Workers prepare pipes used in the drilling of shale gas at a rig operated by Exalo Drilling SA, the oil and gas exploration unit of Poland's PGNiG, also known as Polskie Gornictwo Naftowe I Gazownictwo SA, in Lubocino, Poland, on Wednesday, Oct. 9, 2013. San Leon Energy Plc., an oil and gas explorer with four licenses in Spain, said some of the shale it's studying is comparable to rock in Poland, where it's a leader in using hydraulic fracturing, or fracking. Photographer: Bartek Sadowski/Bloomberg via Getty Images
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