The Salt (and Gas) of Earth
A History of ...
Before there was an understanding of what natural gas was, it posed a mystery to man. Sometimes, lightning strikes would ignite natural gas that was escaping from under the earth’s crust. This would create a fire coming from the earth, burning the natural gas as it seeped out from underground. These fires puzzled most early civilizations, and were the root of myth and superstition. One of the most famous of these flames was found in ancient Greece, on Mount Parnassus around 1000 B.C. A goat herdsman came across what looked like a „burning spring“, a flame rising from a fissure in the rock. The Greeks, believing it to be of divine origin, built a temple on the flame. This temple housed a priestess who was known as the Oracle of Delphi, giving out prophecies she claimed were inspired by the flame.
These types of springs became prominent in the religions of India, Greece, and Persia. Unable to explain where these fires came from, they were often regarded as divine, or supernatural. It wasn’t until about 500 B.C. that the Chinese discovered the potential to use these fires to their advantage. The center of this development was China’s Sichuan Province. The Yangtze River flows along the southern edge of the basin, and numerous tributaries drain south through the rich agricultural lands and into the Yangtze. With its fertile, well-watered soil and mild climate, Sichuan is one of China’s most productive farming regions. Since ancient times, this region has held attractive conditions for human habitation and has been occupied by humans since the dawn of our existence. Many of China’s ancient technical accomplishments came from this region, including sophisticated irrigation techniques and their drilling technology and the
Daifeng engine (1). At the base of all these technology lay the drill which allowed for the systematic exploitation of natural gas reservoirs.
... drilling...
Approximately 5,000 years ago Chinese coastal people were boiling sea water to produce salt. As high density human settlement penetrated further and further inland and increasingly relied on farming, salt, critical to human survival as a vital food supplement and preservative. became a valuable commodity.
The first recorded salt well in China was dug in Sichuan, around 2,250 years ago. This was the first time water well technology was applied successfully to the exploitation of salt and marked the beginning of Sichuan’s salt drilling industry. From that point on, wells in Sichuan have penetrated the earth to tap into brine aquifers, essentially ground water with a salinity of more than 50 g/l. The water is then evaporated using a heat source, leaving the salt behind.
About 2,000 years ago the technology began to evolve. The inhabitants began to dig wells with percussive drilling systems instead of digging them by hand with shovels. By the beginning of the third century AD, wells were being drilled up to 140 m deep. Some rural farmers still used this drilling technique for water wells only few decades ago. Thanks to them and the Imperial Sichuan Salt Industrial Museum the technology is well preserved The drill bit is made of iron, the pipe bamboo. The rig was constructed from bamboo; one or more men stood on a wooden plank lever, much like a seesaw. This lifted up the drill stem about 1 m or so. The pipe was allowed to drop, and the drill bit crashed down into the rock, pulverizing it. Inch by inch, drilling slowly progressed.
It has been speculated that percussive drilling was derived from the pounding of rice into rice flour. While it may seem that this was a fairly crude technology, the methods became quite sophisticated over time. Eventually, these ancient drillers had developed most of the tools and techniques one might see on a modern drilling rig, albeit on a smaller scale and without the benefits of modern machining methods.
At regular intervals in the drilling, the crushed rock and mud at the bottom of the hole needed to be removed. The drill stem would be pulled from the hole using a large wheel, somewhat similar in appearance to that on a modern flexible cable downhole tool truck. A length of hollow bamboo with a leather foot valve would then be lowered to the bottom of the hole. When the tube was lifted, the weight of the mud inside would keep the valve closed, and the contents could be brought to the surface. Drilling would then recommence.
The drilling method on its own is impressive, especially when considering that the rest of the world had nothing comparable in the earlier centuries. But even more impressive are all the techniques the Sichuan drillers developed to overcome common drilling problems such as cave ins, lost tools, deviated wells, and so on. A huge variety of tools and techniques evolved to handle well repair issues.
Many different drill bits were also developed, with different sizes, shapes and compositions, to deal with the different rock types encountered, and the many different drilling requirements. For example, opening the hole at the wellhead required a large heavy bit 3 m long weighing 331 to 551 lb called the “Fish Tail”; the “Silver Ingot” drilled the well bore rapidly, but roughly; the “Horseshoe” bit drilled slowly, but achieved round, smooth, high quality well bores. Hollow logs were used in the near surface as casing.
A major breakthrough, which allowed for deeper wells, was achieved around 1050 AD. Solid bamboo pipe was replaced by thin, light flexible bamboo “cable.” This dramatically lowered the weight of the “drill string,” which made it easier to lift from the surface. 1100 AD Sichuan wells were typically in the depth range of 300 to 400 m. The Sichuan salt producing industry was centered in the city of Zigong, and early photographs show hundreds of producing derricks, salt stove operations, and the Fuxi River jammed with salt trading boats. Brine and natural gas were transported through extensive networks of bamboo pipelines. Wood was initially the fuel used in the evaporation process, but sources of wood became scarce before long due to the scale of the salt production industry. Several energy saving techniques were used during evaporation, but natural gas eventually replaced wood in the brine evaporation process.
... and pumping.
Once established both brine and natural gas were piped through bamboo tubes; from small boreholes the gas could be piped directly to burners where the brine was emptied into cast iron evaporation pans for boiling and producing salt, but the pungent gas piped from depths of some 2,000 ft had to be first mixed with air lest an explosion occur. To remedy this, the gas was first piped into a large wooden, cone-shaped chamber placed 3 m below ground level where another pipe could convey air, thus turning the chamber into a large carburetor. To avoid fires from a sudden surplus of gas, an additional "sky thrusting pipe" was used as an exhaust system.
There is no record of when the use of natural gas exactly began, but clearly the Sichuan locals were drilling down hundreds of feet into the earth to get natural gas and brine already before the start of the Han Dynasty, so at least before 400 B.C. The initial discovery of natural gas may have come as a serendipitous byproduct of the search for brine and salt. Natural gas wells were called fire wells (
火井). Once wells were drilled down to 700 to 800 m, during the Song's Golden Age they could produce both brine and gas from the Jialingjiang group Triassic formations. The salt industry was a huge economic driver, and many large cities in Sichuan were established and flourished,because of the lucrative salt trade.
A key technological advancement at was the introduction of the “Kang Pen” drum at the beginning of the Tang dynasty. This drum sat on top of the wellhead, and the pressure within the drum was controlled such that gas and brine could be produced simultaneously, and efficiently separated. One bamboo pipeline would take away the brine and others the gas.
Notes and Sources:
Generally this is all still OTL. Some stuff may happen a little earlier but the really big divergences will happen later. More is going to be revealed in the next post.
(1) Sterling Engine
Oliver Kuhn:
Ancient Chinese Drilling.
Divestco Inc
Journal of the Canadian Society of Exploration Geophysicists
Author:
Natural Gas as Fuel.
Kaleidoscope Cultural China
Author:
First Oil Wells.
historylines.net
Author:
History of Chinese Invention - The Discovery of Natural Gas.
http://www.computersmiths.com
Author:
History of Natural Gas.
http://naturalgas.org
