Beetaloo Sub-basin Kyalla Shale
[The CSIRO logo animates through shots of various landscapes before finishing on the logo.]
A cross-section of a remote, semi-arid Australian landscape. A gas pipe structure appears, extending vertically into the ground. Layers of earth are coloured in browns, greys, and blues to represent different rock strata.
After gas wells reached the end of their serviceable life, industry operators must carefully seal and decommission them to prevent future leaks.
[A well casing animation shows the steel and cement layers that seal off the wellbore from surrounding rock. A crack appears in the pipes showing a potential leak. The sky animates from day to night several times to show the passing of time.]
But what if a new pathway forms over time through cracks, fractures or along the wellbore itself, allowing gas to escape? How can we ensure these wells maintain their integrity and resist leaks for many decades after decommissioning?
[3 scientists in lab coats are in deep discussion.]
That’s exactly the question we’re tackling head on here at CSIRO.
[A map of Australia, we push in on the Northern Territory and the Beetaloo Sub-basin area appears. The cities of Katherine and Darwin are also shown.]
Our work focuses on the Beetaloo Sub Basin, south east of Katherine in the Northern Territory.
[A female scientist, Dr Elaheh Arjomand addresses the camera directly.]
Strict regulations are in place in the Northern Territory to ensure the proper installation of cement plugs, and to safely decommission the petroleum wells.
[A well casing animation shows the steel and cement layers that seal off the wellbore from surrounding rock. A crack appears in the pipes showing a potential leak.]
However, over the time the bond between the cement casing and surrounding shale rock may deteriorate, potentially compromising the integrity of wells and increasing the risk of contamination.
[Dr Elaheh uses two different machines for tests. Then addresses the camera again.]
That’s why we are investigating whether the slow movement of shale, which is also called creep, can naturally close the gaps and enhance the sealing capacity of rock over time.
[An animated cutaway view shows a cross-section of the earth. Layers of earth are coloured in browns, greys, and blues to represent water and different rock strata. A measuring line drops down showing the depth of the Kyalla Shale barrier from 1000m deep and extending for 500m. Text appears identifying the composition of the shale layer as clay and quartz. The pipeline then animates in, with arrows showing the natural creep and pressure imposed on the pipe.]
One of the formations is being studied for its potential as a natural barrier is Kyalla Shale formation in the Beetaloo Sub Basin.
Kyalla Shale is a thick rock layer composed of fine grained materials such as clay and quartz. Our research shows that chemical treatments can accelerate the natural creep of Kyalla Shale, enhancing its sealing capacity and contributing to long term well integrity during decommissioning.
[Dr Elaheh addresses the camera again. Then b-roll shots of her interacting with different machines in her laboratory.]
When Kyalla Shale is exposed to certain chemical solutions, it softens, and it deforms more easily. These solutions basically alter the way that clay and fluid interact, which leads to breaking down the minerals and changing the rock’s microscopic structure. Some of these chemicals also reduce the friction between shale layers, allowing them to slide and settle more easily. As a result, Kyalla Shale creeps more, especially when exposed to water-based solutions, reducing its strength but increasing its flexibility.
[The animation resumes, showing a predictive model of gas flow underground. It starts with a cracked pipe and reverting to an uncracked pipe as the shale creeps in.]
The camera pulls back to show the cross-section of the earth. The gas pipe extends vertically into the ground. Layers of earth are coloured in browns and greys.
This allows the rock to fill the gaps and prevent the movement of fluids and form an additional barrier during decommissioning.
What we are looking for is a robust natural barrier that seals the gap around the wellbore, to complement those traditional and essential methods of sealing during decommissioning.
[Closing visuals: A CSIRO-logo and the following text – “GISERA – Gas Industry Social and Environmental Research Alliance. gisera.csiro.au.”]
Want to know more? Visit our website.
Kyall Shale in the Beetaloo Sub-basin, NT – GISERA video