Hydrogen injection feasible in certain North Sea fields, study suggests

A new study suggests microbial growth should not greatly impact injection of hydrogen into potential storage sites beneath depleted oil and gas fields offshore north-west Europe.

Concerns had been raised that injecting hydrogen into subsurface porous media could stimulate sufficient microbial activity to consume substantial volumes of hydrogen. This in turn could decrease injection and recovery of the gas, by clogging pores with microbial cells and excretions, and cause corrosion of metal infrastructure.

The study by researchers with the HyStorPor project, which is examining the feasibility of storing hydrogen in UK reservoir rocks, assessed sites at 42 depleted fields in the East Irish Sea, the UK and Norwegian North Sea.

Researchers found that 37 of the fields were  at risk of microbial effects, but that microbial hydrogen consumption was likely to be “negligible to small.”

Hydrogen is seen as a clean alternative to natural gas, also offsetting one main drawback of renewable energy generation – intermittency of supply. But hydrogen also requires suitable temporary storage sites.

Excess renewable energy can be converted to hydrogen through electrolysis (green hydrogen), stored, then drawn down and converted back to electricity during periods of high energy demand.

The paper on the findings, published in Renewable and Sustainable Energy Reviews, was written by scientists from the University of Edinburgh and Clausthal University of Technology, Germany.

“Using real-life depleted gas and oil fields we were able to elucidate where microbial growth is possible and which fields are sterile and hence very suitable for hydrogen storage,” said Eike Marie Thaysen, technical research assistant at HyStorPor.

Other findings were:

• Depleted oil and gas fields with temperatures of more than 122°C (251.6°F) can be considered sterile to microbial growth (five of the 42 fields in the study fulfil this criteria)

• The risk for microbial growth is reduced at extreme salinities but an upper salinity limit for microbial growth has not yet been defined

• Depleted oil and gas fields with low salinity, low temperature and close to neutral pH will likely be most prone to substantial microbial growth.

“This study…also indicates that there are no showstoppers for hydrogen storage in porous media with respect to microbial consumption of the stored hydrogen in fields with favourable growth conditions,” Ms Thaysen added.

“However, our findings need confirmation by laboratory and field experiments on microbial hydrogen consumption at high hydrogen pressures.”

Source: Offshore Magazine