Rock gas outburst becomes more and more serious with the increase of mining depth.

随着煤炭开采深度的增加，岩石与瓦斯突出日益严重，其危害不亚于煤和瓦斯突出。

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Methane is inflammable and explosion hazard gas as the basis of mash gas, firedamp and rock gas.

甲烷作为瓦斯、天然气、沼气等的主要成分，是易燃易爆气体。

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From on production in 1997 to 2002, Paleozoic Erathem carbonate-rock gas pool in Changqing gas field has built up accumulative production capacity of 39.

长庆靖边下古生界碳酸盐岩气藏自1997年投产以来，到2002年底已累计建成年产39。

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Companies are developing gas supplies trapped in shale rock two to three thousand meters underground.

VOA: special.2009.10.23

This causes the rock to break, or fracture,releasing the gas.

VOA: special.2009.10.23

However, the shale rock containing natural gas is separated from underground water aquifers by impermeable layers of rock that do not allow any hydraulic fracturing fluids to migrate into underground water aquifers.

FORBES: The Sierra Club Fails An Environmental Consistency Test

Fracking uses high-pressure liquid pumped deep underground to fracture shale rock and release gas.

BBC: Fracking firm Cuadrilla plans new well at St Annes site

Of course, the fly in the natural gas ointment is fracking, the hydraulic fracturing of underground rock to extract more gas and oil.

FORBES: U.S. Energy Independence in 15 Years?