TWO-CENTRE ROTARY BORING BIT AND METHOD FOR DEEPENING AN EXISTING WELL

摘要

Two-centre rotary boring bit for boring wells, comprising, on the one hand, a pilot tool (1) comprising a body of revolution with an axial core (3) and radial blades (4) bearing cutting elements (5) and, on the other hand, an enlarging tool (2) fitted behind the pilot tool and laterally offset therefrom, the pilot tool having, on its front face, a central region (11) that has no cutting elements in order to allow the creation of a core sample (12), said central region being in communication with a cavity (13) situated between two blades (4) of the pilot tool (1) and serving to remove the core sample toward the periphery of the boring bit.