By the way, the extra amazing thing about the Kola well is that core was collected over the entire well depth. This means that the drill string had to be pulled out hundreds of times during drilling to recover the core, and explains why the project took 20-odd years to complete.
The deepest oil well that I know of is BP's Tiber well: http://www.bp.com/genericarticle.do?categoryId=2012968&c..., 10685 m but probably measured from the rig floor, so about 9400 m actual drilled depth, starting 1259 m subsea.
By the way, the extra amazing thing about the Kola well is that core was collected over the entire well depth. This means that the drill string had to be pulled out hundreds of times during drilling to recover the core, and explains why the project took 20-odd years to complete.