Apparatus for Downhole Milling of Material of a Well Wall

Abstract

A machining unit is for milling material off an, in the position of application, surrounding pipe wall in a borehole in an underground structure. The machining unit is connected to a rotary-drive unit arranged to provide a controlled peripheral speed in a milling unit, and is connected to an axial-drive unit arranged to provide a controlled axial displacement of at least the milling unit, and is connected to a conduit for the supply of fluid. The milling unit is provided with at least two rotatable milling heads which are evenly distributed the periphery of the machining unit and are displaceable, via a milling-head actuator, in the radial direction of the milling unit, and which are connected via a transmission to a pressure-fluid-driven motor arranged in the machining unit.

1 - 10 . (canceled) 
     
     
         11 . A machining unit for milling material off an, in a position of application, surrounding pipe wall in a borehole in an underground structure, wherein the machining unit is connected to a rotary-drive unit arranged to provide a controlled peripheral speed in a milling unit, is connected to an axial-drive unit arranged to provide a controlled axial displacement of at least the milling unit, and is connected to a conduit for the supply of fluid, wherein the milling unit comprises at least two rotatable milling heads which are evenly distributed around the periphery of the machining unit and are displaceable, via a milling-head actuator, in the radial direction of the milling unit, and which are connected via a transmission to a pressure-fluid-driven motor arranged in the machining unit, and wherein a fluid-supply conduit is arranged downstream of the pressure-fluid-driven motor and is provided with one or more first outlets arranged near the milling unit. 
     
     
         12 . The machining unit according to  claim 11 , wherein the milling head is supported in a freely projecting first end portion of a pendulum arm which is provided with a hinge joint in a second end portion and is pivotably mounted in the milling unit. 
     
     
         13 . The machining unit according to  claim 12 , wherein the pendulum arm is connected to the milling-head actuator in the form of a linear actuator connected to the pendulum arm via a link arm. 
     
     
         14 . The machining unit according to  claim 11 , wherein the machining unit is connected to a rotatable drill-pipe string, the rotary-drive unit of the machining unit being a drill-string rotary unit arranged on a surface installation. 
     
     
         15 . The machining unit according to  claim 11 , wherein the axial-drive unit is arranged in the machining unit and is provided with several feeder wheels lying in a plane which is slanted relative to a plane that is perpendicular to the center axis of the machining unit, the feeder wheels being displaceable, via an actuator, between a retracted, inactive position and an active position in which they arc resting against the pipe wall. 
     
     
         16 . The machining unit according to  claim 11 , wherein the fluid-supply conduit is provided with one or more second outlets arranged remotely from the milling unit. 
     
     
         17 . The machining unit according to  claim 11 , wherein a settable packer surrounds a portion of the machining unit and is arranged to separate a milling area in the wellbore from an annulus forming a flow path for return fluid from the machining unit. 
     
     
         18 . The machining unit according to  claim 11 , wherein a fluid-return conduit extends out from the milling unit and, remotely from the milling unit, is provided with one or more inlets arranged to hold back material milled by the milling unit. 
     
     
         19 . The machining unit according to  claim 18 , wherein the fluid-return conduit is connected to one or more return outlets discharging into an annulus forming a flow path for return fluid from the machining unit.