Method of drilling and jet drillilng system

Abstract

A method of drilling into an object comprises providing a drill string in a borehole in the object, the borehole having at its bottom a borehole axis, the drill string comprising a borehole-centralized jet drill head at its lower end, the jet drill head having a drill axis, and comprising a jet nozzle; providing a stabilizer means for the drill string, the stabilizer means determining an inclination angle between the borehole axis and the drill axis; and generating a fluid jet at the jet nozzle, so as to deepen the borehole, wherein the drill string is rotated while deepening the borehole. Another system comprises a drill string with an jet drill head at its lower end, the drill head being provided with a jet nozzle, a stabilizer positioned above the jet drill head, the stabilizer contacting the borehole wall, and means for rotating the drill string.

1 . A method of drilling into an object, the method comprising
 providing a drill string in a borehole in the object, the borehole having at its bottom a borehole axis, the drill string comprising a borehole-centralized jet drill head at its lower end, the jet drill head having a drill axis, and comprising a jet nozzle;   providing a stabilizer means for the drill string, the stabilizer means determining an inclination angle between the borehole axis and the drill axis; and   generating a fluid jet at the jet nozzle, so as to blast with an erosive power on an impingement area of the borehole, thereby deepening the borehole, and wherein the drill string is rotated while deepening the borehole.   
     
     
         2 . A method according to  claim 1 , wherein the fluid jet is an abrasive fluid jet and the jet drill head is an abrasive jet drill head. 
     
     
         3 . The method according to  claim 1  wherein the jet drill head is a self-centralizing jet drill head. 
     
     
         4 . The method according to  claim 1  wherein the stabilizer means is fixed with respect to the drill string while deepening the borehole. 
     
     
         5 . The method according to  claim 1  wherein the stabilizer means is an eccentric stabilizer means. 
     
     
         6 . The method according to  claim 1  wherein the stabilizer means has a largest diameter that is smaller than the borehole diameter. 
     
     
         7 . The method according to  claim 1  wherein at least one radial dimension of the stabilizer means is adjusted in the course of a drilling operation, so as to deepen the borehole along a predetermined trajectory. 
     
     
         8 . The method according to  claim 7 , wherein the stabilizer means has a cross-section that is adjusted while rotating the drill string. 
     
     
         9 . A jet drilling system for drilling a borehole into an object, comprising a drill string with an jet drill head at its lower end, the drill head being provided with a jet nozzle, a stabilizer means for the drill string at a position above the jet drill head, the stabilizer means protruding radially with respect to adjoining drill string parts so as to provide a point of contact with the borehole wall, and a rotation means for rotating the drill string. 
     
     
         10 . The jet drilling system according to  claim 9 , further comprising centralizing means for the jet drill head downhole of the stabilizer means. 
     
     
         11 . The jet drilling system according to  claim 9  wherein the jet drill head has a front end for engaging the borehole bottom and an axis, and wherein the front end has a recess at least in an axial region. 
     
     
         12 . The jet drilling system according to  claim 9  wherein the stabilizer means is adjustable in at least one radial dimension. 
     
     
         13 . The jet drilling system according to  claim 12 , further comprising a control means for controlling the at least one radial stabilizer dimension. 
     
     
         14 . The jet drilling system according to  claim 9  wherein the jet drill head is an abrasive jet drill head.