Managing emissions from above ground storage tanks remains one of the most persistent challenges in the oil and gas industry. Vapours released from tank vents, whether caused by flashing, working losses, or standing losses, are often intermittent, low-pressure, and difficult to measure accurately.
As methane regulations continue to tighten, producers must adopt reliable, high-efficiency solutions to safely control these emissions while maintaining operational integrity.
The Challenge of Low-Pressure Tank Vent Emissions
Most API-style storage tanks are designed to operate at very low internal pressures, typically below 16 oz, with many systems limited to 8 oz or even 4 oz. Under normal operation, vapours are released from the primary tank vent located at the top of the tank.
However, during overpressure events, additional releases can occur through safety devices such as a thief hatch or pressure-vacuum relief valves (PVRVs). These components are designed to protect the tank from structural damage, but they can also become unintended emission points.
Because these tanks operate at such minimal pressure, capturing and directing vapours to an emission control device requires equipment specifically engineered to handle low-pressure gas without introducing backpressure.
Safety Considerations in Tank Vent Combustion
By design, storage tanks allow air to enter the headspace during unloading to prevent vacuum collapse. This oxygen ingress can create a potentially explosive environment when mixed with hydrocarbons.
Some operators introduce blanket gas to displace oxygen and eliminate this concern.
Additionally, tank vapours frequently contain high levels of entrained liquids. Without proper management, these liquids can compromise combustion performance and equipment integrity. Producers often utilize properly designed knock-out drums (KODs) to separate liquids before routing gas to a control device.
Entrained liquids can be detrimental to equipment like Vapour Recover Units (VRUs)
The Measurement Challenge
Tank vent emissions are notoriously difficult to meter directly. In many operations, volumes are estimated using the Gas Oil Ratio (GOR) rather than continuous measurement.
While GOR provides a reasonable estimate, it introduces uncertainty when quantifying methane reduction performance, carbon compliance metrics, and regulatory reporting. (Festa-Bianchet, 2023).
Although there are different meters that can effectively measure low pressure gases, entrained liquids can cause issue. It is important to 1) use a meter that can handle liquids 2) eliminate all liquids prior to measurement.
When reporting, tank emissions are incorporated into solution gas measurements for routine venting so it is important to have an accurate measurement to ensure you are within guideline.
Why an Enclosed Combustor Is the Right Solution
A properly designed enclosed combustor provides a dependable solution for managing tank vent emissions without disrupting tank operations.
Emission Rx Enclosed Combustors are specifically engineered to manage low-pressure gas from above ground storage tanks while maintaining combustion efficiencies greater than 99%.
Key design advantages include:
- Operation at very low inlet pressures (2–16 oz range)
- Minimal system backpressure
- Redundant integrated safety systems to prevent backflash
- Effective handling of entrained liquids
- Smokeless, enclosed combustion
- Compliance with visibility and odour requirements
By pairing low-pressure capability with high destruction efficiency, operators can confidently control intermittent vapours from tank vents.
A Smarter Approach to Methane Reduction
Controlling tank vent emissions is no longer optional, it is a critical component of methane reduction strategy and is increasingly becoming a regulatory concern.
A purpose-built waste gas combustor designed specifically for low-pressure applications provides a safe, compliant, and efficient solution for today’s operating environment.
At EnviroVault, we’re proud to provide our client with Emission Rx Enclosed Combustors and we are even more proud to be the Emission Rx exclusive Canadian distributor. Our engineered solutions help producers reduce emissions, protect personnel and operate with confidence.
References:
Festa-Bianchet, SA, et al. 2023. Methane venting from uncontrolled production storage tanks at conventional oil wells—Temporal variability, root causes, and implications for measurement. Elem Sci Anth, 11: 1. DOI: https://doi.org/10.1525/elementa.2023.00053