Whitepaper: Reducing Methane Venting on Well Pads

In the oil and gas industry, methane (CH4) is one of the key greenhouse gases emitted into the atmosphere. It has a higher impact on global warming than CO2 and is the main component of natural gas. Globally, there are efforts to reduce methane emissions with 110 countries, including the US and Canada, endorsing the Global Methane Pledge to reduce methane emissions by 30% by 2030.  Canada’s climate plan also includes a goal to reduce methane emissions by at least 75% below 2012 levels by In the US, a Methane Reductions Action Plan has also been put in place to tackle methane emissions. The Environmental Protection Agency (EPA) has proposed a new rule to support the plan that would result in a significant reduction in methane emissions from the oil and gas industry. To learn more click here.

One major source of methane emissions in the upstream sector of the oil and gas industry, is the venting of pneumatic devices on well pads. In one study on Alberta upstream oil and gas methane emissions, an estimated 22% of methane emissions came from pneumatic devices alone. Some examples of pneumatic devices on well pads are pressure regulators, and liquid level controls. These devices are necessary for operational or safety reasons, but the fuel gas used to operate them is often vented directly to the atmosphere. The devices vary in their emissions rates with some venting only intermittently, others continuously, and zero-bleed devices not venting gas into the atmosphere at all. Some other notable sources of methane emissions in the oil and gas industry are from tank venting, fugitive emissions from leaking equipment, and compressor seals which are explained in further detail below.

Along with environmental motivations to reduce methane emissions, there is also the economic value to eliminating venting of fuel gas, where the fuel gas that would have been vented to the atmosphere can instead be taken to market and sold. The investment in one of the mitigation strategies listed below, can often pay itself off in only a few years, and in some cases only a few months. The strategies below are divided into two sections: pneumatic device emissions and other well pad emission sources. The mitigation strategies are recommended by the Methane Guiding Principles partnership and the Petroleum Technology Alliance Canada (PTAC).

Mitigation Strategies for Methane Emissions from Pneumatic Devices

Inspect and Maintain Pneumatic Devices

In some cases, when a pneumatic device is not functioning properly it will vent higher levels of gas than it is designed to. It is important to keep an accurate inventory of pneumatic devices and regularly maintain them. Repairing or replacing damaged devices leads to more accurate monitoring performance and a reduction in emissions.

Replace High Bleed Devices with Low Bleed

Replacing high bleed devices with low bleed or intermittent devices, is another way to reduce methane emissions on site. High bleed devices have vent rates typically more than 1 standard cubic meter per hour (scm/h), which results in economic losses and negative impacts on the environment. In some cases, high bleed devices were required to provide fast responses. With improvements in technology, it is recommended by the EPA to reach out to vendors to find newer quick acting lower bleed devices.

Replace Pneumatic Devices with Electric or Mechanical Options

In some instances, pneumatic devices can be replaced with electric or mechanical options. Electric valve controllers now exist that operate with small motors to control valves, which is a possibility if a site has access to electricity supply. Additionally, some pneumatic pumps can also be replaced with standard electric pumps.  As for mechanical device options, these utilize components such as springs, handwheels, or levers. A popular mechanical device that is often used in lieu of pneumatic options, is dump valves that are run mechanically as opposed to pneumatically.    

Utilize Compressed Air to Drive Pneumatic Devices

By replacing fuel gas with compressed air on site, methane emissions are completely eliminated from the pneumatic devices. These air systems typically include a compressor, air dryer, and gas storage tank. The compressors function intermittently when more air pressure is required. From the compressors, the air will travel through an air dryer to remove any water vapour. Water vapour can lead to corrosion or freezing if it is not removed effectively. These air systems are particularly beneficial for well pads with a large volume of pneumatic devices.

Mitigation Strategies for Other Sources of Methane Emissions

Tank Venting

Storage tanks that hold liquid hydrocarbons are a common and significant source of methane emissions. These tanks are kept close to atmospheric pressure. When oil and water enter the tank, gases are released. Tank vents which are meant to equalize the pressure within the tank, will vent the released gas into the atmosphere.  According to PTAC, this venting accounts for 19% of methane emissions in the upstream oil and gas sector. To mitigate this venting of gas into the atmosphere, there are options to capture it. A Vapour Recovery Unit (VRU) can be installed on site to capture vented gas, compress it, and direct it to a pipeline. Otherwise, combustion through flare or enclosed combustors can reduce methane emissions.

Fugitive Emissions from Leaking Equipment

It is common for smalls leaks to occur on site due to wear of pressurized equipment and vibration. These leaks most often take place at equipment sealed joints. These equipment leaks account for 15% of methane emissions on well pads. The number one way to prevent these leaks is to monitor equipment and provide maintenance at regular intervals. If there is any equipment that is frequently leaking, it may be best to replace or eliminate these components.

Compressor Seals

Reciprocating compressor rods are sealed using packing systems and these systems leak a small amount of gas during operation (see Figure 3). As a compressor ages, the packing can begin to wear which results in higher gas leakage through the packing.  One mitigation strategy is to replace the packing and rod when wear of the components is apparent. There are also options to replace the ring material with carbon-impregnated Teflon which has a longer lifespan than conventional ring materials. For more information on mitigation options for compressor seals, visit the EPA’s Reducing Methane Emissions From Compressor Rod Packing Systems.

Figure 3: Reciprocating Compressor Rod Packing
(Sourced from the EPA’s Reducing Methane Emissions From Compressor Rod Packing Systems study )

The drive to reduce or eliminate methane venting on well pads has been steadily increasing and policies have been enacted to support it. To learn more about the mitigation methods mentioned and other methane emission sources that were not covered above, visit Methane Guiding Principles or Recommended Technologies to Reduce Methane Emissions | US EPA.

Westgen Technologies is one of the companies dedicated to eliminating methane emissions from pneumatic devices. Westgen has developed the EPOD™ (Engineered Power on Demand) CA Series which provides clean and dry compressed air for well sites with existing power. The EPOD CA series includes a compressor, an in-line regenerative desiccant dryer, pre- and post- air filtration, remote monitoring capabilities and flow-meter tracking to record information needed for regulatory reporting and carbon credits. All of the equipment is housed within an enclosure that comes pre-commissioned and fully pre-wired to allow for ease of installation on site. Westgen also has AP (Air and Power) and PR (Power Only) EPOD™ product lines available based on the customer’s site requirements. https://westgentech.com/epod-lineup/

There are a number of companies in North America currently utilizing EPODs on their sites. Notably, Shell Canada achieved a greater than 35% overall reduction in greenhouse gas emissions after installing an EPOD compared to previous gas pneumatic designs. Access the case study here.

To learn more about the EPOD™ or request an accurate air estimate/quote, don’t hesitate to reach out info@westgentech.com or visit our website https://westgentech.com/.

Sources:

https://www.epa.gov/sites/default/files/2016-06/documents/ll_pneumatics.pdf https://methaneguidingprinciples.org/best-practice-guides/pneumatic-devices/

https://www.canada.ca/en/environment-climate-change/services/canadian-environmental-protection-act-registry/consultation-reducing-methane-emissions-oil-gas-sector.html

https://www.whitehouse.gov/wp-content/uploads/2021/11/US-Methane-Emissions-Reduction-Action-Plan-1.pdf

https://www.epa.gov/newsreleases/us-sharply-cut-methane-pollution-threatens-climate-and-public-health

https://methaneguidingprinciples.org/best-practice-guides/venting/

Eliminating Emissions from Tanks – Envirovault

https://methaneguidingprinciples.org/best-practice-guides/equipment-leaks/

Photos:

https://www.nriparts.com/products/fisher-4156k-pneumatic-temperature-controllers/388901

https://www.ar-resources.com/valve-products/fisher-d4-control-valve

https://www.emerson.com/documents/automation/product-bulletin-fisher-l2sj-low-emission-liquid-level-controller-en-122672.pdf

https://www.epa.gov/sites/default/files/2016-06/documents/ll_rodpack.pdf

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