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Around 2000 years ago, Chinese in Sichuan province originated deep drilling. The primary motive for deep drilling in China was the search for salt. Even as recently as 1965, 16.5% of China’s salt supplies came from brine pumped out of deep boreholes, making this source of supply second only to sea salt.<br/><br/> The ancient percussive cable drilling system was called 'churn'. The derrick had a height of 11m and all parts of the rig were made from wood (mainly bamboo). A large wooden drum, 5m in diameter, was used to raise and lower the drill. A rocking movement of the balancing beam created the percussive impulses on the bit, which sometimes weighed as much as 140kg. By alternately lifting this tool and letting it fall, the Chinese could achieved a well depth of 600m.<br/><br/> The deep drilling for brine yielded natural gas (primarily methane) from time to time. The boreholes producing methane were known to the Chinese as 'fire wells', thus drilling for natural gas followed and was developed at the same time.<br/><br/> Bamboo tubes were used as pipelines, carrying both brine and natural gas for many miles, sometimes passing under roads and sometimes going overhead on trestles. Among other uses, natural gas was used to heat evaporation pans of brine to make salt.

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