Junggar Basin

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Junggar Basin History

Junggar Basin Regions
Fig. 1 Junggar Basin Regions

The Junggar Basin is a large sedimentary basin in Northwest China, specifically located in Xinjiang that contain the third largest Petroleum reservoirs in all of Asia. The first high yield oil and gas well was first engineered in the eastern region of the basin where they found 500 million tons of high-quality light crude oil and natural gas resources underground in the eastern part of the Junggar Basin over an area of about 2,000 square meters[1]. PetroChina who is Asia's largest oil and gas producer has also found a large natural gas discovery in the northwest region of the basin with a reserve exceeding 100 billion cubic meters. PetroChina has also tapped into 610,000 cubic meters of daily gas flow and 106.3 cubic meters of crude oil at exploration well Hu-1. This is located at the southern rim of the basin over 7,000 meters below the surface[2].

Geologic Setting and Petroleum Elements

The structural features of the basin are made up of the Northern Platform which is made up of the Wulungu depression and Luliang uplift. The Tian Shan Foredeep makes up the south region of the basin while the East and West uplift and Central depression make up the rest of the basin. The Northern Platform is a southerly dipping folded belt that covers a large portion of the basin. This region consists of many rich petroleum resources where up dig migration of petroleum is common[3]. This region is currently where all of the petroleum excavation takes place[3].

Source Rocks

Fig. 2 Petroleum Elements

A source rock is a rock that is rich in organic matter and when it is heated, it will generate oil or gas. These rocks tend to be shales of limestones and can consist up to 10% in organic matter. Source rocks that are from marine origin usually generate oil while Source Rocks that are from Terrestrial origin usually generate gas[4]. The source rocks in this basin mainly consist of lacustrine deposits of more than 1,000 m of Permian oil shale and shale, and of 600 to 1,500 m of Triassic and Jurassic rocks as well as Paleogene mudstone, shale and oil-shale. These are rock formations that were formed at the bottom of very old lakes [3]. These rocks have become very valuable for their petroleum elements but can present a problem because of the low permeability of shales. This can make excavating much more difficult.

Traps and Seals

A seal is a relatively impermeable rock, most commonly a shale, that forms a barrier around the reservoir rock. This is an extremely important component of the petroleum system[5]. The petroleum pools in this basin mainly consist of shale and mudstone seals. This can be a problem if the shale fractures which can cause low permeability which leads to the prevention of hydrocarbons escaping to the surface. The traps in this basin are most commonly fault or stratigraphic types that contain some small fields on the south flank that are anticlinal[3].

Reservoirs

A reservoir is a body of rock that has a high enough porosity and permeability to hold or store fluids. The most common reservoir rock is Sedimentary due to their high porosity compared to igneous and metamorphic rocks [6]. Two thirds of the oil reservoirs in the Junggar basin can be found in Karamay, which is a city located in the north western region of the basin. The Carboniferous oil and gas deposits in this area were accumulated in the Permian period and Mesozoic era sandstones which make up the reservoirs that can be found today.[3] Sandstones are rocks that can be characterized as high permeability and high porosity which makes them good reservoir rocks[7].

Petroleum and Facility Engineering

While the Junggar Basin is a very large basin that has been part of China's oil production since 1955, much of the basin is still underdeveloped. The first well, Ke-1 was located in Heiyoushan area at the northwest edge of the Junggar Basin. This would be the first well in what would become the Karamay oil field which would become the first ten million ton oilfield in western China. The Karamay oil field is responsible for almost 300,000 barrels of oil per day[8]. With the recent discoveries that have taken place in the basin, it is believed that the region is now responsible for producing 1 million barrels of oil per day[9]. Petrochina, who recently had a massive oil discovery had drilled a total of 5 dry wells over the last 50 years until their recent discovery. They have since said they have plans to drill five more exploratory wells in the same region as well Pen 5[10]. While the basin has numerous wells currently responsible for large amounts of oil and gas production, the biggest draw of the Junggar basin is the possible exploration possibilities that could lead to more discoveries similar to PetroChina's Pen 5 well.

Future Petroleum Potential

While oil excavation is currently taking place almost exclusively in the north western region of the basin, oilfield explorers have recently discovered 500 million tons of high-quality light crude oil and natural gas resources in the eastern part of the Junggar Basin. The other regions of the Junggar Basin show great potential for oil and gas resource exploration, and is a possible important alternative area for the development of oil production in Asia as well as China's petroleum reserves[1]. PetroChina has also vowed to spend $22.90 billion over the next several years to boost total oil and gas output in the region to 1 million barrels per day[2]. While oil excavation is already taking place in the Junggar Basin, it is just the tip of the iceberg that could end up being one of the most valuable petroleum regions in the entire world. However, this only matters if the oil is actually recoverable. While the reserve volumes that have been reported from the Junggar Basin might be massive, the Chinese estimates are usually given as oil in place rather than recoverable volumes.[11]

Further Readings

https://www.britannica.com/place/Junggar-Basin

https://www.worldwildlife.org/ecoregions/pa1317

https://www.cia.gov/readingroom/docs/CIA-RDP04T00907R000200170001-3.pdf

References

  1. 1.0 1.1 Times, Global. “500 Million Tons of Oil, Natural Gas Found in NW China's Junggar Basin.” Global Times, www.globaltimes.cn/content/1208484.shtml.
  2. 2.0 2.1 “PetroChina Strikes Big Gas Find in China Xinjiang's Junggar Basin: State Media.” Reuters, Thomson Reuters, 21 Dec. 2020, www.reuters.com/article/us-china-gas-discovery-petrochina/petrochina-strikes-big-gas-find-in-china-xinjiangs-junggar-basin-state-media-idUSKBN28V084.
  3. 3.0 3.1 3.2 3.3 3.4 K.Y. Lee 1985. Geology of the Petroleum and Coal Deposits in the Junggar Basin Xinjiang Uygur Zizhiqu, northwest China. Report 85-230. United States Department of Interior
  4. “Explore the New Oilfield Glossary.” Source Rock | Oilfield Glossary, www.glossary.oilfield.slb.com/en/terms/s/source_rock.
  5. “Explore the New Oilfield Glossary.” Seal | Oilfield Glossary, www.glossary.oilfield.slb.com/en/terms/s/seal#:~:text=1.%20n.%20%5BGeology%5D,of%20a%20complete%20petroleum%20system.
  6. “Explore the New Oilfield Glossary.” Reservoir | Oilfield Glossary, www.glossary.oilfield.slb.com/en/terms/r/reservoir.
  7. “Explore the New Oilfield Glossary.” Sandstone | Oilfield Glossary, www.glossary.oilfield.slb.com/en/Terms/s/sandstone.aspx#:~:text=1.%20n.%20%5BGeology%5D&text=The%20relatively%20high%20porosity%20and,make%20them%20good%20reservoir%20rocks.&text=Pettijohn%20classification%20of%20sandstones.
  8. Xinjiang Oil Province, www.cnpc.com.cn/en/operatediol/201405/2a55baf2e8a9420187880810fe91728f.shtml.
  9. General Energy News. “PetroChina Strikes Big Gas Find in China Xinjiang’s Junggar Basin: State Media.” General Energy News, www.ogj.com/exploration-development/reserves/article/17261552/petrochina-strikes-oil-gas-in-junggar-basin.
  10. OGJ Online Correspondent. “PetroChina Strikes Oil.” StackPath, www.ogj.com/exploration-development/reserves/article/17261552/petrochina-strikes-oil-gas-in-junggar-basin.
  11. Katona, Viktor. “The 'Mega' Oil Field That Will Never Boom.” OilPrice.com, 5 Dec. 2017, oilprice.com/Energy/Crude-Oil/The-Mega-Oil-Field-That-Will-Never-Boom.html.