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Case Studies

Translating project experience to lessons learned and recognizing the needle-movers that affect your compliance

Case Study 1

Case Study 1: Emission Factors Utilizing Production Forecasts for Immediate PTE Evaluations


Between 2017 and 2020, Amerigo received a steady stream of requests to provide upstream clients with permitting strategies and emission forecasts that accounted for the production increases associated with active drilling programs.  Despite differences between client geographic locations and the permitting authority, including Oklahoma, New Mexico, North Dakota, and Texas, we identified an immediate need to create efficiencies that would speed the effort behind emission calculations and reduce opportunities for user error.

The emission forecasts were incorporated into operational and permitting strategy.  Depending on asset/client strategy and market outlook, operations and engineering would evaluate the potential scenarios with our PTE tool. The forecast allowed clients to sit and review potential emission controls/operational restrictions (VRU vs Flare; NGL Unit vs Flare; Flaring Restrictions; Delayed Flowbacks) or capital-intensive modifications to liquids and/or gas gathering facility operations.  In some scenarios, the forecasts were critical to clients’ decision to build temporary facilities authorized to handle temporary production when pipeline capacity was low or facility modifications were not economically feasible.

Case Study 2: The Role of Glycol Circulation Rates in HAP PTE Calculations 

Glycol Dehydrators are an integral tool used in natural gas dehydration and are common in upstream gas production facilities and midstream gas transmission and storage facilities.  The unit removes water content from gas streams to prevent hydrate formation and corrosion.  Both hydrate formation and corrosion are risks to upstream and midstream facilities as they can block pipelines, deteriorate instrumentation/reliability and create leaks.  As a common piece of equipment found throughout oil and natural gas production facilities, glycol dehydration units are regulated under 40 CFR Part 63 National Emission Standards for Hazardous Air Pollutants (NESHAP).  Both major and area sources of HAPs are subject to Subpart HH.  For major HAP sites, the affected sources are dehydration units, storage vessels with flash emissions, ancillary equipment in HAP service and compressors in HAP service.  For area sources with HAPs, the affected source is specific to dehydration units utilizing triethylene glycol (TEG).

Specifically regarding TEG units, all affected TEG units under Subpart HH at either a major or area source must demonstrate compliance with the control requirements, monitoring, recordkeeping and reporting.  TEG units permitted under Federally Enforceable NSR permits will typically meet Subpart HH control requirements.  Compliance demonstration with Subpart HH then becomes a recordkeeping effort to ensure large TEG units (> 3 MMscfd and > 1 tpy benzene) have reduced total air toxic by 95% or reduced benzene to < 1 tpy.  Small TEG units (< 3 MMscfd or < 1 tpy benzene) are exempt from any controls due to small emission rates unless the small dehy is at a HAP Major source – then BTEX emission limits based on site gas throughput must be met.

Case Study 2
Case Study 3

Case Study 3: Emission Inventories: Upstream Midstream Storage Tanks

Annual Emission Inventory (EI) reporting is a critical mechanism used by states to ensure their SIPs are trending to meet the EPA published National Ambient Air Quality Standards (NAAQS). State enforced EI programs collect inventories from affected sources (point, non-point, mobile, etc); the EI data helps states understand the efficacy of their air quality rules and agency efforts to develop improving emission reduction strategies.

These state-level EIs are eventually reported to the US EPA to support the publication of the National Emissions Inventory (NEI) Report - released every three years (next public release will be the full 2020 NEI, expected publish date of March 31st, 2023). The NEI report is a comprehensive and more recently, interactive dataset that provides tools to explore emission trends and source contributions to air pollution. The data is used by the EPA to analyze federal standards in place to protect public health. The comprehensive dataset is the result of extensive state and federal collaboration and can be the basis to develop new strategies or legislation.

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