Method and apparatus for measuring the inside diameter of a metallic pipe in a well
First Claim
1. Apparatus for measuring the inside diameter of a metallic pipe in a well, comprisinga support member, adapted for displacement through the pipe,transmitter means including a transmitter coil disposed on said support member for generating an a.c. transmitter current,receiver means including a receiver coil disposed on said support member a distance from said transmitter coil for producing a receiver voltage in response to the effect of said transmitter current on the pipe, said voltage including a component in-phase with the transmitter current and a component in quadrature to the transmitter current,means responsive to said receiver means and said transmitter means for deriving a signal Δ
- Z representative of the difference between the real and imaginary components of the impedance, defined as the ratio of the receiver voltage to the transmitter current, said real component being in phase with the transmitter current and said imaginary component being in quadrature to the transmitter current, andmeans for deriving a signal representative of the inside diameter of the pipe from said difference signal Δ
Z, based on a predetermined relationship between the difference signal and the inside diameter.
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Abstract
A method and apparatus is disclosed for electrically measuring the inside diameter of a metallic pipe such as oil or gas well casing. The transimpedance of two coaxial coils within the pipe is determined and then resolved into its inphase and quadrature components. The difference of the magnitudes of the two components, ΔZ, is approximated by a function independent of the electrical properties of the pipe but which is a function of the inside diameter of the pipe. The inside diameter is determined from the function in response to the measured ΔZ and may be recorded as a function of travel distance in the pipe.
25 Citations
17 Claims
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1. Apparatus for measuring the inside diameter of a metallic pipe in a well, comprising
a support member, adapted for displacement through the pipe, transmitter means including a transmitter coil disposed on said support member for generating an a.c. transmitter current, receiver means including a receiver coil disposed on said support member a distance from said transmitter coil for producing a receiver voltage in response to the effect of said transmitter current on the pipe, said voltage including a component in-phase with the transmitter current and a component in quadrature to the transmitter current, means responsive to said receiver means and said transmitter means for deriving a signal Δ - Z representative of the difference between the real and imaginary components of the impedance, defined as the ratio of the receiver voltage to the transmitter current, said real component being in phase with the transmitter current and said imaginary component being in quadrature to the transmitter current, and
means for deriving a signal representative of the inside diameter of the pipe from said difference signal Δ
Z, based on a predetermined relationship between the difference signal and the inside diameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- Z representative of the difference between the real and imaginary components of the impedance, defined as the ratio of the receiver voltage to the transmitter current, said real component being in phase with the transmitter current and said imaginary component being in quadrature to the transmitter current, and
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10. A method for determining the inside diameter of a metallic pipe located in a well, comprising
applying a current to a transmitter coil positioned inside the pipe and coaxially thereto, detecting the voltage induced by said current in a receiver coil longitudinally spaced from, and coaxial to, the transmitter coil, said voltage including a component in-phase with the transmitter current and a component in quadrature to the transmitter current, deriving a signal Δ - Z representative of the difference between the real and imaginary components of the impedance, defined as the ratio of the receiver voltage to the transmitter current, said real component being in phase with the transmitter current and said imaginary component being in quadrature to the transmitter current,
deriving a signal representative of the inside diameter of the pipe from said difference signal Δ
Z based on a predetermined relationship between the difference signal and the inside diameter. - View Dependent Claims (11)
- Z representative of the difference between the real and imaginary components of the impedance, defined as the ratio of the receiver voltage to the transmitter current, said real component being in phase with the transmitter current and said imaginary component being in quadrature to the transmitter current,
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12. A method for producing a signal related to the inside diameter of a pipe located in a well, comprising
applying a current to a transmitter coil positioned inside the pipe and coaxially thereto, detecting the voltage induced by said current in a receiver coil longitudinally spaced from, and coaxial to, the transmitter coil, said voltage including a component in-phase with the transmitter current and a component in quadrature to the transmitter current, deriving a signal Δ - Z representative of the difference between the real and imaginary components of the impedance, defined as the ratio of the receiver voltage to the transmitter current, said real component being in phase with the transmitter current and said imaginary component being in quadrature to the transmitter current, said difference signal Z being related to the inside diameter of the pipe and having a reduced sensitivity to the permeability and conductivity of the pipe.
- View Dependent Claims (13)
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14. An apparatus for producing a signal related to the inside diameter of a pipe located in a well, comprising
a support member, adapted for displacement through the pipe, transmitter means including a transmitter coil disposed on said support member for generating an a.c. transmitter current, receiver means including a receiver coil disposed on said support member a distance from said transmitter coil for producing a receiver voltage in response to the effect of said transmitter current on the pipe, said voltage including a component in-phase with the transmitter current and a component in quadrature to the transmitter current, means responsive to said receiver means and to said transmitter means for generating a signal Δ - Z equal to the difference between the real and the imaginary parts of an impedance signal defined as the ratio of the receiver voltage to the transmitter current, said real part being the component in-phase with the transmitter current and said imaginary part being the component in quadrature to the transmitter current, said difference signal Δ
Z being related to the inside diameter of the pipe and having a reduced sensitivity to the permeability and conductivity of the pipe. - View Dependent Claims (15, 16, 17)
- Z equal to the difference between the real and the imaginary parts of an impedance signal defined as the ratio of the receiver voltage to the transmitter current, said real part being the component in-phase with the transmitter current and said imaginary part being the component in quadrature to the transmitter current, said difference signal Δ
Specification