Des biocides dans les tuyaux

Photo: Fred R. Conrad

Décidément, j'en apprends à tous les jours sur l'exploitation du gaz naturel et la méthode controversée de la fracturation hydraulique. Les Québécois auraient intérêt à s'instruire, parce que cette industrie parcourt la vallée du Saint-Laurent à la recherche de profits.

À cause de la pollution et la contamination de l'eau générée par la fracturation hydraulique, l'industrie cherche des méthodes ou des produits moins toxiques. Dans les fluides hydrauliques injectés dans le roc pour le fracturer et en extraire le gaz naturel, l'industrie doit utiliser des biocides. Puisque la pression et la friction augmente la température de l'eau injectée, les bactéries et les moisissures (champignons?) se multiplient et encrassent les tuyaux.

Certaines compagnies de forage utilisent les rayons ultra-violets pour tuer les bactéries. D'autres testent des biocides qui agissent pendant seulement quelques heures puis deviennent non toxiques (?). D'autres compagnies injectent l'eau dans un vortex à une vitesse plus rapide que le son pour tuer les bactéries. Certains biocides utilisés présentement, comme le chlore, ne font que 1% de la recette de fluide de fracturation, mais les compagnies s'entêtent à ne pas vouloir révéler la recette qu'elles utilisent avec l'eau et le sable, plaidant des secrets commerciaux.

De toute façon, même certaines gazières avouent qu'elles devront être plus transparentes et seront forcées à trouver des moyens de réutiliser ou de mieux gérer leurs eaux usées.
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"Companies seek new shale gas technology

Halliburton Co. and Schlumberger Ltd, trying to forestall a regulatory crackdown that would cut natural-gas drilling, are developing ways to eliminate the need for chemicals that may taint water supplies near wells. At risk is hydraulic fracturing, or fracking, a process that unlocked gas deposits in shale formations and drove gains in U.S. production of the fuel. Proposed regulations might slow drilling and add $3bn a year in costs, a government study found. As one solution, energy companies are researching ways to kill bacteria in fracturing fluids without using harmful chemicals called biocides.

“The most dangerous part in the shale frack is the biocide,” said Steve Mueller, chief executive officer at Southwestern Energy Co, the biggest producer in the Fayetteville Shale of Arkansas. “That’s the number-one thing the industry is trying to find a way around.” Biocides are employed because the watery fluids used to fracture rocks heat up when they’re pumped into the ground at high speed, causing bacteria and mold to multiply, Mueller said. The bacteria grow, inhibiting the flow of gas. “You basically get a black slime in your lines,” he said in an interview. “It just becomes a black ooze of this bacteria that grew very quickly.” Halliburton and Schlumberger, the world’s largest oilfield contractors, are among companies seeking biocide substitutes. Houston-based Halliburton said that it’s testing a process using ultraviolet light to kill bacteria in fracking fluid.

Schlumberger, based in Houston and Paris, spoke with Southwestern about testing a biocide that would last only a few hours before becoming nontoxic, Mueller said. “We have not tested it,” he said. “We only know they’re working on it.”
Schlumberger spokeswoman Mary Jo Caliandro, who confirmed the company is testing new technology, declined to comment on any advance before it’s “commercial”. Houston-based Southwestern has tested an ultrasonic technique that moves water faster than the speed of sound through a cone-shaped vortex to kill bacteria before the fluid is sent down the well, Mueller said.

Chemicals, including biocides such as chlorine, make up less than 1 percent of fracking fluids. The rest is water and sand. Companies haven’t identified the chemicals they use, citing competitive reasons. Advocacy organisations such as the Environmental Working Group in Washington have called for lawmakers to require energy companies to disclose the chemicals. “I think the industry’s going to have to be more transparent,” Steven Farris, CEO at Houston-based Apache Corp, the biggest independent US oil producer by market value, said at the Howard Weil Energy Conference in New Orleans.

Gas producers are realising they have to find ways to clean and recycle the water used in hydraulic fracturing, said George P Mitchell, the Houston billionaire who pioneered development of shale gas in the Barnett formation of North Texas. “I think a lot of action is going on to get that done,” Mitchell said. “It’s not an insurmountable task.”"

Excerpts from an article written by David Wethe published in Bloomberg.com here: http://www.bloomberg.com/apps/news?sid=aINvzI7k5xYY&pid=20601087

I learn something everyday about this fraking thing: everybody should try to get ready to force legislation in our province. "Know thy ennemy!"