经济学人下载:天然气是清洁能源吗?

Shale gas extraction
页岩天然气开采

The need to be seen to be clean
天然气是清洁能源吗？

Natural-gas production is booming, but its green image is in question
天然气生产蒸蒸日上，但它的清洁能源形象却受到质疑

May 12th 2011 | AUSTIN, TEXAS AND GOLDEN, COLORADO | from the print edition

DRILL rigs tower over the silos on farms in Pennsylvania. Once-empty mesas in western Colorado, where mule deer and sage grouse ranged freely, now look like a neural network from a bird’s-eye view, with well-pads connected by dirt roads scattered across the landscape.

宾夕法尼亚的农场，一座座钻塔高耸，俯视着贮粮的圆仓。科罗拉多西部的山顶平地，过去这里曾经一片空旷，只有骡鹿和艾草鸡在上面自由徜徉，现在布满钻井，条条土路联接其间，从高处望过去，就像是一幅密密麻麻的神经网络图。

These are the signs of America’s natural-gas boom. Thanks to new drilling technology, and in particular a controversial process called hydraulic fracturing or “fracking,” the size of the proven reserves is growing. At the end of 2009 the United States had estimated reserves of 283.9 trillion cubic feet (8 trillion cubic metres) of natural gas, up 11% from the year before. In 2010 the country produced 22.6 trillion cubic feet of natural gas, up from 18.9 trillion cubic feet in 2005. The price at the wellhead has dropped from $7.33 per thousand cubic feet to $4.16 during the same period.

美国的天然气开采呈现这样一副蒸蒸日上的景象。随着钻井技术，特别是充满争议的水力压裂法（又称破裂法）的广泛采用。已探明的天然气储量不断增加。2009年末，美国估计其天然气储量为283.9万亿立方英尺（合8万亿立方米），比上一年增长了11%。2010年美国开采的天然气为22.6万亿立方英尺。而2005年为18.9万亿立方英尺。同期天然气的出井价也从每立方英尺7.33美元下降到4.16美元。