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.

Claims

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a more detailed description of the embodiments of the disclosure, reference will now be made to the accompanying drawings, wherein:

[0024] FIG. 1 is a section view of a known mud pulse telemetry tool that includes a pressure balance system;

[0025] FIG. 2 is an exploded view of the pressure balance system shown in FIG. 1; and

[0026] FIG. 3 is a sectional view of a system for balancing pressure in a downhole tool in accordance with the disclosure.

DETAILED DESCRIPTION

[0027] It is to be understood that the disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Additionally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure. Finally, all numerical values in this disclosure may be approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, ranges, and proportions disclosed herein or illustrated in the Figures without departing from the intended scope.

[0028] The inventors have discovered that the invasion of the chamber filled with hydraulic fluid by the drilling fluid of the known pressure balance system 40 shown in FIG. 2 may be caused by an excessive wobbling amplitude of the piston along a direction perpendicular to the longitudinal axis of the piston and/or of the stem along a direction perpendicular to the longitudinal axis of the stem.

[0029] Turning to FIG. 3, a system 140 for balancing pressure in a downhole tool in accordance with the disclosure is illustrated. The pressure balance system 140 may be located in the housing 34 of the tool 10, shown in FIG. 1, instead of the pressure balance system 40.

[0030] The pressure balance system 140 includes a piston 144, a cylindrical sleeve 142, a cap 148, a cylindrical stem 136, and a piston stop 139, all of which located inside the pressure housing 34. The piston 144 is positioned inside of the sleeve 142, where it can reciprocate. The piston 144 has an outer surface 110 that is adjacent to an inner surface of the sleeve. A space between the outer diameter of the piston 144 and the inner diameter of the sleeve 142 is sealed using an O-ring 146. The piston 144 has a center hole traversed by the stem 136. The stem 136 can reciprocate in the center hole. The center hole in the piston 144 has a surface 112 that is adjacent to an outer surface of the stem 136. A space between the outer diameter of the stem 136 and the inner diameter of the piston 144 is sealed using a quad seal 156, the illustration of which is schematized. The quad seal 156 is retained in the center hole by a washer 158 and an internal snap ring 160. The cap 148 is located at the bottom end of the sleeve 142. The cap 148 and O-rings 150 are used to create a seal between the sleeve 142 and pressure housing 34. The piston stop 139 is used to stop the piston 44 from coming out of the sleeve 142. The piston 144 is designed to be exposed to drilling fluid on the upper side, and hydraulic fluid on the lower side. The O-Rings 146, 150, and the quad seal 156 are used to isolate the drilling fluid and the hydraulic fluid from each other.

[0031] In some embodiments, the outer surface 110 of the piston 144 may be sized to control a wobble of the piston 144 along a direction perpendicular to a longitudinal axis 114 of the piston 144 and to allow reciprocation of the piston 144 inside the sleeve 142. For example, a diameter of the outer surface 110 of the piston 144 may be sized to control the wobble of the piston 144 and to allow the reciprocation of the piston 144 inside the sleeve 142. The diameter of the outer surface 110 may be determined by routine experimentation. The diameter of the outer surface 110 is preferably not so large as to hinder the reciprocation of the piston 144 inside the sleeve 142. The diameter of the outer surface 110 is preferably not so small as to cause premature wear and invasion of section 120, which is filled with hydraulic fluid, by the drilling fluid present in section 122. Optionally, the diameter of the outer surface 110 of the piston may be sized within a first predetermined tolerance, and a diameter of the inner surface of the sleeve 142 may be sized within a second predetermined tolerance. Alternatively or additionally, an axial length of the outer surface 110 of the piston 144 may be sized to control the wobble of the piston 144 and to allow the reciprocation of the piston 144 inside the sleeve 142. The axial length of the outer surface 110 may also be determined by routine experimentation. The length of the outer surface 110 is preferably not so large as to hinder the reciprocation of the piston 144 inside the sleeve 142. The length of the outer surface 110 is preferably not so small as to cause premature wear and invasion of section 120 filled with hydraulic fluid by the drilling fluid present in section 122.

[0032] In some embodiments, the surface 112 of the hole may be sized to control a wobble of the stem 136 along a direction perpendicular to a longitudinal axis 116 of the stem 136 and to allow reciprocation of the stem 136 through the hole in the piston. For example, an axial length of the surface 112 of the hole may be sized to control the wobble of the stem 136 and to allow the reciprocation of the stem through the hole in the piston. The axial length of the surface 112 of the hole may be determined by routine experimentation. The surface 112 of the hole is preferably not so large as to hinder the reciprocation of the piston 144 inside the sleeve 142. The surface 112 of the hole is preferably not so small as to cause premature wear and invasion of section 120 filled with hydraulic fluid by the drilling fluid present in section 122.

[0033] In order to prepare the pressure balance system 140 for operation, hydraulic fluid is placed inside of the chamber of the pressure balance system 140 in section 120. When the hydraulic fluid fills the chamber, the piston 144 moves upward until it reaches the piston stop 39. A vacuum may then be pulled in the chamber to remove any excess air bubbles. The chamber may then be re-filled again with hydraulic fluid.

[0034] Once the chamber of the pressure balance system 140 has been successfully filled, the piston 144 is moved downward and positioned at a predetermined distance from the piston stop 139. During this downward movement, the excess hydraulic fluid exits out of the chamber. The chamber is then sealed off with a plug, securing the hydraulic fluid inside. This positioning of the piston 144 allows the piston 144 to move within the sleeve 142 in response to the downhole pressure of the drilling fluid and heat expansion of the hydraulic fluid.

[0035] The claimed invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the claims to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the claims.