The final rule for New Source Performance Standards (NSPS) OOOOb and OOOOc aims to reduce flared or vented gas during liquids unloading from gas wells.  

Specifically, it focuses on the reduction of methane and volatile organic compound (VOC) emissions during these events. The updated rule, which went into effect on May 7, 2024, applies to facilities that began construction, modification, or reconstruction after December 6, 2022. In this Delve, we explain well liquids unloading and break down the new NSPS requirements.  

Gas Well Liquids Unloading Overview  

Commonly confused with truck loading, well liquids unloading is the removal of accumulated liquids from a gas well that impedes production.  

NSPS OOOOb applies to all affected gas wells that unload liquids. The regulation is comprehensive, with a wide range of restrictions aimed at reducing emissions during these events. The US Environmental Protection Agency (EPA) requires the use of best management practices to minimize venting or emissions that occur from liquids unloading. These practices include the following: 

   1. Creating a differential pressure to minimize the need to vent a well to unload liquids.  

   2. Reducing wellbore pressure prior to opening the well to the atmosphere.  

   3. Unloading liquids to a separator where feasible.  

   4. Closing all wellhead vents to the atmosphere and returning the well to production as soon as practicable.  

Operators must have a written plan detailing which practices or technologies they will use to reduce emissions. Any deviation from the plan must be reported to EPA. Annual reports must detail the number of events where deviations occurred, along with specifics on when and why the deviation happened, its duration, and what actions were taken to minimize emissions. 

If a closed vent system (CVS) is in use, the operator must document and report compliance, including the best management practice plan. Like above, any deviations must be reported annually to EPA, with details on the date and time of the deviation, its duration, a description of the issue, dates of cover and CVS inspections, whether emissions were identified, and the date of repair. Operators must also maintain records and reports to demonstrate proper design and operation of the control device. 

Initial NSPS OOOOb and OOOOc Compliance 

1.  Submit an initial annual report for your well-affected facility.
2. If you use a non-venting technology or technique, you must do the following: 

• Record the identification of each well (US Well ID) that performs a gas well liquids unloading operation without venting methane and VOC emissions.
• Document the non-venting unloading methods used. If more than one method is applied, maintain records of each non-venting method.
• Record the number of events where unplanned emissions were vented to the atmosphere and note that best management practices were followed to minimize emissions as much as possible. 

      3. If using a venting technology or technique, you must do the following: 

• Employ best management practices to minimize venting of emissions during each gas well liquids unloading operation.
• Maintain the records specified above. 

      4. If required to reduce emissions, you must do the following: 

• Install a closed vent system to capture all emissions and route them to a control device.
• Conduct an initial performance test within 180 days after the first gas well liquids unloading operation.
• Conduct inspections of the closed vent systems, covers, and bypass devices.
• Install and operate continuous parameter monitoring systems, maintain records of the system's operation, and submit reports detailing the dates and times of inspections, bypass alarms, defects, and any identified emissions. 

Continuous NSPS OOOOb and OOOOc Compliance 

If a gas well liquids unloading operation vents emissions to the atmosphere, you must meet one of the following requirements: 

1. Reduce emissions by 95%: Reduce methane and VOC emissions from gas wells by 95% by routing emissions through a closed vent system to a control device.
2. Follow standard practices: Implement work standard practices, including best management practices, to minimize venting of methane and VOC emissions. Comply with recordkeeping requirements and submit relevant information in the annual report. 

For each well-affected facility where all gas well liquids unloading operations do not result in venting, your annual report must include the following: 

1. Identification of each well-affected facility (US Well ID or US Well ID associated with the well-affected facility) that conducts a gas well liquids unloading operation during the reporting period using a method that does not vent to the atmosphere, along with the technology or technique used. If multiple non-venting methods are employed, you must identify each different non-venting liquids unloading method used during the reporting period.
2. Number of gas well liquids unloading operations conducted during the year where unplanned venting to the atmosphere occurred and where best management practices were followed in accordance with your best management practice plan. If no venting events occurred, the number should be reported as zero.
3. Number of liquids unloading events during which unplanned emissions were vented to the atmosphere and where best management practices were followed to minimize emissions as much as possible. 

NSPS OOOOb and Subpart W  

An adjacent regulation to NSPS OOOOb is Subpart W, which requires operators to calculate and report annual emissions within a production basin. The methods used under NSPS OOOOb will directly affect the emissions reported under Subpart W. Specifically, paragraph 98.233(f) of Subpart W outlines the methods for calculating well venting during liquid unloading when natural gas emissions are vented into the atmosphere. If the emissions are routed to a flare, methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions must be calculated and reported for the flare stack in accordance with §98.236(n). 

Questions?  

Trihydro's air quality and regulatory specialists can help you manage NSPS OOOOb and OOOOc compliance. With our expertise in emissions regulations and industry best practices, we can assist you in developing effective strategies for monitoring, repairing leaks, and reporting compliance data.