Western Australia's depleted oil and gas fields could gain a second life with a new report identifying several previously producing fields that could be suitable for storing hydrogen.
The report, which was commissioned by the Geological Survey of Western Australia (GSWA), and prepared by RISC Advisory, identified seven onshore fields as good candidates for hydrogen storage projects, from a total of 23 that were screened.
The seven fields identified as having strong hydrogen storage potential were all depleted gas fields and included, in order of ranking, the Xyris, Yardarino, Beharra Springs, Red Back, Tarantula, Tubridgi and Mondarra gas fields.
The Dongara gas field was just knocked out of the top rankings, despite having the largest estimated storage capacity among the fields studied, at over 450 billion cubic feet.
However, Risc only estimates pure hydrogen storage demand in the near-term at between 1 Bcf and 10 Bcf, meaning Dongara would not make an ideal short to medium-term candidate, which is the reason its potential was downgraded from "strong" to "moderate".
Risc also stated that the Mondarra and Tubridgi fields were technically “very strong” storage candidates, however their overall ranking was downgraded to just "strong" due to existing natural gas storage projects in place at those fields impacting their short-term availability.
Risc noted that small hydrogen developments being proposed near the Perth basin and on WA’s west coast could potentially be suited to using depleted oil and gas fields for transitory hydrogen storage, with those projects only having estimated storage requirements of 5 Bcf to 50 Bcf.
However, it also highlighted the fact that the state’s two largest planned green hydrogen developments, the 50 gigawatt Western Green Energy Hub and the 26GW Asian Renewable Energy Hub, are situated more than 1000 kilometres away from suitable depleted fields.
As a result, Risc recommends alternative storage methods are pursued for these developments, in particular surface storage options. Subsurface salt is also an option, although suitable deposits may still be some distance away from the large green energy hubs, according to Risc.
World first, but with risks
If Western Australia was to pursue utilising depleted fields for hydrogen storage, it could potentially be a world first, with the report noting that subsurface storage of hydrogen in high concentrations is currently limited to a handful of salt caverns in the US and Europe.
However, it adds that storing hydrogen in porous media, such as depleted oil and gas fields or aquifers, poses several challenges and “remains largely unproven”, with the physical behaviors and properties of hydrogen different to those of natural gas.
Risc noted that hydrogen is more chemically reactive, which may affect the reservoir lithology, flow behaviour and seal capacity.
It also highlighted the fact that hydrogen acts as an energy source for subsurface microbial processes which can turn the hydrogen into hydrogen sulphide or react with carbon dioxide to form methane, a highly potent greenhouse gas.
Risc’s report also noted that hydrogen could potentially react with the reservoir formation and not be recoverable, however, added analysis carried out so far indicated this was a low risk.
There is also the risk of hydrogen mixing with any gas remaining in the reservoir, with the re-produced gas then becoming a mixture of hydrocarbon gas and hydrogen, while hydrogen will also dissolve in oil or formation water remaining in a reservoir and may not be recoverable.
With this in mind, Risc stated greater hydrogen losses were likely in depleted oilfields than depleted gas fields due to the solubility of hydrogen in the oil and hydrogen forming unrecoverable residual gas in oilfields.
The study was funded through the state government's WA Recovery Plan, which included A$1 million (US$719,735) for identifying locations suitable for hydrogen storage
The results of the report will inform Stage 2 of the study, which will involve 3D modelling of a small section of the candidate fields identified in the first stage.
"The WA Government has committed A$160 million to making sure Western Australia reaches it potential and becomes a global supplier of renewable hydrogen,” Western Australia’s Hydrogen Industry Minister, Allanah MacTiernan, said on Wednesday.
"Our commitment includes funding a range of studies that will inform the development of Western Australia's hydrogen industry. As we start producing more and more hydrogen, we need to know how we are going to safely move and store it around the state.”
The Western Australian government has set the ambitious target of developing 100 gigawatts of renewable energy by the end of the decade for green hydrogen production, with a goal for that figure to double by 2040.