Indexing for coiled tubing drilling rig

Abstract

The invention provides a coiled tube drilling rig ( 1 ) for drilling boreholes. The rig includes a drum ( 2 ) mounted about a longitudinal axis (B-B) and adapted for receiving a length of semi-rigid tubing ( 4 ) wound onto the drum. An injector unit ( 10 ) is provided for deploying the tubing ( 4 ) along a tubing deployment axis (A-A) and into a borehole, the deployment axis (A-A) being generally orthogonal to and intersecting the drum rotation axis (B-B). An indexing guide ( 11 ), confines the tubing in a indexing zone, between a moveable tangential separation point ( 14 ) on the drum and the deployment axis (A-A), to a deployment plane (X). The plane being defined by the location of the deployment axis and the separation pint ( 14 ). The drum is configured to pivot with respect to the deployment plane around an axis (C-C) substantially collinear with said deployment axis (A-A).

1 . A coiled tube drilling rig for drilling boreholes, the rig including:
 a drum including a drum core, said drum being rotatably mounted about a longitudinal drum rotation axis and adapted for receiving a length of semi-rigid tubing wound onto the drum; and   a deployment assembly including:
 an injector unit for deploying the tubing along a tubing deployment axis and into a borehole, said deployment axis being generally orthogonal to and generally intersecting the drum rotation axis; and 
 an indexing guide for confining the tubing in an indexing zone between a tangential tubing separation point on the drum and the deployment axis, to a deployment plane defined by the tubing separation point and the deployment axis; 
   wherein the drum is configured to pivot with respect to the deployment plane around an indexing axis, said indexing axis substantially collinear with said deployment axis, to accommodate movement of the separation point with respect to the drum as a consequence of the confining of the tubing in the indexing zone.   
   
   
       2 . A drilling rig according to  claim 1 , wherein the deployment plane and indexing guide are angularly fixed with respect to the injector unit about the deployment axis. 
   
   
       3 . A drilling rig according to  claim 2 , further including indexing control means for controlling the relative pivoting of the drum thereby controlling the lateral position of separation point on the drum such that the tubing is wound onto the drum in a predetermined indexing pattern. 
   
   
       4 . A drilling rig according to  claim 3 , wherein the indexed winding pattern includes contiguous parallel windings. 
   
   
       5 . A drilling rig according to  claim 4 , including an actuator for selectively pivoting the drum relative to the deployment plane. 
   
   
       6 . A drilling rig according to  claim 1 , wherein said deployment assembly includes a deployment assembly housing for housing the injector unit and indexing guide. 
   
   
       7 . A drilling rig according to  claim 6 , wherein said drum is mounted in a drum frame and said drum frame is pivotally mounted to said deployment housing. 
   
   
       8 . A drilling rig according to  claim 7 , further including a support cradle for supporting the drum frame and deployment assembly housing. 
   
   
       9 . A drilling rig according to  claim 5 , wherein said actuator is a linear actuator connected between said drum frame and said housing for selectively pivoting the drum relative to the deployment plane. 
   
   
       10 . A drilling rig according to  claim 1 , wherein the injector unit comprises a tractor unit providing an axial thrust force to the tubing, for selectively pushing the tubing into the borehole during drilling or retracting the tubing from the hole. 
   
   
       11 . A drilling rig according  claim 1 , wherein said drum and said deployment assembly are rotatably mounted about an axis substantially collinear with the deployment axis. 
   
   
       12 . A drilling rig according to  claim 1 , adapted for receiving a drilling assembly mounted on the end of the semi-rigid tubing and incorporating an offset feature, causing the drilling assembly to deviate from a straight path as the semi-rigid tubing is advanced by the injector unit during drilling operations. 
   
   
       13 . A drilling rig according to  claim 12 , wherein the drilling assembly includes a conventional down hole motor. 
   
   
       14 . A drilling rig as claimed in  claim 13 , wherein the down hole motor is arranged to drive a PCD drill bit and the drilling assembly also includes a survey and geo-sensing package. 
   
   
       15 . A drilling rig as claimed in  claim 13 , wherein the offset feature comprises a bent-sub housing arranged such that the axis of the drill bit is offset from the longitudinal axis of the coiled tubing in the borehole. 
   
   
       16 . A drilling rig as claimed in  claim 1 , wherein the semi-rigid tubing is deployed into the borehole through a peripheral seal, allowing borehole fluid to be constantly pressurised during drilling operations. 
   
   
       17 . A drilling rig for drilling boreholes, the rig including:
 a drum mounted in a drum frame and arranged for selectively receiving a length of semi-rigid tubing wound onto a drum core of said drum, said drum being rotatably mounted in the frame about a longitudinal drum rotation axis to facilitate winding of the tubing;   a deployment assembly for deploying the tubing into a borehole along a tubing deployment axis, said axis generally orthogonal to and extending radially from the drum rotation axis, wherein said deployment assembly includes:
 an injector unit for providing an axial force to the tubing along the tubing deployment axis; 
 an indexing guide for confining the tubing in an indexing zone between a tangential tubing separation point on the drum and the deployment axis, to a tubing deployment plane being generally coincident with and parallel to the deployment axis; and 
 a deployment assembly housing, for housing the injector unit and indexing guide; 
   a drilling assembly mounted on the end of the semi-rigid tubing and incorporating an offset feature causing the drilling assembly to deviate from a straight path as the semi-rigid tubing is advanced by the injector unit during drilling operations;   a support cradle for supporting the drum frame and deployment assembly;   said drum frame and said housing being rotatably mounted to the cradle about an axis substantially coincident with the deployment axis; and   wherein the drum is configured to pivot with respect to the deployment plane around an indexing axis, said indexing axis substantially collinear with said deployment axis, to accommodate movement of the separation point with respect to the drum as a consequence of the confining of the tubing in the indexing zone.   
   
   
       18 . A drilling rig according to  claim 17 , wherein the deployment plane and indexing guide are angularly fixed with respect to the injector unit about the deployment axis. 
   
   
       19 . A method of indexing tubing in a coiled tube drilling rig for drilling boreholes, the method including the steps of:
 providing a drum for receiving a length of semi-rigid tubing wound onto a drum core of said drum between a pair of end stops, wherein said drum is rotatably mounted about a longitudinal drum rotation axis;   deploying and retracting the tubing along a tubing deployment axis into a borehole from and to the drum respectively, said deployment axis being generally orthogonal to and intersecting the drum rotation axis; and   confining said tubing in an indexing zone between a tangential tubing separation point on said drum and said deployment axis, to a deployment plane defined by the tubing separation point and the deployment axis;   pivoting the drum around an axis substantially collinear with said deployment axis to accommodate movement of the separation point with respect to the drum as a consequence of the confining of the tubing in the indexing zone.   
   
   
       20 . A method according to  claim 19 , further including controlling the relative pivoting of the drum to selectively position the separation point to facilitate a predetermined indexing pattern during winding of the tubing onto the drum. 
   
   
       21 . A method according to  claim 20 , wherein the indexed winding pattern includes contiguous parallel windings. 
   
   
       22 . A method according to  claim 19 , wherein the tubing is deployed and retracted by an injector unit for providing an axial thrust force to the tubing, for selectively pushing the tubing into the borehole during drilling or retracting the tubing from the hole. 
   
   
       23 . A method according to  claim 20 , wherein the tubing is confined to the deployment plane by an indexing guide and wherein the deployment plane and indexing guide are angularly fixed with respect to the injector unit about the deployment axis. 
   
   
       24 . A method according to  claim 23 , wherein said drum, said injector unit and said indexing guide are rotatably mounted about an axis substantially colinear with the deployment axis.