Now You’re Cooking With Gas- Ancient China’s Remarkably Sophisticated Drilling Operation

Come and listen to my story ‘bout a man named Jed – a poor mountaineer, barely kept his family fed. And then one day he was shootin’ at some food, and up from the ground come a bubblin’ crude. Oil, that is – black gold, Texas tea.

Yes, oil: the sticky, fortune-making, war-inspiring, planet-warming liquid that makes the work go round. Today the oil and gas industry is one of the largest on the planet, producing some 12.7 billion litres of crude oil and 10 billion litres of natural gas every single day. Such is humanity’s insatiable appetite for fossil fuels that we will go to the ends of the earth to find it, from the scorching deserts of the Middle East to the bitumen sands of Western Canada to the frigid, crushing depths of the North Sea and the Gulf of Mexico. Yet while it is easy to assume that all this is a relatively recent phenomenon – a symptom of 19th Century industrialization and 20th Century automobile culture, the truth is that we’ve been at this for far longer than you might think. More than a thousand years before Edwin Drake and Mayor Alekseev drilled the first commercial oil wells in the mid-19th century, the ancient Chinese were drilling, extracting, and piping natural gas on a scale that rivalled many modern operations, with surprisingly sophisticated tools still used to this day. This is the incredible story of the Sichuan gas fields.

Sichuan Province lies roughly in the centre of China, bounded by the Himalayas to the west, the Long Men Mountains to the north, and the Hua Ying Mountains and Yangtze River to the south. Blessed with fertile soil, a mild climate, and abundant water, Sichuan is one of China’s most productive agricultural regions, producing a wide variety of crops from wheat and rice to cotton, tobacco, and mulberry bushes for silkworm cultivation. But the region, which lies on the site of an ancient, dried-up ocean, is also blessed with another, far more valuable resource: salt. Vital both as a nutrient necessary for human metabolism and as an agent for preserving food before the advent of refrigeration, salt has been a major driving force in world history for millennia – so much so that the modern expressions “salary” and “worth his salt” are thought to derive from the practice of paying Roman soldiers in salt. Throughout Chinese history, people living near the coast obtained salt by boiling seawater. However, as settlement spread further inland, the logistics of transporting sea salt from the coasts to the interior became increasingly difficult, and people began seeking a new, more local source of the compound. They found it in Sichuan’s deep aquifers of brine, which contained salt concentrations higher than 50 grams per litre. But while this brine sometimes rose to the surface in natural seeps, much of it lay trapped hundreds of metres below the surface, requiring specialized technology to reach and extract.

The first brine wells in Sichuan appeared during the Warring States Period of 480-221 B.C.E. These were commissioned by Li Bing, a legendary administrator and hydraulic engineer for the State of Qin [“Chin”] most famous for creating the Dujiangyan river control system – which, incredibly, is still in use more than 2000 years later. At first these wells were dug by hand, but by the 1st Century C.E. the locals had developed a sophisticated percussive drilling system remarkably similar to early American rigs used in the late 19th and early 20th Centuries. In this system, the top few metres of the well were dug out by hand, with the hole being lined with stones drilled through with circular holes. These holes formed a cylindrical guide for the subsequent drilling operation. Once the wellhead was complete, a bamboo derrick or “heaven cart” was erected overtop. By the early 20th century, some of these derricks reached up to 100 metres in height, rivalling their more famous western counterparts. The drill bit consisted of a long vertical bamboo pole tipped with a cast-iron chisel head, which in turn was connected to a pivoting seesaw-like platform. A worker would repetitively jump on and off this platform, raising and dropping the drill bit onto the bedrock below. Unsurprisingly, this was a slow, tedious process; the drilling speed topped out at less than a metre per day, and it often took months to strike a brine deposit. Despite this, these Ancient Chinese drillers achieved some truly impressive feats. By the Tang Dynasty of 618-906 C.E, they were drilling down to depths of 250 metres. By comparison, early 19th Century American wells topped out at only 150 metres.

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.

From the very start of brine extraction in Sichuan, drillers began encountering pockets of natural gas – composed mainly of methane – trapped beneath the salt. The Jialingjiang formation which feeds Sichuan Province’s abundant brine aquifers was formed by the evaporation of a large inland sea during the mid-Triassic Period, around 225 million years ago. This salt layer forms an impermeable dome which traps large quantities of natural gas, produced by the decomposition of ancient marine zooplankton and algae. At first, this gas was seen as a useless byproduct or even an unwelcome hazard; indeed, the gas was often contaminated with hydrogen sulfide, a highly-toxic gas with could induce nausea, unconsciousness, and even death depending on its concentration. Eventually, however, the gas’s flammable properties were recognized and it began to be used for household lighting, heating, and cooking throughout the region. But it was not until the Second Century C.E. that large-scale gas extraction truly began in earnest, largely in response to a resource depletion crisis. Previously, salt had been produced by boiling brine over wood fires. But as the industry grew and local forests became severely depleted, drillers turned to the abundant supply of natural gas as an alternative source of fuel.

Exploiting Sichuan’s natural gas reserves required the development of yet more advanced technology, including the “Kang Pen” drum. Invented in the late 18^th Century, this device sat atop the wellhead and allowed both natural gas and brine to be extracted and separated simultaneously. Chinese drillers also invented one of the world’s first carburetors to combine natural gas with air, producing an efficient-burning mixture for heating the brine evaporation pans. They even developed a rudimentary understanding of the area’s geology, siting brine wells at the bottom of valleys and gas wells at the top of hills where gas pockets accumulate under salt domes.

But perhaps their greatest achievement was building hundreds of kilometres of bamboo pipelines that carried brine and natural gas as far away as Beijing. As bamboo is naturally divided into closed compartments, building these pipelines was not a matter of simply joining lengths of bamboo together. Instead, the bamboo was split in half, the dividing walls carved away, and the two halves joined back together with lime and Tung oil cement. The joint was further reinforced using twine wound around the outside of the pipe. So durable and gas-tight were these pipes that as recently as the 1950s there were still over 95 kilometres of bamboo pipeline still in operation around the Sichuan city of Zigong.

The vast scale of the Sichuan salt and brine operations had a significant impact on Chinese history and culture. The slow pace of drilling and extraction meant that derricks and boiling facilities had to be manned 24 hours a day. Consequently, some of the first legal contracts in Chinese history were drawn up by Sichuan salt merchants to negotiate the allocation of workers and other resources. On a larger scale, the scramble for valuable salt and gas attracted hundreds of thousands of people and from across China and surrounding countries, creating in a volatile, conflict-ridden frontier melting pot and giving Sichuan the diverse cultural makeup it enjoys to this day.

Sichuan was not the only hydrocarbon extraction operation of the Early Modern period. In the 12^th Century, small oil wells were dug near Naples in Italy, while in the 13^th Century Venetian explorer Marco Polo described oil extraction at Baku, in what is now Azerbaijan:

“A hundred shiploads might be taken from it at one time…this oil is not good to use with food, but it is good to burn and is also used to anoint camels that have the mange. People come from vast distances to fetch it, for in all the countries around it they have no other oil.”

However, none of these operations came close to matching the sheer scale and sophistication of the Sichuan gas fields. Today, the region around Zigong is still a major producer of both salt and gas, producing around 30 billion cubic metres of the latter every year – much of it extracted from wells originally opened hundreds of years ago. Yet despite advancements in technology, the work remains as dangerous as ever. On December 23, 2003, a blowout at a gas well near Chongqing [“Chong-ching”] killed 233 people, poisoned 9,000, and contaminated more than 25 kilometres of surrounding countryside, with the majority of casualties stemming from hydrogen sulfide inhalation. That the disaster was not even worse is largely due to the locals’ nearly 2,000 years of experience with the land and its volatile natural resources. The legacy of these pioneering workers is preserved and celebrated in the Shanxi Salt Museum, housed in a former guild hall built by mid-18^th century salt merchants. Displaying original artefacts as well as detailed models of historic salt and gas-extraction technology, the museum serves as a fitting tribute to a sophisticated industrial operation two millennia ahead of its time.

Expand for References