Drilling apparatus and method for producing a bore

Abstract

A drilling apparatus and a method for producing a bore in a bottom of a body of water from a floating platform that is exposed to lifting motions, such as a wave motion. The drilling apparatus includes a carrier device, a drill string substantially vertically displaceable in an axial direction along the carrier device, a drilling drive for applying torque to the drill string, and a control unit designed to control and reduce the torque of the drilling drive during drilling operation to a threshold value at which the at least one drill string element is further axially displaceable to compensate for lifting motions when there is friction on a contact surface. The drill string includes at least one axially displaceable drill string element and at least one axially extending abutment strip that is in engagement for torque transmission with the formation of the contact surface.

1 . Drilling apparatus for producing a bore in the bottom of a body of water from a floating platform which is exposed to lifting motions, in particular a wave motion of the body of water, comprising
 a drilling drive for applying a torque,   a drill string which comprises at least one drill string element, which is displaceable in the axial direction relative to the drilling drive and comprises at least one abutment strip which extends in the axial direction and is in engagement with the drilling drive and/or at least one abutments trip of a neighboring drill string element for torque transmission with the formation of a contact surface, and   a carrier device along which the drill string is substantially vertically displaceable,   
       wherein 
       a control unit is provided which is designed to control and reduce the torque of the drilling drive during the drilling operation to a threshold value, at which the at least one drill string element is further axially displaceable to compensate lifting motions when there is friction on the contact surface. 
     
     
         2 . Drilling apparatus according to  claim 1   wherein   a detector unit is provided which is designed to identify the lifting motions.   
     
     
         3 . Drilling apparatus according to  claim 2 ,
 wherein   the detector unit is coupled to the control unit and   by means of the control unit the torque can be reduced, if a lifting motion to be compensated is identified by the detector unit.   
     
     
         4 . Drilling apparatus according to  claim 1 ,
 wherein   the drill string is a telescopic drill string with a drill string element lying on the outside and at least one drill string element lying on the inside, in particular a kelly bar.   
     
     
         5 . Drilling apparatus according to  claim 4 ,
 wherein   the telescopic drill string is formed from more than two drill string elements, in particular from three or four drill string elements inserted into each other.   
     
     
         6 . Drilling apparatus according to  claim 4 ,
 wherein   at a lower area of one of the drill string elements located on the inside a drilling tool is arranged.   
     
     
         7 . Drilling apparatus according to  claim 1 ,
 wherein   the friction at the contact surface for compensating the lifting motions is a dynamic friction.   
     
     
         8 . Method for producing a bore in a bottom of a body of water from a floating platform which is exposed to lifting motions, in particular a wave motion of the body of water,
 wherein
 a drilling drive of a drilling apparatus applies a torque to a drill string, whereby the drill string comprises at least one drill string element which is displaceable in a axial direction, 
 the torque is transmitted by means of at least one abutment strip extending in the axial direction at the drill string element, 
 whereby a contact surface is formed in the drilling operation at the at least one abutment strip, 
   wherein   during the drilling operation the torque is controlled and reduced to a threshold value by a control unit, at which a friction force is formed at the contact surface, at which the at least one drill string element is further axially displaceable to compensate a lifting motion.   
     
     
         9 . Method according to  claim 8 ,
 wherein   a telescopic drill string is used, and   the distance between a drilling tool, which is arranged at a lower area of the telescopic drill string, and the drilling apparatus is changed when compensating the lifting motion.   
     
     
         10 . Method according to  claim 8 ,
 wherein   the lifting motions are identified by a detector unit and these are communicated to the control unit.   
     
     
         11 . Method according to  claim 8 ,
 wherein   the drill string is driven further during the control and reduction of the torque.   
     
     
         12 . Method according to  claim 8 ,
 wherein   the friction force at the contact surface is a dynamic friction force.   
     
     
         13 . Method according to  claim 8 ,
 wherein   an analysis unit is provided, by which process data of the torque and the lifting motion are analyzed and documented during the drilling operation.   
     
     
         14 . Method according to  claim 8 ,
 wherein   the torques and lifting motions occurring during the drilling operation are shown in a visual display unit.   
     
     
         15 . Method for producing a foundation element in a bottom of a body of water, wherein
 at least one bore is produced in the bottom of a body of water, and   in the at least one bore the foundation element is produced,   
       wherein 
       at least one bore is produced in accordance with a method according to  claim 8 .