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China’s Record Onshore Well: Technology and Geology

In July 2019, the China National Petroleum Corporation began drilling in the Tarim oilfield in Xinjiang, a province in the northwestern part of the vast country. (The Tarim basin is in southern Xinjiang, bordering foreign countries: it is to the south of Kyrgyzstan and the east of both Tajikistan and Pakistan.)

In January 2020, the CNPC struck oil after drilling 8,882 meters deep. The depth of the drilling (29,140 feet, or more than five miles) is itself an impressive technological achievement by CNPC.  http://www.globaltimes.cn/content/1159236.shtml

But what is fascinating: this strike is the deepest onshore well in Asia. Oil and gas wells in China can be quite shallow (only 200 meters, or 656 feet). They can also go as deep as 5,000 meters (16,404 feet)(without raising -- or rather lowering -- any eyebrows). But this strike is extraordinary.

A ‘Pre-Salt’ Find

It is extraordinary not only for the striking numbers indicating its depth, but because this is the first pre-salt hydrocarbon find in the history of the industry in China.

The term “pre-salt” in such contexts refers to oil found along the continental shores of the geologically ancient continent of Gondwana. In the course of Gondwana’s movements, what was once shoreline has become interior, and some of the planet’s oil deposits have slumbered, buried by the salt laid down there by chronologically distant seas.

Between about 335 and 175 million years ago (according to current thinking), there was but one continent on the planet. This continent geologists call Pangaea, from Greek terms for “all” and “earth.” The term was invented a little more than a century ago, and it was bandied about at a meeting of the American Association of Petroleum Geologists as early as 1926.

About 175M years ago, then, Pangaea began to break up, first with the development of a rift in the middle of what we recognize as the Atlantic Ocean.

Later, Pangaea broke apart along north/south lines, and Gondwana was the southern portion, including roughly present-day Africa, Arabia, India, Australia, and Antarctica. The northern portion was the Eurasia landmass. 

About 140 million years ago, the landmass consisting of the Indian subcontinent split off from Gondwana and headed north. The northern portion of this drifting landmass included large deposits of salt and, beneath them, hydrocarbon reserves. As the Indian plate executed its slow-motion slam into the Eurasian plate, it threw up the vast Himalayan mountain chain. At the top of Mount Everest, one can find marine limestone, a reminder of the sea that had lain between the two landmasses before this collision.

The slow-motion collision continues to this day, and its force continues to plow the old salt deposits, and whatever earlier formations might be below them, into the heartland of Eurasia, inclusive of western China.

Context for the Drill

China is the world’s biggest oil importer. Demand for crude is increasing, and many of the existing wells are maturing, so the CNPC would very much like to lessen the country’s dependence on imports by finding more domestic reserves, and the government regards that as a matter of national security. But this means drilling in more challenging environments … and drilling deeper.  

The drive to explore for domestic crude also means that China is opening the exploration business to foreign companies. Until now, international companies have only been allowed to do this if they setup a joint venture with a local company. But as of May 1, 2020, that restriction will disappear.  

 

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