I don't have a fracking clue!
Fracking, the process of breaking trapped resources like natural gas and oil from shale. It has the potential to release a huge amount of cleaner energy, but it’s also given rise to increasing worries that the process can have sweeping environmental impacts. There is a lot of contradicting information on fracking - so I decided to try and give a two sided approach - and we can learn together.
Why here in the Midlands - hundreds of kilometres away from the Karoo where fracking is going to be occuring in South Africa? Well - it is here in the ecca shale beds that the gas is apparently trapped. However in the Karoo where the fracking will occur - these shale beds are 2.5-5 km under the overlaying earth. So if you want to see the shale beds - come here to KZN! Although the shales that contain the gas are from the Whitehill formation - these mudstones are similar in composition to what you see here in the Midlands formation of the Ecca Shales. Please note that this is not meant to be PRO or ANTI fracking – merely allowing you to come to your own conclusion – and let’s look at the geology only.
| In order to claim this Earthcache, you will need to answer the following tasks and send a mail to me (via my Geocaching profile - load any photos you want to in your log) |
- Look closely at the shale exposed here and describe it - particularly in terms of the particle size, any layering you may see and any organic content you may observe within the rocks). Do you see any evidence of cracks for gas or water to move through in these rocks (look very closely - I am not considering the larger blocky cracks of erosion/weathering - but very fine cracks within the rock structure).
- Do you think fracking and shale gas extraction is good for South Africa? Think in terms of:
- Job creation
- Environmental risks
- Economic development
- Energy source/security
- Any personal feelings/experiences
- Any other aspects you'd like to raise
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Fracking has become an EXTREMELY emotional subject with many high profile activists protesting against the continued exploration. However, this cache is not to make a statement one way or the other - but merely to give you information for you to be a little more educated. I apologise up front for the text heavy description - but this is to give you the tools to make your own opinions. The questions above can be done with far less reading :)
What is Fracking?
Fracking, a.k.a, hydraulic fracturing, or if you’re a total square, hydro-fracking, you know, like that’s the kid who thinks he’s cool, but he’s really kind of out of the loop, so he’s calling it hydro-fracking still. But really you just call it fracking. It’s a technique that’s used to get to incredibly deep deposits of fossil fuels.
How do you frack?
It’s really pretty simple. It starts off like a conventional well, so you drill deep down a few kilometres to the shale layers. Okay, so you’ve got your regular well at what’s called the kick-off point. It’s then gonna take a left or a right, and become a horizontal line, and that can span anywhere from about 300m to almost 2 kilometres. Then they stick something called a well bore – it’s just basically a steel casing, like a big steel pipe - into the well to minimise leaks. And then the actual fracking part takes place.
So you’ve got the well bore completely cemented and in place, and it’s going down about a few kilometers from the kick-off point to shale deposit. And they send down a little tool that has an explosive device incorporated into it. And it blows little holes – a bunch of little holes through the well bore, through the cement, and into the surrounding rock - at the shale layer. Each one will be two or three inches of – like a little mini-shaft. So you’ve got the horizontal well bore, and the cracks are then vertical – perpendicular to it.
Then they plug that up, and then move on and do it again, all the way down the line of this horizontal well – and they blow them up and blow them up and blow them up, and you’ve got all these perforations into the rock. And then all of a sudden now, you are ready to frack.
At this point, they pump a mixture of water and other additives called fracking liquid. This can include particles (including sand or nut shells - to open the cracks), detergents, diesel, polymers, other proprietary chemicals.
Once you start pumping this water down at an incredibly pressurized state, like 9000 PSI (62000 kPa)– by contrast, you know, an air compressor for your air tools in your garage is around 90 PSI (620 kPa) and a tyre is around 45 PSI (300 kPa). 9000 PSI is just an incredibly pressurized state! The water rushes down, and when it hits those perforated areas, it cracks the shale even further. And eventually, the particulate matter, the sand or whatever else that they added, goes into those cracks, and then keeps it open – it keeps the cracks open after the water recedes. But it’s enough because what you’re getting gas out of rock and it just needs a leak. Then once you stop pumping the water, the pressure pushes it back up, and eventually, the use of water is finished. The water that you sent down there comes back up, and then it’s followed by gas.
And that water is waste water that is one of the things at the center point of the controversy.So that’s fracking in a nutshell. It’s complex engineering-wise, but it’s actually kind of simple as a concept, and then the whole thing lasts from preparation – I guess the first drilling to the end of fracking, about four months, but then this well that’s just been developed can produce natural gas for decades, possibly years or decades.
The above graphic is from the US Marcellus shales where fracking is being exploited in the US. These are Devonian aged shales - older than the Ecca shales in southern Africa.
The Ecca Shales
The Ecca Group is a group of sedimentary geological formations found in southern Africa. A component of the Karoo Supergroup, it consists mainly of shales and sandstones, laid down in the sandy shorelines of swamplands during the Permian Period.
The area for the Ecca Group is in the Karoo Basin of South Africa and Lesotho. In the southwestern Karoo Basin, the Ecca Group has a total thickness of approximately 1300 m. There is no single location where the entire vertical section of the Ecca Group is exposed. At Skoorsteenberg in the southwestern basin there is a 900-m exposure of the unit.
The Ecca Group sandstones and shales originated as clastic sediment deposited in a large and shallow inland sea. Swamps and forest vegetation developed at many places and times during its deposition, resulting in widespread coal deposits. Almost all of South Africa's coal resources and one-third of the coal resources in the Southern Hemisphere are in rocks of the Ecca Group.
There is shale gas in the Karoo: mostly methane but also the dry gases ethane, propane, butane and naphtha. Probably a lot, gauging by earlier geological exploration for oil by state exploration company Soekor during the 1960s and early 1970s.
One of these wells near Graaff-Reinet – a borehole drilled in 1968 – had an unstimulated flow rate of 1.84 million cubic feet of gas a day from fractures at a depth of 2 531m.
Shale gas is derived from ancient organic material in the form of algae, spores and pollen deposited in mud in marine or lacustrine (lake) systems. This became buried and lithified – turned into organic-rich shale rock – over hundreds of millions of years.
Oil is produced at a depth of 2km to 4km where the temperature is between 60 and 120ºC, while wet gas – gas with a small amount of condensate in it – is produced at a depth of 4km to 5km and a temperature of between 120 and 150ºC. Dry gas, including methane, is produced only at a depth of between five and six kilometres, where the temperature is in the critical range of 150 to 250ºC.
A deeper burial ends hydrocarbon generation and causes the organic material to turn into graphite.
In the Karoo, shale with the potential to generate dry gas occurs mainly south of latitude 30ºS (Durban lies near this line). Shales with a potential to generate oil occur north of 29ºS, and shales that might generate gas occur in a narrow band between these two and in a long arc through the former.
The billion-dollar question is whether shale gas occurs in the Karoo in commercially viable quantities and, if so, whether it’s possible to extract it at an environmentally acceptable cost.
In South Africa the best methane-producing shales occur in the Ecca Group of rocks from the Permian era, between about 299 and 251 million years ago, named after the Ecca Pass north of Grahamstown.
In the Ecca Group, one band stands out as having a high potential for methane generation: the Whitehill Formation, named after the railway siding between Matjiesfontein and Laingsburg, and to a lesser extent the shales underlying the Whitehill Formation.
What is shale gas?
Shale gas (or the gas that will be taken from the fracking process) is merely natural gas (similar to that obtain offshore at Mossel Bay by PetroSA and in many other parts of the world).
Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other hydrocarbons. Natural gas is an energy source often used for heating, cooking, and electricity generation. It is also used as fuel for vehicles and as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals.
Natural gas is often informally referred to simply as gas, especially when compared to other energy sources such as oil or coal.
Typical fracking site.
Please note that there are many many sites and sources of information. Much is very one sided (depending on who wrote it) – please get varied information to make a decision and be careful of “sensationalist” claims on either side of the argument and check the scientific and credibility of your information. Sources and useful links to get more info:
Cape Argus article - 2011 0 Madness or Miracle
Daily Maverick - Fracking debates in SA
Stuff you should Know podcast - What the Frick is Fracking?
Geological Society of America – Fact vs Fiction of Fracking
What we know and don’t know about fracking
Treasure the Karoo - anti Fracking lobby in SA
Beginners guide to fracking in the Karoo
Truth about fracking - UK gaurdian article
What is fracking website
