Jorge and I had just finished watching James Dean’s last movie, “Giant”, yet again. The movie about an oil tycoon triggered a discussion about very deep holes in the ground. I wondered about how deep anyone has managed to drill down into the planet.
We both knew there are long boreholes in Qatar and some lengthy ones offshore from Eastern Russia. Jorge faintly remembered hearing a news report regarding the world’s deepest artificial point. It was in Northwestern Russia. The drilling had come to a halt due to breakdowns and lack of funding.
We found a list on the Web that answered our question. Indeed, the longest measured depth, regarding the well bore, is offshore from the large Russian island, Sakhalin, near Japan. That oil well is 12,345 metres long. Second longest is the Al Shaheen oil well in Qatar at 12,289 metres. The third deepest, at 12,262 metres is on the Kola Peninsula near Russia’s far Northwestern border with Norway. The Kola statistic of 12,262 metres easily converts to 12.262 kilometres which, in turn, equals 7.619 miles.
The specific project in the Pechengsky District, on the Kola Peninsula, in the USSR, physically began on May 24, 1970. Their goal was not oil and gas exploration. The mission was purely scientific, in that the Soviets wanted to sample the mysterious area where the Earth’s crust and mantle intermingle. This area is called the Mohorovičić discontinuity, abbreviated “Moho”. Researchers realized they’d need to invent different types of mechanical tools in order to drill that deeply into the ground.
Even though the eventual distance of twelve kilometres is far short of the six-thousand kilometres to the mantle, much material and data was collected and is still being analyzed. Many holes were drilled as branches from the central one. The deepest and record holder was accomplished in 1989.
The Soviet project had its start in 1962. It was coordinated by the Interdepartmental Scientific Council For The Study Of The Earth’s Interior And Superdeep Drilling. The work was intended as a parallel to the exploration of Outer Space. An exhaustive survey was made across the vast nation, over the next several years, to find a suitable location for drilling.
Project leaders found the best place to be near the border with Norway. A 61 metre (about 200′) tall enclosure was built to contain the drilling apparatus. A way to avoid the shortcomings and weaknesses of rotating the entire drill shaft was invented. Researchers devised a way to rotate only the end of the shaft.
The necessary force was delivered by forcing the pressurized drilling mud lubricant through the center of the shaft to a turbine like mechanism to spin the drill bit. One other benefit of having only the tip spin, is that the drilling direction can be adjusted and maneuvered. This would be impossible if the shaft rotated. The Soviet rig was designed so core samples could be taken along the entire length of the drilling shaft.
The Soviet researchers discovered that temperatures rise considerably greater than expected as more depth is achieved. Efforts were made to counter the heat problem by deeply chilling the drilling mud before it was pumped down to the rotating bit.
Researchers had estimated that they would be able to drill 15,000 metres where the projected temperature would be 100 C (212 F). That was nearly the technological limit in those days. Instead, when the actual depth of 12,000 metres was reached, the temperature was 180 C (356 F). With such heat, under pressure, the rock is semi liquid. The borehole tended to flow shut whenever drill bits were pulled out for replacement.
Because technological breakthroughs and renovations had yet to be developed, further progress was halted. Drilling was stopped in 1994 at the 12.262 kilometres mark. The projected 15.0 kilometres goal was not reached before technology and funding from the Russian government ran out. The hole was closed by a welded cap. In actual depth, the Kola Superdeep Borehole is still technically the deepest hole ever drilled by humans.
There is an American effort called the “Integrated Ocean Drilling Program”. It is the continuation of the abandoned 1957 program called “Project Mohole”. This time, exploration beneath the thinner ocean floor crust is hoped to yield more data to scientists.
The Blue Jay of Happiness notes that one Soviet scientist said, “Everytime we drill a hole we find the unexpected. That’s exciting, but disturbing.”