METHOD AND APPARATUS FOR MEASURING DEPTH

• US 3,753,294 A
• Filed: 02/24/1971
• Issued: 08/21/1973
• Est. Priority Date: 02/27/1970
• Status: Expired due to Term

• Current Assignee: Georges Attali, Jean-Louis Bernard, John Aitken
• Original Assignee: Georges Attali, Jean-Louis Bernard, John Aitken
• Inventors: Attali, Georges, Aitken, John, Bernard, Jean-Louis
• Primary Examiner(s): Haroian, Harry N.
• Application Number:
  US05/118,263
• Time in Patent Office: 909 Days
• Field of Search: 33/141.5 73/151
• US Class Current: 33/735
• CPC Class Codes: E21B 47/04 Measuring depth or liquid level
• CPC Class Codes: G01B 7/026 for measuring length of cable, band or the like, which has been paid out, e.g. from a reel measuring length of objects while moving G01B7/04
• CPC Class Codes: G01B 7/044 using capacitive means

Abstract

In accordance with illustrative embodiments of the present invention, the distributed capacitance between a conductor and the outer metallic armor of a cable is measured to enable a determination of the instantaneous changes in position of a tool supported by an elastic cable in a borehole. The correction calculated from the capacitance measurement is used to correct cable length measurements derived from a measure wheel which engages and rotates with movement of the cable.

Claims

1. A method of determining the position or changes in position of a tool supported in a borehole by a cable having an electrical parameter which varies in proportion to changes in length of the cable, comprising:

a. deriving measurements representative of the movement of the cable at the surface of the earth;

b. deriving measurements representative of said electrical parameter of the cable; and

c. combining said derived measurements to produce representations of the position or changes in position of the tool in the borehole.

2. The method of claim 1 wherein the cable has an inner conductor and an outer metallic armor and the step of deriving measurements of said electrical parameter includes measuring an electrical parameter between the outer metallic armor and the conductor to produce such measurements.

3. The method of claim 1 wherein the step of combining includes the steps of filtering out the low frequency components of said electrical parameter measurements to retain the high frequency components thereof, and combining the high frequency components of said parameter measurements with said cable movement measurements to produce said representations of the position or changes in position of a tool.

4. A method of determining the position or changes in position of a tool supported in a borehole by a cable having an inner conductor and an outer metallic armor, comprising:

a. deriving measurements representative of the movement of the cable at the surface of the earth;

b. deriving measurements representative of the distributed capacitance between the conductor and the outer metallic armor of the cable; and

c. combining said derived measurements to produce representations of the position or changes in position of the tool in the borehole.

5. The method of claim 4 wherein the step of combining includes the steps of filtering out the low frequency components of said capacitance measurements to retain the high frequency components thereof, and combining the high frequency components of said capacitance measurements with said cable movement measurements to produce said representationS of the position or changes in position of a tool.

6. The method of claim 4 and further including the step of producing representations of a proportionality or calibration correction to said cable movement measurements, and wherein the step of combining includes the steps of combining said derived measurements with said correction representations to produce said representations of tool position or changes in position.

7. Apparatus for determining the position or changes in position of a tool supported in a borehole by a cable having an electrical parameter which varies in proportion to changes in length of the cable, comprising:

a. cable measuring means adapted for engaging the cable for producing a first signal representative of the amount of cable passing said cable measuring means;

b. means adapted for measuring said electrical parameter of the cable and producing a second signal representative thereof; and

c. means adapted for combining said first and second signals to produce an output signal representative of the position or changes in position of the tool.

8. Apparatus for determining the position or changes in position of a tool supported in a borehole by a cable having an inner conductor and an outer metallic armor, comprising:

a. cable measuring means adapted for engaging the cable for producing a first signal representative of the amount of cable passing said cable measuring means;

b. means adapted for measuring the distributed capacitance between the conductor and the outer metallic armor of said cable and producing a second signal representative thereof; and

c. means adapted for combining said first and second signals to produce an output signal representative of the position or changes in position of the tool.

9. The apparatus of claim 8 wherein said means adapted for combining includes means for filtering out the low frequency components of said second signal to leave the high frequency components thereof, and means for combining the high frequency components of said second signal with said first signal to produce said output signal.

10. The apparatus of claim 8 and further including means responsive to said first signal for producing a third signal representative of a proportional correction to be applied to said first signal, and wherein said means adapted for combining comprises means adapted for combining said first, second and third signals to produce said output signal.

11. The apparatus of claim 10 wherein said first, second and third signals are rotations of mechanical linkages and said combining means includes differential gearing means having an output mechanical linkage and means responsive to said first, second and third signals for causing said output linkage to rotate as a function of the changes in position of a tool in a borehole.

12. The apparatus of claim 10 wherein said first, second and third signals are electrical pulses and said means adapted for combining includes logic means responsive to said pulses for producing a first series of pulses representative of increases in total cable length and a second series of pulses representative of decreases in total cable length, and accumulating means for adding one of said series of pulses and subtracting the other series to produce representations of the position of a tool in a borehole.