Interview with Brian Horsfield about shale gas and hydraulic fracturing

Brian HorsfieldBrian Horsfield

April 2013

As a major research centre, the GFZ German Research Centre for Geosciences makes important contributions to a sustainable national and global energy supply, e.g. to use of deep geothermal energy, to use of the underground for different storage purposes and to the identification of reservoirs with conventional and unconventional energy sources. Research into hydrocarbons plays a significant role in this, because it is clear: The transition to energy supply from mainly renewable sources, as planned and initiated in the German “Energiewende”, will take decades. Fossil energy raw materials will remain important in the German, European and worldwide energy mix for many decades to come, and not only due to the worldwide continued rising energy demand. Natural gas plays an increasingly central role in this, because it is the cleanest fossil energy source for combustion. Energy research at the GFZ also deals with natural gas in shales, so-called shale gas, and examines issues that are also important for the shale gas production method of fracking (or its proper name: hydraulic fracturing).

SHIP: What happens in geological formations when large quantities of water, sand and chemicals are injected into them?

Prof. Horsfield: What happens is precisely what is intended: the pressure of the water on the rock causes a network of fine fractures to form in the rock, which improves the flow of gas or oil into the well. In order for fractures to form in the rock, the precisely metered pressure of the water must exceed a critical value, which depends on the prevailing stresses in the deep and the tensile strength of the rock. The propagation of the fractures in the rock can be optimised in advance by precise pre-fracturing geological investigations and computer models. The chemicals support the whole fracturing process, e.g. friction reducers enable the water to be more easily pumped into the deep, and biocides prevent bacterial growth in the fine fractures. The sand grains settle in the induced fractures and prevent them from closing again when the fracturing fluid is pumped back out of the well after the hydraulic fracturing.
SHIP: Is the process examined or tested at the GFZ?

Prof. Horsfield: At the GFZ, for example, the initiation and propagation of the fracture formation in shale under all kinds of different conditions are precisely examined in the laboratory. The results will be used to enable hydraulic fracturing to be carried out in a more targeted way than possible to date. Concepts for improved microseismic monitoring and the necessary tools are being developed at the GFZ, in order to track the fracture formation in rock during hydraulic fracturing even more precisely than before.

The industry-funded European scale project GASH has brought new insights into the shale gas potential of Germany and its neighbours, including novel concepts for secondary porosity formation and the identification of a new source of gas at both very high (>200°C) and very low (biogenic) geological temperatures. The BMBF-funded GeoEn project yielded new insights into the rock mechanical behaviour and nanoscale architecture of rock forming minerals and the chemistry of entrained fluids, thereby improving estimates of both in-place resource potential and the producibility of hydrocarbons.

In parallel to these activities we have devised and implemented a high profile Shale Gas Information Platform whose task is to present the general public and political sphere with facts, thereby pushing science to the fore, ahead of political rhetoric and misinformation from activists on both sides of the shale gas debate.

What is the GFZ's attitude to hydraulic fracturing?

Prof. Horsfield: If the best technologies currently available and strict environmental standards are applied, the production of natural gas from shale using hydraulic fracturing appears to be possible in an environmentally compatible way. However, it is necessary to obtain more in-depth knowledge of several issues. The outstanding questions cannot only be addressed in the laboratory or with computer models, but must also be investigated in the field at research and/or exploration wells (not: production wells). It goes without saying, but should be clearly reiterated here once again: the research is carried out openly and unbiased and the results are published.

SHIP: In fracking, chemicals and high pressure are used to break up rock so that gas can escape. Does this endanger the groundwater?

Prof. Horsfield: Experience with the technology shows that with more than 100,000 shale gas wells worldwide and more than two million hydraulic fracturing operations (not only for shale gas production), there is only one documented case of groundwater contamination with fracturing fluids, which entered groundwater from deeper geological formations. That's very few.

Other sources of danger for the groundwater are improper surface handling of substances, leakages from wells or improper treatment or disposal of wastewater. It is known that groundwater has been contaminated by these pathways. But these risks are rather not related with the hydraulic fracturing itself, i.e. the fracture formation in the rock during shale gas production, they are related to overall oil and natural gas production.

Analysis of thousands of fracture operations for shale gas production shows that 99 % of the fractures are shorter than 350 m. In very exceptional cases they may reach a length of up to almost 600 metres. Therefore it is currently believed that a distance of 1000 metres between the portion of the well to be fractured and freshwater bearing rocks is sufficient to ensure safety of the freshwater.

How high the risk of groundwater contamination is depends on the respective geological conditions, which differ in every case. This can and must be clarified through regional and local geological pre-investigations.

SHIP: Is there a risk of triggering earthquakes?

Prof. Horsfield: The risk of triggering earthquakes large enough to be felt by humans as a result of hydraulic fracturing is classified as being low in scientific studies. Thorough geological pre-investigations, suitable management of the injection pressure and precise seismic monitoring during hydraulic fracturing can further reduce the risk. The reinjection of fracking fluids into geological formations has emerged as a trigger of perceptible earthquakes, rather than the fracking itself. The rate of pumping clearly must be managed properly when disposing of fluids in this way.

SHIP: Fracking is also criticised because it has a poor climate balance; a comparatively large amount of energy is used for the production. Is this really a shortcoming of the method?

Prof. Horsfield: We at GFZ have not carried out any research into this ourselves, but there are now very many scientific studies that show that greenhouse gas emissions during the production of shale gas are only slightly higher than those during the production of natural gas from conventional deposits. The crucial point lies elsewhere: the increasing use of natural gas overall, from conventional and unconventional deposits. 

The International Energy Agency IEA determined in autumn last year that the greater use of natural gas alone is not sufficient to achieve the internationally agreed emission reduction targets. This would require a far more fundamental change in global energy use. This includes, above all, major efforts to improve energy efficiency, development of renewable energy and broad use of new technologies to reduce greenhouse gas emissions, possibly including "carbon capture and storage" (CCS). However, as long as fossil energy sources are still required, natural gas is the first choice en route to a sustainable energy supply.

SHIP: The USA is now relying on fracking to become autonomous in energy policy terms. Is there large potential for the process in other regions of the world?

Prof. Horsfield: Wherever large quantities of shale gas are thought to exist there is potential for large scale domestic production and reduced dependence on imports. However, whether this will actually come true ultimately not only depends on confirmation of the large deposits, but also on very many other factors tied to economics and politics.

SHIP: Are there not sufficient gas deposits worldwide, which can be tapped in conventional ways?

Prof. Horsfield:
There are very large conventional natural gas deposits on Earth. However, approx. 40% of these deposits lie either in West Siberia or in the region of the Persian Gulf, and are therefore in regions which geopolitically speaking are relatively unstable. The same applies to part of the North African deposits; you only have to think of the terrorist attack on a gas production facility in Algeria in January. The search for other (domestic) natural gas deposits can definitely be justified.  And current forecasts of the IEA assume that the demand for natural gas worldwide will increase sharply. If this proves to be true, shale gas will probably have an increasingly large role to play.

SHIP: Thank you!

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The Debate

Interview with Prof. Horsfield