Tag Archives: Flare Gas Measurement

Flare Gas Measurement Innovation: Retain Flow Metering Accuracy Even if Gas Composition Changes

flare-blog-imageIt’s a fact oil wells almost always produce natural gas along with the petroleum. Nine times out of ten, the excess gas (typically hydrocarbons) is flared off or simply vented as-is during upset conditions in the process. The environmental impacts of “flaring” this excess gas into our atmosphere has resulted in government regulations like 40 CFR Part 60 Subpart OOOO (also known as Quad O) as well as new RSR MACT rule for refineries requiring oil & gas companies to report the flare gas emitted.

Traditionally, in upstream oil and gas applications, orifice plates and turbine meters have been used to measure the flare gas to comply with these government regulations.  Thermal mass flow meters are also gaining ground as a reliable and accurate direct mass flow measurement of flare and combustor gas.

The Problem:

Most thermal mass flow meters, however, have an inherent disadvantage in the challenging flare gas measuring application because each well head has its unique and constantly changing characteristics including varying gas composition. Over the lifetime of the well, flare gas composition and density varies, so a typical total flare gas flow measurement error could be as high as 20%. Most thermal flow meters cannot manage these gas composition changes, as they are factory calibrated for a specific gas, and need to be sent back to the factory for recalibration for the new gas composition. This is not only time consuming for the oil & gas operators and engineers, but the flare must be shut down, the thermal meter taken out of the inlet flow, and sent to the factory for recalibration.

Recent Innovation, New Solution:

Today, a new generation of four-sensor “Quad” thermal mass flow meters retains accuracy even if gas composition changes.  Sierra’s QuadraTherm 640i/780i thermal mass flow meter, is becoming a popular choice for flare and combustor (VOC/VRU) measurement due to its unique onboard qMix gas mixing software which allows operators to manage the changes in flare gas composition in the field-no factory recalibration necessary. Operators can use the onboard qMix gas mixing software to select the new gas composition and upload this new gas into the QuadraTherm meter in the field in minutes. The accuracy of the flare gas measurement for this new gas composition is retained improving downtime and  EPA regulation compliance.

Benefits of QuadraTherm thermal mass flow meters in upstream oil & gas applications:

  • High Turndowns 100:1 and measures very low flows
  • Extreme accuracy +/- 0.75% of reading (+/- 0.5% for 780i inline with built in flow plates)
  • High flows up to 60,000 sfpm (0 to 305 smps)
  • Eliminate drift with patented DrySense™ sensor-Lifetime sensor
  • qMix Gas Mixing App manages changes in gas composition in the field—no recalibration needed
  • In-situ ValidCal™ Diagnostics, Dial-A-Gas & Dial-A-Pipe
  • Low and high-pressure hot tap
  • 40 CFR Part 60 (Quad 0), Boiler MACT Greenhouse Gas (GHG) certified

flare-gas-tech-note-thumb

New Flare Gas Measurement Application Tech Note!

Download our new Flare Gas Mass Flow Measuring Tech Note  for more information on how qMix gas mixing software makes QuadraTherm thermal mass flow meters the most flexible and economic solution for flare and combustor gas measurement.

The Challenges of Measuring Flare Gas

flare gas measurement

The associated gas generated from oil production has received a lot of attention recently.   In many areas, the lack of gas collection infrastructure requires this gas to be flared off.  Many jurisdictions now require the flow rate of gas to the flare to be monitored in order to reduce emissions and to allocate taxes, fines and other fees.

Measuring the flow rate of flare gas is challenging because a flare is not a pure gas, but a mixture of many different gases.  In order to correctly measure the flow rate of the constituent gases, the composition of the flare must be known.  This is typically determined by taking a sample (a cut) and processing it through a gas chromatograph (GC).  This composition coupled with the total measured flow rate allows the flow rate of the individual component gases to be calculated.

Once the gas begins to flow from a well, operators need to account for this associated gas from day 1.  This of course requires a flow meter calibrated to measure the flow rate of the flare gas.  Virtually all current flow measurement technology requires a known composition for calibration.  This presents a “chicken or egg” problem, since the composition may not be known at start-up and will change over time, thus rendering the flow meter inaccurate at best and inoperable at worst.

Achieving Flare Gas Measurement Accuracy Regardless of Changing Gas Composition

Recent innovations in immersible thermal flow meter technology provide a solution to this “what came first” problem.  Sierra’s QuadraTherm flow meter can accurately measure the mass flow of gases over a very wide turn-down.  Most importantly, users can change the meter’s calibration in the field to reflect the actual gas composition.  This is made possible by an industry first algorithm called qMix, which uses the NIST RefProp database of gases to calculate the heat transfer properties of complex gas mixtures and thus maintains meter accuracy.

qMix Mathematical Model – How It Works*

QuadraTherm’s advanced mathematical model operates a microprocessor-based system that provides the foundation for making in-the-field compositional compensation. In a thermal mass flow meter, a velocity sensor measures the heat removed from a heated sensor by the flowing gas, while additional sensors measure other heat losses, such as those caused by natural convection, radiation, stem and end loss. The heat removed by the flowing gas is proportional to the mass flow.   In operation, the four-temperature microprocessor-based system measures the resistance of each of four RTD sensors along with the current in the velocity sensor. The resistance values are converted to their four corresponding temperature values, and the current to the velocity sensor is converted to electrical power, or wattage. The four temperatures, the wattage, and the gas composition are the inputs to the system. The gas property algorithms calculate the updated properties of the gas (mass density, dynamic viscosity, thermal conductivity, and heat capacity). The system then computes the total mass flow rate in the pipe line – the desired output.

QuadraTherm meters can thus be stocked on the shelf, so that when a spare or new meter is needed, they can be installed, and the sample gas composition programmed in upon start-up of the well, thus ensuring day 1 flow measurement accuracy.

Download “New Developments in Thermal Dispersion Mass Flow Meters: In-The-Field Compensation for Changes in Natural Gas Composition” for more information on advances of QuadraTherm with qMix.

*Reference: Blog copy reprinted from Olin, J. G. 2014. New Developments in Thermal Dispersion Mass Flow Meters: In-The-Field Compensation for Changes in Natural Gas Composition. Presented at 2014 American Gas Association Operations Conference, Pittsburgh, PA, May 20-23, 2014.

Introducing a Game Changing Flare Measurement Technology

Meet EPA’s Refinery Regulations with our New Game-Changing qMix RealTime Flare Measurement System (FMS)

A refinery at full capacity produces far more gas than it needs. It is not economical to capture it, clean it, compress it, store it, and finally transport it, so it’s flared off. Stringent federal, state, and local laws govern the flaring process. As time has gone on, the laws have become stricter with heavier fines for non-compliant companies.

A Challenging Application

The new EPA 40 CFR Part 63 rule, effective February 4, 2020, now requires oil engineers to provide flow measurement data on 20% of reading at velocities from 0.1 to 1 ft/s and 5% of reading greater than 1 ft/s. For Plant Engineers in the field, this is a very challenging application due to several factors:

  • Very high turndown from 0.1 fps to 1000 fps during an emergency shutdown
  • Constantly changing flare gas compositions
  • Very low pressure drop (5 psig)
  • Asymmetric flow profile, stratification, turbulence, pulsating flow (60” pipe header)

Multipath Ultrasonic flow meters for flare gas have been the traditional instrument used to report flow data to the EPA for compliance. However, there are issues with ultrasonic meters for flare gas that make it an unreliable choice to meet the new EPA 40 CFR Part 63 rule:

  1. Most of the installed base of ultrasonic meters have been calibrated to 1 fps prior to the new rule.
  2. Additionally, very low velocity is difficult for transit time due to small Delta T.
  3. CO2, H2 attenuate the signal, so ultrasonic meters cannot read to low flows in these gases
  4. Stratification causes reflection/refraction at the layer
  5. Turbulence reduces signal strength so the reading is not reliable.

EPA 40 CFR Part 63 requires  flow measurement at much lower rates (0.1 sfps) and individual limits on gas constituents have been imposed. These changes require a gas analyzer and a flow measurement device that can handle low flow rates and changing gas compositions. What oil & gas engineers need to comply with the EPA rule is a mass flow meter with a very large turndown, low-pressure drop, ability to measure down to 0.1 fps and the ability to maintain accuracy even with changing gas composition. Easy integration into the current infrastructure improves speed to compliance and saves on costs.

Meeting EPA Regulations Head on with NEW qMix RealTime FMS System

With Sierra’s new QuadraTherm® qMix RealTime Flare Measurement System (FMS), for the first time a system based on thermal mass flow meters can adjust flow readings when flare gas composition changes within seconds to match real-time readings from a gas chromatograph-retaining accuracy without factory recalibration.

Now Plant Engineers have the perfect solution to comply with EPA Refinery Sector Rule 40 CFR 63 rule which requires refineries to measure and report flare gas measurement at flow rates as low as 0.1 sfps (0.03 smps) where traditional multi-path ultrasonic flow meters can’t operate.

The qMix RealTime FMS harnesses the accuracy and computational power of QuadraTherm thermal mass flow meters and proprietary qMix RealTime software.

Easy Integration to Your Current Process

The system integrates with current flow meters, infrastructure, and gas analyzer to give accurate flows over a wide 1000:1 turndown to meet the low end of EPA regulations at a fraction of the cost.

qMix RealTime FMS is made of three major components:

  • QuadraTherm 640i/780i Thermal Mass Flow Meter
  • qMix RealTime Software Application
  • Window-based laptop computer (included)

When the gas composition changes, the qMix RealTime App, loaded onto the supplied laptop, reads the outputs from your gas analyzer for updated flare gas composition, then creates a new gas composition that is automatically uploaded to the 640i/780i.

With qMixRealTime FMS, users can connect, read, and update new flare gas composition from a gas analyzer-real time with no recalibration need. Engineers will also be able to set update frequency by time or by the percentage change in the gas composition.

Click here to discover more about QuadraTherm qMix Flare Measurement System today.

View all Sierra’s Oil & Gas Flow Measurement Solutions.

Meet EPA Regulations Head-On with the qMix RealTime Flare Measurement System

We are excited to share our latest video, qMix RealTime Flare Measurement System-How it Works, especially if tightening EPA regulations are on your mind.

Last month, the U.S. Senate voted to overturn relaxed requirements for methane emissions, and the U.S. government has begun to strongly enforce previously approved rules. So accurate flare gas measurement is more critical than ever, however, meeting these regulations is easier said than done.

The EPA Refinery Sector Rule 40 CFR 63 requires flow measurement data on 20% of reading at velocities from 0.1 to 1 ft/s and 5% of reading greater than 1 ft/s. For plant engineers in the field, this is a very challenging application due to several factors:

  • Very high turndown from 0.1 fps to 1000 fps during an emergency shutdown
  • Constantly changing flare gas compositions
  • Very low pressure drop (5 psig)
  • Asymmetric flow profile, stratification, turbulence, pulsating flow (60” pipe header)

Multipath ultrasonic flow meters, traditionally the meter of choice for reporting EPA data, are now an unable to successful meet the low end of these regulations:

  1. Most of the installed base of ultrasonic meters have been calibrated to 1 fps prior to the new rule
  2. Additionally, very low velocity is difficult for transit time due to small change in time
  3. CO2, H2 attenuate the signal, so ultrasonic meters cannot read low flows for these common flare gases
  4. Stratification causes reflection/refraction at the layer
  5. Turbulence reduces signal strength so the reading is not reliable.

However, Sierra’s QuadraTherm qMix RealTime Flare Measurement System (FMS) meets this EPA regulation head-on and offers you the perfect solution to comply with EPA Refinery Sector Rule 40 CFR 63 rule which requires refineries to measure and report flare gas measurement at low flow rates as low as 0.1 fps (0.03 smps) where traditional multi-path ultrasonic flow meters can’t operate.

qMix RealTime Flare Measurement System – How it Works

The qMix RealTime Flare Measurement System (FMS):

  • Delivers real-time flare gas flow measurement to accurately measure flows down to 0.1 sfps
  • Meets full range of EPA rule 40 CFR 63 down to 0.1 sfps (0.03 smps) where ultrasonic meters can’t operate
  • qMix RealTime app connects, reads, and updates new flare gas composition from a GC- real-time, no recalibration needed
  • Is easy to install with current ultrasonic flow meters- no process shutdown
  • Highest Accuracy: +/-0.5% of reading (inline); +/-0.75% of reading (insertion)
  • Handles upset conditions at ultra-high flows with wide turndown of 1000:1

The bottom line, you have a tool to compliance with emission monitoring rules. Watch Video to Learn More.

Learn more about qMix RealTime FMS, by downloading the “Solving The Flare Gas EPA Compliance Challenge with Game-Changing qMix RealTime Flare Measurement System (FMS)” application tech guide.

Video created by Sierra Graphic Designer Jose Estevez produced by Erica Giannini.

 

Stay On Top of Methane Metering and Emissions Regulations

As climate concerns continue to dominate the national (and global) conversation, tightening state and federal regulations on methane emissions can pose challenges to new and existing oil and gas producers.

While many may be familiar with New Source Performance Standards (NSPS), which regulate emissions at new wells, it’s important to know the EPA is moving to limit emissions from existing operations as well. This move would be a first, and businesses could be required to recapture up to 95% of methane emissions. Understandably, ensuring compliance with these standards adds an additional layer of complexity to existing operations. But as your trusted gas emissions compliance resource, Sierra offers the information and products you need for maximum flow control in a world of changing standards.

Below, get the answers to some of the most common questions on methane emission compliance with our expert Q and A. And as always, reach out to Sierra for help with all of your flow control needs.

Contact us 

What changes are happening right now at the state and federal level, and what trends should we expect to see in oil and gas regulations regarding methane emissions?

The EPA has proposed broadening the NSPS to include many existing wells.  The proposal would expand and strengthen emissions reduction requirements that are currently on the books for new, modified, and reconstructed oil and natural gas sources, and would require states to reduce methane emissions from hundreds of thousands of existing sources nationwide for the first time.

New rules could require oil producers to capture and report 95% of methane emissions. These rules are resulting in an elevation of the importance of proper monitoring and amplification of the consequences of failing to do so reliably and accurately.

For example, Colorado’s 900 series of rules require operators to measure the volume of all gas vented, flared, or used at an oil and gas location by direct measurement or an approved method of estimation.  Ref: 903.d.(4). This must be reported on the Operator’s Monthly Report of Operations. If the gas is collected and sold, operators will want to measure it in order to monetize the product.

While Colorado currently has some of the nation’s strictest rules regarding venting and flaring, there is every indication that other states will follow.

What is the best way to ensure compliance for these methane rules?

You cannot control what you do not measure.  To comply with existing and future regulations and avoid expensive fines, oil producers should act now to understand their measurement options and be prepared. Accurate direct mass flow measurement is critical to meeting measurement and reporting requirements.

Both proposed and current rules on the books, like EPA 40 CFR Part 60 Subpart OOO, EPA 40 CFR Part 98 Subpart W, and BLM 3175 require recordkeeping and reporting.  I

However, measuring natural gas in flare, combustor, and VOC applications is challenging.  Flow measurement error can be as high as 20% in flare applications over the life of the well due to widely varying compositions and density changes.  Flare rates can also change from very small to very large during upset conditions.

What oil producers need is a direct mass flow meter that can meet these challenges.

Oil producers should look for flow instrumentation that provides:

  • Low-end sensitivity for flares, vents, and leak detection
  • Direct measurement of gas mass flow
  • High accuracy
  • Ability to manage-the-field changes in gas composition
  • Welded, 316 SS sensor construction with no moving parts means no required reporting data lost
  • Totalizer makes monthly reporting easy

How can you improve combustion efficiency?

Part of the equation for oil producers to reduce emissions is to achieve combustion efficiency.

Combustion efficiency is a measure of the effectiveness of the flare in burning  natural gas.  Sufficient oxygen must be provided to burn off the organic compounds in the flare, or a great deal of unburned compounds (soot) will be emitted.

The most effective way to improve combustion efficiency is to use a direct mass flow meter that provides accurate flow measurement of multiple gases under all application variables with a steady flow of oxygen to achieve combustion efficiency.

What is the best method for measuring methane and flare gas?

Thermal mass flow meters are the ideal technology to make accurate flare and combustor gas measurements. They deliver a direct gas mass flow measurement. They can measure from very low flows to the high flows of upset conditions.  In addition, they have no pressure drop, no moving parts, high accuracy and can compensate for changing gas composition.

Traditionally, the dP meter has been the conventional choice in the oil and gas industry.
It measures volumetric flow by employing two pressure transmitters to measure the pressure drop (the differential pressure) across a flow restriction. This results in the dP meter’s inherent shortcomings:

Flow restriction causes pressure drop and it can become clogged, needing frequent maintenance.
dP requires additional calculations to convert volumetric flow to mass flow, the measurement that most often needs to be reported. This reduces accuracy.

Sierra Has the Answer for Measurement and Reporting Requirements

QuadraTherm® 640i Thermal Mass Flow Meters with qMixTM

Sierra recognizes the impact regulations will have on the future of the oil & gas industry.  Our primary goal is to help make you smarter and more productive with precision flow measurement tools. Our QuadraTherm 640i with qMix is your solution to answer regulations and reporting requirements.

  • Low-end sensitivity for flares, vents, and leak detection – ultra-low flow calibration from 0-499 sfpm
  • Direct measurement of gas mass flow
  • High accuracy of +/- 0.75% reading means operators can be confident they are not over or under-reporting gas totals
  • Ability to manage-the-field changes in gas composition without factory re-cal
  • Very reliable welded, 316 SS sensor construction with no moving parts means no required reporting data lost
  • Totalizer makes monthly reporting easy
  • Explosion-proof with cFMus Class I, Div 1 rating
  • Accuracy compliant with BLM 3175 & API 14.10

Download our new Oil & Gas brochure to learn how you can optimize your gas flow measurement and meet regulations using QuadraTherm 640i with qMix.