Pressure monitoring technique

• US 20050199053A1
• Filed: 05/11/2005
• Published: 09/15/2005
• Est. Priority Date: 06/03/2003
• Status: Active Grant

• Current Assignee: Butler T. Glen, Thomas L. Butler
• Original Assignee: Butler T. Glen, Thomas L. Butler
• Inventors: Butler, T. Glen, Butler, Thomas L.
• Granted Patent: US 7,185,536 B2
• Time in Patent Office: Days
• US Class Current: 73/152.55
• CPC Class Codes: E21B 47/06 Measuring temperature or pressure

Abstract

The outlet pressure of a pump that fluctuates rapidly, as is typical of high pressure multiplex pumps, is sensed in a pressure line leading from the main flow line to a damping mechanism. The damping mechanism comprises a pair of small spaced openings, which are preferably adjustable in size. The damping mechanism is ideally a pair of needle valves placed in series so the pressure downstream of the second needle valve fluctuates considerably less than upstream of the first needle valve. The damped pressure is sensed to provide an input to real time graphs showing various pertinent pressure measurements involving the application of pressure, e.g. to monitor downhole tools in hydrocarbon wells. The downhole tools may be fluid driven motors, whipstocks, packers, wiper plugs and the like. In the case of fluid driven or mud motors, a base line pressure taken when the motor is idling is compared to the pressure when the motor is drilling to detect the onset of motor stall.

Claims

1. A pressure monitoring system including

a pressure source having a significantly fluctuating outlet pressure communicating with a mechanism using the fluctuating outlet pressure,

a damper effective to reduce pressure fluctuations in communication with the pressure source, the damper comprising first and second spaced members providing first and second spaced openings and a cavity between the first and second openings, and

a display device responsive to damped pressure.

2. The pressure monitoring system of claim 1 wherein the first and second members comprise valves.

3. The pressure monitoring system of claim 2 wherein the valves are needle valves.

4. The pressure monitoring system of claim 2 wherein the cavity between the first and second openings comprises a flow path between the valves.

5. The pressure monitoring system of claim 1 wherein the first and second openings are adjustable in size.

6. The pressure monitoring system of claim 1 wherein the damper is effective to reduce fluctuations to less than about 1% of average outlet pressure.

7. The pressure monitoring system of claim 1 wherein the damper is effective to reduce fluctuations to less than ¼

of average outlet pressure.

8. The pressure monitoring system of claim 1 wherein the damper is effective to reduce fluctuations to less than 0.1% of average outlet pressure.

9. A monitoring system for a downhole motor powered by liquid pumped down a work string in a hydrocarbon well by a pump, comprising

a pressure sensor exposed to outlet pressure of the pump and providing an output;

a display device for displaying a pressure differential equal to the outlet pressure of the pump when the downhole motor is idling and the outlet pressure of the pump when the downhole motor is under load; and

an assembly for converting the output of the pressure sensor into a value representing the pressure differential and energizing the display device to show the pressure differential in real time.

10. The monitoring system of claim 9 wherein the pressure differential is displayed on the display device as a trace of real time versus pressure.

11. The method of monitoring a downhole motor powered by liquid pumped down a work string in a hydrocarbon well by a pump, comprising

sensing outlet pressure of the pump and providing an output;

determining a series of pressure differential values equal to the outlet pressure of the pump when the downhole motor is idling and a series of outlet pressures of the pump when the downhole motor is under load; and

displaying a value, in real time, representative of the pressure differential.

12. The method of claim 11 wherein the displaying step comprises displaying a trace of the pressure differential versus time.

13. The method of monitoring operations of a downhole tool of the type that is positioned in a hydrocarbon well and operated by pressure supplied from above ground by a pressure source having a fluctuating outlet pressure providing fluctuations that mask pressure responses of operation of the downhole tool, comprising providing a pressure sensing line leading from pressure source;

damping pressure in the pressure sensing line to reduce fluctuations to a value sufficient to reveal operation of the downhole tool;

sensing damped pressure and providing an output; and

displaying a real time trace of damped pressure.

14. The method of claim 13 wherein the pressure is hydraulic pressure.