Method and Device for Reducing Friction Between Helical Members of a Downhole Damper

Abstract

A method for reducing friction between interconnected outer and inner helical members of a downhole damper where the damper includes an outer damper body and an inner damper body, and where the outer and inner damper bodies are telescopically movable relative each other, the outer and inner damper bodies being biased in the extending direction, and where one of the outer and inner damper bodies are connected to a drill bit workable at a borehole face, and where the other of the outer and inner damper bodies is connected to a torque and force transmitting member, and where the outer and inner helical parts are arranged so as to retract the bit from the face when torque applied by the torque and force transmitting member exceeds a preset value, wherein the method includes letting a relative movement between the inner and outer body force lubricant to flow between the helical members.

1 . A method for reducing friction between interconnected outer and inner helical members of a downhole damper where the damper includes an outer damper body and an inner damper body, and where the outer and inner damper bodies are telescopically movable relative each other, the outer and inner damper bodies being biased in the extending direction, and where one of the outer and inner damper bodies is connected to a drill bit workable at a borehole face, and where the other of the outer and inner damper bodies is connected to a torque and force transmitting member, and where the outer and inner helical parts are arranged so as to retract the bit from the face when torque applied by the torque and force transmitting member exceeds a preset value, wherein the method includes:
 letting a relative movement between the inner and outer body force lubricant to flow between the helical members.   
     
     
         2 . A method according to  claim 1 , wherein the method further includes:
 arranging a closed first cavity filled with lubricant at a first end party of the helical members;   arranging a closed second cavity filled with lubricant at a second end party of the helical members;   shrinking the closed first cavity of lubricant and expanding the closed second cavity of lubricant when the inner helical member is moved towards the first cavity of lubricant.   
     
     
         3 . A downhole damper where the damper includes an outer damper body having an outer helical member, and an inner damper body having an inner helical member operable interconnected with the outer helical member, and where the outer and inner damper bodies are telescopically movable relative each other, the outer and inner damper bodies being biased in the extending direction, and where one of the outer and inner damper bodies is connected to a drill bit workable at a face, and where the other of the outer and inner damper bodies is connected to a torque and force transmitting member, and where the outer and inner helical parts are arranged so as to retract the bit from the face when torque applied by the torque and force transmitting member exceeds a preset value,
 wherein a closed first cavity is defined by the inner damper body, a first bore in the outer damper body, the outer helical member and a first cylindrical part of the inner damper body, and where closed second cavity is defined by the inner damper body, a second bore in the outer damper body, the outer helical member and a second cylindrical part of the inner damper body, and where the first and second cavity are positioned at opposite ends of the outer helical member.   
     
     
         4 . A downhole damper according to  claim 1 , wherein the inner helical member includes helical splines with at least a first or a second contact area. 
     
     
         5 . A device according to  claim 1 , wherein at least one of the contact areas have pockets.