Fluid level monitoring and control system

• US 5,035,581 A
• Filed: 11/17/1989
• Issued: 07/30/1991
• Est. Priority Date: 11/17/1989
• Status: Expired due to Term

• Current Assignee: Weatherford Artificial Lift Systems Incorporated (Weatherford International PLC)
• Original Assignee: Damon C. Mcguire, Danny G. Mcguire, Denver C. Mcguire, Mark E. Sudberry
• Inventors: McGuire, Damon C., Sudberry, Mark E., McGuire, Denver C., McGuire, Danny G.
• Primary Examiner(s): Smith, Leonard E.
• Assistant Examiner(s): Scheuermann, David W.
• Application Number:
  US07/438,583
• Time in Patent Office: 620 Days
• Field of Search: 417/36, 417/40, 417/41, 417/44, 417/63, 340/612, 340/618, 73/313, 73/304 R, 200/84 R
• US Class Current: 417/36
• CPC Class Codes: E21B 47/008 Monitoring of down-hole pump systems, e.g. for the detection of "pumped-off" conditions
• CPC Class Codes: E21B 47/009 Monitoring of walking-beam pump systems
• CPC Class Codes: E21B 47/047 Liquid level measuring depth or liquid level using radioactive markers E21B47/053
• CPC Class Codes: E21B 47/113 using electrical indications; using light radiations
• CPC Class Codes: F04B 49/04 Regulating by means of floats F04B49/025 takes precedence
• CPC Class Codes: G05D 9/12 characterised by the use of electric means

Abstract

A system for monitoring and controlling the level of a fluid in a vessel, particularly applicable to controlling the pump operation at an oil well. The system includes a fluid level sensing unit having a plurality of sensors positioned at selected levels in the well casing outside the tubing string. The sensors operate independently to detect the presence of fluid and emit electrical signals which are received by a data conversion and sending unit immediately above the fluid level sensing unit in the well casing. The data conversion and sending unit converts the signals into discreet digital data bits which can be transmitted sequentially in one conductive wire to a data management and pump control unit at a convenient location nearby, usually at the well site. Thus, there is no need for a wire extending from each sensor. The data bits received by the data management and pump control unit are converted to a visual display in a light emitting diode panel. A pump flip-flop automatically operates the pump operating assembly in responsae to the rise and fall of oil or fluid in the well. The data from the sensors also is fed to a computer which stores the data for later retrieval. The computer also calculates other useful information and generates graphics which assist in the management of the oil recovery process.

Claims

1. A system for monitoring and controlling the level of fluid in a vessel, comprising:

a plurality of sensors supported at selected levels in the vessel, wherein each such sensor is capable of inputting an electrical signal and, in response thereto, outputting a first electrical signal if the sensor is submerged in fluid and a second electrical signal if the sensor is not submerged, and wherein the input and output of each sensor is independent of each other sensor;

means for transmitting an electrical signal to each of the sensors;

means for converting the electrical signals output by the sensors into digital signals;

means for receiving the digital signals from the electrical signal converter means and converting the digital signals to a humanly perceivable form; and

means responsive to the digital signals for adjusting the fluid level in the vessel to a preselected fluid level.

2. The system of claim 1 wherein the means for converting the electrical signals output by the sensors into digital signals comprises:

a tri-state converter gate for each sensor for receiving the signal output by that sensor, each such gate capable of outputting a first digital signal if a first electrical signal is received from the sensor and a second digital signal if a second electrical signal is received from the sensor, the output of the gate being activated by an electrical pulse;

and wherein the system further comprises;

means for generating electrical pulses;

means for counting the pulses in repeating sequences, each such sequence comprising a pulse corresponding to each of the sensors; and

means for decoding the counted pulses and directing each such pulse in response thereto to the corresponding tri-state gate.

3. The system of claim 2 wherein the means for receiving and converting the digital signals into a humanly perceivable form comprises:

register means for receiving the sequence of digital signals from the means for converting the electrical signals into digital signals;

means for presenting the digital signals in a humanly perceivable form; and

driver means for transmitting the sequences of digital signals from the register means to means for presenting the digital signals in a human perceivable form.

4. The system of claim 3 further comprising:

means for including in the sequence of digital signals output by the electrical signal converter means a subsequence of digital signals which designate the end of each sensor sequence and a subsequence of digital signals which designate the beginning of each sensor sequence;

and wherein the register means comprises;

shift register means for receiving the sequence of digital signals output by the electrical signal converter means;

decoder means for selecting out the subsequences designating the beginning and end of the sensor sequence;

data register means for receiving the sensor sequence from the shift register means;

means responsive to the decoder means for one-shot loading of the sensor sequence from the shift register means into the data register means; and

means responsive to the decoder means for resetting the shift register means.

5. The system of claim 4 wherein the means for presenting the digital signal in a human perceivable form comprises light emitting diodes.

6. The system of claim 1 wherein each sensor is a switch comprising:

a housing comprising a hollow perforate body;

a first conductive contact element in the housing, and

a second buoyant conductive contact element in the housing below the first contact element and supported for movement relative to the level of fluid in the housing between a first position in which there is no contact with the first contact element and a second position in which there is contact with the first contact element.

7. The system of claim 1 in which each of the sensors comprises a pair of electrodes supported a distance apart for sensing the resistance therebetween so that the first electrical signal indicates low resistance and the second electrical signal indicates high resistance, and in which the means for converting the electrical signals output by the sensors into digital signals includes:

means for receiving the first and second electrical signals and outputting a first selected voltage in response to input of a first electrical signal from the sensor and a second selected voltage in response to input of a second electrical signal from the sensor;

a tri-state converter gate for each sensor for receiving the first and second selected voltage, each such gate capable of outputting a first digital signal if a first selected voltage is received from the sensor and a second digital signal if a second selected voltage is received from the sensor, the output of the gate being activated by an electrical pulse;

means for generating electrical pulses;

means for counting the pulses in repeating sequences, each such sequence comprising a pulse corresponding to each of the sensors; and

means for decoding the counted pulses and directing each such pulse in response thereto to the corresponding tri-state gate.

8. The system of claim 7 in which each of the sensors further comprises an infrared light emitting diode and a phototransistor disposed a distance from the diode, the phototransistor being capable of receiving light emissions from the diode and in response thereto emitting a first electrical signal if the light transmission is high and a second electrical signal is the light transmission is low;

and wherein the system further comprises means for activating and deactivating the phototransistor whereby the sensor selectively outputs either the first and second signals from the phototransistor or the first and second signals from the pair of electrodes.

9. The system of claim 1 further comprising a data management means for receiving and storing signals from the electrical signal converter means, and for later retrieving the stored signals in accordance with predetermined programming.

10. The system of claim 1 wherein the fluid level adjustment means comprises:

a pump for removing fluid from the vessel;

a pump operating assembly for operating the pump; and

a pump flip-flop circuit responsive to digital signals from selected sensors for turning on and turning off the pump operating assembly.

11. The system of claim 1 wherein each sensor comprises means for measuring electrical resistance in the vessel and wherein the first signal is indicative of low resistance and the second signal is indicative of high resistance.

12. The system of claim 11 wherein the means for transmitting an electrical signal to each of the sensors comprises means for transmitting the electrical signals to the sensors sequentially in a selected order, and wherein the means for receiving the digital signals from the electrical signal converter means comprises means for receiving the digital signals sequentially in a selected order corresponding to the order in which the electrical signals are input into the sensors.

13. The system of claim 12 wherein the digital signals are converted to a visually perceivable form.

14. The system of claim 1 wherein the means for transmitting an electrical signal to each of the sensors comprises means for transmitting the electrical signals to the sensors sequentially in a selected order, and wherein the means for receiving the digital signals from the electrical signal converter means comprises means for receiving the digital signals sequentially in a selected order corresponding to the order in which the electrical signals are input into the sensors.

15. The system of claim 14 wherein the digital signals are converted to a visually perceivable form.

16. A system for monitoring and controlling the level of fluid in a vessel, comprising:

a plurality of sensors supported at selected levels in the vessel;

means in each sensor for measuring electrical resistance in the vessel, such means capable of receiving an electrical signal and, in response thereto, outputting a first electrical signal if the sensor is submerged in fluid, a second electrical signal if the sensor is not submerged;

means in each sensor for measuring light transmission in the vessel at the level of the sensor, such means capable of receiving an electrical signal and, in response thereto, outputting a first electrical signal if the light transmission is high and a second electrical signal if the light transmission is low;

means for transmitting an electrical signal to each of the sensors;

means for controlling the operation of the light transmission measuring means and the electrical resistance measuring means so that the sensor outputs the electrical signals from a selected one of the light transmission measuring means and the electrical resistance measuring means;

means converting the electrical signals output by the sensors into digital signals;

means for converting digital signals from the electrical signal converter means into a humanly perceivable; and

means responsive to the signals for adjusting the fluid level in the vessel to a preselected fluid level.

17. The system of claim 16 wherein the light transmission measuring means comprises:

means for emitting light; and

means for receiving light from the light emitting means.

18. The system of claim 17 wherein the light emitting means is an infrared light emitting diode and the light receiving means is a phototransistor.

19. The system of claim 16 wherein the means for measuring electrical resistance in the vessel comprises a pair of electrodes supported a distance apart for sensing the resistance therebetween.

20. The system of claim 19 wherein the light transmission measuring means comprises:

means for emitting light; and

means for receiving light from the light emitting means.

21. The system of claim 20 wherein the light emitting means is an infrared light emitting diode and the light receiving means is a phototransistor.

22. A system for monitoring and controlling the level of fluid in a vessel, comprising:

a plurality of sensors supported at selected levels in the vessel;

means in each sensor for measuring electrical resistance in the vessel, such means capable of receiving an electrical signal and, in response thereto, outputting a first electrical signal if the sensor is submerged in fluid, and a second electrical signal if the sensor is not submerged;

means for transmitting an electrical signal independently to each of the sensors;

means for converting the electrical signals output by the sensors into digital signals;

means for converting digital signals from the electrical signal converter means into a humanly perceivable; and

means responsive to the signals for adjusting the fluid level in the vessel to a preselected fluid level.

23. The system of claim 22 wherein the means for measuring electrical resistance in the vessel comprises a pair of electrodes supported a distance apart for sensing the resistance therebetween.