Pressure Balance System for Top Mount Pulser

Abstract

For balancing pressure in a downhole tool between a first section filled with hydraulic fluid and a second section filled with drilling fluid, a system utilizes a sleeve located inside a housing of the downhole tool, a piston located inside the sleeve. A stem traverses the piston through a hole in the piston. The stem is used to couple a solenoid to a valve system of the downhole tool, for example. The piston is sized to control a wobble of the piston and to allow reciprocation of the piston inside the sleeve. The hole in the piston is sized to control a wobble of the stem and to allow reciprocation of the stem through the hole in the piston.

What is claimed is: 
     
         1 . A system for balancing pressure in a downhole tool between a first section filled with hydraulic fluid and a second section filled with drilling fluid, the system comprising:
 a sleeve located inside a housing of the downhole tool;   a piston located inside the sleeve, the piston having one side exposed to the hydraulic fluid and another, opposite side exposed to the drilling fluid; and   a stem traversing the piston,   wherein the piston has an outer surface adjacent to an inner surface of the sleeve, the outer surface of the piston being sized to control a wobble of the piston along a direction perpendicular to a longitudinal axis of the piston and to allow reciprocation of the piston inside the sleeve.   
     
     
         2 . The system of  claim 1 , wherein a diameter of the outer surface of the piston is sized to control the wobble of the piston and to allow the reciprocation of the piston inside the sleeve. 
     
     
         3 . The system of  claim 2 , wherein the diameter of the outer surface of the piston is sized within a first predetermined tolerance. 
     
     
         4 . The system of  claim 2 , wherein a diameter of the inner surface of the sleeve is sized within a second predetermined tolerance. 
     
     
         5 . The system of  claim 1 , wherein a length of the outer surface of the piston is sized to control the wobble of the piston and to allow the reciprocation of the piston inside the sleeve. 
     
     
         6 . A system for balancing pressure in a downhole tool between a first section filled with hydraulic fluid and a second section filled with drilling fluid, the system comprising:
 a sleeve located inside a housing of the downhole tool;   a piston located inside the sleeve, the piston having one side exposed to the hydraulic fluid and another, opposite side exposed to the drilling fluid; and   a stem traversing the piston through a hole in the piston,   wherein the hole in the piston has a surface adjacent to an outer surface of the stem, the surface of the hole being sized to control a wobble of the stem along a direction perpendicular to a longitudinal axis of the stem and to allow reciprocation of the stem through the hole in the piston.   
     
     
         7 . The system of  claim 6 , wherein a length of the surface of the hole is sized to control the wobble of the stem and to allow the reciprocation of the stem through the hole in the piston. 
     
     
         8 . The system of  claim 6 , wherein the piston has an outer surface adjacent to an inner surface of the sleeve, the outer surface of the piston being sized to control a wobble of the piston and to allow reciprocation of the piston inside the sleeve. 
     
     
         9 . The system of  claim 8 , wherein a diameter of the outer surface of the piston is sized to control the wobble of the piston along a direction perpendicular to the longitudinal axis of the piston and to allow the reciprocation of the piston inside the sleeve. 
     
     
         10 . The system of  claim 9 , wherein the diameter of the outer surface of the piston is sized within a first predetermined tolerance. 
     
     
         11 . The system of  claim 9 , wherein a diameter of the inner surface of the sleeve is sized within a second predetermined tolerance. 
     
     
         12 . The system of  claim 8 , wherein a length of the outer surface of the piston is sized to control the wobble of the piston and to allow the reciprocation of the piston inside the sleeve. 
     
     
         13 . A method for balancing pressure in a downhole tool between a first section filled with hydraulic fluid and a second section filled with drilling fluid, the method comprising:
 providing a sleeve inside a housing of the downhole tool;   providing a piston inside the sleeve;   providing a stem through a hole in the piston; and   filling the first section with hydraulic fluid,   wherein the piston has an outer surface adjacent to an inner surface of the sleeve, the outer surface of the piston being sized to control a wobble of the piston along a first direction perpendicular to a longitudinal axis of the piston and to allow reciprocation of the piston inside the sleeve, and   wherein the hole in the piston has a surface adjacent to an outer surface of the stem, the surface of the hole being sized to control a wobble of the stem along a second direction perpendicular to a longitudinal axis of the stem and to allow reciprocation of the stem through the hole in the piston.   
     
     
         14 . The method of  claim 13 , wherein a diameter of the outer surface of the piston is sized to control the wobble of the piston and to allow the reciprocation of the piston inside the sleeve. 
     
     
         15 . The method of  claim 13 , wherein a length of the outer surface of the piston is sized to control the wobble of the piston and to allow the reciprocation of the piston inside the sleeve. 
     
     
         16 . The method of  claim 13 , wherein a length of the surface of the hole is sized to control the wobble of the stem and to allow the reciprocation of the stem through the hole in the piston.