Production Module: Measurement Protocol

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1 Production Module: Measurement Protocol Authors: Dan Zimmerle, Tim Vaughn, Clay Bell, Colorado State University Laurie Williams, Fort Lewis College Matthew Harrison, AECOM STATUS: Final Special Note The attached document is the protocol utilized for the study, and was developed prior to field campaign. With the exception of grammatical corrections, the protocol is included intact as it was utilized for the field study, with one exception: 1) Notes have been added where significant deviations from the field plan occurred during operations. These are discussed in more details in the main body of the report. 1.0 Overview This document provides an overview of the field measurement plan for production facility measurements at natural gas production facilities (well pads) in the RPSEA target basin. The overall goal of the RPSEA project is to reconcile aircraft mass balance and facility-based emissions estimates at the facility and subbasin level. Separate measurement protocols will be utilized for each O&G sector included in the study transmission compressor facilities (downwind measurements only); Gathering facilities (onsite and downwind measurements); distribution facilities (onsite measurements); distribution and gathering pipelines (onsite measurements); and production (onsite and downwind measurements). The Production Module: Measurement Protocol provides an overview of the methane emission measurement collection and conduct of field teams. The specific objective of the production system field measurements is to: Quantify total facility-level methane emissions from representative well sites, including production activities and gas well liquids unloadings. We shall achieve the project objective by making measurements of methane emissions on a number of partner facilities using onsite, source level measurement techniques and downwind using two downwind measurement methods dual tracer flux, and OTM 33A methods (high-frequency measurements of emissions and Gaussian plume modeling, see separate document Production Module: OTM33A Protocol). A fundamental aspect of the project is to pair the two measurement techniques at multiple sites, allowing a comparison of the measurement techniques and, potentially, a better estimate of measurement uncertainty. To the greatest extent possible, measurements will also be conducted contemporaneously with aircraft overflights to emphasize the spatial and temporal alignment between facility-based ground-level measurements and aircraft measurement and mass balance methods, including some aerial sampling at a facility level. Each team in the group will operate, measure and consolidate results independently for each facility measured, maintaining the integrity and independence of the paired measurements. 2.0 Measurement Techniques The project will utilize three different, independent measurement methods to estimate methane emissions from production sites: 1 P a g e

2 Onsite source-by-source measurements. A downwind vehicular-based measurement methodology known as OTM33A. The dual tracer flux method, which correlates the concentration of tracer gases released near the emission source(s) with the methane concentrations downwind of the facility. These measurements will be made contemporaneous to the greatest extent possible. Contemporaneous measurements are defined as measurements made on the same day with no significant changes in equipment state occurring between the two measurements. Given temporal variations in emissions, performing same day downwind and onsite measurements is a critical aspect of the study design. Although same day measurements are not truly simultaneous because of the nature of the two measurement techniques, it should help reduce the effects of changes in operations on the emissions and allow more direct comparison of two independent facility-level emission estimates. We shall also note any changes in operations and other parameters that might influence emissions during the measurement period. Same day measurements will require coordination between different survey teams. The OTM33A downwind measurements will be performed the University of Wyoming. Onsite measurements will be performed by AECOM and, for SWN sites, by SWN personnel acting under the supervision of Colorado State University (CSU) observers. Tracer flux measurements will be performed by Aerodyne Research, Inc. In this section we provide a brief overview of the onsite and OTM33A techniques and how they will be utilized during the project. 2.1 Onsite measurements and observations Onsite measurements will be performed by a project-supported contractor AECOM or SWN personnel, typically measuring separately at different facilities. Onsite teams will conduct comprehensive leak surveys followed by direct measurement of accessible fugitive and vented methane emissions (non-combustion) at natural gas well sites in the project sub-basin, between 9/28/15 and 10/16/15. The protocol for detection of emission sources, and measurement of emission rates, is provided in Annex 4: Onsite Detection and Measurement Protocol. Potential emission sources for inclusion of the onsite measurement plan include normal packed and sealed surface equipment leak emissions, such as emissions from flanges, screwed connectors, valve packing, pressure relief valve seats, and open-ended lines. Where compressors exist on the wellsite, compressor fugitive emissions will be measured, including the emissions from specialized compressor equipment leak sources such as rod packing vents, blowdown line open ended line (OEL) vents, and starter line OEL vents. Emissions from all pneumatic controller loops on the site will be measured. Note: During field campaign, it was observed that the actuation frequency of pneumatic controllers was so infrequent that it was not practical to measure them with the resources available. Since the participant companies have switched the majority of chemical injection pumps to solar/battery power, the team does not anticipate the need to measure pneumatically powered pumps. The team will also examine the produced water storage tanks to determine if any emissions are coming from those systems. 2 P a g e

3 Note: In the field campaign, some gas-powered chemical pumps were noted. These were not measured. The participant companies will also have some gas well liquids unloadings that vent gas to the atmosphere. For sites with gas well liquids unloadings, it is assumed they are a mix of automated plungers on a fast time cycle, and some manually-initiated unloadings. The team plans to gather data on the occurrence and frequency of unloadings that might occur on a site being measured, but direct measurements of these events are not part of the primary goal since the team would have to devote a large amount of time to obtain a few measurements. Instead, emission factors (emissions per event for manual unloadings, and emissions per event for automated plunger unloadings) from the University of Texas study on the mid-continent basin in 2013 will be combined with frequency, or activity factor data to produce an emission estimate from the site. Downwind measurements will also attempt to capture these discontinuous emissions. No measurements are planned for field compressor engine exhaust, flares, nor dehydrators at well sites, however their presence and certain data on their size will be collected so that their contribution to the site emission rate can be reasonably estimated. Leak surveys of well production sites, will be performed using an Optical Gas Imaging (OGI) camera such as the methane-tuned FLIR GasFindIR or Opcal EyeCGas thermal gas imaging camera. in the leak survey will consist of a walk around at each site by a trained camera operator. A leak will be defined as an observed plume in the OGI camera viewing screen. Emission rates for any leaks observed by the camera will be measured primarily with a Bacharach Hi Flow sampler (Hi Flow). Pneumatic emissions may be measured with an inline flow meter (Fox Flow meter, model #FT2A), or in some cases with a HiFlow sampler. In cases where the in line flow meter is used, it will be inserted into the power gas supply line to the pneumatic controller, after the partner company escort has temporarily shut off the power gas supply. Once the meter is inserted, the partner company escort will restore flow of power gas to the pneumatic device, and the device will be allowed to operate several minutes without data recording. Data recording will then begin and last for as long as possible while on site. AECOM plans to have 4 such meters, so that 4 pneumatic devices could be read simultaneously. In the case of tanks, the tank top vents, hatches, and pressure relief valves will be scanned by OGI camera. If emissions are observed, but appear to be small enough to safely measure by high-flow, then the team will deploy the Hi Flow sampler. In some cases, access by manlift will be required. If leaks appear to be too large to safely or effectively deploy the sampler, then the downwind teams will be called in to see if they can separate the tanks emissions out as a unique and separately quantified source. If the OTM33A team is unable to do so, the Aerodyne tracer team may be called to perform this task. With the permission from the partner company, digital photographs will be taken of all significantly large or atypical emissions sources and any other sources where photographs would be helpful when analyzing or reporting the measurement results. Electronic data recorded on the Hi Flow sampler will be recorded in a paper record on site data sheets. Measurement teams will measure methane emissions from each observed emission points (as noted above) within each facility that can be accessed safely. Emission sources that cannot be accessed safely from the ground, will be measured if the a bucket truck or manlift is available. 3 P a g e

4 Optional task. Though not a primary goal, if directed to do so by the CSU team leads, measurement teams may perform some limited flow measurements of gas volumes released during liquid unloadings. These would be solely for the purpose of determining whether the downwind teams could accurately quantify such a discontinuous emission. Measurements will be taken using a temporary stack affixed to a tank vent that is equipped with a gas velocity measurement instrument (Fox Thermal Instruments, Model #FT3). Grounded metal or metal lined tubing will be used to prevent static discharge. Measurement teams will consist of a 2-person team to each well pad facility. One team member will conduct leak surveys using the OGI camera, another team member will measure observed leak rates. When that task is complete, the team members will switch to pneumatic measurements. The onsite team will be accompanied by one CSU observer. If there are insufficient CSU resources at any time during the survey, the CSU observer will accompany the partner company team doing measurements, allowing the AECOM team to proceed without an observer. Responsibilities of the onsite observer include documenting the site configuration and state of the site during measurement. Noted items will include: 1) Number of wells at site, whether the wells have plunger lifts. 2) Equipment associated with the site. The operating pressure of the separator. If compressors exist, the operating mode of the compressor (running, or idle-pressurized, or idledepressurized). 3) If well liquids unloadings occur, observer will note frequency and duration and time of unloadings if possible. 3) Pneumatics list brand, models, function, location and operating mode (intermittent, low bleed, high bleed), if that can be determined. 4) General description of the immediate, visible surroundings of the facility fenceline to be confirmed by partner company operations personnel (at least the first meters), especially any unusual equipment or facilities near the site. 5) Any unusual configurations, etc. The on-site observer will fill out a data sheet, and maintain a log of observations as long as either the onsite or downwind team is conducting measurements. Observed leaks will not be repaired, unless the leak presents a safety concern, until after other measurements (tracer, OTM, aerial) have been completed. It is requested that the partner companies allow the observer to utilize a digital camera on site to record photographic evidence. These photos will not contain any identifying marks which could be utilized to track the photograph to the site where the photograph was taken. Photographs will only be utilized as an internal memory aid during subsequent data analysis and not publically released. 2.2 OTM33A This is a facility-scale, downwind method using high-frequency measurements of methane concentration and Gaussian plume modeling. A core assumption of the technique is that the emissions originate at a 4 P a g e

5 single near point source location. Therefore, the method is limited to small facilities where emissions originate in a small area and/or a single (point) emissions source dominates total facility emissions. In practice, this limits the method to measurement of well pads and other small facilities, such as metering and regulation (M&R) stations. Site access is not required for the OTM33A method, though may be helpful under certain land cover and road configurations. The technique is described in detail in the OTM33A Protocol document. Briefly, the concept of OTM 33A is to determine the flux of methane and volatile organic compounds (VOC) from a source by approximating the time-averaged plume from that source as a Gaussian plume. Methane is measured with a Picarro cavity ringdown spectrometer and VOC with an Ionicon proton transfer reaction time of flight mass spectrometer (PTR-TOF 8000). Both instruments make concentration measurements at two Hertz. Based on rapid wind measurements from a 3-D sonic anemometer, a Pasquill stability class for the local boundary layer can be determined. This stability class is used to determine the width of the average Gaussian plume based on an empirical lookup table developed by the EPA. For the lookup table to be valid, measurements must be made in close proximity to a source (between 20 and 200 meters) and with wind speeds between 1 and 7 meters per second [U.S. EPA, 2014]. When close access is feasible, an infrared camera (FLIR GF300) is used to more exactly pinpoint the source location. The plume is measured from a 13-foot tall mast on the University of Wyoming Mobile Laboratory to minimize surface effects from the ground or the mobile lab itself. High-speed measurements (2-Hertz or faster) are carried out over a period of approximately 20 minutes to give good averages of wind speed, turbulent intensity, methane and VOC concentration, and the standard deviation of the wind in all 3-dimensions. There are a number of data flags that indicate if the model is not valid given current wind speeds or turbulence or if the observed plume shape cannot be accurately simulated by the Gaussian model. If none of the data flags are triggered, the model will output an estimate of the flux (or emission rate) from the specific source being measured. With appropriate ambient wind speeds, the accuracy of the OTM-33a technique has been determined to be roughly ±30% based on a series of controlled-release studies conducted by the University of Wyoming and the U.S. EPA. Note: OTM-33a confidence intervals were re-evaluated and changed during post-campaign analysis. A 95% CI for the OTM33A technique was estimated as +117/-46% of the measured value using test release measurements conducted by the University of Wyoming and the U.S. EPA. 3.0 Site selection See Screening and Guided Measurement Protocol document for details on screening method and site selection process. 4.0 Onsite Equipment Onsite measurement teams will utilize the following equipment, or equivalent: FLIR GasFindIR thermal imaging camera Opcal EyeCgas thermal imaging camera Bacharach High flow sampler Fox flow meters, model #FT2A Fox Thermal Instruments, Model #FT3 5 P a g e

6 July Aug Sept Oct Final Report Digital camera Notebook computer 5.0 Measurement Planning In advance of on-site measurements, CSU has provided a specific data request to study partners to determine which emission sources at the study sites require advanced planning to be adequately tested. 6.0 Proposed Measurement Timeline The measurements will be made during a 3 week measurement campaign beginning on Monday, September 21, 2015 and ending Saturday, October 10, Note: Measurement campaign was later extended to four weeks. Task Preparation of protocols Review and approval of measurement protocols by RL, TRC, Other? Site selection X X Set up site-access contracts X X Field Measurements X X 7.0 References Czepiel, P. M., Mosher, Shorter, J. H., McManus, J. B., Kolb, C. E., Allwine, E., Lamb, B. K. and Harriss, R.C., Landfill Methane Emissions Measured by Static Enclosures and Atmospheric Tracer Methods, J. Geophys. Res. 101, 16,711-16,719, 1996 Lamb, B., Shorter, J. H., McManus, J. B., Kolb, C. E., Mosher, B. W., Harriss, Allwine, E. J., Blaha, D., Siverson, R., Howard, T., Lott, R. A., Siverson, R., Westberg, H., and Zimmerman, P., Development of Atmospheric Tracer Methods to Measure Methane Emissions from Natural Gas Facilities and Urban Areas, Environ. Sci. Technol., 29, , Scheutz, C; Samuelsson, J; Fredenslund, A.M.; and Kjeldsen, P. (2011). Quantification of multiple methane emission sources at landfills using a double tracer technique. Waste Management, 31: Shorter, J. H., McManus, J. B., Kolb, C. E., Allwine, E. J., Lamb, B. K., Mosher, B.W., Harriss, R. C., Partchatka, V., Fisher, H., Harris, G. W., Crutzen, P. J. and Karbach, H. J., Methane Emission Measurements in Urban Areas in Eastern Germany, J. Atmos. Chem. 24, , Shorter, J. H., McManus, J. B., Kolb, C. E., Allwine, E. J., Siverson, R., Lamb, B. K., Mosher, B. W., Harriss, R. C., Howard, T. and Lott, R. A., Collection of Leakage Statistics in the Natural Gas System by Tracer Methods, Environ. Sci. Technol., 31, , P a g e