Earth drilling apparatus and method

Abstract

Well drilling and well casing placement are carried out by a process in which a drill string and surrounding casing are advanced while being rotated, preferably in opposite directions. The process is preferably carried out using a drill rig having a mast that is movable along its direction of elongation and a casing rotation table fixed to the mast.

1 . A process for drilling a well using a drill rig comprising an elongated mast having upper and lower ends, a mast support, a top head for rotating a drill string, the top head being movable lengthwise along the mast, and a casing rotator connected to the mast, the casing rotator having upper and lower sides and a rotatable chuck for gripping and rotating a length of well casing, the process comprising a sequence of steps in which:
 a length of drill pipe is connected to the top head;   a length of well casing is slid onto said length of drill pipe while the length of drill pipe is connected to the top head until the end of said length of drill pipe remote from the top head is exposed;   the length of drill pipe is connected to the upper end of a drill string having a cutting bit at its lower end, thereby lengthening the drill string;   the length of well casing is connected to the upper end of a well casing surrounding the drill string, said well casing surrounding the drill string having a drive shoe at its lower end, thereby lengthening the well casing;   drilling of the well is carried out by rotating the drill string by means of the top head, and simultaneously rotating and lowering the well casing into the well by means of the casing rotator;   the process further comprising:
 repeating the foregoing sequence of steps until the well casing is inserted to a desired depth. 
   
     
     
         2 . The process according to  claim 1 , in which the repetition of said sequence of steps is discontinued, and, with the well casing inserted to said desired depth, drilling is continued by connection of additional lengths of drill pipe to the drill string, and rotating the drill string by means of the top head. 
     
     
         3 . The process according to  claim 1 , in which the casing rotator is fixed to the mast, the mast is movable lengthwise relative to the mast support, and the well casing is lowered by repeatedly moving the mast lengthwise relative to the mast support, and relative to the top head. 
     
     
         4 . The process according to  claim 1 , in which the step of rotating the drill string by means of the top head, and simultaneously rotating and lowering the well casing are carried out by rotating the drill string and rotating the well casing in opposite directions. 
     
     
         5 . A process for drilling a well using a drill rig comprising an elongated mast having upper and lower ends, a mast support, a top head for rotating a drill string, the top head being movable lengthwise along the mast, and a casing rotator having upper and lower sides and a rotatable chuck for gripping and rotating a length of well casing, wherein the casing rotator is mounted at a fixed position along the length of the mast, and wherein the mast is movable relative to the mast support along the mast's direction of elongation, the process comprising:
 connecting a first length of drill pipe to the top head;   sliding a first length of well casing onto said first length of drill pipe while the length of drill pipe is connected to the top head until the end of said first length of drill pipe remote from the top head is exposed, said first length of well casing having an upper end and a lower end, the lower end being in the form of a drive shoe having an annular cutting bit;   passing a part of the first length of well casing and a part of the first length of drill pipe extending through the first length of well casing through the casing rotator;   with a bit attached to said end of the length of drill pipe, causing the top head to rotate the first length of drill pipe and causing the casing rotator to rotate the first length of well casing while lowering the mast along the mast's direction of elongation toward a lowered condition, thereby simultaneously forming a bore hole with said bit, enlarging the bore hole with said drive shoe, and introducing the first length of well casing into the bore hole;   repeatedly disengaging the casing rotator from the length of well casing, raising the mast and the casing rotator while allowing the top head to remain at a substantially constant height, reengaging the casing rotator with the length of well casing and resuming rotation of the well casing, thereby continuing the simultaneous formation of the bore hole, enlargement thereof and introduction of the length of well casing; when the casing rotator is in its lowered condition and the upper end of the first length of casing and the top head are both located adjacent the upper side of the casing rotator, disconnecting the top head from the drill pipe, raising the top head on the mast, attaching an additional length of drill pipe to the top head, sliding an additional length of well casing onto said additional length of drill pipe attached to the top head, connecting the additional length of drill pipe to the first length of drill pipe, connecting the additional length of well casing to the first length of well casing; and   resuming simultaneous drilling, bore hole enlargement and well casing insertion by causing the top head to rotate the connected lengths of drill pipe and causing the casing rotator to rotate the connected lengths of well casing; and   repeatedly disengaging the casing rotator from the additional length of well casing, raising the mast and the casing rotator while allowing the top head to remain at a substantially constant height, reengaging the casing rotator with the additional length of well casing, and resuming rotation of the well casing, thereby continuing the simultaneous formation of the bore hole, enlargement thereof, and introduction of the length of well casing.   
     
     
         6 . The process according to  claim 5 , in which the step of causing the top head to rotate the first length of drill pipe and causing the casing rotator to rotate the first length of well casing, and the step of causing the top head to rotate the connected lengths of drill pipe and causing the casing rotator to rotate the connected lengths of well casing, are both carried out by rotating the top head and casing rotator in opposite directions. 
     
     
         7 . A drill rig comprising:
 an elongated mast;   a mast support;   a top head for rotating a drill string, the top head being movable lengthwise along the mast; and   a casing rotator having a rotatable chuck for gripping and rotating a length of well casing;   wherein the casing rotator is mounted at a fixed position along the length of the mast; and   wherein the mast is movable relative to the mast support along the mast's direction of elongation, whereby a casing can be moved into a well by simultaneous rotation of the chuck and lengthwise movement of the mast.   
     
     
         8 . A drill rig according to  claim 7 , in which the top head and casing rotator are capable of rotating in opposite directions.