Subsea well pressure monitor

• US 5,172,112 A
• Filed: 11/15/1991
• Issued: 12/15/1992
• Est. Priority Date: 11/15/1991
• Status: Expired due to Fees

• Current Assignee: ABB Vetco Gray, Inc. (GE Aerospace)
• Original Assignee: ABB Vetco Gray, Inc. (GE Aerospace)
• Inventors: Jennings, Charles E.
• Primary Examiner(s): ELDRED, JOHN W
• Application Number:
  US07/792,846
• Time in Patent Office: 396 Days
• Field of Search: 367/141, 340/850, 340/853.1, 340/854.6, 340/856.3, 340/856.4, 166/336, 166/337, 166/363, 166/364
• US Class Current: 340/850
• CPC Class Codes: E21B 47/001 for underwater installation
• CPC Class Codes: E21B 47/06 Measuring temperature or pressure
• CPC Class Codes: E21B 47/117 Detecting leaks, e.g. from tubing, by pressure testing
• CPC Class Codes: G01B 11/16 for measuring the deformation in a solid, e.g. optical strain gauge
• CPC Class Codes: G01L 19/086 for remote indication

Abstract

A pressure measuring device will measure pressure in a subsea tubular member. The device includes a stationary unit mounted to the exterior of the tubular member and a movable unit that will be lowered into position next to the stationary unit whenever pressure is to be monitored. The stationary unit has a strain gage which will monitor pressure by measuring strain in the tubular member. The stationary unit has a light emitter which will emit pulses corresponding to pressure measured. The stationary unit has a photocell which will receive a light beam from the movable unit. The light beam and photocell provide power for the stationary unit. The movable unit has a receiver which receives any light pulses from the light emitter and correlates them to a pressure measurement.

Claims

1. An apparatus for measuring pressure in a subsea tubular member, comprising in combination:

a stationary unit mounted to the tubular member and a movable unit adapted to be lowered into the sea and placed adjacent the stationary unit when pressure is to be measured, the stationary unit comprising;

a sensor capable of sensing pressure in the tubular member;

circuit means connected to sensor for providing an electrical indication correlating with the pressure sensed by the sensor;

a light emitter connected to the circuit means for emitting light pulses to the movable unit that correlate with the electrical indication;

a photocell connected to the circuit means and the light emitter for supplying electrical power to the circuit means and light emitter when the photocell receives light from the movable unit;

the movable unit comprising;

a light source for supplying a light beam to the photocell; and

a phototransistor for receiving the light pulses from the light emitter and converting the light pulses into an electrical indication correlating with the light pulses received by the phototransistor to enable the pressure in the tubular member to be determined.

3. The apparatus according to claim 1 wherein the sensor comprises a strain gage mounted to the exterior of the tubular member that senses stress in the tubular member due to internal pressure.

5. The apparatus according to claim 1 wherein the light source comprises a laser.

2. The apparatus according to claim wherein the sensor comprises a strain gage that senses stress in the tubular member due to internal pressure.

4. The apparatus according to claim wherein the electrical indication provided by the circuit means to the light emitter is a signal, the frequency of which correlates with the pressure sensed.

6. An apparatus for measuring pressure in a subsea tubular member, comprising in combination:

a stationary unit mounted to the exterior of the tubular member and isolated from the interior of the tubular member by a tubular wall of the tubular member;

a movable unit adapted to be lowered into the sea and placed adjacent the stationary unit when pressure is to be measured;

pressure sensor means in the stationary unit for sensing pressure in the tubular member by sensing stress in the tubular wall of the tubular member and for converting the pressure sensed into an electrical signal;

light emitter means connected to the pressure sensor means for emitting light pulses to the movable unit that correlate with the electrical signal received from the pressure sensor means;

photocell means connected to the pressure sensor means and the light emitter means for supplying electrical power to the pressure sensor means and the light emitter means when the photocell means receives light from the movable unit;

light source means mounted to the movable member for supplying light to the photocell means; and

light receiver means mounted to the movable member for receiving the light pulses from the light emitter means and converting the light pulses into an electrical indication to enable the pressure in the tubular member to be determined.

7. The apparatus according to claim 6 wherein the pressure sensor means comprises a strain gage.

8. The apparatus according to claim 6 wherein the light source means comprises a laser.

9. The apparatus according to claim 6 wherein the light receiver means comprises a phototransistor.

10. The apparatus according to claim 6 wherein the light pulses emitted by the light emitter means have a frequency that correlates with the pressure in the tubular member.

11. An apparatus for measuring pressure in a subsea tubular member, comprising in combination:

a stationary unit mounted to the tubular member and a movable unit adapted to be lowered into the sea and placed adjacent the stationary unit when pressure is to be measured, the stationary unit comprising;

a strain gage mounted to the exterior of the tubular member for sensing strain in the tubular member;

a variable oscillator circuit connected to the strain gage for providing an electrical signal with a frequency that varies depending upon the strain sensed by the strain gage;

a reference oscillator circuit that provides an electrical signal with a frequency that is substantially constant, the difference between the frequency of the reference oscillator circuit and the variable oscillator circuit correlating to the pressure in the tubular member;

a light emitter connected to the variable oscillator circuit and the reference oscillator circuit for emitting light pulses to the movable unit that have a frequency that is the difference in frequency between the variable oscillator circuit and the reference oscillator circuit;

a photocell connected to the strain gage, variable oscillator circuit, reference oscillator circuit and the light emitter for supplying electrical power when the photocell receives light from the movable unit;

the movable unit comprising;

a light source for supplying a light beam to the photocell; and

a phototransistor for receiving the light pulses from the light emitter and converting the light pulses into an electrical indication to enable the pressure in the tubular member to be determined.

12. The apparatus according to claim 11 further comprising:

means connected with the phototransistor for determining the frequency of the pulses emitted by the light emitter to determine pressure.

13. A method for measuring pressure in a subsea tubular member, comprising in combination:

mounting a stationary unit to the exterior of the tubular member;

lowering a movable unit into the sea adjacent the tubular member;

emitting light from the movable unit to the stationary unit;

converting the light received from the movable unit to electrical power in the stationary unit;

sensing strain in the tubular wall of the tubular member and converting the strain sensed into an electrical signal by using the electrical power;

emitting light pulses from the stationary unit to the movable unit that correlate with the electrical signal by using the electrical power; and

receiving the light pulses from the stationary unit and converting the light pulses into an electrical indication to enable the pressure in the tubular member to be determined.

14. The method according to claim 13 wherein the step of converting the strain sensed into an electrical signal comprises:

varying an oscillator frequency in accordance with strain sensed;

comparing the oscillator frequency to a reference frequency; and

emitting the light pulses at a frequency proportional to the difference between the oscillator frequency and the reference frequency.