By Sherrie Wilson

Could rocks hold the key to a healthier planet? Image: Pacific Northwest National Laboratory.

Our scientists in Western Australia are busy developing technology that could significantly reduce emissions of greenhouse gases. One of the exciting technologies being explored is carbon capture and storage (CCS).

CCS involves capturing carbon dioxide (CO₂) that would otherwise be released into the atmosphere, compressing it, piping it to a suitable site, and injecting it into deep geological formations where it can be stored safely for millions of years.

They are currently looking at core samples taken from the south west of Western Australia, to determine whether the rock below can be used for the secure storage of CO_2. The rock needs three features to be suitable:

1. Sufficient pore spaces in which CO₂ can be contained (porosity)
2. Pathways connecting the pore spaces for the CO₂ to move through (permeability)
3. A solid, sealing layer of rock on top of the porous, permeable layer, to stop the CO₂ moving outside the target area (seal).

Scientists have offered a delicious example of why these geological features are important.

Choca-block

The humble Tim Tam is a lot like a reservoir rock – only tastier! Image: Flickr.

Let’s consider a Tim Tam and an Aero bar as two possible types of reservoir rock and milk as our CO₂. Both chocolate bars have plenty of porous space in them, yet if you bite an end off each and try to use them as a straw to draw milk through, the permeability of the Tim Tam will allow the milk to be pulled through the porous spaces into your mouth, but the Aero bar won’t.

The Aero bar, although seriously delicious, has no chance of holding your milk. Image: Trypophobia.com

This is because the Aero bar, although porous, does not have any channels connecting the spaces and therefore the milk cannot move through the chocolate. The principle is the same for the reservoir rock needed to store CO₂. The CO₂ needs to be able to move through the rock and fill all the porous spaces.

Hard-core pore

To help visualise the spaces inside the rock where CO₂ (or oil, natural gas or formation waters) will move through and be stored, we’ve teamed up with Lithicon Australia to bring the core samples to life. Lithicon Australia use a type of CT scanner and leading-edge analysis to produce 3D photographs of the core samples. From those images they are able to print physical 3D models.

Solid as a rock: this model demonstrates the solid grains that make up the reservoir rock.

These models represent a seriously tiny piece of the original core sample (0.8 of a millimetre in diameter). They also help us recognise that the spaces where CO₂ (and oil and gas) sit within rock are not the big caverns that we often envisage, but a series of very small interconnected spaces.

Look at those pores! This model represents the pore spaces and channels that connect them inside the rock.

With ongoing advancement and increasing accessibility of printing technology, it’s likely that 3D models like these will be utilised more often in future projects, which will provide us with exciting new ways to visualise and analyse geological formations.

As you can see from the core samples (which are equivalent to the rocks from Western Australia) the rock is likely to be sufficiently porous and permeable. Scientists are excited by these initial results, but suggest the core samples are just the first step in a long line of processes that must be undertaken for CCS to begin.

But our use of 3D printing is not limited to the geological sector. The Lab 22 3D printing facility was established in October 2012 and is already being used to manufacture a range of prototype products including biomedical implants, chemical processing and aerospace parts.

Recently we have also used 3D printing to build a new generation of hi-tech fish tags made of titanium, with the aim of tracking big fish such as marlin, tuna, swordfish, trevally and sharks for longer periods.