We must find economical methods for extracting oil from shale.
我们必须找到从页岩中采油的经济方法。
《新英汉大辞典》
2
Our known fossil fuel reserves are soaring. New finds of coal, natural gas, oil, tar sands, and oilshale keep growing, not declining.
已知的矿石燃料储备猛涨；不断有新的煤矿、天然气、石油、焦油砂和油页岩被发现；人口数量也在增长。
3
Oilshale (or kukersite) and limestone deposits, along with forests which cover 47% of the land, play key economic roles in this generally resource-poor country.