The best chart I’ve seen for some time:
What it describes is quite complex, so bear with me. A small Australian geothermal company, Geodynamics, has been drilling deep experimental wells at a desert site called Innamincka. These are EGS – “hot dry rocks” wells, not hydrothermal; the hot water reservoir isn’t there waiting for you, it must be engineered. After you finish drilling your well into a very large lump of hot granite, you inject water down it at high pressure – 2,000 psi or so, a fifth of that used in gas fracking. The water expands existing tiny cracks – microfractures – and with luck creates a web of channels as far as a second, extraction well. Pump up that now superheated hot water, expand to steam, and run it through a turbine. That’s an EGS geothermal plant: 24-hour, unobtrusive, zero-carbon, safe, long-lived. But still experimental, and financially nail-biting. Getting the geology right is critical and very difficult.
The crack-making creates microshocks. These can be detected with sensitive equipment (and, rarely, without them). The chart is a record of all the microshocks detected during a test period of three weeks from a well called Habanero-4. It captures:
- the relative magnitudes of the microshocks (by the size of the spheres)
- their spatial location in two-and-a half dimensions (the depth is roughly indicated by the occlusion of the deeper bubbles by the shallower)
- the development of the reservoir stimulation over time, using colours.
The grey dots aren’t explained, I think they must be the pattern from a previous test using Habanero-1 as the injector well. Here, Fig. 2.
You can see immediately that the fracture zone spread with time some distance north from the well – perhaps a surprise to the drillers, as the previous wells are south of Habanero-4.
The chart, like a cloud chamber experiment, lets our visual brains synthesize an immense amount of information. The software is presumably 3D, so you could view the seismic cloud from the side, or play a speeded-up movie.
A great deal is riding on a very few active EGS projects. Hydrothermal resources – underground hot water – are easier to tap but tectonically localised. (There are plenty in the Rift Valley, Central America, Iceland, Indonesia, and the Philippines). Deep lumps of hot granite are more or less everywhere, enough to give us all the backup we could ever need for cheaper wind and solar energy. The technology gets marginal support: the US DoE funds just two small projects into cheaper hard-rock drilling, spallation with Potter Drilling (there’s also a Swiss team at Einstein’s ETH in Zurich), and laser assistance with Foro Energy. Peanuts.
The coloured bubble cloud chart could be used to show spatial trends for a variety of discrete but causally linked events: infections, crimes, bankruptcies, foreclosures, innovations.
Here´s an unrelated use of bubbles to make a point:
It´s clever agitprop, but of course you don´t really learn anything.