That's because there is often water under the rock.

那是因为岩石下面经常有水。

youdao

The two injection sites being surveyed for the new carbon-sequestration project are under about 100 meters of water, and about 2, 500 to 3, 500 meters down in the rock.

为实施这项新的固碳项目科学家考察了两个注入地点，在约一百米水下，约2,500至3,500米的岩石深处。

youdao

Under the same conditions the maximum water-flow in rock fracture is about 30—40 times that in the clay fracture.

指出粘土裂缝中最大水流量要比相同条件下基岩裂缝水流量小30—40倍。

youdao

Getting at the oil can be tricky, and not just because it lies under as much as 9, 000 meters of water and rock.

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The drilling technique, which uses sand, water and chemicals under high pressure to extract oil and natural gas from rock formations, has helped Eagle Ford oil production grow by 184% last year compared with 2011, according to the Railroad Commission of Texas, which regulates the state's oil and gas exploration and production.

WSJ: From Oil, a Land Rush��WSJ Mansion

Fracking involves the injection of water containing a surfactant and various other chemicals under high pressure into a source rock e.g. shale, causing the latter to fracture and release natural gas (principally methane).

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