Extraction of water depends on two properties of the aquifer: porosity and permeability.

水的开采取决于含水层的两个性质：孔隙度和渗透性。

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Environmentalists strongly oppose shale-gas extraction due to fears that fracking may contaminate water supplies, the oil-sands industry because it is energy-intensive and dirty, and deep-water drilling because of the risk of oil spills like last year's Gulf of Mexico disaster.

WSJ: Big Oil Companies Are Shifting Their Focus Back to the West

Still, the MIT report points out that shale-gas extraction uses less water than other industries, and indeed than other sources of energy.

ECONOMIST: Shale gas��s poor image in Europe is largely unjustified

For BP Amoco's soft-spoken CEO, Sir John Browne, deep water offers the prospect of the largest untapped reserves and the lowest-cost means of extraction.

FORBES: Going deep