N°28I quarterlyI JaNuary 2013 Insights | 31 Environment Following the recent French ban on shale gas extraction by hydraulic fracturing, CEREGE1researcher Bruno Goffé assesses progress on alternatives. Shale Gas Extraction: alternativesneeded By CharlINe ZeItouN q these sediment Btion of shale gas and oil by uS). oklahoma,layers, 300 millionyears old, containshale gas (-ased on current knowledge,there is no certainty that extrac hydraulic fracturingposes no signifi- cant threat to health and the environ- ment,” said an official statement by France’s President François Hollande in September. Since this technique, now banned by French authorities, is the only known extraction method, recent appli- cations for permits in France have all been rejected. FracturIng rock “Shale gas is trapped in low porosity rocks located at depths of 2000 to 3000 meters, and it doesn’t rise to the surface on its I own, unlike commonly exploited natural © DoPC gas,” explains geologist Bruno Goffé. To extract it, the most obvious solution is to fracture the rock in points out. The issue of ground water more. Other techniques could potentially order to let it seep through. This is done by drilling into the contamination by shale gas, chemicals be used that have not yet been tested. One source rock and setting off small explosions to pierce the wall mixed with water, or subsequently-added of these is the thermal method, which of the tube inserted into the wellbore. Hundreds of cubic meters solvents, has also been raised. “This has consists in heating the rock so as to force of water mixed with sand and gelling agents are then injected in fact happened, but it isn’t due to the the water up to the surface and bring the into the wellbore at high pressure to create and propagate cracks extraction process in itself,” he adds. “It gas with it. “Lastly, it is essential to im- in the rock, and ensure that they remain open. “By decompres- stems from bad practice, especially in prove our knowledge of the underground sion, the gas is then brought to the surface, together with the countries where public standards are not by carrying out basic research. This is injected water and that contained in the rock,” Goffé explains. as rigorous as in France, leading to poorly- where public research comes in. It would sealed wellbores or the improper use of enable us to identify and anticipate prob- causesForconcern hazardous products that are sometimes lems, adapt our legislation, and undertake “In Switzerland, France, and the UK, this technique has been directly discharged into watercourses.” monitoring and observation in the long known to trigger earthquakes, albeit of little magnitude (2-3 on run,” says Goffé. These studies would also the Richter scale). And these risks can be controlled,” Goffé alternatIvetechnIques make it possible to get a clearer picture of “First of all, the chemicals used for hy- France’s underground resources, whether draulic fracturing can be replaced by renewable or not. environmentally-friendly products, such 01.Centre européen de recherche et d’enseignement de Bruno goFFÉ as gelling agents used in food processing,” géosciences de l’environnement (CNRS / Aix-Marseille Université / IRD / Collège de France). a specialist in geological resources, he is a Goffé explains. “Using microporous scientific representative at CNrS’s National minerals called zeolites as a model, it Institute forearth Sciences andastronomy should be possible to design novel blends (INSu), and a senior researcher at theeuropean CoNtaCt INformatIoN: Center forresearch andteaching in which, once pumped in, crystallize as a CereGe,aix-en-Provence. environmental Geosciences (CereGe). porous material that lets the gas through, Brunogoffégoffe@cerege.fr>DR while keeping pollutants in.” But there’s
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