DOWNHOLE PRESSURE COMPENSATING DEVICE

• US 20140014352A1
• Filed: 03/29/2012
• Published: 01/16/2014
• Est. Priority Date: 03/30/2011
• Status: Active Grant

• Current Assignee: Welltec A/S
• Original Assignee: Welltec A/S
• Inventors: Hallundbk, Jrgen
• Granted Patent: US 9,458,695 B2
• Time in Patent Office: Days
• US Class Current: 166/320
• CPC Class Codes: E21B 34/08 responsive to flow or pressure of the fluid obtained E21B34/10 takes precedence
• CPC Class Codes: E21B 43/1195 Replacement of drilling mud; decrease of undesirable shock waves
• CPC Class Codes: E21B 47/017 Protecting measuring instruments

Abstract

The present invention relates to a downhole pressure compensating device for use in combination with a downhole tool, comprising a housing with a chamber and an internal hollow section, a first piston dividing the chamber into a first section and a second section, the first section being in fluid communication with a first fluid port, the second section being in fluid communication with a borehole through a second fluid port, and a first spring disposed within the second section to exert a pressure on the first piston to enable the conservation of an overpressure in the first section. Furthermore, the device comprises a second piston, a second spring disposed between the first piston and the second piston, and an overpressure channel arranged in the first or the second piston, which overpressure channel, when the second spring is in a compressed condition, provides fluid communication between said first and second sections. The present invention further relates to a downhole system comprising a wireline, a mating tool such as a driving unit and/or an operational tool, and a downhole pressure compensating device according to the invention. The present invention also relates to a downhole system comprising a wireline, a mating tool such as a driving unit and/or an operational tool, and a downhole pressure compensating device according to the invention.

Claims

1. A downhole pressure compensating device for use in combination with a downhole tool, comprising:

a housing with a chamber and an internal hollow section,

a first piston dividing the chamber into a first section and a second section, the first section being in fluid communication with a first fluid port, the second section being in fluid communication with a borehole through a second fluid port, and

a first spring disposed within the second section to exert a pressure on the first piston to enable the conservation of an overpressure in the first section,

wherein the device further comprises;

a second piston,

a second spring disposed between the first piston and the second piston, and

an overpressure channel arranged in the first or the second piston, which overpressure channel, when the second spring is in a compressed condition, provides fluid communication between said first and second sections.

2. A downhole pressure compensating device according to claim 1 comprising at least a pressure connection to a mating tool in a tool string.

3. A downhole pressure compensating device according to claim 2 wherein the mating tool is a driving unit.

4. A downhole pressure compensating device according to claim 1 wherein the second section of the compensating device is in fluid communication with the inside of an electrical motor unit and/or a hydraulic pump unit.

5. A downhole pressure compensating device according to claim 1 wherein the first spring, the second spring, the first piston and the second piston are arranged coaxially with the longitudinal centre axis of the compensating device.

6. A downhole pressure compensating device according to claim 1, wherein at least one of the first spring, the second spring, the first piston and the second piston has been arranged non-coaxially with the longitudinal centre axis of the compensating device non-circumscribing the internal hollow section.

7. A downhole pressure compensating device according to claim 6, wherein the compensating device is arranged non-coaxially with a longitudinal centre axis of the tool.

8. A downhole pressure compensating device according to claim 1, wherein the second piston is partly arranged inside the first piston.

9. A downhole pressure compensating device according to claim 1, wherein the first piston is partly arranged inside the second piston.

10. A downhole pressure compensating device according to claim 1, wherein the first section of the chamber is filled with a pressurised hydraulic fluid such as oil with predetermined characteristics.

11. A downhole pressure compensating device according to claim 1, further comprising electrical sensors for monitoring a temperature inside the device and/or pressures in the first and second sections and/or positions of the first and second pistons for producing a feedback signal to a control system.

12. A downhole pressure compensating device according to claim 1, further comprising at least a switch wherein the compensating device can be controlled by the at least a switch connected to the control system to adapt to changes in environmental conditions based on the feedback signal.

13. A downhole pressure compensating device according to claim 1, wherein the device comprises a plurality of first and/or second springs.

14. A downhole system comprising:

a wireline,

a mating tool such as a driving unit and/or an operational tool, and

a downhole pressure compensating device according to claim 1.

15. A downhole tool system comprising:

at least a mating tool such as a driving unit and/or an operational tool, and

a downhole pressure compensating device according to claim 1.