How deep into the ground do we have to go to tap the resources we need to keep the lights on? How deep into the ground are we able to go? These are the sort of questions that spur invention and lead to groundbreaking discoveries.
The first oil well drilled in Texas in 1866 was a little over 100 feet deep: the No 1 Isaac C. Skillern struck oil at a depth that, from today’s perspective, is ridiculously shallow. Ten years ago, the latest data from the Energy Information Administration shows, the average depth of U.S. exploration oil wells was almost 7,800 feet. It’s safe to assume that over these past ten years, the average well depth has only increased from there.
Yet the world’s deepest oil well is not in the United States. It’s in Russia, off Sakhalin Island and it extends 15 km or 49,000 feet into the ground. The production well, referred to as O-14, was completed in 2017 by Rosneft and Exxon, beating five previous world records for deepest wells, all drilled at the same field: Chayvo.
But is the O-14 really 49,000 feet deep? The short answer is no, because there is one little catch: directional drilling.
Unfortunately, not all news sources on the internet are familiar with it, so if you Google “the world’s deepest oil field”, the top results will tell you it’s either the O-14 or one of its Chayvo predecessors.
A 2017 infographic from Fuel Fighter offered some impressive context for the supposedly massive depth of the Rosneft/Exxon well. A well that is 49,000 feet deep is, for example, deeper than the highest building in the world—the Burj al Khalifa in Dubai—is tall. The Burj is a meager 2,722 feet tall by comparison.
The well at Chayvo is, according to the infographic, also deeper than the world record for a hot-air balloon flight: 21,000 feet. It is also deeper than Mount Everest is tall, at 29,000 feet. And that’s not all. The newest well at Chayvo extends deeper into the ground than planes can fly in the air. The standard commercial airline flight height is 39,000 feet.
“Impressive” is too weak a word for these kinds of depths. “Amazing” would be more apt—if only this depth were true.
There is a difference between a well’s actual vertical depth and the total depth of a well that is drilled first vertically and then at an angle from the vertical hole. This is called directional drilling and is increasingly popular in the oil and gas industry.
Rosneft states it on its website, in a press release on the completion of O-14, that the total depth of the well, including the vertical and the directional section, is 15 km, of which the non-vertical section extends 14.13 km, or 46,900 feet.
In other words, the true vertical depth of the well is less than 1 km or 3,280 feet. The so-called “measured depth” (the 15 km/49,000 feet) is impressive as well, of course. It is simply not the same as the “true vertical depth” that would have lent credence to all those amazing comparisons with buildings and flight heights.
And then, this year, someone called out all the media who carried the Fuel Fighter infographic on their mistake. In an April 2019 article for climate change website Watts Up with That, David Middleton noted that the information about the deepest well was misleading because it was drilled directionally.
The True Top Spot
So, if not the O-14, which oil well is the deepest in the world? In terms of true vertical depth, the Bertha Rogers No 1 natural gas well in the Anadarko Basin used to be the deepest in the world, at over 31,400 feet. Unfortunately, at this depth the drillers struck liquid sulfur, which put an end to plans to continue drilling.
In terms of vertical depth, though, BP’s Tiber field in the Gulf of Mexico, drilled by the infamous Deepwater Horizon, became the location for the deepest oil well. The Tiber well’s depth – true vertical depth – was more than 35,000 feet.
There is also a record-breaker in terms of water depth: Maersk Drilling’s Raya-1 well offshore Uruguay was drilled in water depths of 3,400 meters or 11,156 feet.
Setting the Record …. Straight
So, the deepest oil well in the world is not actually the world’s longest, and that’s fine. After all, the purpose of Rosneft and Exxon was to pump oil, not see how far they can go into the ground: a feat in which serious challenges abound.
In drilling, it’s all about pressure and resistance. The deeper you drill, the greater both the pressure and the resistance. To make matters more interesting, there is also the issue of higher temperature deep in the ground. The deeper you go, the hotter it becomes as you approach the Earth’s mantle, which, near its border with the crust, can reach temperatures of 1,000 degrees Celsius or 1,832 degrees Fahrenheit. So, the temperature in an ultradeep borehole is not just higher than surface temps: it tops 180 degrees Celsius at a depth of 12 km, or 39,370 feet.
How do we know? We know because of the deepest hole drilled by humans into the Earth’s crust. That was not drilling for oil, though. The Kola superdeep borehole, drilled in Russia’s Far East during the ‘70s and early ‘80s, was drilled simply to see how far into the ground we can go. Apparently, 12 kilometers was the maximum at the time before technical difficulties related to pressure, resistance, and heat became overwhelming.
For all the media misunderstanding surrounding them, the Chayvo wells – all but one of them record-breakers in total measured depth – are evidence of a trend that we are already seeing across the world. The era of the gushers when oil didn’t just flow out but burst out, is long over. The remaining oil reserves we have are deeper and harder to find, not just in Russia’s Far East. We might see some day a well whose true vertical depth is indeed almost 50,000 feet. As long as it’s economically viable.
By Irina Slav for Oilprice.com