Advanced Completions Tools Turn Salt Caverns into Viable Hydrogen Storage Sites
Byline by: Nathan Snoke, Global Hydrogen Account Manager
Salt caverns provide an ideal environment for hydrogen storage, but they also pose construction and management challenges due to impure salt deposits. The right completions tools can help ensure hydrogen remains in its underground storage caverns for the long-term.
Hydrogen plays a crucial role in decarbonization strategies[1]. By 2050, it will make up an estimated 10% of global energy demand[2]. Possible uses for hydrogen include the conversion of solar and wind power to hydrogen, also known as green hydrogen, and the creation of blue hydrogen from natural gas and captured CO2. These hydrogen types can provide power for various applications, such as business, residential, and transportation.
As hydrogen grows as part of the energy mix, long-term storage becomes a challenge. The characteristics of salt render it ductile, impermeable, and inert to natural gas, making salt caverns a practical option for hydrogen storage. They offer a more viable option than porous underground storage but come with construction challenges. In addition, hydrogen storage remains an emergent concept with very few sites in existence and there is a lack of information or operators with construction experience for hydrogen storage sites.
The Advantages of Salt Cavern Storage
Geologists identified three types of formations that can store hydrogen: saline aquifers, depleted oil and gas reservoirs, and salt caverns. Of the three, salt caverns show the most promise for long-term storage of hydrogen because of their ductility, inert properties, low permeability, and low requirements for gas cushions over depleted oil and gas wells or aquifers.[3] They don’t have as much storage capacity as other types of formations, but salt caverns do allow for more injection cycles and production. They also require less gas to remain stable.
In addition, salt formations can form a strong seal due to their low porosity and permeability. The high saline environment helps prevent the growth of microorganisms that could contaminate hydrogen stores and cause leakage.
Salt Caverns Pose Construction and Management Challenges
As ideal as salt caverns may seem, they do come with storage challenges. Impurities such as carbonate and claystone can develop in salt caverns when they form. Injection cycles may also create creep, causing the salt cavern to shift and introduce geomechanical challenges. Anhydrite, quartz, and shale impurities in the salt may cause cavern shape irregularities. These can all lead to potential hydrogen leakage.
Hydrogen’s smaller molecular size, higher diffusivity level, and lower viscosity make it more prone to leakage from its storage site than natural gas. Some traditional oil and gas well technologies may not provide an adequate seal for hydrogen storage sites.
Specialized Completions Tools Help Seal Hydrogen Storage Sites
Operators must understand how hydrogen impacts materials and elastomers as part of storage sites, as well as the types of completion technology available to seal and maintain the formation integrity during injection cycles. Advanced completions technologies, which provide better performance under long-term hydrogen exposure and help protect against leakage, emerge as an optimal choice for hydrogen storage sites.
A recent operator pilot program required the adaptation of oil and gas technology for underground hydrogen storage. The pilot program would prove the feasibility of hydrogen storage with methods similar to natural gas storage and would pave the way for more underground hydrogen storage sites.
Halliburton supplied tubing-retrievable safety valve (TSRV) technology with proven reliability. This type of safety valve, installed in gas injector wells, remains reliable for decades. Documented case studies show that it stays in place, even in subsea conditions, for more than 20 years.[4] Halliburton also supplied production packers designed for unconventional operations and no-go landing nipple systems ideal for high-pressure and high-temperature conditions. The test sub contained 64 pre-stressed metallic and 150 non-metallic mineral specimens to examine how the cavern would perform under long-term hydrogen exposure.
Pilot Program Highlights Viability of Salt Caverns with Completion Tools
The team observed surface pressure and temperature ranges up to 2,900 psi and 107°F (42°C) at the test site. It cycled the safety valve more than 75 times over two site visits, but the safety valve did not leak on the high-performance rod piston seals or body connections. The valve’s inflow was also tested, and its performance exceeded accepted oil and gas criteria E. The packer withstood the salt cavern’s conditions, with zero recorded pressure buildup throughout the demonstration period. All the supplied materials and tools remained in the well for 12 months, with 11 months of hydrogen exposure, before successful retrieval.
Post-retrieval baseline tests showed that the safety valve experienced no issues with operational or seal performance, and the packer performed as expected. The material sub remained intact, with a successful specimen retrieval. These material test sub-samples lay the foundation for further research and development of hydrogen storage solutions.
The pilot program proved that oil and gas technology can provide completions for salt caverns used for hydrogen storage. As Halliburton examines the material test sub-samples and develops new technologies, we will be able to help customers increase their use of salt caverns for hydrogen storage.
Halliburton leads the charge with its Material Science Centre of Excellence and in-house research and development labs. It explores new ways to use field-tested technology to move the energy transition forward.
To learn more about how Halliburton engineers the future of energy, visit www.halliburton.com/lcs.
Nathan Snoke is the Global Account Manager of Hydrogen at Halliburton. In this role, he is responsible for driving the success of Halliburton’s Hydrogen strategy through technology, customer relationships, and service delivery. He brings more than 20 years of global energy industry experience.
Snoke returned to Halliburton in 2024 after serving as Senior Vice President of Global Business Lines for Flotek Industries. Prior to Flotek, Snoke’s 17-year career at Halliburton included various domestic and international roles related to strategy development, business planning, and execution.
Snoke holds a Master of Business Administration from the University of Denver and a Bachelor of Science in Finance from Liberty University.
[1] Strategic Intelligence (weforum.org)
[2] Underground hydrogen storage in caverns: Challenges of impure salt structures – ScienceDirect
[3] https://www.sciencedirect.com/science/article/pii/S001282522300288X#bb0030
[4] SP TRSV 21 years field proven reliability – Case Study (halliburton.com)