In the Otway Project Stage 2, CO2CRC is investigating the ways carbon dioxide (CO2) can be permanently stored in saline formations - deep porous rocks containing formation water. This is a very common type of rock formation with the potential to store many years' worth of CO2 emissions. In Stage 1, the carbon dioxide was stored in a depleted gas reservoir.
The first experiment for Stage 2 is designed to test an aspect of underground CO2 storage called residual gas trapping. In residual gas trapping the CO2 is stored in the porous rock in tiny bubbles, disconnected from each other so they cannot flow out. It is an important aspect of CO2 storage, because the CO2 can't move through the reservoir and so remains fixed underground.
To test how much CO2 is stored in this way the research team will undertake a series of extractions from and injections into the Paaratte Formation at depths of around 1400m. Formation water will be extracted before a relatively small amount of pure CO2, around 180 tons, will be injected. Formation water with dissolved CO2 is then re-injected and the amount of CO2 trapped is measured using pressure sensors, tracer concentrations, temperature and borehole measurements. The extracted water will be stored in large water tanks during operations and re-injected at the end of the experiment.
Planning and engineering of Stage 2 works began with the drilling of a new well, CRC-2. Other facilities include the water tanks and CO2 tanks. Field construction activities should be complete by early 2011, with the first trials in the first half of the year. The experiment itself will take around two months.
Timeline of the first experiment for Stage 2
During Stage 1, CO2CRC researchers will extracted carbon dioxide (CO2) rich gas from a gas well (Buttress).The gases were compressed and piped to a deeper depleted natural-gas field (Naylor). Here, the CO2 was injected through the new CRC-1 well and safely stored two kilometres below the Earth's surface.
The 65,000 tonnes of carbon dioxide rich gas that CO2CRC has injected and stored is significantly less than the amount of natural gas originally held in the Naylor field, increasing confidence that the site will be able to safely store the gas without affecting the region's geology.
What happened in Stage 1?
Buttress -1 Site - Production
CO2-rich gas (80% CO2; 20% methane) is extracted from an existing well, processed and compressed. CO2 is transported via a new, underground, 2.25 km long, stainless steel pipeline.
CRC-1 Site - Injection
Over 65,000 tonnes of the CO2-rich gas stream at supercritical state was injected into a depleted gas reservoir - the Waarre C Formation - at a depth of 2050 metres. CO2 migrated up-dip within the 31m thick reservoir sandstone capped by the impervious thick seal rock (the Belfast Mudstone).
Naylor-1 Site - Monitoring
CO2 was detected months after the start of injection at the Naylor-1 site. Monitoring is also being carried out in the atmospheric, surface and near surface domains.