It has nothing new – in the United Kingdom they already used it in the 50s, before man stepped on the Moon and when the world was spinning with the Cold War – but hydraulic fracturing, popularly known as fracking, continues to generate an intense debate between supporters and detractors. He does it today, just like he did yesterday and, surely, he will do it tomorrow.
The former, like the Independent Petroleum Association of America (IPAA), defend their ability to “Safely unlocking abundant natural resources”, the wealth it generates and even its beneficial effect on the environment, by “reducing the emission of greenhouse gases”. At the opposite pole, critical voices They warn of contamination and, above all, the risk of earthquakes.
The debate on its impact, served
The technique is not difficult to understand. Roughly, it is used to extract fossil fuels trapped underground, at considerable depths. The companies drill the rock layers and thanks to the injection of water with chemical additives and sand at high pressures they manage to fracture it and release the hydrocarbons. Beyond the detractors who warn of pollution or its impact on health, one of its biggest “buts” is the risk of generating earthquakes.
A study published six years ago in the Bulletin of the Seismological Society of America (BSSA) concluded for example that fracking had been the cause of the chain of earthquakes that shook Poland Township, in Ohio, USA in March 2014. Five of the earthquakes that were then analyzed, with magnitudes between 2.1 and 3 on the Richter scale, they had been precisely registered one kilometer from Hilcorp Energy’s extraction area.
“The rocks that supported the weight of the ones they had on top of them no longer do so and the whole terrain is re-set, reorganized and that generates earthquakes that may be greater or less, but are inevitable,” explained physics professor Antonio Ruiz de Elvira in 2015, in a blog of The world, after detailing the procedure followed during fracking.
Studies on its footprint on the environment
A German-Canadian research team has just deepened our knowledge of the relationship between earthquakes and hydraulic fracturing. In an article published in Nature Communications, experts from the Geological Survey of Canada, Ruhr-Universität Bochum (RUB) and McGill University detail how they have identified a new type of earthquake linked to fracking. The funny thing is its peculiarities. How Europa Press collects, tends to be slower and longer than conventional ones with a comparable magnitude.
For their study, the team recorded around 350 earthquakes in a network of eight seismic stations surrounding an injection well, all separated by a few kilometers and in western Canada. When studying the data, the experts found that about 10% of earthquakes they had unique characteristics that suggest that they broke more slowly, a peculiarity similar to that seen in volcanic areas.
Researchers to date –collect RUB in a statement– They had detected two processes linked to earthquakes related to hydraulic re-structuring. In one, the fluid pumped into the rock creates a pressure surge that removes existing faults and causes an earthquake. In the other, the increase in pressure of the fluid by injection into the subsoil causes changes in elastic stress in the surrounding rocks that can lead in turn to landslides and earthquakes.
The slow earthquakes that they have just recorded would be the result – for the German-Canadian team of researchers – in an intermediate way between the conventional earthquake and asismic landslide, which indirectly shows that this type of phenomenon can occur near wells. Experts have called it hybrid frequency wave earthquakes (EHW). If the shaking of a conventional one of magnitude 1.5 had calmed down in about seven seconds In the study data set, that of an EHW of equal magnitude would shake more than 10.
“We assumed that induced earthquakes behave like most other earthquakes and have roughly the same rupture velocity of two to three kilometers per second,” says RUB’s Rebecca Harrington. The study shows that this is not always the case.
Research applications are far from remaining in the theoretical sphere. “If we understand at what point the subsoil reacts to the hydraulic fracturing process with movement that does not result in an earthquake and consequently does not cause damage to the surface, ideally we could use that information to adjust the injection procedure”, zanja Harrington.