Hydrogen's low viscosity is the dominant reservoir engineering problem in porous media storage. Injecting hydrogen into a formation containing cushion gas or formation water produces a strongly unfavourable mobility ratio, which means the hydrogen fingers through rather than displacing uniformly. On withdrawal, the produced stream is a mixture of hydrogen and whatever it fingered through, and purity may fall below what the offtaker requires. Purification on withdrawal is possible and expensive, and predicting mixing behaviour is central to assessing whether a site is viable.

Microbial activity is the loss mechanism without a natural gas analogue. Hydrogen is an energy source for several classes of subsurface microorganisms: methanogens convert it with CO2 to methane, sulphate reducers convert it with sulphate to hydrogen sulphide, and acetogens produce acetate. All three consume stored hydrogen, and the sulphate reducers additionally produce a toxic and corrosive contaminant. Activity depends on temperature, salinity, pressure, nutrient availability and the microbial community present, and salt caverns are relatively hostile to it while depleted fields and aquifers frequently are not.

Material compatibility differs from natural gas service. Hydrogen embrittlement affects high strength steels, and the susceptibility depends on strength, microstructure, stress and hydrogen partial pressure. Wells, tubulars, valves, seals and surface equipment specified for natural gas may not be suitable for hydrogen, and existing infrastructure being considered for conversion requires assessment rather than assumption. Elastomer compatibility and permeation are also different.

Finally, the field evidence base is thin outside salt caverns. Several hydrogen storage pilots in porous media have been conducted or are underway, and town gas containing high hydrogen fractions was stored historically, but the operating experience is limited compared with natural gas storage. Engineering judgement in this field currently rests more on laboratory work, modelling and analogue reasoning than on demonstrated performance, and being explicit about that is part of assessing a project honestly.

By the end of this training, participants will be able to:

• Describe hydrogen properties and their consequences for subsurface storage behaviour
• Compare storage site options and assess their suitability and technical maturity
• Evaluate cushion gas options and predict gas mixing and purity on withdrawal
• Assess microbial hydrogen consumption risk and its dependence on reservoir conditions
• Evaluate geochemical reactions between hydrogen, formation minerals and brine
• Identify and quantify hydrogen loss mechanisms in a storage system
• Assess material compatibility including hydrogen embrittlement for wells and facilities
• Describe salt cavern hydrogen storage engineering and operating practice
• Assess porous media storage feasibility and its uncertainties
• Specify monitoring programmes and assess a hydrogen storage project against current evidence

The training develops hydrogen behaviour from its physical and chemical properties and applies it to storage engineering, distinguishing throughout between what is demonstrated and what is projected. Mixing, loss and purity calculations are worked through for representative sites. Microbial and geochemical risk is assessed against reservoir conditions using published experimental work. Salt cavern operating experience is examined in detail as the proven case, and porous media pilots are examined for what they have and have not established. Material compatibility is developed against current standards and test data.

Organisations sending participants to this training will:

• Assess hydrogen storage opportunities on current technical evidence rather than on assumption
• Screen sites for microbial and geochemical risk before committing to characterisation
• Specify materials and well designs suitable for hydrogen service
• Plan realistically for purity and purification requirements
• Evaluate conversion of existing gas storage assets to hydrogen service
• Build capability in a field where technical judgement is currently scarce

Participants will:

• Understand how hydrogen differs from natural gas in the subsurface
• Assess site suitability and identify the risks specific to hydrogen
• Predict mixing, loss and purity behaviour
• Specify materials and integrity requirements for hydrogen service
• Distinguish demonstrated capability from projection in project proposals
• Build a capability in an area of rapid activity growth

• Reservoir engineers assessing hydrogen storage projects
• Gas storage engineers considering conversion to hydrogen service
• Geoscientists characterising hydrogen storage sites
• Well, materials and integrity engineers working on hydrogen systems
• Facilities engineers on hydrogen storage and handling projects
• Project and commercial staff developing hydrogen storage
• Regulatory and permitting personnel

Upon successful completion of this training course, delegates will be awarded an official Certificate of Completion issued by the Petroleum Engineers Association (PEA), an ISO 9001:2015 certified training organization. The certificate carries 10 Credits and formally records the total learning hours completed.

Each certificate is signed by the Course Facilitator and the CEO of the Petroleum Engineers Association, and serves as verifiable proof of professional training that delegates can present to employers and professional bodies worldwide.