Apparatus for the random straight or directional drilling into underground formations

摘要

An apparatus for drilling a drill hole (1) with an alternatively straight or curved centre line into underground formations comprises a rotary drilling tool (2; 102; 202; 302; 402; 502; 602; 702) which can be connected to a drill-pipe string (4) and means (5, 7) for driving the drill-pipe string (4) in slow auto-rotation for the straight drilling as well as for aligning and securing free of auto-rotation the drill-pipe string (4) for the directional drilling. The rotary drilling tool (2; 102; 202; 302; 402; 502; 602; 702) has a housing (3) in which a deep-hole motor (13, 14) is arranged and a cutter shaft (16) connected to the rotor (14) of the deep-hole motor (13, 14) and carrying a rotary drill bit (21) at its end projecting out of the housing (3) is mounted. Close to the rotary drill bit (21), the rotary drilling tool (2; 102; 202; 302; 402; 502; 602; 702) has a first stabilisation point (22), and provided at a distance above the latter is at least one second stabilisation point (25). During operation of the rotary drilling tool (2; 102; 202; 302; 402; 502; 602; 702) for drilling a drill hole (1) with a curved centre line, the rotary axis (19) of the cutter shaft (16) and an imaginary bottom extension of the part of the main tool axis (27) running at the level of the second stabilisation point (25) enclose a deflection angle ( alpha ) opening towards the rotary drill bit (21). In this arrangement, the rotary drilling tool (2; 102; 202; 302; 402; 502; 602; 702) is of a design which, during directional drilling of the rotary axis (19) of the cutter shaft (16), predetermines alignment with an imaginary straight connecting line (28) between the curve centre and the base point (26) of the curved centre line of a drill hole (1), to be drilled with the rotary drilling tool (2; 102; 202; 302; 402; 502; 602; 702), at a setting angle ( beta ) of 90 DEG as an upper limit value.