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Assessment of Pneumatic Controller Emission Measurements using a High Volume Sampler at the Oil and Natural Gas Production Pads in Utah
Stovern, M., A. Eisele, AND E. Thoma. Assessment of Pneumatic Controller Emission Measurements using a High Volume Sampler at the Oil and Natural Gas Production Pads in Utah. Presented at AWMA Air Quality Measurement Methods and Technology, Chapell Hill, NC, March 15 - 17, 2016.
This is a presentation for the AWMA Air Quality Measurement Methods and Technology meeting related to a previously approved extended abstract. The title of the extended abstract and the presentation is Assessment of Pneumatic Controller Emission Measurements Using a High Volume Sampler at Oil and Natural Gas Production Pads in Utah. This work outlines beginning measurement method development efforts for this source.
Oil and Natural Gas (ONG) production facilities have the potential to emit greenhouse gases such as methane (CH4) and other hydrocarbons (HCs) to the atmosphere. ONG production sites have multiple emission sources including storage tank venting, enclosed combustion devices, engine exhaust, pneumatic controllers and uncontrolled leaks. Accounting for up to 37.8 percent of CH4 emissions, pneumatic controllers are one of the most significant sources of CH4 in ONG production field operations. Recent measurement studies used the only commercially-available high volume sampling (HVS) technology (Bacharach Hi Flow Sampler, Bacharach, Inc., New Kensington, PA) to quantify CH4 emission rates of pneumatic devices on ONG production pads and compare to inventory estimates. Other studies indicate that this HVS may malfunction, causing underestimates of emissions in certain scenarios encountered in ONG production and should not be used for some sources such as heavy emissions from condensate storage tanks. The HVS malfunction can occur on relatively large emissions, where the measured leak concentrations exceed 5%, and is ascribed to a sensor transition failure in the instrument. The HVS malfunction is believed to be exacerbated by several factors (large emission rates, amount of non-CH4 HCs in the emission stream, non-optimal HVS calibration frequency, firmware, and emission measurement coupling geometries). The degree to which HVS measurements of emissions from pneumatic controllers on ONG production sites may be affected by this malfunction is not known, but the malfunction could be more of an issue in basins with significant production of liquids (due to higher amounts of non-CH4 HCs). This HVS does not include a built-in data quality indictor (DQI) that detects the occurrence of malfunction condition. To support both emission inventory and compliance activities, accurate methods to quantify CH4 and HC emission rates from pneumatic controllers and other ONG production sources are critically important. This extended abstract describes use of the Bacharach HVS in conjunction with supporting measurements to quantify emissions from pneumatic controllers at several ONG production facilities. The supporting measurements act as DQIs to help ensure proper operation of the HVS and represent the first steps in developing an augmented HVS protocol with additional quality assurance checks. The study took place at ONG well pads located in the Uinta Basin from September 22-24, 2015. The well pads that were surveyed were all subject to 40 C.F.R. 60 subpart OOOO7 and thus had pneumatic controller emission limits of 6 scfh. The measurements were collected by the EPA with the oil and gas companies providing site access and safety oversight. For reporting purposes, the identities of the companies will remain anonymous.