Methanol Injection
Summary
The oil and gas industry relies heavily upon glycol dehydrators using triethylene glycol (TEG) to remove water from natural gas. While glycol dehydration is effective at removing water vapor from the natural gas stream and preventing the formation of hydrates, this process results in significant methane and volatile organic compounds emissions. Replacing a glycol dehydrator with methanol injection inhibits hydrate formation and eliminates dehydrator emissions.
Description
Hydrate formation in natural gas can be inhibited by injecting additives to the gas (e.g., adding a hydrate inhibitor, such as methanol, to the gas stream). Injecting methanol into the natural gas stream inhibits the formation of methane hydrates by lowering the temperature at which hydrates form. Replacing a glycol dehydrator with methanol injection can reduce hydrate and ice formation, eliminate dehydrator emissions, and be a more efficient and simpler method of preventing flow line plugging.
Field personnel require training on the operation of methanol pumps and the proper handling and storage of methanol. The pumps, however, are no more complex than the glycol pumps they replace. In addition, packaged methanol injection units are readily available and feature metering, solar powered pumps, a chemical storage tank, and all the auxiliary equipment necessary. Use of such packages reduces installation expense and the need for extensive training, operation, and monitoring of methanol injection.
Applicability
Use of methanol injection to reduce ice and hydrate formation is most applicable to produced gas flow lines susceptible to low ambient temperature and high pressure (as a rough rule of thumb, methane hydrate will form in a natural gas system if water is present at a temperature as high as 40 degrees Fahrenheit and a pressure as low as 170 pounds per square inch gauge. However, replacement of a glycol dehydrator with methanol injection may not be suitable for production sites where produced gas is used on-site (e.g., sites with gas-fueled compressor and pump engines) due to the presence of methanol in the gas.
Methane Emissions Reductions
Methane emission reductions can be determined by taking the difference in emissions from the source before and after the specific mitigation action was applied. For replacing glycol dehydrators with methanol injection, this means calculating emissions from the glycol dehydrators given that this mitigation option would not result in methane emissions. Glycol dehydrators are an integrated system with multiple components and methods to operate and reduce emissions. Because there are multiple glycol dehydrator configurations and unique parameters to consider, such as the volume of natural gas and water content, a default emission factor is not available to adequately estimate emissions. Alternate methodologies for estimating emissions from glycol dehydrators include the use of simulation software, which can model emissions from the glycol dehydrator for the existing configuration and after implementation of the mitigation option. Further information on calculating glycol dehydrator emissions using simulation software is available in subpart W of EPA’s Greenhouse Gas Reporting Program at 40 CFR 98.233(e).
The calculation methodology in this emissions reduction section is based upon current information and regulations (as of August 1, 2023). EPA will periodically review and update the methodology as needed.
Other Benefits
In addition to reducing emissions of methane, replacing glycol dehydration with methanol injection may:
- Reduce maintenance: Replacing glycol dehydrators with methanol injection reduces the operating costs, maintenance, and downtime inherent to the use of a glycol dehydrator.
- Reduce product losses: Installing methanol injection reduces the amount of gas that would have been emitted from pneumatic controls and glycol circulation pumps associated with glycol dehydration, which can then be sold as product.
Lessons Learned
References
Anderson, D., Fourqurean, G., & Fourqurean, M. (2004). Dehydration technologies: Methanol injection [Presentation]. Natural Gas Star 2004 Implementation Workshop, Houston, TX, United States. https://www.epa.gov/sites/default/files/2017-06/documents/anderson_2004aiw.pdf (587 KB)
Carroll, J. (2020, May 12). Natural gas hydrates – A guide for engineers, Fourth Edition. Gulf Professional Publishing. https://doi.org/10.1016/C2019-0-04277-X
Estaban, A., Hernandez, V., & Lunsford, K. (2000). Exploit the benefits of methanol [Presentation]. 79th Gas Processors Association, Atlanta, GA, United States. https://www.bre.com/PDF/Exploit-the-Benefits-of-Methanol.pdf (296 KB)
Process Ecology. (2015, June 2). Methanol injection rate for natural gas hydrate prevention – Be careful what simulators tell you!https://processecology.com/articles/methanol-injection-rate-for-natural-gas-hydrate-prevention-be-careful-what-simulators-tell-you
Please Note: This platform reflects experiences and lessons learned from voluntary program partners. Some of these emission sources and technologies are now regulated at the federal, state, and/or local level in the United States and in other countries. The end user is solely responsible for complying with any and all applicable federal, state, and local requirements. For information on U.S. regulations for the oil and gas industry, refer to eCFR. EPA makes no expressed or implied warranties as to the performance of any technology and does not certify that a technology will always operate as advertised. Mention of names of specific companies or commercial products and services does not imply endorsement.