DEEP DRILLING FOR NATURAL GAS

The Chinese developed a drilling method by the first century BC and wereable to drill boreholes up to 4800 feet deep. The deepdrilling for today's suulies of oil and natural gas isa development from these Chinese techniques.The size of Chinese drilling equipment was remarkable. Derrick could rise as much as 180 feet above ground. Tubes for extracting could be as much as 130 feetlong. At the top of a borehole would be a shaft dug with spades, reaching down to the level of hard rock, whether this was one foot or dozens of feet down. Once the rock level is reached stones with holes through the middle were stacked one on top of another to ground level all perfectly centered so that a long hol 8 to 14 inches wide extended down through them all from ground level to rock level. Then the drilling would begin. A drill would be suspended by bamboo cables from a derrick. Cast iron was available at the time , so cast iron drilling bits were available. These would be dropped on to the rock, and any depth from an inch to three feet a day might be drilled. A deep borehole often takes years to drill.

The bamboo cables were made of strips 40 feet long. A single-strength cable would be used down to 1500 feet, but at depths greater than that, the cable was of double thickness.The strength of hemp rope is 750 punds per square inch. The bamboo is nearly four tons per square inch.