JPH0466995B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for measuring the point at which a pipe becomes stuck in a borehole, and more particularly for measuring the location of a free point in a pipe without the need for mounting the device on the pipe wall. related to a device for measuring

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 occurs because the strata surrounding the borehole 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 find the point along the borehole, often thousands of feet below the surface, where the pipe is becoming 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. The bore pipe is then stretched longitudinally or torsionally, and relative movement between the two fixing members fixes the members to the pipe wall at a position above the point where the pipe becomes stuck. It's about knowing that.
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, the stuck point is 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. Additionally, 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. As shown in Bender U.S. Pat. No. 2,686,039, a high frequency oscillator 10 is tuned by a coil 12 to a frequency of 20 to 50 KHz and lowered into the axial bore of the stuck bore pipe. . 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 increases with the stress above the stuck point. Due to the different permeability of the pipe being applied, the frequency of the oscillator changes. 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 the relatively high frequency required to inductively couple the pipe to the oscillator's tank circuit. The depth of penetration of high frequency electromagnetic waves is limited by the skin drop, thus limiting the overall accuracy and reliability of this technique. Additionally, the sensitivity of Bender's device is such that the teaching of a single data-recording motion detects the stuck point of not allowing sufficient tolerance for changes in permeability for different pipe materials and sizes. Therefore, it is limited.

Other conventional instruments have means for measuring the magnetic permeability of pipes or tubes, but these are generally used only in caliper instruments to measure the thickness and inner diameter of unstressed pipes. for example,
Schlumberger Limited UK Patent Application No.
No. 2,037,439 and US Pat. No. 2,992,390 issued to Dewitte 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 inner diameter, one to measure the casing thickness, and one to measure the casing thickness.
One is used to measure the magnetic permeability of the casing wall. Variations in each of these parameters influence each other, and by measuring all three simultaneously, they can compensate for each other and provide highly accurate thickness measurements. Schlumberger's UK patent application discloses two data recording methods with two coils for magnetic permeability measurements, but only in relation to a caliper instrument, and none of these proposals have been commercially fully developed. The best fixed point detector has yet to be completed.

Although the prior art is well equipped with methods and apparatus 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 drawbacks of the prior art and provides a non-contact magnetic fixed point detection method that uses relatively low frequencies to detect changes in magnetic permeability that occur in a stressed pipe within a borehole. By providing a container, a very excellent device is formed. Thus, an effective apparatus and method is provided for locating stuck points along a borehole into which a bored pipe section is placed.

SUMMARY OF THE INVENTION The present invention includes an apparatus for measuring the stuck point of a pipe within a borehole by providing a pair of coils spaced a predetermined distance apart on a common axis. The excitation coil is energized at a relatively low, preselected frequency, and the coil is lowered within the drilled pipe when the pipe is in its normally unstressed condition. The output data of the receiving coil is taken. Stress is then applied to the sidewall of the pipe and the process is repeated to obtain a second data set. 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 invention detects the location of a stuck point in a bored pipe in a borehole of the type in which an instrument descends down a ferromagnetic pipe section to detect changes in magnetic permeability in the pipe. We have an improved method to do this. 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 pipe in an unstressed condition. 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 a point of change in permeability that represents the stuck position of the pipe within the borehole.

In yet another aspect, the above-described method of generating the first data includes determining the depth within the borehole of the stuck point and determining the approximate weight of the bore pipe above the stuck point. The calculations are made to apply a lifting force to the drill string in the borehole to substantially remove compressive forces from the bore pipe in the area of the stuck point. The step of generating the second data then includes applying a compressive force to the drill string within the borehole to increase the stress within the bore pipe section in the region of the stuck point. The step of generating the second data also includes a step of applying a torsional load to the drill string in the borehole to impart a high torsional stress to the portion of the drill pipe in the region of the stuck point. This method also includes the first and second
The coils are separated from each other by a prescribed distance of about 6 inches (15.24 cm) and include a step for energizing the first coil at a frequency of about 130 Hz.

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. This machine 11 consists of a crown block 13 provided at the top of the machine and a traveling block 1 hooked onto the upper end of a drill string 18.
It is equipped with a tensioning device having 4. The drill string 18 is constructed of a plurality of end-threaded drilling pipes 15 connected in series in a conventional manner. A drill bit 22 is positioned at the lower end of drill string 18 by drill collar 19. Drill bit 22 serves to cut through formation 24 to form 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 path passing through the center of each drill pipe 15 constituting the drill string 18 from the accumulation storage hole 27 near the surface of the well 28. It's being pushed out. metal case 29
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, the annulus 16 between the drill stem 18 and the sidewall 20 of the borehole 12 defines a return flow path for drilling mud. The muddy water is pumped to an accumulation hole 26 near the above-ground part 28 of the well by a pump device 30.
It's being extracted from. 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, drilling mud is forced down through the string 18 and into the borehole through the opening in the drill bit 22, cooling and smoothing the drill bit and removing formation cuts that occur during the drilling operation. part back 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 FIG. 1, a depression has occurred in the wall of the drilling hole around the drill stem 18, and the point
As shown in the figure, the pipe portion 15a is becoming stuck inside the borehole. The device of the invention functions to locate this point S along the length of the borehole 12 and the drill stem 18 and measure its distance from the well above ground to determine if it is stuck in the borehole 12. 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, a device can be brought into the borehole 12 to remove the joint 15a and then start the drilling operation.

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 bore pipe by means not shown. The necessary wire line tracks, guide pulleys, etc. are positioned in the conventional manner above the borehole above the surface of the well to operate the instrument while controlling the weight on the bit 22 and drill string 18 by the crown block 13 and traveling block 14. are doing.

Still referring to FIG. 1, an instrument 10 constructed in accordance with the principles of the present invention is lowered into borehole 12 and through the central passage of drill string 18 by a wire (not shown). The wire line is conventional and consists of a sheathed coaxial two-conductor cable that provides the mechanical and electrical connection between the instrument 10 and the wire line control and monitoring equipment at the surface. . The instrument 10 is lowered through a central opening in the drill string 18 to locate a point S 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 bore pipe, eddy currents are generated in the wall of the bore pipe. The pattern and strength of the eddy currents are related to the magnetic permeability of the material that makes up the pipe. A preferred method of measuring the magnetic permeability associated with eddy currents in a bored pipe is to use a receiver coil to detect the electromagnetic field generated by the eddy currents in the pipe material. Generally, the measurement parameters are determined by classical eddy current equations.

The above equation defines a magnetic flux density equal to B at depth d within the material. Where: Bo = Magnetic flux density at the surface d = Depth (cm) f = Frequency (Hz) μ = Magnetic permeability ρ = Resistance (micro-ohm cm) t = Time (sec) vs. depth within the material The amplitude change in magnetic flux density is as follows.

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

The magnetic flux induced in the bore pipe by the input signal thus generates eddy currents, which in turn form electromagnetic fields. This secondary magnetic field, generated by the flow of eddy currents in the pipe, is detected by the receiver coil. If the input signal and all other variables are held constant, the signal on the receive coil will vary in amplitude and phase as a function of the pipe's permeability.

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 becoming stuck. This includes crown blocks and traveling blocks 13 and 1.
This is accomplished by pulling the drill string upwards with a preselected force by 4. For example, an upward force of 20,000 pounds (9880 Kg) will produce a measurable elongation in the drill string 15. By knowing the extent to which a steel bore pipe of a known type will be stretched by a preselected force, an operator can calculate the length of the pipe from the ground surface where the stretch occurs to the point S at which it becomes stuck. can.
In this method, the approximate location of the stuck point S of the bore pipe 15 is determined to an accuracy of several hundred feet. Depending on 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, the weight of the pipe down to that depth and the weight of the pipe from the part 15a at the stuck point can be calculated. It is possible to calculate the amount of upward force required to substantially remove it. This reduces the stress state within the pipe section 15a to approximately zero in the region of the stuck point S.

A first data of the permeability of the drilled 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 records the permeability of the drill string along the approximate region where the pipe is believed to be stuck. The driller then applies a preselected stress to the pipe in the area of the stuck point. Stresses applied to the drill string 18 in the area of the pipe section 15a can be either by pulling the string to put a high tension on the pipe, by releasing the weight of the drill string onto the area section and compressing the pipe, or by pulling the string and compressing the pipe. It can be formed by twisting the string.

If the drill string 18 in the region of the section 15a and the stuck point S is in a mechanically stressed state, second permeability data of the drilling pipe are obtained by the device 10. This stressed data is then compared to unstressed data for the same area.
This comparison clearly points to a point at the bottom of the drill hole where the stress on the drill string is suddenly removed, ie, below the stuck point S. Also, an instrument 10 used in connection with the device of the invention
near its lower end section 15a and a means of attaching a chemical cutter or the like for a string shot which separates or cuts the bore pipe immediately above the stuck point S and removes the drill string at the top of the borehole. have.

2A-2E, a series of longitudinal cross-sectional views of instrument 10 constructed in accordance with the principles of the present invention are illustrated. 2C-2E, a portion of the device housing portion of instrument 10 is shown having an outer cylindrical housing or shell 41 formed from a non-magnetic material, such as a non-magnetic stainless steel alloy. The outer wall of the housing is relatively thick to protect the internal coils and electronics of device 10. The housing 41 is also designed to withstand shocks caused by explosive ammunition used to uncouple the joints of the bored pipes in the borehole 12 in the event that the stuck point S is located. It is configured. As shown in FIG. 2B, the upper end of the cylindrical housing 41 is connected to a cylindrical shaft 42 having a central opening 43 formed therethrough. The central shaft 42 is screwed into a socket 44 at the upper end of the instrument housing 41. As shown in FIG. 2A, the upper end of the shaft 42 has a mechanical and electrical connection socket portion 4 for receiving and coupling the lower end of a coaxial wire line (not shown).
5, and 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 spring guide section 46 is provided adjacent to the socket section 45, and this guide section 4
6 is formed with a plurality of azimuthally spaced guide slots 47 which receive one end of a centering spring 48. 2nd B
As shown, the other end of centering spring 48 is attached to lower guide slot 49 of lower bushing 51. Preferably, there are three centering springs 48 spaced 120 degrees apart about the axis of the instrument. The helical spring assembly 52 ensures that the three centering springs 48 center the axis of the instrument 10 within the central axis of the bore pipe opening.

Referring to the portion of device 10 shown in FIGS. 2A and 2B, central opening 43 includes a coaxial conductor 50.
is provided, the conductor 50 being electrically isolated from the sidewalls of the central opening 43 and providing power and signals from the central conductor of the coaxial wire line to the apparatus portion 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.
The electronic circuitry also sends AC voltage data signals to the earth's surface via wire lines.

As shown in FIGS. 2C and 2D, the device 1
0's non-magnetic outer shell 41 houses an excitation coil 61, which has a winding wound a number of times around a core 62 of magnetic material. The receiving coil 63 is disposed a preselected distance d from the excitation coil 61 and has a plurality of windings wound around an insulated coil core 64 . The two coils 61 and 63 are spaced apart from each other by a preselected distance by a coil spacer 65, which is attached to the opposing flanged ends of each coil core 62 and 64. There is. Electronic circuitry located within chamber 54 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 described below.

The lower portion of the device 71 shown in FIG. 2E has means 72 for attaching the lower end to an explosive charge or chemical cutter depending on the particular drilling condition. In addition, the lower end 71 is provided with a connector 73 for coupling signals from the wire to the ground to detonate explosive munitions or to activate a chemical cutter. This action is necessary to separate the drilling pipe 15 located in the vicinity of the stuck point from the rest of the drill string above it and to remove the string. In this manner, the stuck portion of the string can be removed or bypassed and appropriately disposed of by well 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 connected to the drive amplifier 8 by an oscillator 81.
2 to generate an AC change in magnetic flux.
This change in magnetic flux is used to generate eddy currents in the wall of the bore pipe, shown schematically at 15. A voltage is induced in the receiving coil 63 by the magnetic flux caused by the eddy current flowing in the affected pipe wall. The output from the receiving coil 63 is sent to the receiving amplifier 83.
is connected to a peak detector 84 which 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.
is 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. DC power supply 8
9 supplies DC voltage via wire line 86 to power the electronic device, drive excitation coil 61, and receive signals from pickup coil 63. Recording device 88 is of the conventional strip recorder type that generates data on the permeability of the pipe as a function of the position of the wireline instrument along the borehole. and,
A mechanical graph is created for comparison. Alternatively, the recording device 88 may include data storage and processing means for recording, analyzing, and comparing successive data directly to produce a variable output thereof.

In the method and apparatus of the present invention, it has been found that there are several important parameters that must be satisfied for complete operation of the apparatus. For example, the frequency at which the excitation coil 61 is driven is important for maximum sensitivity and accurate measurement of 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.

Referring now to FIG. 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. It is shown. The lower curve 91 shows the normalized received voltage value for a spacing of approximately 5 inches (12.7 cm) between the opposing ends of the exemplary coil 61 and receive coil 63. Peak sensitivity in this interval occurs at a frequency of approximately 130Hz.
Similarly, curve 92 shows the receive coil voltage with approximately 7 inches (17.78 cm) spacing between the coils, with similar peak sensitivity occurring in the 130-150 Hz range. Upper curve 93 shows a spacing of approximately 6 inches (15.24 cm) between the excitation coil and the receive coil, providing maximum receive voltage sensitivity at a frequency of approximately 130 Hz.
In this way, the operating excitation frequency is approximately 130Hz and the distance between the excitation coil and the receiving coil is approximately 6 inches (15.24cm).
Optimum results have been obtained for a spacing of , where the highest sensitivity has been obtained for detecting changes in the permeability of a ferromagnetic pipe as a function of stress within the pipe.

As generally discussed above, the apparatus of the present invention illustrated in the circuit shown in FIG.
Rather, a phase detector can also be provided at the output of amplifier 83. 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 magnetic permeability of the stressed pipe in the region of the stuck point.

Next, referring to FIGS. 5A and 5B,
A block diagram of the circuit shown in FIG. 3 is shown. In particular, the excitation coil 61 is driven by an oscillation circuit 81 having a crystal oscillator 101 connected via a frequency dividing counter 102 . crystal oscillator 1
01 operates at a frequency in the 1MHz range, and the counter 10
Output leads 103, 104 and 1 through 2
05 and AND/OR selection gate circuit 10
6. AND/OR selection gate 10
6 is of the type CD4019B which properly drives the bridge coil drive circuit 107.

The drive circuit 107 is composed of four field effect transistors (FETs) 108, 109, 110 and 111. FETs 108 and 109 are connected in tandem, and FETs 110 and 11
1 also operates in tandem. AND/OR selection gate circuit 106 turns on FETs 108 and 109 for a preselected period, then FET 110
and 111 are turned off for a preselected period of time before being turned on. In this way, sense transistors 108-110 are protected from overloading and damage. The square wave switching signal from the FETs is driven through capacitors 114 and 115 and smoothed into a sinusoidal wave by inductance coils 112 and 113. It is converted into an 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, receiver coil 63 connects capacitor 1 to the input of amplifier 83.
21, this capacitor 121 is connected to a first stage amplifier 122, and the output of this amplifier is connected to a second stage amplifier 123. The output of the second amplifier 123 is connected to a pair of series connected amplifiers 1 connected in a peak detector arrangement.
24 and 125. Detector 84
The output of is connected to a voltage-to-frequency converter 85 via a coupling resistor 126. converter 85
has a comparator amplifier 128 connected to control the operating frequency of the pulse generator 131 via an integrating amplifier 127 and a switch 132.
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. The wire line 9 also supplies a DC voltage between the sheath 9b and the center conductor 9a connected to a power supply 89, which supplies an input voltage of 30 volts to 15
First voltage regulator 141 dropping to volts
have. A second voltage regulator 142 is coupled to regulator 141 and provides a low 7.5 volt supply voltage suitable for operation of the operational amplifier of the circuit.

As mentioned above, oscillator 81 is used by bridge drive circuit 107 to drive excitation coil 61. This is approximately 128−130 for the excitation coil.
Generates AC changes in magnetic flux with a frequency of Hz. 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 surface via line driver 134 and wire line 9 where it is received and recorded by a count rate meter.

To summarize the operation, the first magnetic permeability data of the steel wall of each section of the drilling pipe 15 is transferred through the wire line to the drill string stuck with all stress removed as described above. Collected over a region of points. The drill string is then stressed by applying a force to the surface drilling pipe by 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 borehole pipe 15 that is stuck in the borehole. The explosive charge provided at the lower end of instrument 10 is then immediately detonated from the ground and torque is applied 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 can also be actuated 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 method and apparatus shown and described have been characterized as preferred, many modifications and changes may be made without departing from the spirit and scope of the invention as defined in the claims below. It is clear that it can be done.

[Brief explanation of drawings]

FIG. 1 is a side partial cross-sectional view of a drilling machine forming a borehole, and FIGS. 2A-2E show a series of stuck point detection instruments constructed in accordance with the principles of the present invention. FIG. 3 is a block diagram of the device of the present invention;
4 is a series of graphs showing receiver coil output voltage and excitation frequency as a function of spacing between coils in the apparatus of FIG. 2; FIG. 5A and FIG.
FIG. B is a block diagram of one embodiment of a circuit used in connection with the apparatus of the present invention. DESCRIPTION OF SYMBOLS 10... Instrument, 11... Drilling machine, 12... Drilling, 15... Drilling pipe, 18... Drill string, 22... Drill bit, 28... Well above ground part, 61... Excitation coil, 63... ...receiving coil,
81... Oscillator, 82... Drive amplifier, 83...
Receiving amplifier, 84... Peak detector, 85... Voltage to frequency converter, 86... Wire line, 87...
Count rate meter, 88...recording device, 89...DC voltage power supply.

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, 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 device according to claim 1,
The device wherein the first coil is disposed about 6 inches (15.24 cm) from the second coil. 3. The device according to claim 2,
The device wherein the alternating frequency is about 130Hz. 4. The device according to claim 1,
Said means for stressing and unstressing said pipe comprises a crown block of a drilling machine disposed at the top of the borehole. 5 A section of ferromagnetic pipe is placed in the borehole to drill the borehole, and is of the type provided at a point along the borehole in order to prevent the boring pipe from becoming immovable within the borehole. An improved method for detecting the location of a point, comprising: providing a wire instrument that descends within a borehole pipe disposed within a borehole to sense the magnetic permeability of said pipe; generating a magnetic flux and inducing the magnetic flux in the boring pipe; receiving a magnetic flux signal generated from an 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 the borehole pipe to generate first permeability data for the pipe in an unstressed state; moving the instrument along the borehole pipe; generating second permeability data for the pipe under stress; and comparing the first and second permeability data to determine a permeability representative of the point at which the pipe in the borehole becomes stuck. Detect changes in magnetic flux. The method comprising the steps of: 6. The method according to claim 5, comprising:
The step of generating the first data includes calculating the depth within the borehole of the stuck point, calculating the approximate weight of the bore pipe above the stuck point, and determining the depth of the stuck point within the borehole. the step of applying an upward force to the drill string of the drill string to substantially remove all compressive forces on the drill pipe above the stuck point. 7. The method according to claim 6, comprising:
The step of generating the second data includes applying a compressive force to the drill string in the borehole to increase stress in the portion of the drill pipe at the stuck point and to concentrate the stress on the stuck point. said method, comprising the step of facilitating the detection of stress applied by said method. 8. The method according to claim 6, comprising:
The step of generating the second data includes applying a torsional load to the drill string in the borehole to create a high torsional stress on the portion of the drill pipe at the stuck point, so that the drill string on the stuck point The method includes steps for facilitating the detection of concentrated stress. 9. The method according to claim 5, comprising:
the step of providing the device includes providing first and second coils within a non-magnetic outer housing;
The method includes the steps of generating and receiving a magnetic flux in the bore pipe section and generating a signal responsive to changes in the magnetic flux within the bore pipe indicative 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 further comprises disposing the coils approximately 6 inches apart from each other; The method comprises the step of: exciting the magnetic field at a frequency of about 130 Hz. 11, wherein the first and second permeability data of a borehole pipe are in the form generated by an instrument lowering the borehole pipe, an improved method for detecting where the borehole pipe becomes stuck within the borehole; a wire line device disposed within the device, a first excitation for generating an alternating frequency magnetic flux to induce eddy currents in the side wall of the pipe within the borehole; 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 representing a characteristic of the magnetic flux generated from the current; and comparing said first and second data to detect a change in magnetic permeability of said pipe wall, thereby determining the location of the stuck point. and means for defining. 12. The apparatus of claim 11, wherein the first and second coils are disposed about 6 inches (15.24 cm) apart from each other, and the first coil is energized at a frequency of about 130 Hz. said device. 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. Device. 14. The apparatus according to claim 11, wherein the data signal generating means combines 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. 15. The apparatus of claim 12, further comprising means for separating a portion of the drilled pipe within the borehole, said means being disposed adjacent to said device and said means for separating said portion of said stuck pipe. Said device adapted to separate said bore pipe in the vicinity of a point.