Underreamer with Radial Expandable Cutting Blocks

Abstract

A cutting tool ( 1 ) for widening the diameter of a borehole and method thereof is disclosed. The cutting tool ( 1 ) comprises a housing ( 2 ) having cavity ( 10 ) in which a moveable activation element ( 6 ) is arranged. The activation element ( 6 ) is moved in an axial direction and is connected to one or more cutting blocks via a mechanical coupling ( 15 ). The mechanical coupling ( 15 ) transfers the axial movement of the action element into a radial movement of the cutting blocks. An activation unit ( 24 ) pushes the activation element ( 6 ) towards a stopping position which in turn causes the cutting blocks ( 11 ) to move out of the housing. The activation unit ( 24 ) further pulls the activation element back towards its starting position which in turn causes the cutting blocks to move back into the housing. The cutting blocks ( 11 ) extend into one or more cavities formed in the activation element, thereby increasing the travel-to-expansion ratio. The cutting blocks can be replaced by stabiliser blades ( 20 ) which are used to stabilise the drilling in the expanded borehole.

1 . A cutting tool for widening the diameter of a borehole, comprising:
 a housing having a top end, a bottom end and a first outer surface, wherein the housing defines a longitudinal direction and a transverse radial direction,   at least one moveable cutting block having at least one cutting element, each cutting block being arranged in a first opening located in the first outer surface and configured to move in the radial direction between a retracted position and an expanded position relative to the housing,   at least one moveable activation element arranged relative to the at least one cutting block and configured to move along the longitudinal direction relative to the housing for activation of the at least one cutting block   wherein   the housing comprises a cavity connected to the first opening in which the at least one cutting block and the at least one activation element are arranged, wherein the cavity is arranged between the first outer surface and an inner surface of the housing.   
     
     
         2 . A cutting tool according to  claim 1 , wherein the activation element is further connected to an activation unit arranged in the cavity, wherein the activation unit is configured to drive the activation element. 
     
     
         3 . A cutting tool according to  claim 2 , wherein the activation unit is arranged in a chamber inside the cavity, the chamber being sealed off from the rest of the cavity. 
     
     
         4 . A cutting tool according to  claim 2 , wherein the activation unit comprises a linear actuator connected to a control unit configured to control the operation of the activation unit. 
     
     
         5 . A cutting tool according to  claim 1 , further comprising a mechanical coupling comprising a first set of guiding elements, e.g. a pin, configured to engage a second set of guiding elements, e.g. through hole, wherein one of the first and second sets of guiding elements is arranged on a third surface of the at least one cutting block and the other set of the guiding elements is arranged on a fourth surface on the at least one activation element facing the third surface. 
     
     
         6 . A cutting tool according to  claim 1 , wherein the at least one activation element comprises a cavity or through hole located on an outer surface, wherein at least a part of the at least one cutting block extends into the cavity or through hole. 
     
     
         7 . A cutting tool according to  claim 1 , wherein the ratio between the relative axial movement of the at least one activation element and the relative radial movement of the at least one cutting block is between 1:1 and 1:100. 
     
     
         8 . A cutting tool according to  claim 1 , wherein the cutting tool comprises a spring element configured to apply a spring force to the activation element, the spring element being arranged relative to the activation element inside the cavity. 
     
     
         9 . A cutting tool according to  claim 1 , wherein the cutting tool further comprises at least one stabiliser blade arranged in at least one second opening located on the first outer surface, wherein the at least one stabiliser blade is moveably connected to the at least one activation element. 
     
     
         10 . A method for operating a cutting tool according to  claim 1 , wherein the method comprises the steps of:
 moving the at least one activation element in the longitudinal direction relative to the housing, and further moving the at least one cutting block in the radial direction out of the housing towards an expanded position,   wherein   the at least one activation element is arranged in a cavity in the outer surface, wherein said at least one activation element is moved along the cavity by an activation unit further arranged in the cavity.   
     
     
         11 . A method according to  claim 10 , wherein a linear actuator drives the at least one activation element, wherein the operation of the linear actuator is controlled by a control unit. 
     
     
         12 . A method according to  claim 10 , wherein the longitudinal movement is transferred into the radial movement by using a mechanical coupling located between the at least one activation element and the at least one cutting block. 
     
     
         13 . A method according to  claim 11 , wherein the method further comprises the step of:
 monitoring at least one parameter of the drilling fluid passing through the cutting tool via the control unit, and further detecting when the at least one parameter has reached a predetermined level within a predetermined time window, or   communicating with a remote unit via the control unit, wherein the remote unit and the control unit control the operation of the cutting tool.   
     
     
         14 . A method according to any  claim 10 , wherein one end of the at least one cutting block extends into an opening located on the at least one activation element, wherein the one end is at least moved further into the at least one activation element when the cutting block is moved towards the retracted position.