Directional drilling equipment has been developing from conventional whipstock rotary assemblies over downhole motors with bent housing to navigational motors. A self-contained downhole automatic closed loop system is recognized as being the next major development milestone. As a first step such a drilling tool which automatically compensates for any deviation from the vertical direction has been introduced within the German scientific super-deep drilling project KTB. Technical function of the tool as well as recent field experience is reported.

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