When the well reaches a pool, oil usually rises up the well because of its density difference with water beneath it or because of the pressure of expanding gas trapped above it.

当井和一个水池相接时，油通常会从井里上升，因为它与井下的水的密度不同，或者因为停留在它上方的膨胀气体的压力。

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Its geology is ideally suited to storing carbon dioxide—in depleted oil-and-gas fields in the North Sea, as well as in saline aquifers, deep porous rocks full of salty water.

英国地理上对封存二氧化碳十分理想，可存入北海已废弃的油气田、地下盐碱含水层或是充满盐水的深层多孔岩石。

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Petroleum engineers devise ways to identify and extract underground reservoirs of oil, natural gas, steam, and hot water, as well as using the empty reservoirs for the safe disposal of waste.

石油工程师想方设法从地下储存库中提取石油，天然气，蒸汽，热水并用储存库安全处理废物。

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But technological advances and improvements in recovery methods, as well as reduction of water usage and greenhouse gas emissions, have made oil sands a viable and popular option for the future of U.S. energy.

FORBES: America's Energy Future May Lie In Canada's Oil Sands