 6 A simulated emission estimate can thus be assigned 95% confidence intervals at 33.4% and 334% of the measured value. A hypothetical 200 kg/hr simulated emission using the Gaussian dispersion methodology above, and lacking any further replicates or statistical information is thus assigned 95% confidence intervals of [66.8 kg/hr, 668 kg/hr]. These asymmetric error bars imply that while we may routinely underestimate emissions by a lot, we will more rarely overestimate emissions by much. 4. Dataset Treatment The data set was manually divided into plumes by identifying periods with enhancements above background. The ethane/methane enhancement ratio was further used to separate data segments since different ethane content in periods of enhanced methane is a good indicator of disparate sources. The iterative forward dispersion calculation was applied to each data segment. Then, the results of these calculations were filtered to eliminate any invalid simulation results. These can occur when an experimental plume is so broad that the simulated radial distance between the source and the measurement location equals or exceeds the maximum allowed distance (10 km). Other reasons for failed S7

8 simulations include zero wind magnitudes, as when weather station winds were calm and no local mobile wind measurement was available; wind bearings pointing along the drive path such that the plumes are not transected; and stationary measurements, again with no plume transect. The simulation results were then manually inspected by plotting the simulated sources and drive paths on Google Earth. When imagery showed equipment near the simulated source locations, the data point was classified, eg. well pad. Many sources do not have clearly distinguishable equipment, especially for plumes of biogenic origin (eg. livestock) and smaller magnitude emissions. The resulting dataset is available for download as part of this Supplementary Information as a Microsoft Excel file, Barnett_plumes_paper.xlsx. 5. Well production data on oil and gas wells Figure S6 shows the plotted production of gas and oil wells in the Barnett. These data come from the DI Desktop database (October 2013) and include well data compiled from state regulatory agencies. 1 While gas production spans a majority of the study area, oil production is concentrated in the North and West areas of the map. Figure S6. Map of production volumes (DI Desktop 1 ) for gas and oil wells in the Barnett. 6. Detailed Treatment All plumes underwent the iterative forward dispersion simulation as described in Section 1, as is appropriate for sources of unknown emission magnitude from unknown source location. For a selection of facilities, the calculation was refined by fixing the position of the source(s). These two fixed-source methods are referred to as follows: 1) fixed position simulation and 2) multiple fixed sources simulation. The first method, fixed release location (single source), involves fixing the release location to the latitude/longitude of a candidate point source. Only a single point source is allowed in this method. A sample figure is shown below. The iterative forward method result is also shown for comparison. S8

9 Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right. In some cases, sub-facility level emission sources are distinguished during close passes such that the single point source approximation used above is not appropriate. The second method, multi-source fixed S9

10 release position, thus involves summing the result of several individual equipment-level fixed source simulations. Locations and source magnitudes are chosen manually, and adjusted until the simulation best matches the shape of the final result. Figure S8. Results of a multi-source fixed release position simulation. The top panel shows the methane mixing ratio as a function of time (gold) along with the results of the simulation (red). The bottom left panel shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The individual fixed source locations are shown as yellow markers on the map. The sizes of the yellow markers are proportional to the magnitude of the simulated release. The individual source coordinates (latitude and longitude) and release magnitudes (g/sec) tabulated to the lower right. 7. Well pad Distribution The distribution of well pads was investigated separately from the full dataset of methane emitters (Figure S9). The full dataset is available in the accompanying Microsoft Excel file, Barnett_plumes_paper.xlsx. The iterative forward dispersion results have been augmented/improved with the fixed release position and multi-source fixed release position results, when applicable. These well pads have been classified by inspection of satellite imagery. There is some experimenter uncertainty in the classification based on map imagery alone. Detailed comparison to a database of known well locations could enhance this classification, as could an image analysis technique as described in Zavala-Araiza et S10

11 al. 10 While it is assumed that this well pad dataset fall squarely in the production 3 sector of the natural gas industry, there may be some overlap with the gathering sector. 6,7 A small gathering station with no compression may be difficult to distinguish from a well pad based on maps alone since much of the visible equipment is in common (condensate or water tanks; de-hi s). We expect such errors to be minimal in this dataset. The distribution is highly skewed, with 14 % of well pads contributing to 60 % of the emissions. This skew is comparable to that exhibited by the full dataset of emitters (Figure 1 of manuscript), suggesting no difference in sampling biases between the well pads and the sum of all methane emitters. Selected data points from the higher-emitting fat-tail have been used in a companion publication 10 to supplement a more representative well pad dataset. The largest emissions in this distribution are 5 times greater than the largest well pad emissions in this more representative dataset. Figure S9. Distribution of 53 well pad methane emissions. S11

12 8. Individual Facilities 8.1. Processing Plant, Bridgeport TX This processing plant is described in greater detail in the publication by Lavoie et al. 5 Figure S10. Results of a multiple fixed sources simulation. Facility plume acquired on nearby road. Wind bearing was manually set to 140 degrees. See Figure S8 caption for full descriptions of traces. S12

13 Figure S11. Results of a multiple fixed sources simulation. Facility plume 763 acquired on nearby road. See Figure S8 caption for full descriptions of traces. S13

14 Figure S12. Results of a multiple fixed sources simulation. Facility plume 764 acquired on a distant road. Wind bearing was manually set to 165 degrees. See Figure S8 caption for full descriptions of traces. S14

15 Figure S13. Results of a multiple fixed sources simulation. Facility plume 765 acquired on a distant road. Wind bearing was manually set to 165 degrees. See Figure S8 caption for full descriptions of traces. S15

16 Figure S14. Results of a multiple fixed sources simulation. Facility plume 399 acquired in October on nearby road. Wind bearing was manually set to 180 degrees. See Figure S8 caption for full descriptions of traces. S16

17 8.2. Processing Plant, Eagle Mountain TX Figure S15. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. S17

18 Figure S16. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. S18

19 8.3. Processing Plant, Pecan Acres TX Figure S17. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells S19

20 indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. Figure S18. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel S20

21 shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces Processing Plant, Rhome TX Figure S19. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel S21

22 shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces Gathering Station, Denton TX Figure S20. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel S22

23 shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces Gathering Station, Cleburne TX Figure S21. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel S23

24 shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. Plume Compressor Station, Eagle Mountain TX Plume 50 Figure S22. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. Figure S23. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. S24

25 Plume 57 Plume 59 Figure S24. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. Figure S25. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. S25

26 8.8. Compressor Station, Justin TX Figure S26. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. Figure S27. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. Figure S28. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. S26

27 8.9. Compressor Station, Rhome TX Figure S29. Results of a multiple fixed sources simulation. See Figure S8 caption for full descriptions of traces. S27

28 8.10. Compressor Station, Denton TX Figure S30. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored S28

29 squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. Figure S31. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel S29

30 shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces Well pad, Boyd TX Figure S32. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is S30

31 indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces Well pad, Justin TX Figure S33. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is S31

32 indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces Well pad, Dish TX We drove by these plumes multiple times, and the facility in question (in Dish, TX) is visible from the road. These plumes are re-simulated using the multiple known sources method in the tab labeled Large Facilities. Two possible emission sources on the Well pad were chosen: the condensate/produced water tank battery and a section of above-ground piping, possibly a wellhead. A summary of the results is shown below. Table S1. Summary of results from the Well pad in Dish, TX Facility Name Facility Latitude Facility Longitude Simulated Plume Emission ID (gram/sec) kg/hr Notes Paper Name Well pad, Dish TX Dish Wellpad used bearing of 162 deg used bearing of 168 deg used bearing of 163 deg Figures for each of the plumes are shown below. S32

33 Plume 0 Figure S34 Plume 3 Plume 6 Figure S35 Figure S36 S33

34 Plume 7 Plume 220 Figure S37 Figure S38 S34

35 8.14. Well pad, Fort Worth TX Figure S39. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored S35

36 squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. Figure S40. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel S36

37 shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. Figure S41. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily S37

38 coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. Figure S42. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The S38

39 chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces Well pad, Haslet TX S39

40 Figure S43. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. S40

41 8.16. Well pad, Newark TX Figure S44. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. S41

42 8.17. Well pad, Krum TX Figure S45. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-redyellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. S42

43 8.18. Piping, Eagle Mountain, TX This source was intercepted near the gate of the processing plant in Eagle Mountain (see Figure S22). A section of piping is visible in satellite imagery to the side of the road. Figure S46. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs (green) point into the oncoming wind. The 50 trial source locations for the iterative forward dispersion simulation are shown as open circles, colored according to chi-squared (better fit at darker points). The S43

44 chosen source position is indicated as a red number (emission ratio in g/sec). In a second calculation, the source location is fixed. This location is shown as another red number ( above) not necessarily coincident with the open circles from the iterative calculation. The wind bearing for this fixed source calculation is fixed to the vector between the peak mixing ratio and the release. The middle right panel shows the location of the measurement (black marker) relative to the entire basin, with oil and gas wells indicated in purple, orange and yellow, and major facilities with GHG reporting requirements as colored squares. Finally, the bottom panel shows the methane mixing ratio (solid gold) along with the iterative forward dispersion result (gold dotted line) and the fixed release location result (red dotted line). Emission magnitudes and coordinates for each are noted at the bottom right.figure S7 caption for full description of traces. Figure S47. Iterative dispersion and fixed position simulations of a methane plume. See Figure S7. Comparison of an iterative forward dispersion and a fixed release location simulation. The top left panel shows methane, ethane, carbon monoxide and carbon dioxide mixing ratios as a function of time. The top right panel shows the correlation plot yielding the ethane/methane enhancement ratio (mol/mol). The middle left graph shows the transect of interest, colored by methane mixing ratio (black-red-yellow). Wind barbs S44