JPH0339561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus and method for electromagnetically measuring the inner diameter of a cylindrical metal pipe, and more particularly to an electronic inner pipe caliper. More specifically,
The present invention relates to an apparatus and method for logging the internal diameter of tubular members, such as casings, of oil and gas wells.

It is often necessary to measure the internal diameter of a pipe. This is particularly necessary, for example, for the casing of an oil well or for a series of tubing disposed within an oil well for pumping oil or gas from the well.

Such metal pipes are buried underground and therefore cannot be accessed for measurements. The inner and outer surfaces of such metal pipes are susceptible to corrosion. This corrosion is caused, for example, by injection fluids or corrosive fluids in the earth. Additionally, this pipe is subject to internal wear due to pump rods or wire lines pumped into the well. Also, wear can be caused by drilling or finishing operations using drill pipes.

Measuring pipe wear due to corrosion or wear is important in order to apply protective treatments or repair or replace pipes as necessary.

Of course, the internal diameter of the pipe in an oil well can vary depending on wall thickness and nominal pipe diameter tolerances.

Since there is a pressing need to measure the inner diameter of buried metal pipes, various devices have been developed for this purpose. Most of these conventional devices use a mechanical feeler that is pressed against the inner wall of the pipe by spring means. When one of these fillers becomes biased due to pipe depressions, cracks, and other corrosion or erosive effects, an electrical signal is generated that is used to record such bias. This is, for example,
This is done by combining a magnet with the filler described above. The magnet is rotated and passed successively through the various feelers such that any deflection of the feelers changes the reluctance of the magnetic path, thereby inducing and recording an electrical signal. Alternatively, the potentiometer can be combined with a filler,
A signal proportional to the bias of the filler is generated.

Some of these conventional mechanical feeler calipers use two sets of feelers, one set that measures the maximum penetration of the filler and the other set that continuously measures the average penetration of the filler. Measure.

However, such mechanical feeler type pipe calipers have several drawbacks. For example, such devices are unable to detect vertical cracks or cracks in pipes. pipes are covered with paraffin, scale or non-metallic substances;
This may mask defects within the pipe. Needless to say, the filler cannot distinguish between a metal pipe and a non-metallic material covering the pipe. Therefore, certain depressions covered with hardened hydrocarbons etc. will not be detected.

Finally, each of the many fillers described above can scratch the pipe or scrape off the protective coating of the pipe. Even if the pipe is not covered with a protective coating, further corrosion can occur due to the scratching caused by the filler. Therefore,
The mechanical filler type devices described above can cause changes in the inner diameter of the pipe that they are intended to measure.

U.S. Pat. No. 3,417,325 discloses an all-electric caliper for measuring the inside diameter of metal pipes, in which the cylindrical housing of a sonde is adapted to be moved through an oil well casing or the like. It supports a transmitter coil and a receiver coil on top. The transmitter is excited with an alternating current of about 10 to 50 kilohertz per second. The voltage induced in the receiver coil is taken as a measure of the average internal diameter of the pipe to be measured.

However, as a practical matter, U.S. Patent No. 3417325
The measurement results of the device disclosed in the above publication are erroneous if the electrical conductivity, or the magnetic permeability, or both the electrical conductivity and the magnetic permeability, of the pipe to be measured changes. As a practical matter common in the oil field, the conductivity of steel tubular equipment ranges from 2.6×10 ⁶ /m to 7.8×10 ⁶ /m.
It varies within the range. Furthermore, as is well known, the magnetic permeability of oil field tubular equipment varies considerably depending on mechanical shock, heat treatment, etc. to which the equipment is subjected.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an internal pipe caliper operating on an electrical principle which eliminates the disadvantages of the prior art devices mentioned above.

It is another object of the present invention to provide an internal pipe caliper that is substantially insensitive to the electrical conductivity and magnetic permeability of the pipe and produces a signal representative of the internal diameter of the pipe.

Yet another object of the invention is to provide a wellbore logging system for logging borehole casing or tubing that provides an accurate log of casing inner diameter versus depth, independent of changes in casing conductivity or permeability. The objective is to provide a logging device.

Briefly described, the objects, features and advantages of the present invention include a transmitter coil in which an alternating current excitation current is generated, and a transmitter coil extending longitudinally from the transmitter coil for generating an induced voltage in response to the transmitter current. This is the result of installing two coaxial coils in the pipe, including a receiver coil placed at a distance. A circuit is also provided for generating an impedance signal proportional to the ratio of the receiver voltage to the transmitter current. The impedance signal is decomposed into vector components including a quadrature impedance signal and an in-phase impedance signal.

In one aspect of the invention, means are provided responsive to the quadrature impedance signal and the in-phase impedance signal to generate a corrected measurement output. This corrected measurement output is used to generate a signal representing the inner diameter of the pipe.

In another aspect of the invention, means are provided for linearly combining said quadrature impedance signal and said in-phase impedance signal to produce a corrected measurement output having reduced sensitivity to the magnetic permeability and conductivity of the metal object. generate.

In yet another aspect of the invention, the quadrature impedance signal and the in-phase impedance signal are determined as a function of the internal radius a ₁ of the pipe and a parameter τ that is proportional to the ratio of pipe permeability to pipe conductivity. A means is provided for simultaneously solving two expressed nonlinear forms.

In yet another aspect of the invention, the above two equations are first solved simultaneously by assuming that τ is equal to zero, then an estimate of a ₁ is determined from the first equation, and the second An iterative calculation method is provided for determining τ from the equation, using this new value of τ in the first equation to determine a new value of a ₁ , and repeating the above method until convergence is obtained. be done.

The invention, as well as other objects and advantages thereof, will be better understood from the detailed description given below with reference to the drawings.

FIG. 1 shows an electric caliper device 1 according to the present invention.
0 is abbreviated. The device 10 is a tubular member;
For example, the inner diameter of the casing 20 of the drilling well 16 is measured.

The device includes a downhole sonde 12, a downhole electronic cartridge 13, and ground equipment 14.
The sonde 12 is suspended within a tubular section or casing 20 by an armored cable or wireline 18 for movement therethrough. The drilling well hole 16 has a casing 20
The device 10 is designed such that as it moves up and down within the casing 20, it measures the internal diameter of the casing as a function of the drilling depth. wire line or cable 18
cables with a single conductor (called a monocable) or multiple conductors (e.g. 7 conductors with 7 conductors)
linear cable).

The ground device 14 includes a sonde 1 in a casing 20.
2 as well as the position of the sonde 12.
receive, process, and display signals sent from
and communicates with sonde 12 via cable 18 for recording.

Cable driven mechanical transducer 22
and linkage 23 provide a position signal that indicates the depth of sonde 12 within wellbore 16 . Generally, transducer 22 is connected to wireline 18
It is in the form of a calibrated pressure wheel that is pressed against the casing and generates electrical pulses when the wheel is rotated by movement of the sonde 12 within the casing.

The hole lowering device includes a sonde 12, an electronic cartridge section 13, a pair of centering tools 27a and 27b,
A tip or nose member 28 and a cable head adapter 30 are included. The downhole device is connected to the cable 18 via a cable head adapter 30.

The sonde 12 has caliper coils 50, 60 for making electromagnetic measurements as a function of the depth of the sonde within the casing. A signal is generated that is proportional to the inner diameter of the casing. Also, another signal is generated representing the ratio of casing magnetic permeability to casing electrical conductivity.

Before describing the equipment present in electronic cartridge 13 or ground equipment 14, the theoretical basis of the invention will be explained with reference to FIG.

FIG. 2 shows a theoretical model of two coaxial coils 50, 60 separated from each other by a longitudinal distance L, both of which are arranged coaxially within a pipe or casing 20. . The inner radius of the above pipe is denoted by a ₁ and its outer radius by a ₂ . The radius of receiver coil 60 is designated b ₂ and the radius of transmitter coil 50 is designated b ₁ . The electrical characteristics of the medium 1 in the pipe are represented by magnetic permeability ε ₁ , magnetic permeability μ ₁ , and conductivity σ ₁ . Similarly, various electrical characteristics of the pipe are expressed as ε ₂ , μ ₂ , and σ ₂ .

Applying Maxwell's equation using FIG. 2 as a basis results in the following equation.

Z=V/J (1) where Z represents the impedance ratio of coils 60, 50 and V represents the voltage induced in receiver coil 60 in response to current J flowing through coil 50. Impedance Z can be written as follows.

Z = Z ₀ + Z _p (2) where Z ₀ is the part of the impedance caused by the direct coupling between the transmitter and receiver coils and Z _p is the part of the impedance caused by the drop in the pipe 20. This is the part of the impedance that occurs.

So we can write as follows.

Z ₀ = −2iωμ ₁ b ₁ b ₂ ∫ ^∞ ₀ I ₁ (λb ₂ )K ₁ (λb ₁ )cosλLdλ (3) Z _p =−2iωμ ₁ b ₁ b ₂ ∫ ^∞ ₀ I ₁ (λb ₁ )I ₁ (λb ₂ ) γ ₁ (λ) cosλLdλ (4) Here, γ ₁ (λ)=−K ₁ (λa ₁ )−λa ₁ TK ₀ (λa ₁ )/I ₁ (λa ₁
)−λa ₁ Ti ₀ (λa ₁ )(5) i=√−1 Here, I ₁ , K ₁ , I ₀ , and K ₀ are Betzel functions.

Equation (4) is equivalent to Equation (5) for γ and Equation (6) for T.
can be expanded as follows.

Z _p =Z ₁ +Z ₂ +Z ₃ +… (7) Here, the electrical conductivity of the pipe is high.

That is, Measured impedance between the above coils
Zmeas has a real part and an imaginary part (quadrature part). That is, Zmeas=ReZmeas+iImZmeas (10) Therefore, for small T, T ² is extremely small, Z ₃ = 0, and ReZmeas+iImZmeas=i(|Z ₁ | − | Z ₀
|) +ReZ ₂ +iImZ ₂ .

From equation (9), since T has equal real parts and quadrature parts, ReZmeas=ReZ ₂ =iImZ ₂ .

Therefore, it becomes as follows. That is, ImZmeas=|Z ₁ |−|Z ₀ |+ReZmeas (11) △Z=ReZmeas−ImZmeas=|Z ₀ |−|Z ₁ |
(12) Equation (12) shows the following relationship.

△Z=ReZmaes−ImZmeas=2ωμ ₀ b ² (ZINT0−ZINT1) (13) Here, the coils 50 and 60 have the same diameter b, the permeability of the medium 1 is the permeability of free space μ ₀ , and It is.

If T from equation (9) is not negligibly small, then

ReZ−imZ/2ωμ ₀ b ² = (ZINT0−ZINT1)+τ ² ZINT3 −√2τ ³ ZINT4+τ ⁴ ZINT5+… (15) ReZ−imZ／2ωμ ₀ b ² =τ/√2ZINT2+τ ² ZINT3 −τ ³ /√2ZINT4+… Here , ZINT0=∫ ^∞ ₀ I ₁ (λb)K ₁ (λb)cosλLdλ (16) ZINT1=∫ ^∞ ₀ I ₁ ² (λb)K ₁ (λa ₁ )/I ₁ (λa ₁ )cosλL
dλ(17) ZINT2=∫ ^∞ ₀ I ₁ ² (λb)/I ₁ ² (λa ₁ ) cosλLdλ(18) ZINT3=∫ ^∞ ₀ (λa ₁ ) I ₁ ² (λb) I ₀ (λa ₁ )/I ₁ ³ (λa
₁ ) cosλLdλ (19) ZINT4=∫ ^∞ ₀ (λa ₁ ) ² I ₁ ² (λb) I ₀ (λa ₁ )/I ₁ ⁴ (λ
a ₁ ) cosλLdλ (20) ZINT5=∫ ^∞ ₀ (λa ₁ ) ³ I ₁ (λb) I ₀ (λa ₁ )/I ₁ ⁵ (λa
₁ ) cosλLdλ (21) , a ₁ represents the internal radius of the pipe, b represents the radius of the transmitter coil and the receiver coil, L is the distance between the transmitter coil and the receiver coil, and I ₁ ( λb) is the modified Betzel function of the first kind, K ₁ (λa ₁ ) is the modified Betzel function of the second kind, I ₀ (λa ₁ ) is the modified Betzel function of the first kind, and λ is the integral where μ ₀ is the free-space permeability, ω = 2πf is the radian frequency of the alternating transmitter current, μ _r is the relative permeability of the pipe under measurement, and σ is the relative permeability of the pipe under measurement. It is electrical conductivity.

Therefore, measure the impedance between the coils, decompose this impedance into a quadrature (imaginary) component and an in-phase (real) component, take the difference between these components, and calculate a ₁ that satisfies equation (14). By determining the pipe 20 from equations (13) and (14)
An accurate determination of the internal radius a ₁ can be made.

Conveniently, equation (14) can be converted to various values of △Z.
Calculate in advance as a function of a ₁ . Fit one polynomial to the functional relationship between a ₁ and △Z, or a ₁ =f(△Z) (23).

This polynomial is stored in the memory of a digital computer located in the ground equipment 14, thereby making it easy to determine a ₁ when ΔZ is measured as a function of depth within the drilling well 16. be able to do so.

Alternatively, equation (13) may be predetermined over a range of values of ΔZ and a ₁ to create a table of values, which is stored in digital memory within ground equipment 14. This digital memory is then addressed with the measured ΔZ value and generates a signal a ₁ representing the internal diameter of the pipe.

If T is not negligibly small, first obtain an initial estimate of the internal radius a ₁ of the pipe by assuming τ=0. Then, using this initial estimate of a ₁ , ZINT2, ZINT3, ZINT4 and
Find the value of ZINT5 (assuming τ is sufficiently small and high-order coefficients in the expansion equation can be ignored).
Next, τ is determined from the formula ReZ/2ωμ ₀ b ² =−τ/√2ZINT2+τ ² ZINT3 −τ ³ /√3ZINT4 in formula (15). This new value of τ is used in the equation ReZ/2ωμ ₀ b ² = (ZINT0−ZINT1)+τ ² ZINT3 −√2τ ³ ZINT4+τ ⁴ ZINT5+ . . . in equation (15).

The above steps are repeated until the values for τ and a ₁ converge, ie, the changes from one iteration to the next are sufficiently small.

FIG. 3 shows the electronic circuitry necessary to implement the invention. Caliper coils 50, 60 are shown within casing 20. The transmitting coil 50 is
It is excited by a 65.5KHz crystal oscillator via an adder circuit 101 and a driver circuit 102. To excite transmitter coil 50 with a constant current, a current sensing resistor provides an output to sense amplifier 104 that is proportional to the current flowing through the transmitter coil. The output of the sense amplifier 104 is applied to a rectifier 105, and the rectified error signal is applied to a differential error amplifier 106 and compared with a reference signal. The error signal from the error amplifier 106 is sent to the summing amplifier 101.
A feedback constant current circuit is created.

The signal from the current sensing resistor 103 is provided to a phase lock loop oscillator 110, which
A reference signal that is in quadrature (for example, 90° out of phase) with the transmitter current on lead wire 111 is connected to lead wire 111.
A reference signal is generated on lead 112 above and in phase (eg, 180° out of phase) with the transmitter current. This current reference signal also applies to switch network 12.
given to 0. Additionally, a ground signal on lead 116 is provided to switch network 120. Through the switch circuitry 120,
The receiver voltage on lead 115 as well as the current signal on lead 113 and ground signal 116 are applied to phase sensitive detector 130, thereby making phase sensitive detector (PSD) 130 independent of temperature and time. It is possible to provide a quick means to calibrate against misalignment and drift associated with The signal from the switch network 120 is passed through a differential amplifier 121 and a bandpass filter 122 to the PSD.
130. This bandpass filter has a bandpass frequency that is substantially the same as the frequency of oscillator 100.

The output of PSD 130 is given to low pass filter 131. The output of the filter during logging operations replaces the in-phase and quadrature components of the voltage signal measured and directed at coil 60 relative to the phase of current-exciting transmitter coil 50.
Switch S connects the lead wire 11 multiple times every second.
1, 112, thereby taking multiple output readings every second, effectively confirming that the coils 50, 60 are measuring for each depth location. Several outputs of the synchronous and quadrature components are obtained and further processed as described above to produce an internal diameter measurement and a τ measurement indicative of the permeability to conductivity ratio of the pipe.

The circuit of FIG. 3 is preferably located within the electronic cartridge 13, but alternatively the circuit of FIG.
Apart from the input and output leads for 0 and 60, they may be located partially or wholly within the ground equipment. Preferably, the signal from the phase-sensitive positive detector 130 is routed to the ground equipment circuit 14 by an in-hole telemetry circuit and an out-of-hole demodulation circuit similar to that shown in U.S. Pat. No. 4,292,588, discussed herein. give to

Coils 50 and 60 may also be shielded in a conventional manner to prevent electric field coupling if logging is being performed in a salt water environment.

Horikui's log regarding the casing inner diameter is the first
Obtained via the apparatus shown in FIGS. and 3, the processing steps described above are preferably performed within the ground equipment 14. The log is generated by correlating the depth signals of the coils 50, 60 via the measurement wheel 22 connected to the ground equipment 15, as is well known in the well logging art. A recorder 100 is provided to log the casing inner diameter versus the depth of the coils 50,60. A parameter τ, which is proportional to the ratio of magnetic permeability to conductivity, is also recorded as a function of logging depth.

Figures 4A and 4B illustrate the effectiveness of the present invention in measuring the internal diameter of tubular devices of varying conductivities. Figure 4A shows
tubular brass, with different magnetic permeability to conductivity ratios;
This shows that there is considerable variation in the apparent internal diameter of pipes for stainless steel, aluminum and other ferrous pipes.
The results of FIG. 4A were obtained in the conventional method of estimating the inner diameter based solely on the magnitude of the received voltage of the receiver coil 60. FIG. 4B shows that the error in the estimated value of the pipe inner diameter has been significantly reduced by applying the corrections shown by equations (13) and (14) above.

FIG. 5 shows the expected error in measurements using first-order corrections of equations (13) and (14) and second-order corrections of equations (15) to (22). The error curve in the figure is shown as a function of μ/σ of the tube under test, and the casing inner diameter is 10.16
cm (4 inches), 12.7cm (5 inches), 15.24cm
(6 inches) and 17.78 cm (7 inches). As can be seen from the figure, a significant reduction in the casing inner diameter error is obtained for large μ/σ ratios.

Although the invention has been described above with reference to an embodiment thereof, this embodiment is given by way of example only. Various changes may be made in the details and implementation of the embodiments described above without departing from the spirit and scope of the invention. Although the present invention has been described above with respect to casing inner diameter measurements of casings in dug oil or gas wells, the present invention
Suitable for measuring the inside diameter of all pipes where access to the inside is the only practical measurement method. The invention described herein is suitable for measuring oil and gas pipelines, for example.

[Brief explanation of the drawing]

FIG. 1 is an elevational view showing a downhole device and a ground device for calipers of tubular instruments according to the present invention, and FIG. 2 is a theory of transmitter coils and receiver coils for measuring the inner diameter of metal tubular members. FIG. 3 is a block diagram illustrating an electronic circuit suitable for making measurements in accordance with the present invention; FIG. 4A is a perspective view showing a typical model;
4B and 4B are graphs showing the error correction efficiency according to one form of the invention, and FIG. Figure 2 is a graph shown as a function of ratio. 12...Sonde, 13...Cartridge, 14
...Ground equipment, 18...Wire line, 22...
Transducer, 50... Transmitter coil, 60
... Receiver coil, 100 ... Oscillator, 105 ...
... Rectifier, 110 ... Phase lock loop oscillator, 120 ... Switch network, 122, 131
...Filter, 130...Detector.

Claims (1)

Claims: 1. Transmitter means comprising: a support member; a transmitter coil disposed on said support member for generating an alternating current transmitter current; said transmitter coil and receiver coil disposed within a metal pipe; receiver means including said receiver coil disposed on said support member at a distance from said transmitter coil for generating a receiver voltage in response to said transmitter current when disposed in said support member; An apparatus for measuring the inside diameter of a metal pipe, comprising means for generating an impedance signal in response to the receiver means and the transmitter means, the impedance signal being proportional to the ratio of the receiver voltage to the transmitter current; means for decomposing a signal into its quadrature component (ImZ) and its in-phase component (ReZ); means for generating a corrected measurement output in response to said ImZ component and said ReZ component; and means for generating a signal representative of the inner diameter of the pipe in response to a measurement output. 2. The corrected measurement output generating means comprises an ImZ component and a
2. The measuring device according to claim 1, further comprising means for linearly combining ReZ components. 3 The means to linearly combine the ImZ component and
3. A measuring device according to claim 2, further comprising subtraction means for generating a difference signal indicating the difference between the ReZ component and the ReZ component. 4. The means for generating the inner diameter signal of the pipe is
4. Measuring device according to claim 1, 2 or 3, characterized in that it comprises means for filtering the corrected measurement output. 5 means for generating a signal indicative of the internal diameter of the pipe, means for storing a numerical indication of the internal diameter of the pipe as a function of a difference signal; and for addressing the storage means with the difference signal. 4. A measuring device according to claim 3, further comprising means for generating an inner diameter signal proportional to the inner diameter of the pipe. 6 The corrected measurement output generation means
Claims characterized in that it comprises means for filtering the ReZ components based on a model for each said component representing each said component as a non-linear combination of at least two properties of the metal pipe. The measuring device according to item 1. 7. The processing means of the filter is characterized in that it is equipped with means for simultaneously solving two nonlinear forms expressing the ImZ component and the ReZ component as functions of a ₁ and τ, where a ₁ is the internal radius of the pipe. represents,
7. The measuring device according to claim 6, wherein τ is a coefficient proportional to the ratio of the magnetic permeability of the pipe to the electrical conductivity of the pipe. 8. Claims 1, 6 or 8 further comprising means for generating a signal indicative of the permeability to conductivity ratio of the pipe in response to the corrected measurement output. Measuring device according to item 7. 9. A wellbore logging device, the metal pipe having a wellbore casing, a support member adapted to move through the wellbore casing, and a transmitter coil and a receiver. a transmitter coil is coaxially disposed on the support member, transmitter means and receiver means are connected to ground equipment via a wireline cable, and the support member is axially disposed within the pipe. and means for recording a signal representative of the internal diameter of said pipe as a function of distance along said pipe, characterized in that the frequency of the alternating current transmitter current is approximately 65 KHz. Claims 1, 2,...
...or the measuring device according to item 8. 10. generating an impedance signal between two coaxial coils in a metal pipe, the impedance being the ratio between the current exciting the transmitter coil and the voltage induced in the receiver coil;
Further, decomposing the impedance signal into vector components including a quadrature impedance signal and a common mode impedance signal, and generating a difference signal (ΔZ) proportional to the difference in magnitude of the quadrature impedance signal and the common mode impedance signal. A method for measuring the inner diameter of a metal pipe, comprising: generating an inner diameter signal representative of the inner diameter of the pipe in response to at least the difference signal (ΔZ). 11 The step of generating the inner diameter signal converts the quadrature impedance signal and the common mode impedance signal into a ₁
and the step of simultaneously solving two nonlinear equations expressed as functions of τ,
11. The measuring method according to claim 10, wherein a ₁ represents the internal radius of the pipe, and τ is a coefficient proportional to the ratio of the magnetic permeability of the pipe to the electrical conductivity of the pipe. 12 The steps of simultaneously solving two equations are (a) estimating the internal radius of the pipe (a ₁ ) by assuming τ = 0, and (b) calculating the second equation using the estimated a ₁ above. From the above formula of τ
(c) using the new value of τ in the first above equation to calculate a ₁
and (d) repeating the above steps until the values for τ and a ₁ converge.
12. The measuring method according to claim 11, comprising the step of repeating steps (b) and (c). 13 further comprising: moving the transmitter coil and the receiver coil together axially within the pipe; and recording an internal diameter signal as a function of distance along the pipe, the ratio of magnetic permeability to conductivity. Claims 10, 11 or 1, characterized in that a signal is recorded as a function of distance along said pipe.
Measurement method described in Section 2.