How to Right Size a Vapor Recovery Unit (VRU)

Using a Vapor Recovery Unit (VRU) to augment emissions control is an effective way to simultaneously reduce tank flaring and venting as well as generate additional revenue.


A VRU captures tank vapor gas, rich in BTU content, so it can be sold instead of flared or lost to venting. In many situations, this is not a trivial matter, because tank vapor gas can exceeding 3000 BTU, making some of the most valuable gas on the wellsite!


Put simply, a VRU converts waste gas emissions into a valuable revenue stream. Waste gas emissions can be recovered from casingheads, oil storage tanks, produced water tanks, heater treaters, glycol separators and other process equipment.


There is more to the story, however, than simply installing a VRU and walking away from the well site. Choosing the right size VRU is a critical factor in Facilities Optimization. Choosing a VRU with a compressor that is oversized for the situation results in higher than needed purchase or lease costs and will typically consume more fuel or power than required, driving up Lease Operating Expense (LOE).


Reasons to “Right Size” your VRU

There are several reasons to ensure your VRU is sized correctly for your production facility.


Regulatory requirements. Keep in mind that for production facilities and well sites in Texas, the Texas Commission on Environmental Quality (TCEQ) requires a VRU to be able to handle the highest and lowest expected volumes of Volatile Organic Compound (VOC) emissions. Different requirements and standards exist for federal permits (Title V) and other states, including Colorado, New Mexico, North Dakota, and others.


Minimize lease costs. VRU costs typically vary with compressor size, with larger units costing more than smaller ones. Choosing an oversized VRU means you are paying more, either in purchase cost or lease payments, than needed. Right sizing helps conserve capital expenditures and better align capital intensity with an asset’s economic value.


Minimize fuel and power expenses. Larger compressors use more fuel or electric power than smaller ones, meaning an oversized unit will cost more to function than needed, resulting in higher than necessary Lease Operating Expense. Right sizing better aligns LOE with actual tank vapor volumes, improving the economic life and value of your oil and gas assets.


Minimize maintenance and repair costs. Larger VRUs cost more to maintain and repair than smaller units. Right sizing your VRU will help keep maintenance and repair costs as low as possible.


Maximize reliability. Employing a VRU that is too small for the actual tank vapor volume will place more stress and wear on the unit, potentially resulting in faster wear of parts and equipment, which can impact system reliability from unplanned production downtime.


System integrity and emissions. VRUs operate as part of an overall system and an undersized unit can place additional stresses on other process equipment and/or result in higher emissions from venting and flaring of tank vapor gas unable to be processed fast enough. An oversized unit combined with inefficient piping can also create excess stresses on downstream equipment as well as the VRU.


Factors for Right Sizing Your VRU

At Platinum, our core competency of Facilities Optimization is focused on decreasing facility energy use, increasing equipment reliability, and reducing overall operating costs. In other words, doing more with less by boosting output or throughput using less energy.


Right sizing your VRU is an important part of oil and gas facilities optimization and Harnessing the Full Potential of Your Well Site. When operating at “full potential” a well site is operating cost-efficiently, free of operational constraints and in compliance with applicable regulations.


Factors for correctly sizing a VRU include:

  • Expected production volumes, including expected peaks and valleys

  • Production stream composition and flow

  • Expected tank vapor volume quantification

  • Tank pressures and Pressure Relief Valve (PRV) settings

  • Gas composition and tank vapor BTU content

  • Well site power gensets

  • Oil and produced water storage systems

  • Expected future development plans

  • Capacity of other process equipment on the well site or facility

  • Regulatory requirements

  • Well site or facility configuration, including equipment placement

  • Piping, including sizing, angles, and type(s)

One of the most important factors for determining the correct VRU size is estimating the volume of actual vent gas. Although some “rules of thumb” exist and can be helpful, the best practice is direct measurement and simulation testing, which usually involves measuring the vent gas coming directly off the tanks through a common vent line for a 24-hour period.


This method provides accurate and reliable data for determining the flow and volume of tank vapor gas available for capture and sale.


Plan for the Surge!

In addition to the 24-hour data from a direct measurement and simulation test, pay attention to variation in production during the test interval!


Production optimization often results in sudden production surges entering the storage tanks, both oil and water, causing rapid increases in tank pressures.


Your VRU needs to be able to handle surge production to prevent PRV valves from opening and subsequently venting valuable tank vapor gas, resulting in VOC emissions and lost revenue.


Benefits of Right Sizing Your VRU

Benefits of choosing the right VRU for your well site or facility include:


  • Maximized long-term economic value of your oil and gas assets

  • Better environmental performance

  • Regulatory compliance

  • Efficient and profitable operations

  • Reduced risk

A properly sized VRU will help you optimize the total performance of your well site or facility, maximizing its long-term economic value and environmental performance.


The Platinum Advantage


Platinum VRUs punch above their power ratings. Platinum VRUs typically move 30% more gas volume for the same horsepower rating as competing units, because of our innovative design and quality materials. Our efficient, class-leading design means that in most cases a smaller and less expensive Platinum unit will do the same job of a larger and more expensive unit to significantly capture and sell more rich-BTU gas and put out the flare.


Flexible Fleet™ lease agreements. Our Flexible Fleet lease agreements allow you to move VRUs from one site or facility to another at will and without burdensome paperwork. That allows you to move larger units from an older site further down the decline curve that produces less tank vapor to a newer drill. That allows you to tailor VRU capacity to the individual site and to your entire field.


Contact us today at sales@platinumcontrol.com to learn more about our solutions and how we can help you harness the full potential of your well site.

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