“Unlocking the Secrets of Ancient China’s Ingenious Gas Drilling: A Hidden History of Energy Innovation”
But perhaps more impressive than the sheer depths reached were the wide variety of specialized tools and technique the Sichuan drillers developed to tackle common drilling problems – many nearly-identical to those used in today’s oil and gas industry. For instance, different drill bits were used for different stages of the drilling process or for cutting through different kinds of rock. Long, heavy bits called “Fish Tails” were used to start wells, “Silver Ingot” bits drilled rapidly but roughly, while “Horseshoe” bits drilled slowly but produced smooth, round boreholes. Tools were also developed to deal with broken-off drill bits, caved-in wells, and deviating boreholes. For example, every so often mud composed of pulverized rock and groundwater would accumulate in the borehole and had to be cleared out. This was accomplished using a length of hollow bamboo with a hinged flap valve at one end, which was lowered down the borehole. When the device was lifted out of the well, the weight of the mud in the tube forced the valve shut, allowing the mud to be lifted out. A similar device was used to extract brine once the well was completed. To repair a caved-in well, bundles of straw were lowered down to the cave-in site, where they would absorb water and expand to plug the hole. This plug was then reinforced with a special cement made of lime and Tung oil, whereupon drilling would continue, boring through the repaired cave-in.
Around 1050 C.E., Sichuan drillers achieved a major breakthrough when they replaced their old, solid drill pipes with flexible bamboo cables. These were much lighter than the old technology and could be wound around a rotating drum, allowing drilling derricks to be smaller and even greater depths to be reached. In 1835, the Shenghai Well became the first in the world to reach 1 kilometre in depth. At this time the region’s annual salt production was 150,000 tons and growing, with the industry racing to meet the demands of a Chinese population already nearing half a billion. The rolling hills of Sichuan became carpeted with sprawling forests of bamboo derricks, while the Fuxi river was choked with trading boats carrying valuable salt to all corners of China. But this remarkable industrial operation was only made possible by another of the region’s abundant natural resources: natural gas.
