They drilled through several layers of rock to reach the oil.

他们钻透了几层岩石寻找石油。

《牛津词典》

Below the water table and rock is oil.

地下水和岩石下面是石油。

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Both oil and gas are less dense than water, so they generally tend to rise upward through water-saturated rock and sediment.

石油和天然气的密度都比水小，所以二者通常会浮在被水浸泡的岩石和沉积物的表层。

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On federal lands, Shell has been researching methods to cook oil out of the shale (basically oil-soaked rock) without mining it or polluting groundwater.

FORBES: OutFront

Operated by Anadarko with 30%, that well was another monster, going down more than 31, 000 feet in 5, 800 feet of water, and discovering a remarkable 1, 000 feet of oil-bearing rock with very promising reservoir properties.

FORBES: Tiny Dallas-Based Oil Company Scores Two Giant Deepwater Discoveries In One Week

Bissell found out that some rock oil was a by-product obtained by drilling for salt.

FORBES: Magazine Article