Petroleum and natural gas

UNESCO Courier, Oct, 1988

It is probably a conservative estimate to say that the Chinese were burning natural gas for fuel and light by the fourth century BC. The deep boreholes drilled for brine also yielded natural gas from time to time. These methane gas deposits tended to occur under the brine, but many boreholes, including those intended for brine, yielded only natural gas and were known to the Chinese as "fire wells". These boreholes were being drilled systematically for brine by at least the first century BC, so that deep supplies of natural gas were tapped from that date by boreholes going down over 100 metres. And the systematic search for natural gas itself by deep drilling is recorded in the second century AD.

Chang Quin 347 recorded in his book Records of the Country South of Mount Hua:

"At the place where the river from Bupu joins the Huojing River, there are fire wells; at night the glow is reflected all over the sky. The inhabitants wanted to have fire, and used to ignite the gas outlets with brands from household hearths; after a short time there would be a noise like the rumbling of thunder and the flames would shoot out so brilliantly as to light up the country for several dozen li around. Moreover they use bamboo tubes to 'contain the light', conserving it so that it can be made to travel from one place to another, as much as a day's journey away from the well without its being extinguished. Whenit has burnt no ash is left, and it blazes brilliantly." .

Bamboo pipelines did indeed carry both brine and natural gas for many kilometres, sometimes passing under roads and sometimes going overhead on trestles.

The ignition and use of the natural gas for light and fuel posed problems which were successfully overcome by the ancient Chinese. Old texts describe in some detail the complicated arrangements which were eventually adopted to control the burning of natural gas. The gas from the "fire wells' was fed first into a large wooden chamber about 3 metres below ground level over the mouth of the borehole. It was basically a cone- shaped barrel into which an underground pipe also conveyed air. The chamber therefore acted as a great carburettor, feeding into banks of pipes which led to other smaller conical chambers which rested on the surface of the earth. These too took in air, with a variety of entry pipes which could be opened or closed, so that a fine-tuning of the 'engine' was possible by a continuous manipulation of the fuel/air mixture. If the pressure of the mixture were to flag, dangerous flash-backs and explosions could occur, so the main chamber would be opened up further. But fires could result if the mixture were too rich, so surplus gas was allowed to escape through what was called a 'sky thrusting pipe" exhaust system.

Flames less than 50 cm high were used for other purposes, such as providing lights in certain Sichuan towns. The gas was also available for heating in these towns, though details of how it was employed are lacking. It seems doubtful that proper gas stoves existed, and it is more likely that the heating applications were generally for cooking and boiling uses.

Other portable heat sources included petroleum products, which often went under the name of 'stone lacquer" because they looked like lacquer but seeped from the stones.

The domestic uses of petroleum products seem to have been confined to modest applications such as oil lamps and oil-fired torches, but they were used on a large scale for breaking up rocks by fire. Since burning oil could burn in water, boulders in harbours were sometimes broken apart by having burning oil poured over them.