JPS6157795A - Apparatus for measuring free point of pipe becoming non-movable in drill pit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring the point at which a pipe loses its dynamic dimension within a borehole, and more particularly, to
This invention relates to a device for magnetically measuring the location of free points in a pipe without the need for installation.

2 History of the Prior Art When drilling through geological formations to form oil and natural gas wells, it often occurs that the drilling pipe becomes stuck within the borehole that is being formed. This is a perforation! This occurs when the surrounding strata collapse or cave in. It can also occur as a result of fluid uptake and uplift of the formations below certain boreholes, which restricts the movement of the borehole pipe within the borehole. This can also occur for many other reasons. When this phenomenon occurs, the perforated pipe becomes jammed and the operation ceases, and no action can be taken to dig deeper into the perforation until the stuck pipe is removed.

The first step in removing a stuck pipe in a borehole is to locate the point along the borehole, often thousands of feet below the surface, where the pipe is stuck. A number of techniques have been developed over the years for locating a free point of pipe within a borehole so as to remove the section of pipe above the stuck section. The most popular technique is to lower an instrument into the central passage of a bore pipe and attach a pair of relatively movable sensor members to the inner wall of the pipe. We then know that the bore pipe is stretched longitudinally or torsionally and that the relative movement between the two fixing members fixes the members to the pipe wall at a position above the stuck point of the pipe. That's true. Of course, the stresses in the drill string induced from the ground surface are only reflected by the portion of the drill string that is above the stuck portion. If a pair of sensors is affixed to the wall of the pipe below the stuck point and the drill string is stressed, there will be no relative movement between the two members.

In this way, stuck points are detected by taking measurements while continuously moving the sensor along the inside of the drill pipe. However, this type of device is relatively slow due to the time required to sequentially install and remove the sensor elements, making the operating time of the drilling machine very expensive. Furthermore, this contact type stuck pipe detector also requires complex mechanical or magnetic means for attaching the sensor member to the pipe wall.

A well-known property of ferromagnetic pipe is that the magnetic permeability of the material changes as a function of the stress applied to the material. Other conventional stuck point detection devices utilize this principle rather than mechanical stretching of the pipe. The use of this technique allows the use of fixed point detectors of non-contact construction that do not require engagement with the side walls of the pipe. Bender U.S. Pat. No. 2.686.
As shown in No. 039, a high frequency oscillator 10 is tuned to a frequency of 20 to 50 KHz by a coil 12, and a high-frequency oscillator 10 is tuned to a frequency of 20 to 50 KHz, and a
This will be lowered. The coil is inductively coupled to the wall of a steel pipe that loads the coil and is therefore part of the tuned tank circuit of the oscillator 10. The magnetic permeability of the pipe determines the degree of loading of the coil 12 and thus the inductance of the tank circuit and the frequency of the oscillator. As the coil passes through a stuck point in the stressed bore pipe, the permeability of the unstressed pipe below the stuck point changes to the stressed point above the stuck point. The frequency of the oscillator changes due to the different permeability of the pipe. Although Bender's device can detect stuck points without physically attaching a sensor to the pipe wall, the device has a number of inherent drawbacks. Perhaps the greatest of these drawbacks is that the pipe is limited by the tank skin drop of the oscillator, thus limiting the overall accuracy and reliability of the technique. Additionally, the sensitivity of Render's device is limited by the teaching of a single data recording operation to detect the stuck point, which does not allow for sufficient tolerance for changes in permeability for different pipe materials and sizes. Limited.

Other conventional instruments have means for measuring the magnetic permeability of pipes or tubes, but these are generally only used in Caliva instruments to measure the thickness and inner diameter of unstressed pipes. For example, Schlumt)erger
UK Patent Application No. 4037, 43 of T, imited
No. 9 and US Pat. No. 2,992,390, all issued to Dewitt IC, utilize various aspects of magnetic permeability for pipe measurements.

For example, the British patent application to Schlumberger describes an instrument for measuring the wall thickness of well casings by means of magnetic flux. Three pairs of transmitter and receiver coils are used, one to measure the internal diameter, one to measure the casing thickness, and one to measure the permeability of the casing wall. has been done. Variations in each of these parameters affect each other, and by measuring all three simultaneously, they compensate for each other and provide highly accurate thickness measurements. Schlumber
ger's UK patent application discloses two data recording methods with two coils for magnetic permeability measurements, or only in connection with a caliper instrument, none of these proposals being fully commercially available. The best fixed point detector has yet to be completed.

Although the prior art is well equipped with methods and equipment for below-bore measurements of pipe permeability, the problem of accurately detecting the location of a stuck pipe within a borehole still remains. The device of the present invention overcomes the shortcomings of the prior art and uses a relatively low frequency to detect changes in magnetic permeability that occur in a stressed pipe within a borehole. By providing a moving point detector it forms a very superior instrument. This 6L sea urchin 1゛ bent pipe) 119
An effective apparatus and method for locating the missing point along the perforation in which the hole is inserted is provided.

SUMMARY OF THE INVENTION The present invention comprises an apparatus for measuring the stuck point of a pipe in a borehole by providing a pair of coils placed on a common axis (a specified distance apart). Energized at a relatively low, preselected frequency, the coil is lowered through the perforated pipe when the pipe is in its normally unstressed condition. The output data of the receive coil is taken. A stress is applied to the sidewall and the process is repeated to take a second data. The two data are compared and the change in the signal received by the coil indicates the location of the stuck point within the borehole.

The change in signal is a result of the change in magnetic permeability between the stressed and unstressed conditions of the bore pipe above and below the stuck point.

In another aspect, the present invention detects the location of a stuck point in a bored pipe provided in a borehole of the type in which an instrument descends a ferromagnetic pipe section to detect changes in magnetic permeability in the pipe. We have an improved method. This improvement includes a wire wire instrument having a pair of spaced apart coils that travel down the bore pipe to detect the permeability of the pipe. A primary magnetic flux of alternating frequency is generated from one coil of the instrument and directed into the wall of the bore pipe. A secondary magnetic flux signal generated by the eddy currents induced in the bore pipe is detected by the instrument's receiver coil as an indication of magnetic permeability. The instrument moves along the drilled pipe within the borehole to generate first magnetic permeability data from the unstressed pipe. The instrument then moves along the drilled pipe within the borehole and generates second permeability data from the pipe under stress.

The first and second data are then compared to find the point of change in permeability that represents the stuck position of the pipe within the borehole.

4) In the other 4) p-phase, the method described above for generating the first data calculates the depth of the stuck point within the borehole, and calculates the approximate depth of the drilled pipe of the stuck point. The weight is calculated and a lifting force is applied to the drill string in the borehole to substantially remove compressive forces from the bore pipe in the area of the stuck hole. after that,
The step of generating the second data includes applying a compressive force to the drill string in the borehole to increase stress in the drill pipe section in the area of the stuck point. The steps to generate data are:
The method includes the step of applying a torsional load to the drill string in the borehole to apply a high torsional stress to the drill pipe section in the region of the stuck point.

The method also includes the step of separating the first and second coils in the instrument by a prescribed distance of about 6 inches (15,24 m) from each other and energizing the first coil at a frequency of about 1301 (z). are doing.

For a complete understanding of the invention, other objects and advantages, reference should now be made to the following description in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a drilling machine 11 is shown disposed on top of a borehole 12. As shown in FIG. The machine 11 is equipped with a pulling device having a crown block 13 mounted on the upper part of the machine and a traveling block 14 hooked onto the upper end of the drill song 8. The drill string 18 is constructed by connecting a plurality of drilling pipes 15 in series with threaded ends in a conventional manner. A drill bit 22 is positioned at the lower end of drill string 18 by drill collar 19 . The drill bit 22 serves to cut through the formation 24 and form the borehole 12. Drilling mud water 26 passes through the annular portion 16 from the opening of the bit 22 to the ground surface along an axial passage passing through the center of each drill pipe 15 constituting the drill string 18 from an accumulation storage hole 27 near the surface road of the well. It is being pushed out. A metal case 4 is shown positioned in the borehole 12 near the surface to maintain the integrity of the top of the borehole 12.

Still referring to FIG. 1, drill stem 18 and borehole 12
The annular portion 16 between the side wall 20 and the side wall 20 forms a return flow path for drilling mud. Mud water is pumped out from the accumulation hole 26 near the well area L section 28 by a pump device 30. The muddy water passes through a muddy water supply pipe 31 connected to a central passage extending in the longitudinal direction of the drill string 18 . In this way, the drilling mud is forced down through the string 18 and is present in the borehole through the opening in the drill bit 22, cooling and smoothing the drill bit as well as reducing the amount of water generated during the drilling operation. Return the strata cut to the surface. A fluid drain pipe 32 is connected from the annular passage 16 above the surface of the well, connecting the return mud flow from the borehole 12 to the mud hole 26.

Furthermore, as shown in Figure 1, a depression has occurred in the wall of the drill hole around the drill stem 8, and as indicated by point S, the pipe portion 15a cannot move within the hole. The device of the present invention functions to locate this point S along the length of the borehole 12 and the drill stem 18 and measure the distance from the surface of the well, and to determine the distance from the well above ground. All free parts of the bored pipe 15 above the fixed pipe joint 15a can be removed. Once all the pipes on the free point S have been removed, the device is brought into the borehole 12 and connected to the joint 15a.
can be removed and the digging operation can then begin.

It will be appreciated that the apparatus of the present invention includes a wire line instrument that is lowered through a central hole formed in each section of the drilling pipe by means not shown. Necessary wire line tracks, guide pipes, etc. are positioned in the usual manner above the borehole above the surface of the well, and then installed in the crown block 13.
The tool is drilled while controlling the heavy phase applied to the bit 22 and drill string 18 by the traveling block 14.

Still referring to FIG. 1, an instrument 10 constructed in accordance with the principles of the present invention is provided with a perforation 12 by a wire (not shown).
The drill string is lowered through the center passage of the drill string. The wire line is conventional and consists of a sheathed coaxial two-conductor cable 1', which provides the mechanical and electrical connection between the wire line control and monitoring equipment at the surface of the instrument 11. is being carried out. Equipment 10
is lowered through a central opening in the drill string 18 and finds a point 8f that is immobilized by a measurable change in the physical properties of the associated pipe.

It is well known that when a ferromagnetic member, such as a bore pipe, is stretched, compressed or twisted, the permeability of the member changes. Furthermore, when a magnetic field is induced in the wall of the perforated pipe, eddy currents are generated in the length of the perforated pipe. The pattern and strength of the eddy currents are related to the magnetic permeability of the material that makes up the pipe. ↑4r! A preferred method of measuring permeability associated with eddy currents in a perforated pipe is to use a receiver coil to detect the electromagnetic field generated by the eddy currents ζ in the pipe material. In general, the measurement parameter is classically determined to be equal to the magnetic flux density B at the depth d within the space. Here, Bo = magnetic flux density at the ground surface d - depth in centimeters) f = frequency (I - (z) μ = magnetic permeability ρ - specific resistance (micro-ohm centimeters) 11 hours (seconds) The amplitude change in magnetic flux density with respect to depth is determined by the following equation.

The phase change with depth d is given by the following equation.

Input 18 bow to 11 perforated pipe (II (
The bundle is this, l+koI/te vortex'tlRdr -f 1
M cow 1/, d'+'i1'+tY, rllr, i;
tJ: f,-,.

Form an electromagnetic field. This tertiary magnetic field, generated by the vortex flow in the pipe, causes the receiving coil to
detected. If the input signal and all other variables are held constant, the signal at the receiving coil will vary in amplitude and phase as a function of the permeability of the pipe.

Still referring to FIG. 1, the method of the present invention includes several steps that increase accuracy and reliability in critical underbore measurements. A driller faced with a stuck pipe can use the device 10 to approximate the depth within the borehole 12 to which the pipe is stuck. This is accomplished by pulling the drill string upwards with a preselected force by the crown block and traveling blocks 13 and 14. for example,
An upward force of 20,000 bonds (7 in 9,880) produces a measurable elongation in the drill string 15. By knowing the extent to which a steel bore pipe of a known type will stretch with a preselected force, an operator can stretch the pipe from the ground surface where the stretching occurs to the point 8 where it becomes stuck. In this method, it is possible to calculate the total
The approximate location of the stuck point S of the bored pipe 15 is determined to an accuracy of several hundred feet. The approximate length of the pipe between the above-ground part of the well and the stuck point S at the bottom of the borehole extends to its depth; the weight of the pipe below and from the part 15a at the stuck point; It makes it possible to calculate the amount of upward force required for removal. This reduces the stress state within the pipe section 15a in the area of the stuck point S to approximately zero.

A first data of the permeability of the bored pipe is taken when the pipe section 15a is supported in a substantially zero stress state in the region of the stuck point S.

This data means that the pipe is stuck,
The permeability of the drill string is recorded along the approximate region. The driller then applies a preselected stress to the pipe in the area of the stuck point. Pipe part 15a
The stress applied to the drill string 18 in the region of can either pull the string to put a high tension on the pipe, release the weight of the drill string onto that region and compress the pipe, or put a twist in the drill string. It can be formed by

When the drill string 18 in the region of the section 15a and the stuck point S is in a mechanically stressed state, permeability data of the drilling pipe wS2 are obtained by the device 10. This stressed data is then compared to unstressed data for the same area. This comparison is clearly drills) I
]The point at the bottom of the perforation where the stress on the song is suddenly removed,
In other words, it indicates the point below the point S that cannot move.

The instrument 10 used in connection with the device of the invention also includes:
Near its lower end part 15a and stuck point S
It has means for attaching a chemical cutter or the like for string shot to separate or cut the drill pipe immediately above the hole and remove the drill string at the top of the hole.

2A-2E, a series of longitudinal cross-sectional views of instrument 10 constructed in accordance with the principles of the present invention are illustrated. Referring first to FIGS. 2C-2E, a portion of the device nosing portion of the instrument 10 is shown having an outer cylindrical nozzle or shell 41 formed from a non-magnetic material such as a non-magnetic stainless steel alloy. ing. The outer wall of the housing is relatively thick to protect the internal coils and electronics of device 10. The housing 41 is also configured to withstand the impact caused by an explosive charge used to uncouple the joint of the drilled pipe in the borehole 12 in the event that a stuck point S is found. has been done. Second
As shown in Figure B, the upper end of the cylindrical nousing 41 is connected to a cylindrical shaft 42, which has a central opening 43 formed therethrough.

The central axis 42 is located at the socket 4 at the upper end of the instrument housing 41.
4 is screwed into place. As shown in Figure 2A, axis 4
The upper end of 2 is a mechanical and electrical connection socket 45 for receiving and connecting the lower end of a coaxial wire (not shown).
The wire line is used to lower the instrument 10 into the central opening of the bore pipe and to provide communication between the instrument and the necessary power and control equipment at the surface. An upper end spring guide part 46 is provided adjacent to the socket part 45, and the guide part 46 receives one end of the center concentration spring 48. A guide slot 47 is formed. Second
As shown in Figure B, the other end of the centering spring 48 is attached to the lower guide slot 49 of the lower bushing 51. The circumference of the axis of the instrument is 1ZII [9 lily. Three central concentration springs 48 are provided with the same circle spaced apart.
is preferred. The helical spring assembly 52 has three centering springs 48 that hold the center of the axis of the instrument 10 open 1]
ensuring positioning within the central axis of the section (I-).

Referring to the portion of the apparatus 10 shown in FIGS. 2A and 2B, the central opening 43 is provided with a coaxial conductor 50 that is electrically isolated from the sidewalls of the central opening 43 for power and signal transmission. is supplied from the center conductor of the coaxial wire line to the apparatus section of the instrument via a connector assembly 53.

A conductor 50 connects between the wire line and electronic circuitry within a housing 54 (FIG. 2D) to provide DC power from the ground to the fixture 10.
from the electronic circuitry, and sends AC voltage data signals from the electronic circuitry to the earth's surface via wire lines.

As shown in FIGS. 2C and 2D, the non-magnetic outer shell 41 of the device 10 houses an excitation coil 61 which is connected to a core 62 of magnetic material.
It has a winding wound around it many times. Receiving coil 6
3 is disposed a preselected distance d from the excitation coil 61 and has a plurality of windings wound around a rounded edge feeding coil core 64. Two fills 61. F6 and 6
3 is the coil spacer 651 that is selected in advance.
Building 111, 1 fl IT blocks are spaced apart,
The coil spacer fi5g, the name coil core h2j,
It is pasted on 11 parts of the tsuba-shaped poems with numbers i and 64 facing each other. The electronic circuitry located within chamber 5.1 is used to generate the excitation signal and measure the received signal in accordance with the teachings of the present invention, and includes the circuitry detailed below.

The lower part of the instrument 71 shown in FIG. 2E has means 72 for attaching the lower end to an explosive charge or a chemical cutter depending on the particular piercing condition.

Fourth, the lower end 71 is provided with a connector 73 that connects the signal from the wire to the ground to detonate explosive munitions or activate a chemical cutter. It is necessary to separate the drilling pipe 15 located in the vicinity of the stuck point from the rest of the drill string and remove the string. In this manner, the stuck portion of the string can be removed or bypassed and appropriately disposed of using known techniques.

Referring now to the block diagram of FIG. 3, it is shown how the entire system operates. As shown, the excitation coil 61 is driven by an oscillator 81 via a frequency amplifier 82,
Generates A and C changes in magnetic flux. This change in magnetic flux is 15.
It is used to generate eddy currents in the wall of the bore pipe, which is shown schematically in the figure. A voltage is induced in the receiving coil 63ζ by the magnetic flux caused by the eddy electric fluid flowing in the affected pipe wall.The output from the receiving coil 63 is connected to a peak detector 84 via a receiving amplifier 83. 84 measures the peak voltage of the output of the amplifier 83. The output of peak detector 84 is connected to a voltage to frequency converter 85 which generates a series of output pulses. The frequency of the pulses from a voltage controlled oscillator provided within voltage-to-frequency converter 85 is controlled by the value of the signal from peak detector 84. The output signal from transducer 85 is sent to the surface via wire line 86 where it is connected to count rate meter 87.
supplied to A signal representing the frequency of the bottom of the drill hole is generated by a count rate meter 87 and recorded on a recording device 88 as a function of instrument position.

The DC power supply 89 supplies DC voltage via the wire line 86 to power the electronic device ζ, drives the excitation coil 61f, and receives a signal from the pickup coil 63. Recording device 88 is of the conventional strip recorder type which generates data on the permeability of the pipe as a function of the position of the wire line instrument along the borehole. A mechanical graph is then formed for comparison. Alternatively, the recording device f188 may include data storage and processing means for recording, analyzing, and comparing sequential data directly to produce a variable output thereof.

In the method and device of the invention, several 1's must be satisfied for complete operation of the device d.
It has been reported that there are certain parameters. For example, the frequency at which the excitation coil 61 is driven fiI+-4- is important for maximum sensitivity and accurate measurement of the permeability below the borehole. It is also noted that the spacing d between the excitation coil 61 and the receiver coil 63 is particularly important, and that the maximum sensitivity to changes in magnetic permeability in the steel bore pipe is related to the excitation frequency present in the device. It has been discovered. 4, a series of three overlapping graphs of output voltage for constant input as a function of excitation frequency for each of three different distances between excitation coil 61 and receiver coil 63 is shown. The lower curve 91 shown represents the normalized receive voltage value for a spacing of approximately 5 inches (12,76n) between the opposing ends of the exemplary coil 61 and receive coil 63. Peak sensitivity in this interval occurs at a frequency of approximately 130 Hz. Similarly, curve 92 has a spacing of about 7 inches between the coils.
7,783), with similar peak sensitivities occurring in the 130-150 Hz range. The upper curve 93 shows that a spacing of approximately 6 inches (15.24 crn) between the excitation and receive coils provides maximum received voltage sensitivity at a frequency of approximately 1301 (z). Optimal results are obtained with an operating excitation frequency of approximately 130,112, and a spacing of approximately 6 inches (15.24.W) between the excitation coil and the voice receiving coil, where the stress in the ferromagnetic pipe is The highest sensitivity has been obtained in detecting changes in the magnetic permeability of the ferromagnetic pipe.

As generally noted above, the apparatus of the present invention illustrated in the circuit shown in FIG. 3 may also include a phase detector at the output of amplifier 83 rather than amplitude detector 84. Of course, the phase detector needs to be connected to the output of the amplifier 82 as a reference phase in order to detect the phase change of the signal of the receiving coil 63 with respect to the drive signal of the excitation coil 61. The change in phase is used to detect the change in permeability of the stressed pipe in the region of the stuck point.Referring now to FIGS. 5A and 5B, in FIG. A block diagram of the illustrated circuit is shown. In particular, the excitation coil 6
It is driven by an oscillation circuit 81 having four crystal oscillators 101 connected via a frequency dividing counter 102. The crystal oscillator 101 operates at a frequency range of 1MTl7°, and the output lead wire 1 (13, 1
04 and 105 and supplied to the AND10R selection gate circuit 106.

The AND10R select gate 106 is of the type CD4019B which properly drives the bridge coil drive circuit 107.

The drive circuit 107 includes four field effect transistors (FETs).
) 1 (38, 109, 110 and 1.11. FETs 108 and 109 are connected in tandem, and Ti' E 'l'' 110 and 111 also operate in tandem.

ANT) 10II, the selection gate circuit 106 is FET
108 and 109 are turned on for a preselected period of time and then turned off for a preselected period of time before Ti' ET 1111 and 111 are turned on. In this way, the sense transistors 108-110 are protected from overloading and damage.
actuated through inductance coils 112 and 1
13, it is converted into a smooth sinusoidal excitation signal.

In this way, the excitation coil 61 is driven by a sinusoidal signal of a preselected AC frequency.

Still referring to FIGS. 5A and 5B, the receiver coil 63 is connected to the input of an amplifier 83 via a capacitor 121, which is connected to the amplifier 1 of the first stage [l].
22, and the output of this amplifier is connected to the second stage amplifier 123. The output of the second amplifier 123 is connected to a pair of series connected amplifiers 124 and 125 connected in a peak detector configuration. Detector 8
The output of 4 is connected to a voltage-to-frequency converter 85 via a coupling resistor 126. Converter 85 connects pulse generator 1 via integrating amplifier 127 and switch 132.
31 has a comparison amplifier 128 connected to control the operating frequency of 31. The output of the voltage-to-frequency converter 85 is coupled via an operational amplifier type driver 133 to a line driver 134, which provides a series of line voltage pulses to the wire line 9 for transmission to surface equipment. . Further, the wire line 9 supplies DC1i pressure connected to a power source 89 between the exterior 9b and the center conductor 9a,
Power supply 89 has a first voltage regulator 141 that steps down the 30 volt input voltage to 15 volts. A second voltage regulator 142 is coupled to regulator 141 to generate a low supply voltage of 7.5 volts suitable for operation of the operational amplifier of the circuit.

As mentioned above, the oscillator 81 is connected to the bridge drive circuit 107.
To. It is used to drive the L-shaped excitation coil 61. This produces an AC change in magnetic flux at a frequency of approximately 128-130 Hz in the excitation coil. The signal induced in the receiving coil 63 is amplified via an amplifier 83 and then measured by a peak detector 84. The output of peak detector 84 is connected to a voltage to frequency converter 85 which generates a series of output pulses having a frequency representative of the input voltage. This output pulse is returned to the ground via line driver 134 and wire line 9, and is received and recorded by a count rate meter.

An overview of the operation shows that the first magnetic permeability data of the steel wall of each part of the drilling pipe 15 is moved through the wire line with all stress removed from the drill string as described above. Collected for the area of missing points. The drill string is then stressed by applying a force to the surface drilling pipe through longitudinal extension, compression or rotational torque, and a second set of data is collected along the same region of the pipe. By comparing the two data, a sudden change in the magnetic permeability value of the stuck point S is detected due to the difference in stress above and below the stuck point. The change in magnetic permeability indicated by the comparison of these two data pinpoints the location of the joint of the bored pipe 15 that is stuck in the borehole. Then, the lower end ζ of the instrument 10
The explosive charge is immediately detonated from the ground while applying a torque to the string to separate the top of the drill string from its joint. Alternatively, a chemical cutter on the lower end of the instrument may also be activated to cut a portion of the drill string and remove its upper portion from the borehole.

As described above, it is believed that the operation and structure of the present invention will be apparent from the above description.

While the illustrations and the described method and apparatus are characterized as preferred, the following claims do not constitute a departure from the spirit and scope of the invention as described.
It will be obvious that many modifications and changes may be made to this invention.

[Brief explanation of drawings]

FIG. 1 is a side partial cross-sectional view of a drilling machine for forming a borehole; FIGS. 2A-2F are successive enlargements of a stuck point detection instrument constructed in accordance with the principles of the present invention; FIG. 3 is a block diagram of the apparatus of the invention, and FIG. 4 shows the excitation on the receive coil output voltage as a function of the spacing between the coils in the apparatus of FIG. Figures 5A and 5B are diagrams of one embodiment of a circuit used in connection with the apparatus of the present invention. 10... Instrument, 11... Excavation machine, 1
2...Drilling, 15...Drilling pipe, 1
8...Drill string, 22...,...
Drill bit, %... Well aboveground part, 61...
... Excitation coil, 63 ... Receiving coil, 81
...Oscillator, 82 ...Drive amplifier, 8
3... Receive amplifier, 84... Peak detector, 85...-'119 vs. frequency transformer,
86...Wire line, 87...Counting rate i
t, 8B...recording capacity, 89...T)
C voltage power supply. Patent applicant: NL Industries Inc.

Claims (1)

[Scope of Claims] 1. A device for detecting a location where a ferromagnetic pipe section becomes stuck in a borehole by measuring magnetic permeability, the device comprising: a first device that generates a magnetic flux at an alternating frequency in the pipe; a second coil for receiving a magnetic flux signal from the pipe and generating magnetic permeability data for the pipe; means for stressing and releasing stress from the pipe in the stuck region; means for recording first and second magnetic permeability data of the pipe when the pipe is in a first unstressed state and when the pipe is in a second stressed state; and means for comparing second data to detect changes in magnetic permeability due to changes in stress in the pipe to define the location of a point stuck within the borehole. 2. The apparatus of claim 1, wherein the first coil is approximately 6 inches (15.5 inches) from the second coil.
24 cm). 3. The device according to claim 2, wherein the alternating frequency is about 130 Hz. 4. The apparatus of claim 1, wherein said means for applying and releasing stress on said pipe comprises a crown block of a drilling machine disposed above the borehole. 5. A ferromagnetic pipe section is placed in the borehole to drill the borehole, and is of the type provided at a point along the borehole within the borehole, such that the boring pipe cannot be immobilized within the borehole. An improved method for detecting the location of lost spots, comprising: providing a wire instrument that descends within a bore pipe disposed within a borehole to sense the magnetic permeability of said pipe; generating a magnetic flux to induce the magnetic flux in the boring pipe; receiving a magnetic flux signal generated from the eddy current in the boring pipe with a receiving coil of the device as a signal representing the magnetic permeability of the boring pipe; moving the instrument along a drilled pipe within the borehole to generate first magnetic permeability data for the pipe in an unstressed state; moving the instrument along the drilled pipe within the borehole; generating second magnetic permeability data for the pipe under stress; and comparing the first and second magnetic permeability data to represent a point at which the pipe in the borehole becomes stuck. Detect changes in magnetic permeability. Said method comprising the steps. 6. The method according to claim 5, wherein the step of generating the first data calculates the depth of the stuck point within the borehole, and the depth from the stuck point is calculated. calculating an approximate weight of the upper bore pipe and applying an upward force to the drill string in the borehole to substantially remove all compressive forces on the bore pipe above the stuck point; The method comprising: 7. The method according to claim 6, wherein the step of generating the second data includes applying a compressive force to the drill string in the borehole to determine the length of the borehole pipe at the stuck point. said method, comprising the steps of: increasing the stress on said stuck point; and facilitating the detection of the concentrated stress on said stuck point. 8. The method according to claim 6, wherein the step of generating the second data includes applying a torsional load to the drill string in the borehole to determine the length of the borehole pipe at the stuck point. The method comprises the steps of applying high torsional stress to the part and facilitating the detection of stress concentrated on the stuck point. 9. The method of claim 5, wherein the step of providing the device includes providing first and second coils within a non-magnetic outer housing to generate magnetic flux in the bore pipe section. and generating a signal responsive to a change in magnetic flux within the bore pipe representative of the magnetic permeability of the bore pipe. 10. The method of claim 9, wherein the step of providing first and second coils within the device comprises:
The method further comprises arranging the coils about 6 inches apart from each other and energizing the first coil at a frequency of about 130 Hz. 11. An improvement for detecting a location where the boring pipe becomes stuck in the borehole, wherein the first and second magnetic permeability data of the boring pipe are generated by an instrument lowering the boring pipe. a wire line device disposed within the device and generating an alternating frequency magnetic flux to induce eddy currents in the side wall of the pipe within the borehole; an excitation coil; a receiving coil spaced apart from the drive coil for receiving magnetic flux signals generated by eddy currents flowing in the bore pipe; means for generating a data signal indicative of a characteristic of magnetic flux generated from eddy currents; and detecting a change in permeability of the pipe wall by comparing said first and second data, thereby determining the point of the stuck point. and means for defining a location. 12. The apparatus of claim 11, wherein the first and second coils are approximately 6 inches (15.
24cm) apart, and the first coil is approximately 130H
Said device being excited at a frequency of z. 13. The apparatus of claim 11, wherein the data signal generating means generates a signal characteristic of the magnitude of the received magnetic flux generated by the flow of eddy currents in the pipe wall. Said device. 14. The apparatus according to claim 11, wherein the data signal generating means comprises a received magnetic flux generated by the flow of eddy currents in the pipe wall and a magnetic flux generated by the excitation coil. said device for generating a signal having the characteristic of a phase difference between said device; 15. The apparatus of claim 12, further comprising means for separating the portion of the drilled pipe within the borehole, said means being disposed adjacent said device and said means for separating said portion of said immobilized pipe. said device adapted to separate said bore pipe in the vicinity of a point at which said bore pipe is separated;