In this country, fracking is usually understood to mean gas fracking.

What is the difference between the technology used to extract gas and geothermal energy?

The difference is that when gas is extracted, what is known as hydraulic fracturing (“fracking”) is usually used: a liquid containing various chemicals and proppants is pumped underground to break up rock and keep newly created cracks open.

When it comes to geothermal energy, i.e. the extraction of heat from the earth, one usually speaks of hydraulic stimulation.

Existing cracks in the subsoil are widened by overpressure.

The latter is done with pure water without additives.

Geothermal energy - i.e. geothermal energy - can also be tapped into conventionally.

Why do you work with the fracking method at all?

As with oil and gas, where conventional deposits have been used in Germany up to now, geothermal energy can either be extracted conventionally or through hydraulic stimulation.

There are still many untapped hot water deposits.

They can be opened up first.

In the meantime, we are researching the stimulation of geothermal deposits in order to be ready in ten or twenty years to use geothermal energy in places where it is not yet possible today.

What distinguishes the unconventional from the conventional deposits?

The rock in conventional deposits is very porous and permeable.

It is filled with plenty of hot water and the hot water can easily flow through and be tapped there.

With unconventional geothermal energy - the so-called petrothermal geothermal energy - you have hot rock through which water cannot flow.

Here you need cracks through which cold water can flow, in order to then heat up like in a heat exchanger on the rock and finally be available for the heat supply.

In the field of geothermal energy, the fracking method is still in the research stage.

where do you stand

The technology has now been tested in Germany at around a dozen locations in all relevant geothermal regions: in the North German basin, in the Upper Rhine Graben, in the southern German Molasse Basin.

The most promising projects worldwide are currently being carried out in the USA and – shortly – in Switzerland.

If the projects are successful, there is a good chance that petrothermal geothermal wells will also be tested further in Germany and will be used commercially in the foreseeable future.

In the current energy crisis, politicians are repeatedly calling for the ban on gas fracking to be lifted.

What good would that do?

Nothing in the short term.

In the next one to two years will mainly help to save energy and diversify the import of raw materials.

In the long term, we need a way to ensure the supply of heat.

Geothermal energy offers a perspective for this.

The potential of normal, conventional geothermal energy alone without stimulation is so great that today's technology could cover a quarter of Germany's heat requirements if the extraction sites were expanded.

In fact, so far only about one percent of the German heat supply is covered by deep geothermal energy.

What dangers do you see in connection with the fracking method?

In the case of fracking in general, groundwater and surface water contamination and induced seismicity, i.e. the triggering of small earthquakes, are mentioned above all.

Also the methane emissions, especially with shale gas.

However, no chemicals are used in geothermal energy, which is why there is no risk to groundwater or surface water.

In the case of shale gas, it depends on which fluid you use and how well the well and the drilling site are shielded from the environment.

Since deep drilling is a standard technology that has been tried and tested for decades, the risk of leakage is relatively small.