Apparatus and method for a pressure monitoring device

• US 6,279,405 B1
• Filed: 06/07/1999
• Issued: 08/28/2001
• Est. Priority Date: 06/07/1999
• Status: Expired due to Term

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Charles D. Totty, Kenneth K. Clark
• Inventors: Totty, Charles D., Clark, Kenneth K.
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): Mack, Corey D.
• Application Number:
  US09/327,771
• Time in Patent Office: 813 Days
• Field of Search: 738/614.2, 738/615.2, 738/615.8, 73/32.R
• US Class Current: 73/861.42
• CPC Class Codes: G01F 1/363 with electrical or electro-mechanical indication G01F1/37 and G01F1/38 take precedence
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14
• CPC Class Codes: G01L 9/0022 of a piezoelectric element

Abstract

A differential pressure monitoring device utilizing two crystalline frequency sensors exposed to different pressures for generating two signals which are combined by a frequency mixer. Two offset based frequency crystal sensors are each exposed to different pressures and the resulting frequencies are mixed to measure the pressure differential between the two crystals. When the crystals are exposed to a common pressure, the crystals have an offset based frequency response that is consistent with pressure. When the two crystals are exposed to pressures, the offset frequencies are mixed together to create a differential frequency that is precisely related to the differential in the pressures placed on the two different crystal sensors.

Claims

1. A characteristic well bore pressure monitoring and calculation apparatus, comprising:

a singular first frequency signal crystal to generate a first frequency signal responsive to changes in a well bore pressure characteristic;

a second sensing means with a single offset frequency signal crystal to generate a second frequency signal responsive to changes in said well bore pressure characteristic; and

a signal receiving means to monitor said first generated frequency signal and said second generated frequency signal and calculate a frequency differential between said first and second signals.

2. The characteristic monitoring apparatus of claim 1, further comprising:

a flow restriction means intermediately separating said first and said second signal crystals to measure a fluid flow rate.

3. The characteristic monitoring apparatus of claim 1 wherein said first sensing means is positioned within a first dimensioned section of a well bore.

4. The characteristic monitoring apparatus of claim 1 wherein said second sensing means is positioned within a second dimensioned section of a well bore.

5. The characteristic monitoring apparatus of claim 1 wherein said signal receiving means is a frequency signal mixer.

6. A method for measuring a pressure differential over a known vertical displacement in a fluid column, comprising:

generating a first frequency signal responsive to changes in fluid well bore pressure with one frequency signal crystal;

generating a second frequency signal responsive to changes in said fluid well bore pressure with one offset frequency signal crystal;

monitoring said first and said second signal frequencies with a signal mixer; and

calculating a pressure differential based on said first signal and said second signal frequencies.

7. A method for measuring a fluid flow rate within a well bore comprising:

exposing a single first frequency signal crystal to a first fluid pressure within a well bore and exposing a single second frequency signal crystal to a second fluid pressure within a well bore;

generating a first frequency signal responsive to changes in fluid well bore pressure characteristic with said single first frequency signal crystal;

generating a second frequency signal responsive to changes in said fluid well bore pressure characteristic with said single frequency signal second crystal; and

monitoring said first and second generated frequency signals and calculating the frequency differential between said frequency signals.

8. The method of claim 7 wherein said first and second fluid pressures are effectuated via a flow restriction means.

9. A method for measuring a fluid density, comprising:

generating a first frequency signal responsive to changes in a well bore pressure characteristic with a single first frequency signal crystal;

generating a second frequency signal responsive to changes in said pressure characteristic with a single offset frequency signal crystal, wherein the distance between said first frequency signal crystal and said offset frequency signal crystal is known;

monitoring said first generated frequency signal and said second generated frequency signal with a signal mixer;

calculating the pressure differential based on said first and said second generated signal frequencies;

calculating a fluid density based on said pressure differential and said distance between said first frequency signal crystal and said offset frequency signal crystal.