The primary research focus of NGL is to provide certainty to government and industry regarding the viability and safety of large-scale geological storage of CO₂.
The NGL infrastructure will include comprehensive facilities to support the collective research partner capabilities, which can be applied to the complete value chain.
The first stage of the carbon storage process is about locating a suitable site for storage. Some of the factors in determining a suitable site include proximity to an emission source and the geology of the subsurface.
This stage of the research process typically consists of screening a number of potential storage sites to identify one or several possibilities that have the best characteristics for storing carbon. This is mainly done through examining existing data, geological maps and cross-sections.
Once the best potential sites have been identified by the screening process, more detailed scientific studies need to be performed to make sure there are no obvious geological barriers to proceeding. Important aspects that must be determined are how much CO₂can be stored (capacity), how secure the storage formation is (containment), and at what rate the CO₂can be injected into the reservoir (injectivity).
To answer these questions, researchers perform measurements and experiments on the rocks and fluids, and build sophisticated computer models of the storage site. The data and models are used to calculate the likely volume of CO₂that can be stored and predict how it will be contained by baffles, seals or barriers. At the end of this stage of research, a single site can be confidently identified as suitable and then the actual design of the storage site begins.
Research at this stage is focused on determining the number of injection and monitoring wells required, where these wells need to be drilled, and whether this design can support the volume and proposed rate of CO₂injection. Additional data is collected during this phase including drilling of wells, rock experiments and updating of geological models.
Much of our understanding around designing sites has come from small pilot-scale tests that inject in the order of 100,000 tonnes of CO₂such as the Otway site in Victoria, Australia.
A parallel activity to the work focussed below ground, is the research challenge about how to get captured CO₂to the storage site. This depends on how far away the site is to from the emission source and whether there is existing infrastructure such as roads or railways. In commercial operations CO₂ is typically transported by pipeline however trucks may be used during pilot-scale evaluations.
One of the key ways in which researchers are investigating how to make CCS commercially-viable is by finding more efficient and economical ways of processing and transporting CO₂. This involves understanding how impurities impact the behaviour of CO₂during transport and storage. The potential impacts of different impurities can be tested in NGL’s purpose-built gas processing laboratory at The University of Western Australia.
Monitoring is performed prior, during and post CO₂injection, and is a critical component of the carbon storage process as it demonstrates that the injected CO₂is safely and securely stored for the long-term.
Computer simulations of how the CO₂will behave during and after injection developed during the site evaluation and design phases can be compared with actual observations made by monitoring equipment installed in wells or by surface methods such as seismic imaging. These observations will be used to update reservoir models and demonstrate to regulators and community how the site is performing.
Assurance monitoring can involve testing the soil, groundwater and atmosphere surrounding the storage site to confirm that the stored CO₂is not migrating to these areas.
Eventually carbon storage sites will be closed and decommissioned. The decommissioning may take several years or more and monitoring will continue through this activity until the site is deemed closed. At this time the site enters a post-closure stage and can be formally handed over to specific agencies who take on any related liability.
Post-closure monitoring will continue for between 5 to 10 years, or even longer, depending on the regulatory framework in place at the location of the storage site. This ongoing monitoring is performed to further ensure the CO₂will be safely trapped but will be less frequent than when the site was operational.
The long-term fate of the stored CO₂is such that some will gradually dissolve in saline water in the rock pores and some will react with rocks to form new minerals thereby locking it within the subsurface permanently.