The Lone Star Producing Company’s oil exploratory hole, Bertha Rogers, was 9.583 metres deep, and the worlds deepest hole between 1974 and 1979, where the Soviet Union broke the record with the Kola Superdeep Hole.
The drilling was done with the largest land based drilling rig in the world. The Loffland Bros. Rig 32.
It took the bore cuttings 8 hours to reach to surface, while drilling. Total cost of the well was between 6.000.000 and 7.000.000 US$ depending on the source.
The drilling stopped April 13th 1974, after 504 days of drilling, when they hit a pocket of molten sulfur that melted the drill bit. During drilling they encountered temperatures up to 246 degrees Celcius, and 24.850 psi of pressure.
Gas was discovered at 4.000 metres, and the well produced natural gas until July 1997. The Bertha Rogers well was plugged and abandoned.
Unfortunately we haven’t got the precise location (please post a comment if you do), but according to the United States Geological Survey its very close to Clinton Sherman Airport and Burns Flat in Washita County, Oklahoma. EDIT: Thanks Hallvor for supplying coordinates for the well. Much appreciated!