Variable diameter piston assembly for safety valve

Patent metadata

Field	Value
Publication number	US-2016273304-A1
Application number	US-201314396546-A
Country	US
Kind code	A1
Filing date	Dec 31, 2013
Priority date	Dec 31, 2013
Publication date	Sep 22, 2016
Grant date	—

Abstract

Disclosed are subsurface safety valves having a reduced spread between opening and closing pressures. One safety valve includes a housing having a piston bore defined therein and configured to receive hydraulic fluid pressure, the piston bore providing an upper bore having a first diameter, a lower bore having a second diameter, and an intermediate bore interposing the upper and lower bores and having a third diameter, wherein the third diameter is greater than the second diameter and the second diameter is greater than the first diameter, and a piston assembly movably arranged within the piston bore and comprising an upper piston operatively coupled to a lower piston, wherein the upper piston sealingly engages the upper bore and the lower piston sealingly engages the lower bore, wherein, when the upper piston is arranged in the intermediate bore, the hydraulic fluid pressure acts on the lower piston.

First claim

What is claimed is:

1 . A safety valve, comprising:
a housing having a piston bore defined therein and configured to receive hydraulic fluid pressure, the piston bore providing an upper bore having a first diameter, a lower bore having a second diameter, and an intermediate bore interposing the upper and lower bores and having a third diameter, wherein the third diameter is greater than the second diameter and the second diameter is greater than the first diameter; and a piston assembly movably arranged within the piston bore and comprising an upper piston operatively coupled to and axially offset from a lower piston, wherein the upper piston is configured to sealingly engage the upper bore and the lower piston is configured to sealingly engage the lower bore, wherein, when the upper piston is arranged in the intermediate bore, the hydraulic fluid pressure acts on the lower piston.

2 . The safety valve of claim 1 , wherein the upper piston comprises:
a body having a piston head; at least one dynamic seal arranged about the body and configured to seal against an inner wall of the upper bore; and a first labyrinth seal interposing the piston head and the at least one dynamic seal.

3 . The safety valve of claim 1 , wherein the lower piston comprises:
a body; a dynamic seal arranged about the body and configured to seal against an inner wall of the lower bore; and a labyrinth seal arranged about the body.

4 . The safety valve of claim 1 , further comprising:
a piston rod that extends longitudinally from the piston assembly through at least a portion of the piston bore; a flow tube operably coupled to the piston rod and movably arranged within a flow passage defined in the safety valve in response to the movement of the piston assembly; and a valve closure device movable between an open position and a closed position and adapted to restrict fluid flow through the flow passage when in the closed position, wherein the flow tube is adapted to shift the valve closure device between open and closed positions.

5 . The safety valve of claim 1 , further comprising a power spring arranged within a lower chamber defined within the housing and configured to bias the piston assembly upwardly within the piston bore.

6 . The safety valve of claim 1 , further comprising a spacer member arranged between the upper and lower pistons and operably coupling the upper and lower pistons.

7 . The safety valve of claim 1 , wherein the upper bore exhibits a first length and the lower bore exhibits a second length greater than the first length.

8 . The safety valve of claim 1 , wherein the upper bore exhibits a first length and the lower bore exhibits a second length less than the first length.

9 . The safety valve of claim 1 , further comprising:
a distal bore and an intermediate distal bore provided in the piston bore, wherein the intermediate distal bore interposes the lower bore and the distal bore and the distal bore has a fourth diameter greater than the second diameter; and an additional piston operably coupled to the lower piston and forming part of the piston assembly, the additional piston being configured to sealingly engage an inner wall of the distal bore, wherein, when the lower piston is arranged in the intermediate distal bore, the hydraulic fluid pressure acts on the additional piston.

10 . A method of actuating a safety valve, comprising:
conveying hydraulic fluid pressure to a piston bore that provides an upper bore having a first diameter, a lower bore having a second diameter, and an intermediate bore interposing the upper and lower bores and having a third diameter, wherein the third diameter is greater than the second diameter and the second diameter is greater than the first diameter; axially displacing a piston assembly movably arranged within the piston bore as the hydraulic fluid pressure acts on an upper piston of the piston assembly that sealingly engages the upper bore; and axially displacing the piston assembly further within the piston bore as the upper piston enters the intermediate bore and the hydraulic fluid pressure acts on a lower piston of the piston assembly that sealingly engages the lower bore, wherein the upper piston is coupled to the lower piston.

11 . The method of claim 10 , wherein conveying the hydraulic fluid pressure to the piston bore comprises conveying hydraulic fluid to the piston bore via a control line.

12 . The method of claim 10 , wherein the upper piston comprises a first dynamic seal and a first labyrinth seal, the method further comprising:
sealingly engaging an inner wall of the upper bore with the first dynamic seal; and axially displacing the piston assembly with the first labyrinth seal as the first dynamic seal exits the upper bore into the intermediate bore.

13 . The method of claim 12 , wherein the lower piston comprises a second dynamic seal and a second labyrinth seal, the method further comprising:
conveying the hydraulic fluid pressure past the upper piston as the first dynamic seal exits the upper bore into the intermediate bore; and sealingly engaging an inner wall of the lower bore with the second dynamic seal, whereby the hydraulic fluid pressure acts on the lower piston and moves the piston assembly.

14 . The method of claim 13 , further comprising gradually transitioning the hydraulic fluid pressure from the upper piston to the lower piston with the upper labyrinth seal.

15 . The method of claim 10 , wherein the piston assembly further comprises a piston rod that extends longitudinally through at least a portion of the piston bore and is operably coupled to a flow tube movably arranged within a flow passage defined in the safety valve, the method further comprising:
axially displacing the flow tube as the piston assembly moves within the piston bore; and moving a valve closure device with the flow tube from a closed position, which restricts fluid flow through the flow passage, to an open position.

16 . The method of claim 10 , further comprising compressing a power spring as the piston assembly is axially displaced by the hydraulic fluid pressure.

17 . The method of claim 16 , further comprising:
reducing the hydraulic fluid pressure within the piston bore; biasing the piston assembly upwardly within the piston bore with the power spring arranged within the piston bore; engaging the piston assembly on an up stop arranged in the piston bore; and generating a mechanical seal between the up stop and the piston assembly.

18 . The method of claim 10 , further comprising:
advancing the piston assembly within the piston bore until engaging a down stop arranged in the piston bore; and generating a mechanical seal between the piston assembly and the down stop.

19 . The method of claim 10 , wherein the upper bore exhibits a first length and the lower bore exhibits a second length that is greater than or less than the first length.

20 . The method of claim 10 , wherein the piston bore further provides a distal bore and an intermediate distal bore, wherein the intermediate distal bore interposes the lower bore and the distal bore, and the distal bore has a fourth diameter greater than the second diameter, the method further comprising:
axially displacing the piston assembly further within the piston bore as the lower piston enters the intermediate distal bore and the hydraulic fluid pressure acts on an additional piston of the piston assembly that sealingly engages the distal bore and is operably couple

Assignees

• Halliburton Energy Services Inc

Inventors

• Vick Jr James Dan
• Scott Bruce Edward

Classifications

• F16K31/1221

  one side of the piston being spring-loaded · CPC title

• F16K1/2007

  specially adapted operating means therefor (operating means per se F16K31/00) · CPC title

• E21B2200/05

  Flapper valves · CPC title

• E21B34/10 Primary

  operated by control fluid supplied from outside the borehole · CPC title

• E21B2034/005

  Fixed Constructions · mapped topic