Piston Design for Downhole Pulser

Abstract

A measurement while drilling (MWD) tool includes a sensor, an encoder operably connected to the sensor and a pulser operably connected to the encoder. The pulser includes a linearly acting bidirectional piston that operates a poppet valve. The poppet valve is designed to completely or partially interrupt the flow of fluid through the MWD tool. The selective operation of the piston-driven poppet valve creates pressure signals that are carried through the fluid. The piston assembly that drives the poppet valves includes wear rings that improve the performance and durability of the piston.

What is claimed is: 
     
         1 . An acoustic pulse generating component for use in connection with a downhole drilling tool, the acoustic pulse generating module comprising:
 a piston assembly, wherein the piston assembly includes a piston having a wear ring; and   a drive assembly configured to move the piston assembly.   
     
     
         2 . The acoustic pulse generating component of  claim 1 , wherein the wear ring comprises a thermoplastic wear ring. 
     
     
         3 . The acoustic pulse generating module of  claim 2 , wherein the wear ring comprises an ultra-high molecular weight polyethylene wear ring. 
     
     
         4 . The acoustic pulse generating module of  claim 1 , wherein the wear ring comprises an oil-impregnated nylon wear ring. 
     
     
         5 . The acoustic pulse generating module of  claim 1 , wherein the wear ring comprises a ceramic wear ring. 
     
     
         6 . The acoustic pulse generating module of  claim 1 , wherein the piston comprises:
 a proximal end;   a distal end;   a central portion between the proximal end and the distal end; and   a ring seat within the central portion, wherein the wear ring is seated in the ring seat.   
     
     
         7 . The acoustic pulse generating module of  claim 1 , wherein the drive assembly comprises one or more solenoids configured to rapidly reciprocate the piston assembly within the pulse generating module. 
     
     
         8 . A drilling tool comprising:
 a sensor;   an encoder operably connected to the sensor; and   a pulser operably connected to the encoder, wherein the pulser comprises:
 a piston assembly, wherein the piston assembly includes a piston having a wear ring; and 
 a drive assembly configured to move the piston assembly. 
   
     
     
         9 . The drilling tool of  claim 8 , wherein the wear ring comprises a thermoplastic wear ring. 
     
     
         10 . The drilling tool of  claim 8 , wherein the wear ring comprises an ultra-high molecular weight polyethylene wear ring. 
     
     
         11 . The drilling tool of  claim 8 , wherein the wear ring comprises an oil-impregnated nylon wear ring. 
     
     
         12 . The drilling tool of  claim 8 , wherein the wear ring comprises a ceramic wear ring. 
     
     
         13 . The drilling tool of  claim 8 , wherein the piston comprises:
 a proximal end;   a distal end;   a central portion between the proximal end and the distal end; and   a ring seat within the central portion, wherein the wear ring is seated in the ring seat.   
     
     
         14 . The drilling tool of  claim 8 , wherein the drive assembly comprises one or more solenoids configured to rapidly reciprocate the piston assembly within the pulse generating module. 
     
     
         15 . The drilling tool of  claim 8 , wherein the piston assembly further comprises:
 a piston shaft; and   a poppet valve.   
     
     
         16 . The drilling tool of  claim 16 , wherein the piston has an outer diameter and wherein the pulser further comprises:
 a central bore having an inner diameter, wherein the inner diameter of the central bore is nominally the same as the outer diameter of the piston; and   an orifice, wherein the orifice is sized to admit the poppet valve.   
     
     
         17 . A measurement while drilling (MWD) tool comprising:
 at least one sensor configured to output a measurement signal representative of a measurement of a condition selected from the group consisting of torque, inclination, magnetic direction and position;   an encoder configured to encode the measurement signal into a command signal;   a pulser operably connected to the encoder and configured to transmit an acoustic signal through a fluid medium in response to the command signal, wherein the pulser comprises:
 a piston assembly, wherein the piston assembly includes a piston having a wear ring; and 
 a drive assembly configured to move the piston assembly. 
   
     
     
         18 . The MWD tool of  claim 17 , wherein the wear ring is manufactured from a material that exhibits a low coefficient of friction. 
     
     
         19 . The MWD tool of  claim 18 , wherein the wear ring is manufactured from a material selected from the group consisting of plastics and ceramics. 
     
     
         20 . The MWD tool of  claim 19 , wherein the wear ring is manufactured from a material selected from the group consisting of ultra-high molecular weight polyethylene and oil-impregnated nylon.