Complicated lithology and abundant oil types of Carboniferous and Permian volcanic rocks cause the evaluation of oil and gas and water difficult in Santanghu basin.

三塘湖盆地石炭系、二叠系火山岩岩性复杂，油质类型丰富，造成油气水评价困难。

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Extracting heat from very hot, dry rocks presents a more difficult problem: the rocks must be fractured to permit the circulation of water, and the water must be provided artificially.

从极热的而干燥的岩石中提取热量，暴露出了一个更加困难的问题：必须击碎岩石以保证水的循环，而水必须是人工提供的。

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As for the market, when it approaches water it meets all sorts of obstacles: water is difficult to move, difficult to measure, difficult to price and often difficult to charge for, since many people think it should be free.

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TOHL, a start-up that produces flexible piping that can be deployed from helicopters to distribute water in difficult-to-reach areas or disaster zones, says it has spent the money on things such as testing its new system with a Chilean mining company and acquiring a patent.

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Second, the issue of combined sewer overflows is one of the most difficult water-quality issues faced by cities with old infrastructure like New York City.

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