Boost Profitability, Maximize Throughput, and Reduce Emissions through Fuel Gas Conditioning
Compressor engine performance is a critical factor in maximizing the operational efficiency, throughput, and profitability of gathering stations. The performance of natural gas fired engines, however, is directly affected by the quality of fuel gas, making Fuel Gas Conditioning (FGC) a top priority for compressor station operators.
The primary function of compressor stations is to move natural gas through a pipeline (i.e., a gathering system or transmission line) by boosting pressure to keep the gas moving through the network. Compressor stations typically utilize reciprocating engine compressors, which are frequently powered by the natural gas being compressed. Although this makes compressor stations extremely self-reliant, it does make them vulnerable to less-than-ideal fuel gas quality and the inherent inefficiencies and reliability related issues of higher knock and increased VOC emissions.
In this article, we compare traditional Field Gas Conditioning technologies, including J-T Skids and residue gas lines, with the MaCH4 NGL Recovery Solution from Coldstream Energy for delivering a consistent supply of lean pipeline-quality fuel gas.
Impact of Fuel Gas Quality on Engine Performance
Raw natural gas production often includes natural gas liquids (NGLs) like ethane, propane, butane, and other heavier hydrocarbons. These increase the heating value of the gas and can condense out of the gas stream, especially in winter. Additionally, the makeup of natural gas can differ significantly from one field to another creating challenges for using unconditioned produced gas as a fuel.
The disadvantages of using unconditioned produced gas as fuel include: (a) burns up valuable NGLs that could have been recovered and sold, (b) generates higher VOC emissions from combusting the heavier hydrocarbons in fuel gas, and (c) reduces compressor engine efficiency resulting in decreased power performance and overall throughput.
When NGLs are left in produced gas used as fuel, they increase its potential for detonations, as measured by a lower Methane Number for reciprocating engines (or Wobbe Index in the case of natural gas fired turbines). Consequently, fuel gas containing NGLs can derate engine performance and efficiency, reducing overall throughput and wear and tear on moving parts.
Lean fuel gas, which has a lower heavy hydrocarbon content, burns more cleanly and efficiently, resulting in better engine performance and lower emissions. This not only extends the lifespan of the compressor engines but also reduces operational costs by minimizing the need for frequent maintenance and repairs. The MaCH4 solution ensures that the fuel gas used by the compressors is of the highest quality, enhancing the overall reliability and efficiency of the gas gathering system, ultimately helping to optimize compressor station performance and profitability.
LEARN MORE: Best Practices for Optimizing Compressor Station Performance
Fuel gas quality plays a pivotal role in engine performance and overall compressor station efficiency. Recovering NGLs from “wet” gas laden with heavy hydrocarbons is an essential part of fuel gas conditioning, and operators have several options to choose from for achieving this goal with each having its own set of pros and cons.
J-T Skid
J-T Skids can be used to liquify gases in the production stream and are commonly used on well sites due to their simplicity and compact size. Operating on the principle of the Joule-Thomson (JT) Effect, these units utilize a JT Valve to reduce pressure without mechanical force. As gas experiences a rapid pressure drop, it cools, causing heavier NGLs to condense out, resulting in a leaner gas stream with higher methane content.
Pros:
- Marginally better engine performance from burning a fuel gas conditioning to be “just good enough.”
- Simple operation, widely available technology, small operational footprint.
- Some incremental NGL revenue.
- Relatively low maintenance (no reciprocating parts).
Cons:
- Produces only a marginal improvement of fuel quality that is “just good enough” for fuel gas that may meet the minimum specification, but not good enough to eliminate an engine derate and reduction in throughput.
- The JT effect reduces the temperature of all gases in the production stream, including water vapor, making them vulnerable to freeze ups resulting in unexpected downtime.
- Reliable operation usually requires additional investment in dehydrators, methanol injection systems and related methanol consumption, and/or additional compression capacity to make up for the inefficiencies.
- The reliability of methane injection systems can be a single point of failure, for example if a methane pump goes down, then so does the compressor station.
- Burning less than ideal fuel gas generates high relative emissions.
- Performance is dependent on ambient temperatures and available pressure drop and can only be used in high pressure systems (>1,000 psi).
Verdict: Best to use in remote locations for treating lower gas volumes in areas where electric power is unavailable and/or NGL content is lower.
Residue Line Fuel
Running a residue gas line from a gas processing plant to a nearby compression facility delivers lean, pipeline quality fuel gas to compressor engines.
Pros:
- Access to lean, pipeline quality fuel gas.
- Combust cleaner for reduced emissions, compared to J-T gas.
- Maximizes compressor engine performance.
Cons:
- Time-consuming and expensive to install.
- Additional capital outlays may reduce overall ROI.
- Potential variability in gas quality and consistency.
- Ongoing costs for maintenance and repair, potential for creating fugitive emissions.
- Can not be moved when decommissioning a station.
- May result in additional costs if the gas gathering contract does not include a fuel allowance.
Verdict: Often considered the “gold standard” of optimization but can be expensive and time-consuming to implement. Best used when your compressor station is located near processing facilities where residue gas is readily available, facilitating easier logistics and integration into existing infrastructure. Generally, it is not feasible for remote locations.
READ MORE: White Paper – Best Practices for Optimizing Compressor Station Performance
PSA Technology-Based Solution: MaCH4 NGL Recovery Solution for Fuel Gas Conditioning
The MaCH4 NGL Recovery Solution from Coldstream Energy is a PSA technology-driven solution for generating residue line quality gas without the time and expense of a residue line. The MaCH4 solution uses patented, proven Pressure Swing Adsorption (PSA) technology that allows you to recover NGLs instead of burning them up in fuel gas for increasing revenue and reducing emissions.
The MaCH4 solution proved its value proposition in a rigorous pilot project with Iron Horse Midstream that was converted into a permanent installation.
In the Pilot, the MaCH4 NGL Recovery Solution was benchmarked against a J-T Skid. The Pilot employed a 4-bed PSA system with a compressor package delivering high-pressure feed gas to the MaCH4 unit. The MaCH4 unit generated a lean fuel gas stream for the compressor station engines and recovered significantly more heavy hydrocarbons remaining in a gaseous state for later processing at a gas processing plant.
MaCH4 Technology Beats J-T Skid:
- Eliminated engine derating, for a horsepower increase of up to 9% for maximum throughput and fee-based revenue.
- Delivered cryogenic-like recovery performance without low temperature requirements, capturing 60% C2 and 95% C3+ heavy hydrocarbons on site, separating valuable NGLs, and boosting profits.
- Over 70% fewer VOCs were emitted when operating on fuel produced by the MaCH4 unit compared to J-T fuel gas.
Importantly, the MaCH4 unit also delivered significant economic benefits by recovering and selling valuable NGLs instead of burning them in the fuel gas. Based on a field gas BTU value approximately 1,305 BTU/scf at the Pilot site, the total annual NGL value recovered would be greater than $1.2MM for a 7,500 HP Compressor Station.
READ MORE: MaCH4 Technology White Paper (PDF Download)
Conclusion
Using lean, pipeline quality fuel gas to maximize engine performance is one of the most significant things operators can do to optimize the operational efficiency and profitability of compressor stations.
In the field, the MaCH4 solution from Coldstream Energy delivers cryogenic quality NGL recovery without low temperature requirements, outperforming J-T skids and providing pipeline quality fuel gas without an expensive residue line.
The MaCH4 NGL Recovery Solution uses patented, proven Pressure Swing Adsorption (PSA) technology that delivers cryogenic-like NGL recovery along with a lean, high-quality fuel gas without the expense of a residue line. This groundbreaking application of PSA technology has proven itself in a long-term field trial with Iron Horse Midstream, a leading midstream operator.
Contact us today to learn more about the MaCH4 NGL Recovery Solution and how it can optimize your compressor station efficiency, profitability, and emissions performance.
About Coldstream Energy
Coldstream Energy, based in Houston, Texas, is a leader in innovative natural gas conditioning and separation technology to maximize profits and minimize emissions for upstream and midstream operators.
At Coldstream Energy, we are passionate about our commitment to improving air quality and reducing waste of the Earth’s valuable resources. A sustainable oil and gas industry is the foundation of the modern global economy, providing affordable and reliable energy. At this pivotal time, our technology provides a tremendous opportunity to capture valuable resources that otherwise would be wasted by combusting NGLs in compressor engines or flaring natural gas. Not only is converting “field gas” into valuable products good for the environment, but it is also just good business.
Our solutions are engineered to recovery Natural Gas Liquids (NGLs) efficiently and effectively for maximizing the value of natural gas production streams. We use proven technologies for recovering heavy hydrocarbons (C3+) from produced gas and tank vapors, generating incremental revenue, boosting operational efficiency, and improving environmental performance.
Our flagship MaCH4 NGL Recovery Solution is a breakthrough application of proven Pressure Swing Adsorption (PSA) technology for use in the oil and gas industry and is the simplest and fastest way to achieve cryogenic-quality NGL recovery and lean compressor engine fuel gas.
Contact
Matt Thompson
SVP Sales & Marketing
ColdStream Energy, LLC
mthompson@coldstreamenergy.com
