Washpipe seal

Abstract

A controlled leakage seal assembly having a first stationary portion adapted to be connected in substantially fluid-tight relation to a source of drilling fluid and a second portion adapted to be connected in substantially fluid-tight relation to a rotary portion including a washpipe. The seal includes a first housing and a stack of radially inwardly extending, spaced apart annular stators, and a second seal housing and stack of spaced apart radially outwardly extending annular rotors. The stators and rotors are interleaved with one another and axially spaced apart by a working clearance. The stators and said rotors combine to define an elongated radially and axially extending tortuous path. The seal assembly permits the washpipe and the first and second housings to rotate relative to each other in substantially fluid-tight relation except for the drilling fluid passing along the tortuous path between the rotors and stators and allows the drilling fluid to enter an outlet region at greatly reduced pressure.

1 . A seal assembly for controlling leakage of drilling fluid between a first stationary portion adapted to be connected in substantially fluid-tight relation to a source of drilling fluid and a second portion adapted to be connected in substantially fluid-tight relation to a rotary portion including a washpipe and a drill string, said first seal portion including a first housing and a stack of radially inwardly extending, spaced apart annular stators and a second seal portion including a second housing and stack of spaced apart radially outwardly extending annular rotors, said stators and said rotors being interleaved with one another and being axially spaced apart from one another by a working clearance, said stators and said rotors combining to define an elongated radially and axially extending tortuous path from an inlet region at one axial end of said stack of stators and rotors for receiving drilling fluid confined at high pressure and directing said fluid along said tortuous path to an outlet region at the other axial end of said stack of stators and rotors, said seal assembly permitting said washpipe and said first and second housings to rotate relative to each other in substantially fluid-tight relation except for said drilling fluid passing along said tortuous path between said stacks of rotors and stators, and allowing said drilling fluid to enter said outlet region at greatly reduced pressure.  
   
   
       2 . A seal assembly as defined in  claim 1 , wherein each of said stators and each of said rotors includes a large plurality of radially closely spaced apart, circumferentially extending lands and grooves.  
   
   
       3 . A seal assembly as defined in  claim 1  wherein said stators and said rotors having working faces that are spaced apart by a working clearance of from about 0.010 to about 0.090 inches.  
   
   
       4 . A seal assembly as defined in  claim 1  wherein said stators and said rotors are held in a said interleaved position by spacers lying between the radially outer margins of said stators and lying between the inner margins of said rotors.  
   
   
       5 . A seal assembly as defined in  claim 4  wherein said spacers are confined by means for exerting a compressive force thereon.  
   
   
       6 . A seal assembly as defined in  claim 5  wherein said means for exerting a compressive force includes Belleville washers.  
   
   
       7 . A said assembly as defined in  claim 1  wherein said outlet region for receiving said drilling fluid at said greatly reduced pressure is an annular chamber.  
   
   
       8 . A seal assembly as defined in  claim 1  wherein said seal assembly further includes means at said outlet region for directing said drilling fluid toward a return path, and a flow meter disposed in said return path.  
   
   
       9 . A seal assembly as defined in  claim 7  which further includes a flow meter disposed downstream of said annular chamber.  
   
   
       10 . A seal assembly as defined in  claim 1  wherein at least one group of said rotors and stators includes radially extending axially directed working faces having plural land and groove formations thereon to further retard the radial flow of drilling fluid through said seal assembly.  
   
   
       11 . A seal assembly as defined in  claim 4  wherein said stators and said rotors include close radial spaces between said rotors and said stators and said spacers, thereby providing a portion of said tortuous path.  
   
   
       12 . A seal assembly for controlling leakage of drilling fluid between a first stationary portion connected in substantially fluid-tight relation to a source of drilling fluid and a second portion connected in substantially fluid-tight relation to a rotary portion including a washpipe and a drill string, said first seal portion including a first metal housing and a stack of radially inwardly extending, spaced apart annular stators in the form of thin disks, and a second seal portion including a second metal housing and stack of spaced apart, radially outwardly extending annular rotors in the form of thin disks, said stators and said rotors being interleaved with one another and being axially and radially spaced apart from one another by a working clearance of from about 0.010 inches to about 0.090 inches, the faces and end portions of said stators and said rotors combining to define an elongated, radially and axially extending tortuous path from an inlet region at one axial end of said stack of stators and rotors for receiving drilling fluid confined at high pressure and directing said fluid along said tortuous path to an outlet region at the other axial end of said stack of stators and rotors, said seal assembly permitting said washpipe and said first and second metal housings to rotate relative to each other in substantially fluid-tight relation except for said drilling fluid passing along said tortuous path between said stacks of rotors and stators, and allowing said drilling fluid to enter said outlet region at greatly reduced pressure.  
   
   
       13 . A seal assembly as defined in  claim 11  wherein at least one group of said rotors and stators includes radially extending axially facing surfaces having plural land and groove formations thereon to retard the flow of drilling fluid through said seal.