Ben Fletcher, Manager of Oil & Gas Industries at Fisher Control Valves, recently published an article in the October 2022 issue of World Oil.
It is titled “Achieving the Zero Emission Well Pad of the Future” and it discusses the latest round of EPA regulations, and automation solutions which can be deployed to address them. The article is summarized below.
World-wide government entities are targeting greenhouse gas emission reductions, with a particular focus on eliminating methane emissions from natural gas-powered pneumatic controls at well sites. This article highlights the methods energy companies are using to address these rules, and it offers ideas for leveraging the upgrade opportunity to maximize production and profitability.
Well pad emission issues
Many oil and gas well sites are located in remote areas. The control requirements at the well head are not complicated, but they do require basic instruments and control valves, each of which requires a source of energy to operate. In the absence of compressed air or electrical power, many companies have used natural gas to operate their pneumatic instruments and valves.
This concept works reliably, but it creates an environmental issue because pneumatic controllers and control valve positioners bleed constantly and vent on every stroke. Since the instruments are using natural gas instead of air, they continuously emit methane and have been cited as one of the largest contributors of methane emissions in the oil & gas industry. In response, both the U.S. and Canadian governments have passed regulations to curtail these types of methane emissions (Figure 1).
“Low Bleed” instruments must bleed <6 SCFH of natural gas in normal operation. “Zero Bleed” instruments are generally defined as venting only intermittently, with zero bleed at steady state. “Zero Emission” devices vent no natural gas at all. More stringent worldwide emissions regulations are being finalized, but the U.S. EPA hopes to reduce well pad and pipeline emissions from pneumatic devices to essentially zero.
As Ben describes, there is a silver lining to these rules:
The regulations might appear to be burdensome and expensive to implement, however there are significant saving opportunities to be gained if a company approaches these types of projects wisely.
Savings through upgrades
A single natural gas-powered pneumatic pressure controller and associated pneumatic control valve with positioner bleeds up to 80 SCFH of natural gas annually, costing $1,400 per year per control loop in lost gas production.
Eliminating this natural gas emission is obviously good for the environment, but it also directly improves the bottom line. Ben describes one firm that is leading the charge in eliminating this major source of greenhouse gas:
EQT, the largest natural gas producer in the United States, recently released a roadmap for implementing their well site instrument upgrade projects, and other companies can learn from their experience.
When faced with a well site upgrade, EQT considers three alternatives:
- Installing air compressors to run the existing pneumatic instrumentation and valves
- Using nitrogen to run the existing instrumentation and valves
- Replacing the instrumentation and valves with electric devices
As Figure 2 shows, the best option for EQT depends on the number of natural gas-powered devices and the production rate of the well, since higher production requires the valves to stroke more often.
While air compressors and/or nitrogen can make sense in some cases, conversion to electricity (electrification) is often the best choice for wells with high production rates, new well sites, and wells with relatively few devices.
Benefits of electrification
The initial cost of well electrification can be high since all pneumatic devices are being replaced. However, electrification pays for itself through improved control strategies, the ability to remotely monitor and control, and improved diagnostics to quickly resolve problems—and of course the complete elimination of emissions.
The cost for these upgrades can be reduced by replacing existing on/off and control valve actuators with low-cost, low-power electric actuators (Figure 3).
Ben discusses the advantages:
These actuators only require low voltage (12V and/or 24V) and low current yet provide reliable control and diagnostics. Electric valves combined with electronic instruments enable advanced control strategies that are not easily implemented with pneumatic instruments, and this improved control results in more efficient operations.
Electrification has enabled significant emissions reductions and improved production on oil separators and enhanced oil recovery well sites. Here are a few examples:
- Electronic control valves installed on oil separators in North Dakota reduced losses by 80% and improved oil flow measurement accuracy by 5%.
- Electronic transmitters and control valves installed on plunger lift wells were able to better control and measure the resulting gas surge flow. This improved gas flow measurement saved about $85,000 a year on an average well.
- Electronic controls and valves installed on a rod lift well were able to maintain enough backpressure on the well to maximize gas flow while maintaining liquid production. This generated approximately $2,000/day in increased production on a 250 bbl/day well.
Upgrade products underway
Several energy companies are rapidly implementing these and other well pad instrument upgrades to get ahead of the regulations, and to take advantage of the improved production and cost savings.
EQT initiated a $20 million project to replace 9,000 well instruments over the next two years, and it expects to reduce methane emission intensity by 65%. Chesapeake Energy is investing $30 million to replace 19,000 well instruments in a similar two-year period. That project should reduce reported greenhouse gas emissions by 40% and methane emissions by 80%.