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Etats-Unis : Accident dans un puits de gaz de schiste en Pennsylvanie

avril 21, 2011
par

Reuters, Mis à jour le 20.04.11 à 23h25, in 20minutes.fr

Des milliers de litres d’eaux usées de forage s’échappent mercredi d’un puits de gaz de schiste en Pennsylvanie à la suite d’une explosion, rapportent les autorités.

L’accident s’est produit pendant une opération de fracturation hydraulique, qui consiste à injecter de l’eau, du sable et des produits chimiques afin de briser les roches.

Les eaux usées ont commencé à jaillir du puits, exploité par Chesapeake Energy <CHK.N>, mardi vers 23h45. Les habitants de Leroy Township, dans le comté de Bradford, ont été évacués, a précisé le groupe, qui ne fait état d’aucune victime.

Les autorités locales s’inquiètent de l’impact de cet accident sur l’environnement, a déclaré un responsable des secours du comté.

‘Equipment failure’ blamed in well blowout

By Laura Legere (Staff Writer)n Published: April 21, 2011, in Citizensvoice.com

Thousands of gallons of natural gas drilling waste fluids spilled onto a farm and streams for over 12 hours Wednesday after a driller in Bradford County lost control of a well late Tuesday.

The Atgas 2H well operated by Chesapeake Energy Corp. in LeRoy Township blew out during the hydraulic fracturing process at around 11:45 p.m., swamping the lined well pad and overflowing into a field, a small tributary and Towanda Creek, state environmental regulators said

Seven families were asked to evacuate the area until the well could be brought back under control, Chesapeake said in a statement, adding that no one was injured in the incident and no gas was emitted to the atmosphere.

The identities of the seven families evacuated from the area were unknown late Wednesday. However, Canton Fire Chief Kim Jennings reported that the evacuees were placed in local motels.

Jennings said Canton firefighters as well as Western Alliance Ambulance personnel were on the scene throughout the day, standing by and making certain that any equipment needs were met. Jennings said the Canton Fire Department left the scene late Wednesday night, but would be available at any time if the situation at the drill site would become unsafe.

Chesapeake described the problem as "an equipment failure." Neither the company nor regulators with the state Department of Environmental Protection could provide a precise estimate of how much fluid was spilled.

Emergency crews were able to stop the fluid from flowing into Towanda Creek by Wednesday afternoon, but crews struggled to regain control of the well into Wednesday evening. The well control specialty firm Boots and Coots was brought to the site from Texas, Department of Environmental Protection spokeswoman Katy Gresh said.

It was unclear Wednesday where exactly the well was leaking or why, but officials on site described the leak as originating from below the frack valve stack, an above-ground piece of equipment that controls pressure during the fracking process.

"Evidently the crack is in the top part of the well below the blowout preventer," Skip Roupp, the deputy director of the Bradford County Emergency Management Agency said Wednesday afternoon, referring to a device used in emergency situations to choke off flow from a well. "They don’t really know what happened yet because they don’t have it controlled yet."

At least eight DEP personnel were on scene sampling the unnamed tributary and Towanda Creek as well as eight private water supplies, Gresh said. There was no evidence the spill killed fish, she said.

The Atgas 2H well is part of a six-well pad in a remote area on LeRoy Mountain about 13 miles west of Towanda.

The hydraulic fracturing, or fracking, stage of well development takes place after a well is drilled and involves injecting millions of gallons of water, sand and chemicals underground at high pressures to crack the rock and release the gas trapped there.

A portion of that fluid returns to the surface laden with salts, metals and radioactivity that occurs naturally in the shale formation and is mobilized by the fracturing process. The wastewater, called flowback water, spewed from the Atgas well on Wednesday. The exact composition of the spilled fluid had not been determined.

Chesapeake Energy, one of the state’s most active Marcellus Shale drillers, has been issued 30 notices of violations from the DEP for its operations in the state this year. The company has been cited 284 times for violations since the start of 2008 and has been subject to 58 enforcement actions by environmental regulators, according to DEP records.

Unlike a blowout at a Clearfield County gas well in June – the most serious well control incident in the state’s Marcellus Shale to date – the blowout in LeRoy Township never spewed a geyser of waste fluid into the air, Gresh said.

In the June incident, at a well owned by EOG Resources, natural gas and wastewater shot 75 feet into the air after drillers hit unexpectedly high pressures underground.

Gresh reported around 9 p.m. that DEP representatives were still at the scene and she had not yet been informed that the situation was under control.

When asked at the site if Chesapeake will later resume drilling the well, Brian Grove, director of corporate development for Chesapeake Energy, said he could not say until the situation is brought under control, allowing the company to make that determination.

C.J. Marshall, staff writer, contributed to this report.

Read more: http://citizensvoice.com/news/drilling/equipment-failure-blamed-in-well-blowout-1.1135482#ixzz1K9dGAHnZ

Gaz de schiste: des forages suspendus aux Etats-Unis après un accident

(AFP) – 22/04/11

PHILADELPHIE (Etats-Unis) — Des équipes de secours sont parvenues vendredi à colmater un puits de gaz de schiste en Pennsylvanie (est des Etats-Unis) où une explosion s’est produite deux jours plus tôt, mais l’opérateur du puits a suspendu ses forages dans la région.

La gravité de l’accident du point de vue écologique n’était pas connue vendredi mais la compagnie Chesapeeke Energy a suspendu toutes ses opérations de forage en Pennsylvanie dans l’attente des résultats d’une enquête.

Des milliers de litres de liquides potentiellement toxiques se sont répandus, mais on ignorait l’ampleur de la fuite. Un porte-parole du département de Protection de l’environnement de Pennsylvanie, Paul Spadoni, a indiqué que des échantillons avaient été prélevés pour déterminer l’étendue et la nature des dégâts.

Le puits est situé près de la ville de Canton, à plus de 200 km au nord de Philadelphie.

Cet accident a déjà fait ressurgir la polémique autour de la fracturation hydraulique, très contestée par les militants écologistes et les riverains qui en dénoncent les dangers.

La fracturation hydraulique consiste à injecter sous très haute pression un mélange d’eau, de sable et de produits chimiques dans des puits pour fissurer la roche, afin d’extraire le gaz piégé dans la matrice rocheuse.

La méthode risque de polluer les puits d’eau douce très utilisés par les agriculteurs de la région.

En dépit de la controverse, ce type de forage est en expansion en Pennsylvanie et le reste des Etats-Unis. Les prix élevés du gaz encouragent la prospection et la fracturation hydraulique permet d’atteindre des gisements très profonds.

Si ces forages procurent du travail dans des régions économiquement dévastées, la liste des produits chimiques contenus dans le liquide injecté, dressée récemment par le département de Protection de l’environnement, est dénoncées par les écologistes. Plusieurs de ces produits sont en effet cancérigènes.

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