DOWNHOLE PISTON PUMP AND METHOD OF OPERATION

• US 20110100641A1
• Filed: 11/03/2009
• Published: 05/05/2011
• Est. Priority Date: 11/03/2009
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Briquet, Stephane, Milkovisch, Mark
• Granted Patent: US 8,613,317 B2
• Time in Patent Office: Days
• US Class Current: 166/373
• CPC Class Codes: E21B 33/1275 inflated by down-hole pumping means operated by a down-hole drive
• CPC Class Codes: E21B 49/10 using side-wall fluid samplers or testers
• CPC Class Codes: F04B 47/04 the driving means incorporating fluid means
• CPC Class Codes: F04B 47/08 the motors being actuated by fluid

Abstract

A method, according to one or more aspects of the present disclosure, for operating a positive displacement pump of a downhole tool comprises supplying a hydraulic pressure to the pump to actuate a two-stroke piston to displace fluid at least partially through the downhole tool; moving the piston in a first stroke direction; and reversing the direction of the piston upon completion of the first stroke of the piston. Completion of a stroke may comprise a head of the piston substantially abutting an end wall of a chamber of the pump.

Claims

1. A method, comprising:

supplying a hydraulic pressure to a positive displacement pump of a downhole tool to actuate a two-stroke piston to displace fluid at least partially through the downhole tool;

moving the piston in a first stroke direction; and

reversing the direction of the piston upon completion of the first stroke of the piston.

2. The method of claim 1 wherein reversing the direction of the piston comprises monitoring the hydraulic pressure.

3. The method of claim 2 wherein monitoring the hydraulic pressure comprises measuring the hydraulic pressure in a hydraulic circuit between an energizing pump and the pump.

4. The method of claim 2 wherein monitoring the hydraulic pressure comprises at least one of measuring the hydraulic pressure in a hydraulic circuit between an energizing pump and the pump and a measuring a characteristic of the energizing pump associated with the hydraulic pressure supplied.

5. The method of claim 1 wherein the direction of the piston is reversed in response to the hydraulic pressure achieving a threshold pressure.

6. The method of claim 1 wherein completion of a stroke comprises a head of the piston substantially abutting an end wall of a chamber of the pump.

7. The method of claim 1 further comprising reducing the speed of the piston as it approaches completion of the first stroke direction.

8. The method of claim 7 wherein reducing the speed of the piston comprises absorbing energy of the piston.

9. The method of claim 7 wherein reducing the speed comprises reducing the flow of a hydraulic fluid supplying the hydraulic pressure to the pump.

10. The method of claim 1 wherein reversing the direction of the piston comprises:

monitoring the hydraulic pressure supplied to the pump; and

reversing the direction in response to achieving a threshold pressure in the hydraulic pressure.

11. The method of claim 10 wherein monitoring the hydraulic pressure comprises measuring the hydraulic pressure in a hydraulic circuit between an energizing pump and the pump.

12. The method of claim 10 wherein monitoring the hydraulic pressure comprises at least one of measuring the hydraulic pressure in a hydraulic circuit between an energizing pump and the pump and a characteristic of the energizing pump associated with the hydraulic pressure supplied.

13. The method of claim 10 wherein completion of a stroke comprises a head of the piston substantially abutting an end wall of a chamber of the pump.

14. The method of claim 13 further comprising reducing the speed of the piston as it approaches the completion of the first stroke.

15. An apparatus, comprising:

a pump assembly for pumping a fluid at least partially through a downhole tool, the assembly comprising;

a two-stroke displacement unit including a piston having a first head positioned in a first cylinder and a second head positioned in a second cylinder;

a first pump chamber formed between the first piston head and an end wall of the first cylinder;

a second pump chamber formed between the second piston head and an end wall of the second cylinder;

a control system providing hydraulic fluid via a hydraulic circuit to the displacement unit to move the piston in two stroke directions; and

a dampening device connected with the displacement unit to reduce the speed of the piston as it approaches completion of the stroke.

16. The apparatus of claim 15 wherein the dampening device comprises a choke hydraulically connected in the hydraulic circuit, wherein the choke is operable to reduce the flow of hydraulic fluid to the displacement unit.

17. The apparatus of claim 15 wherein the dampening device is positioned in at least one of the cylinders of the pump.

18. The assembly of claim 15 wherein the dampening device comprises:

a first dampening device disposed in the first cylinder between the first piston head and a distal wall of the first cylinder; and

a second dampening device disposed in the second cylinder between the second piston head and a distal wall of the second cylinder.

19. A method, comprising:

disposing a downhole tool having a pump assembly hydraulically connected to a flow line extending at least partially through the downhole tool in a borehole, the pump assembly comprising a two-stroke displacement unit including a piston having a first head positioned in a first cylinder and a second head positioned in a second cylinder;

a first pump chamber formed between the first piston head and an end wall of the first cylinder;

a second pump chamber formed between the second piston head and an end wall of the second cylinder; and

a control system providing hydraulic fluid via a hydraulic circuit to the displacement unit to move the piston in two stroke directions in response to the hydraulic pressure of the hydraulic fluid; and

reversing the direction of the piston stroke in response to the hydraulic pressure achieving a threshold pressure.

20. The method of claim 19 wherein:

the method further comprises reducing the speed of the piston as it approaches completion of the stroke;

the threshold pressure is associated with completion of the stroke;

completion of the stroke comprises substantially abutting one of the first and the second piston heads with the respective end wall of the first chamber or the second chamber;

reducing the speed of the piston comprises reducing the flow of hydraulic fluid supplied to the displacement unit; and

the method further comprises absorbing energy from the piston as it approaches completion of the stroke.