Evaluating Natural Gas Emissions from Pneumatic Controllers from Upstream Oil and Gas Facilities in West Virginia
Citation:
Footer, T., E. Thoma, D. Johnson, N. Clark, S. Herndon, AND C. Murral. Evaluating Natural Gas Emissions from Pneumatic Controllers from Upstream Oil and Gas Facilities in West Virginia. Atmospheric Environment: X. Elsevier B.V., Amsterdam, Netherlands, 17:NA, (2023). https://doi.org/10.1016/j.aeaoa.2022.100199
Impact/Purpose:
Advancement in energy extraction technologies has driven unprecedented expansion of oil and natural gas (ONG) production in many regions of the U.S. Methane, ozone precursors, and hazardous air pollutants, such as benzene, are emitted as part of ongoing ONG production operations. A growing body of research indicates that fugitive leaks and equipment/process malfunctions are important ONG emissions categories that may not be properly reflected in emission inventories. These stochastic sources can produce significant impacts to near-source populations, regional air sheds, and greenhouse gas budgets. Environmentally sustainable development of ONG assets requires improved understanding and management of these sources. Development of cost-effective approaches to rapidly detect and control unnecessary emissions, along with a deeper understanding of overall emission levels and atmospheric effects are important research themes in this space. Under its next generation emissions measurement (NGEM) program, ORD is working to develop and use new measurement, modeling, and inventory approaches relevant to EPA partners, industry, and communities. The following research paper describes a field study that used two NGEM technologies, optical gas imaging (OGI) and full flow sampler (FFS), to detect and measure emissions from pneumatic controllers (PCs), an important emission source category for ONG production. The study surveyed 15 ONG production sites in West Virginia documenting PC systems supporting 66 working wells. Using a PC-specific OGI survey protocol, 251 low actuation frequency PCs passed OGI inspection indicating low closed bleed rates, whereas 140 liquid level PCs exhibited OGI detectible continuous emissions in the majority of cases. Time-resolved FFS measurements of methane emissions from these PCs defined three basic emission categories, two of which were nonoptimal and were associated with higher emissions indicative maintenance or process issues. Forty one percent of the liquid level IPC pilot exhaust vents exhibited normalized mean emissions rates in excess of the 13.5 scf/hr whole gas PC emission factor and possessed nonoptimal temporal emission profiles. The highest single PC pilot vent emission was from a malfunctioning unit with a continuous methane mean emission rate of 129 scf/hr. An analysis of FFS emission measurements compared to liquids production per PC unit employed indicated that production sites operating at higher than normal liquid throughput rates had a higher potential for anomalous IPC operations and higher emissions. This paper with supplemental information describes these findings and provides suggestions for site engineering best practices that facilitate OGI diagnostics of liquid level PCs during routine leak inspection surveys.
Description:
In April of 2018, an optical gas imaging (OGI) and full flow sampler (FFS) emissions measurement study of pneumatic controllers (PCs) at 15 oil and natural gas production sites in West Virginia was conducted. A total of 391 PC systems supporting 66 working wells were found. All were classified as snap-acting intermittent PCs (IPCs) that should ideally exhibit regular actuation cycles with cessation of supply gas emissions (low closed bleed rate) between actuation events. Using a PC-specific OGI inspection protocol with an assumed detection threshold band maximum of 2.0 scf/hr, 251 low actuation frequency IPCs passed OGI inspection indicating closed bleed rates likely below this level. A total of 140 liquid level IPCs were found with 132 of these servicing gas/liquid separation processing units (GPUs). These more frequently actuating and larger volume IPC systems exhibited OGI detectible continuous emissions in the majority of cases. Time-resolved FFS measurements of methane (CH4) emissions from liquid level IPC exhaust vents defined three basic categories, two of which were nonoptimal and were associated with higher emissions indicative IPC maintenance or process issues. Forty one percent of the liquid level IPC pilot exhaust vents exhibited normalized CH4 mean emissions rates in excess of the 13.5 scf/hr whole gas IPC emission factor (EF) and possessed nonoptimal temporal emission profiles. The highest single IPC pilot vent emission was from a malfunctioning unit with a continuous CH4 mean emission rate of 129 scf/hr. An analysis of FFS emission measurements compared to liquids production per IPC unit employed indicated that production sites operating at higher than normal liquid throughput rates had a higher potential for anomalous IPC operations and higher emissions. Due to combined liquid level IPC exhaust vents and other factors, OGI detection of potential maintenance issues was more difficult in these cases compared to low actuation frequency IPCs. Site engineering best practices that facilitate OGI diagnostics of liquid level IPCs during routine leak detection and repair (LDAR) surveys are described.
URLs/Downloads:
DOI: Evaluating Natural Gas Emissions from Pneumatic Controllers from Upstream Oil and Gas Facilities in West Virginia