US3039544A - Method of and means for determining the inclination of well pipes - Google Patents

Description

Jue 19, 1962 C J. MCWHORTER METHOD OF AD MEANS FOR DETERMINING THE INCLINATION 0F WELL. PIPES Filed June 25, 1959 j fa/A ATTR/VEY June' 19, 1962 c. J. MowHoRTER 3,039,544

METHOD OF AND MEANS FOR DETERMINING THE INCLINATION oF WELL PIPEs 2 Sheets-Sheet 2 Filed June 25, 1959 Cu//en d M C W/mr fer INVENToR.

Afro/Mfr l United States Patent() 3,039,544 METHOD F AND MEANS FOR DETERMINING THE INCLINATION 0F WELL PPES Cullen J. McWhorter, Houston, Tex., assignor to Houston Oil Field Material Company, luc., Houston, Tex., a

corporation of Delaware Filed June 25, 1959, Ser. No. 822,903 Claims. (Cl. 175-45) This invention relates to `a method of and apparatus for logging wells, and more particularly to a method of determining variations in the inclination `of a well pipe for the purpose of locating the point at which the pipe is stuck in a. Well, and to an improved inclino-meter for use in carrying out such a method.

In the drilling and operation of wells, such as oil and gas wells, it is customary to produce a Well bore by the use of a tubular drill string, having at its lower end a drill which is rotated with the string, the string being usually of somewhat smaller external diameter than the diameter of the bore, and drilling Amud being circulated through the string and through the bore outside of the string during lthe drilling operation to lubricate the drill `and to carry away the cuttings formed thereby. The bore of a well produced in this manner may deviate substantially from the vertical yand in wells of substantial depth such deviation frequently takes place in different directions so that the bore is curved at various locations. Under some circumstances, such as when the drilling takes place in inclined formations, or 'when alternately soft and hard formations are encountered, the drill may be deflected in a manner to produce relatively sharp curves or bends, sometimes referred to as dog legs.

ln carrying out well drilling or other operations in wells the drill stern or other well -pipe lwill follow generally the curvature or inclination of the bore and when the well pipe is substantially smaller in diameter than the bore, which is usually the case, the pipe engages the wall of the bore at various locations throughout the length of the bore, so that the inclination of the pipe varies and is different from the inclination of the bore at some locations and may even assume a somewhat spiral shape.

It is often desirable to determine the inclination of the well bore, `or of the drill stem or other pipe therein, such `as the well casing or tubing, especially for the purpose of locating a dog leg or other irregularity in the bore likely to interfere with the insertion or withdrawal of the well pipe, or to locate the point at which the drill stem has become stuck in the Well due -to caving of the formation, settling of the drilling mud, or'from other causes.

Heretofore, in attempting to locate the point at which a well pipe should be disconnected or cut oif, when such a pipe has become Stuck in a well, it has been customary to make use of instruments of the strain gage type, which may be lowered into the well pipe and held stationary therein while the stress or strain on the pipe is varied to indicate by deformation of the pipe whether the pipe at a particular location is free or stuck. By this method it is possible to locate within rough limits the por-tion of the pipe which is stuck and the portion which is free by relatively few readings, but this method has the disadvantage that it is necessary to make a separate test at each of a large number of longitudinally spaced locations in order to accurately locate the point at which the pipe is stuck.

The current procedure in determining the point at which a string of pipe may be freed is to take la series of readings in the pipe at lower and lower levels until a point is found where no readings can be obtained which is indicative of the fact that the stress or strain at this point cannot be varied due to the stuck condiion of pipe above his point.v Generally these readings will diminish from full 3,039,544 Patented June 19, 1962 ICC readings in totally free pipe to zero at some point well below the top of caved in formations or settlings that are binding the pipe. This is due to the fact that torque or tension is transmitted through the top portion of the loose material around the pipe and a certain amount of free travel is established in this loose formation by the usual working of the pipe by the operator in lan eifort to free the pipe. This free travel is often misleading as to the -true degree of stuckness of the pipe and often results in the pipe being backed olf or cut at a depth well below the top of the formation that is binding it. When this happens it is often impossible to pull the freed portion of pipe from the bore hole necessitating a 4second cut or back ofi, or, if the freed portion can be pulled out of the binding material the top portion of the iis-h may be filled by this material falling into it and future iishing operations may be impeded.

In the inclinometer method, described more fully hereinafter, this condition of stress and strain transmitted through the loose formation is not so much a factor. Changes in tension and in the amount of torque present in free pipe will cause the pipe to repose in the bore hole in different conditions of convolutions =and/ or spirals. This is especially true if the free pipe in one condition is under -a considerable tension as shown in FIGURE 1A, and another condition of being relaxed with weight of upper sections bearing down on it as shown in FIGURE 2A. Normally, under tension the pipe would reside on the low side of the bore hole (all -bore holes have some deviation from a true vertical) and generally conform to the contour of this low side. When under compression, the pipe would bow out at intervals from this low side and rest approximately against the opposite wall of the bore hole. This produces a series of convolutions or curves in the pipe 4that causes the pipe at one point to have less inclination and at another point to have more inclination than it had when under tension, lf there is loose formation surrounding the pipe it cannot have the freedom of side to side movement to produce changes in inclination because it would require a very considerable force to produce side movement of the pipe against the restraining forma- -tion Eand this force is not sufiicient since it is derived from the weight of upper sections applied at the relatively small angles in the pipe in relation to the bore hole.

Thus, if an inclinometer log is run of a section of pipe, part of which is free and part stuck, under conditions of tension and compression, there will be a sharp change between the character of the two logs at the point Where the binding formation begins, which is the desirable point at which to attempt a `cut or back o'if of the pipe. This change in character of the inclinometer logs in f-ree pipe can be induced by a change in the amount of torque applied since twisting a string of pipe will cause it to assume a spi-ral condition with resultant changes in inclination at different points.

The inclinometer instrument may be used to make readings at selected points like instruments currently in use, but the amount of change in deviation will vary from point to point. Any reading, however, will indicate that the pipe is free and readings can be checked at la slightly different depth to avoid points where the inclination of the pipe does not change appreciably between conditions of tension or compression.

The present invention has for an important object the overcoming of the above disadvantages of the methods heretofore employed in logging the variations and inclinations of a well bore or of a pipe located in such a bore, by the use of an improved method of and means for continuously measuring the inclination of the bore or pipe throughout its length.

Another object of the invention is to provide a method for accurately locating the stuck portion of a pipe which is stuck in a well bore.

A further object of the invention is to provide an inclinometer of improved construction and sensitivity, for use in measuring very small variations in inclination from the vertical.

Another object of the invention is the provision of an inclinometer which is electrically operated and by which a continuous record or log of the changes in inclination of a well bore or of a pipe located therein may be made.

A further object of the invention is to provide a method of accurately locating the stuck portion of a string of pipe stuck in a well bore which comprises making a continuous record of the amount of deviation of the pipe from the vertical throughout a substantial length of the pipe including a portion of the pipe at the location where the pipe is stuck, applying a force to the pipe to change the inclination of the free portion of the pipe, making a con tinuous record of the deviation of the pipe from the vertical throughout said length of the pipe, and comparing the two recordings to locate a region in the pipe where the inclination of the pipe remains substantially unchanged.

Another object of the invention is to provide a method for locating the stuck portion of a string of pipe stuck in a well bore which comprises making a continuous record of the variation in inclination throughout the length of the pipe including a portion of the pipe at the location where the pipe is stuck, while the pipe is in a relaxed condition, exerting a pull on the upper end of the pipe to change the inclination of the pipe throughout the free portion of the pipe, making a continuous record of the variation in the inclination of the pipe throughout said length of the pipe, while maintaining the pulling force on the upper end of the pipe, and comparing the two recordings to locate the portion of the pipe in which the inclination remains substantially unchanged.

A further object of the invention is to provide a method of placing a well pipe in condition to be disconnected which includes determining the variations in inclination of the pipe throughout a portion of the length of the pipe to determine the condition of stress in the pipe in said portion and applying a force to the pipe to place the pipe in a desired condition of stress.

A still further object of the invention is to provide an inclinometer of simple design and rugged construction whose sensitivity and accuracy is substantially unaifected by the extreme conditions of hard usage to which instruments of those characteristics are likely to be subjected when used in well logging operations.

The above and other objects and advantages of the invention may best be understood from the following detailed description constituting a specification of the same, and considered in conjunction with the annexed drawings wherein- FIG. l is a fragmentary, partly diagrammatic view, illustrating the method and apparatus of the invention showing the inclinometer of the invention partly broken away and partly in cross-section located in the well pipe in a well bore, the recording mechanism employed therewith being shown diagrammatically;

FIGURE lA is a fragmentary, vertical, central, crosssectional view on a reduced scale, of a portion of a well bore showing a well pipe positioned therein, and showing a location at which the pipe is stuck in the well, the pipe being shown in the position which it occupies during one stage of the method of the invention;

FIGURE 2 is a fragmentary front elevational View of a portion of a chart showing a typical form of the continuous record made by the method and apparatus of the invention, and indicating the variation in the inclination from the vertical of a well pipe in a well bore;

FIGURE 2A is a view similar to that of FIGURE lA, showing the typical variation in the inclination of a well pipe corresponding to the recording of FIGURE 2 during another stage of the method of the invention.

FIGURE 3 is a fragmentary, vertical, central, cross sectional View, on a somewhat enlarged scale, of a portion of a well bore, showing a well pipe therein with the inclinometer of the invention in an operable position in the pipe, the pipe being shown partly broken away and partly in cross-section;

FIGURE 3A is a fragmentary, front elevational view on a somewhat enlarged scale of a portion of a chart showing a typical recording indicating the variations of the inclinometer of the invention as the inclinometer passes downwardly through the pipe, illustrated in FIGURE 3; and

FIGURE 4 is a vertical, central, cross-sectional view, on an enlarged scale, showing details of construction of the operating elements of the inclincmeter of the invention.

Referring now to the drawings in greater detail, the method and apparatus of the invention are particularly useful in connection with the drilling and operation of wells, such as oil wells, the bore of such a well being indicated at B, which bore may be provided with a casing or liner C, extending downwardly from its upper end throughout a portion of the bore, and having an inner pipe or tubing T, of substantially smaller diameter than the bore, which extends below the lower end of the casing C and which is illustrated as being stuck in the well bore, as by the caving of the surrounding formation as shown at F, or the accumulation of drilling mud, sand, or the like, in the bore about the exterior of the pipe.

Under these conditions, it is desirable to accurately locate the zone in the well bore in which the pipe is stuck, so that the pipe may be cut or disconnected at a point above the stuck portion to permit the portion above to be removed from the bore and the subsequent carrying out of washover operations by which the stuck portion of the pipe may be recovered from the well.

The apparatus by which the method of the invention is carried out comprises an inclinometer enclosed in a suitable housing 10, connected at its upper end to the lower end of a cable l2, by which the inclinometer may be lowered into the well pipe, and which is operated by suitable winding mechanism 14 rotatably mounted in any convenient manner above the upper end of the well. The cable 12 is of the conductor line type having one or more suitably insulated conductors therein by which electric current may be supplied to the inclinometer and through which current may iiow to suitable recording mechanism by which a continuous record of variations in the inclination of the well pipe may be recorded.

The inclinometer mechanism of the invention, as best seen in FIGURES l and 4 includes an elongated tubular element 16 located in the housing 19 and whose upper end 18 is closed and whose lower end extends into the upper end of an open receptacle 20 supported in the bottom of the housing. The lower end of the tube 16 opens into the interior of the receptacle 20 in spaced relation to the bottom of the receptacle and the tube and receptacle contain a column of `a heavy liquid, preferably mercury, whose upper end is located rat a predetermined level 22 in the tube caused by the pressure of air in the housing acting Vupon the surface of the liquid in the receptacle. The housing 10 may be completely closed Iand `sealed to maintain the pressure in the housing at any desired pressure and to prevent variations in the pressure of the external atmosphere from causing changes in the effective length o-f the column of liquid. An induct-ance coil 24 surrounds the tube near its upper end and within the tube a core 26 of magnetic material such as ferrite or other suitable material having a high magnetic permeability is movably positioned in contact with the upper end of the mercury column in position for longitudinal movement in the tube relative to the inductance or tank coil 24 to vary the inductive eect of this coil in an oscillator circuit in accordance with the longitudinal movement of the inductor in the tube. The coil 24 is connected as by means of `conductors 28 into an electrical circuit including an oscillator 30 of conventional construction, located in the upper end of the housing Il) and is in turn connected by the conductors of the cable 12 to the recorder mechanism at the surface.

The recorder mechanism may be of usual construction including a coupling transformer 32, having a primary winding 34 of low impedance connected in circuit with the oscillator 3ft, through the conductors of the cable 12, and with a suitable source of direct current supply, such as that indicated at 36, and having a secondary winding 33 which is connected in circuit with a receiver 40 Whose output is supplied to an electrical recorder 42 of usual construction, which includes a chart or tape 44 upon which the record is made.

The oscillator 30 is constructed to generate an alternating current at a frequency which is determined by the size of the capacitors in the oscillator and the inductance of the tank coil 24 when direct current is supplied to the oscillator from the source 36 through the primary winding 34 of the transformer 32 and through the conductors of the cable 12. The frequency of the current generated by the oscillator may be of the `order of 40 kilocycles and this alternating current is transmitted through the cable 12 to the coupling transformer 32 and through the transformer and bypass condensers, not shown, to ground land thus back to the oscillator. The alternating current from the oscillator is superimposed on the direct current and generates an alternating current of the same frequency in the secondary 38 of the coupling transformer. The direct current passing through the primary has no effect on the secondary, So that -a separation of the alternating current from the direct current is effected by the coupling transformer in the receiver 40, shown in FIGURE l. There is another oscillator (not shown) provided in the receiver whose function is to provide a reference frequency which may be controlled by the operator. This reference frequency of oscillation may be set to equal the frequency being generated by the instrument in the well. The receiver also includes a frequency mixing circuit which produces no output as long as the frequency of the oscillator 30 and the frequency of the oscillator in the receiver lare equal, but when one of these frequencies changes, there is generated in the mixer device an alternating potential whose frequency is the difference between the two frequencies being fed into the device. rfhis is known as a beat frequency. This .beat frequency is amplified in the receiver and fed through a rectifier network in the receiver which produces a direct current output from the receiver whose magnitude is directly proportional to the beat frequency. The output from the receiver is fed directly into the recorder 42, shown in FIGURE l, which produces a record on the chart 44 indicating variations which take .place in the frequency of the current from the oscillator 30. Thus, as long as the frequencies of the currents from the oscillator 30 and those from the oscillator in the receiver remain the same, the record on the chart 44 will be a straight line, but upon the occurrence of a Variation in the frequency of the current from the oscillator 3), the direction of the line on the chart will be changed accordingly, indicating a deviation of the inclinometer from the vertical.

In practice, the inclinometer is suspended vertically before lowering it into the well and the receiver 4t)` is adjusted to produce Zero beat frequency or zero output, 'and the recorder, likewise is adjusted to indicate zero, so that the pen 46 of the recorder, shown in FIGURE l, will make a straight line longitudinally moving on the chart 44. In this position of the inclinometer, the effective length of the mercury column supporting the core 26 will be shortest, and the core will be at its farthest point of movement relative to the tank coil 24; causing the inductance of the tank coil to be at a minimum and the frequency of the oscillator 3@ to be at a maximum.

In this condition of the apparatus, any variation of the inclinometer from the vertical, regardless of the di- 6 will produce a decrease in the frequency of the current from the oscillator 30 due to movement of core 26 toward the coil 24 caused by a change in the effective length of the mercury column, causing the pen of the recorder to move laterally on the chart 44 to indicate such change of inclination.

It will be apparent that by varying the impedance in the electrical circuit between the receiver 40 and the recorder 42, the instrument may be calibrated to produce more or less `lateral movement of the pen 46 upon the occurrence of a predetermined amount of change in the inclination of the inclinometer. For example, the rst calibration maybe such as to produce a full scale deflection of the recorder for a deviation of the inclinometer of l degree. Subsequent calibrations may be made requiring a 2 degree inclination in the inclinometer'to produce full scale deflection of the recorder or the instrument may be calibrated to require 3 or 4 degrees or more inclination of the inclinometer to produce full scale deflection of the recorder to adjust the recorder to record the maximum deviation likely to be encountered in a well bore.

lf this inclinometer is run in a -bore hole or through a string of pipe in a bore hole it is possible to record deviation from the vertical as a function of depth as indicated in FIGURE 2. Such a recording will show sudden changes in deviation in a bore hole, commonly called dog legs, which might be missed by a directional sur- Vey made at intervals in the bore hole.

The change in the inclination of pipe as before described is necessarily small because of the relatively close proximity of the walls of the bore hole to the pipe. This condition will vary as will the forces causing changes in inclination but in general it may be stated that the change will be of the order of l degree to 2 degrees or less. In some instances of heavy sections such as drill collars, the change may be as small as one-third of one degree. It is apparent, therefore, that an inclinometer must be sensitive and have a high degree of resolution to successfully record such changes in deviation. As before mentioned the most sensitive calibration sitting should produce a full scale deflection of the recorder for a change of only one degree. On such a scale, 1/3 of one degree change (or 20 minutes) will appear as 1/3 of full scale which is easily discer'nable.

At the point where a string of pipe is stuck, it may be found that the deviation from the vertical is relatively large as for example 9 degrees. If the sensitivity calibration step is set high enough for example l0 degrees for a full scale deflection of the recorder, then 9 degrees will appear on the chart on the extreme right, and if the variations in deviation of the pipe were only 1A of one degree, then the changes which can be recorded in inclinometer logs between the conditions of tension and compression will appear small in comparison with the full scale of the log.

To offset this condition, the beat frequency oscillator in the receiver may be adjusted in a direction to reduce the beat frequency an amount equivalent to say 8 degrees: then a reading of 9 degrees will appear on the log in the same place as a l degree reading would before. This will create an artificial zero and then by using a sensitivity step of say 2 degrees for full scale, it is possible to record differential inclinometer logs to reveal positively small changes in inclination even though the total inclination of the string were large.

The inherent sensitivity of this device may be seen from the fact that the inductance of a tank coil of an oscillator whose natural frequency is in the order of 40 kc. has a very profound effect on the oscillator. In other words, changes in the position of a tuning inductance within the tank coil will sharply change the natural frequency of oscillation. Specifically, a change of only .O01 inch either in or out of the tank coil (shown in FIGURE 4) by the inductor will shift the frequency of oscillation by as much rection of such deviation,

as 30 cycles. If an inclinometer tube 30 inches long is inclined l degree from the vertical, the length of the column of 'mercury will be increased .0045 inch, which will cause the inductor t'o move this amount into the tank coil and will produce 4.5 times 30, or 135 cycles change. This will be more than 2 cycles change for each minute of change in deviation and easily falls within the previously described minimum requirement of 1 degree for a full scale deliection of the recording equipment.

The inciinometer instrument will be sensitive to changes in the internal diameter of the pipe. In FIGURE 3, the instrument moving down inside an inclined section of pipe will be disposed on the low side and the nose of the instrument will be deected toward the center of the pipe on reaching an internal reduction in diameter, such as may be caused by a coupling 50, thus causing a momentary increase in `deviation and a kick or jog on the inclinometer log away from Zero. The reverse will happen as the instrument passes through such an internal reduction back into the original pipe size, as indicated at 54. Thus internal upset points will show as a kick, followed by reversal. Reduction in pipe size will show as an outward curvature of the line of the recording and an increase in pipe size will show as an inward curvature of the line.

The inclinometer instrument may be used to find the condition at which tension and compression are equal at a given point in a string of pipe above the stuck point. If the instrument is positioned at a point where it had been observed (from logs or static readings) that a change in inclination occurred between tension and compression in the pipe and starting with a relaxed condition (compression) to slowly raise the string of pipe at the surface until a change in reading is first observed; this rst show of change will be at the moment tension iirst arrived at the location of the instrument and will be a neutral point and will give an operator suircient and accurate information for backing o the pipe at this point.

It will, of course, be apparent that any suitable device, such as a direct current meter may be substituted for the recorder mechanism 42 when it is desired merely to indicate to the operator when the stuck point is reached without making a record of the variations in inclination of the pipe.

In carrying out the method of the invention, the inclinometer is lowered inside of the string of pipe whose variation in inclination it is desired to determine and current is supplied to the inclinometer in the manner previously described, and the changes in inclination of the inclinometer are recorded as we show above, with the pipe in a relaxed condition in the bore. As the inclinometer is lowered in the bore, the deviation of the instrument from the vertical will be continuously recorded on the chart 44. When the inclinometer reaches the bottom, an upward pull may be exerted on the string of pipe, which will tend to reduce the variations in inclination throughout the free portion of the string above the stuck portion, and the inclinometer may be moved upwardly through the pipe while the pipe is maintained in this condition to make a second recording of the variations in inclination. By comparing the two recordings thus produced, it will then be possible to accurately locate the portion of the pipe which is stuck in the bore and the portion which is free above the stuck portion, to determine where the pipe shall be disconnected or cut olf to permit the removal of the free portion. During the carrying out of the method in this manner, it will be apparent that the stuck portion of the pipe will be held against being affected by the upward pull exerted on the string, so that the variations in inclination of the stuck portion will remain substantially the same While the variations in the inclination of the free portion of the pipe will be changed, so that the location where the free portion of the pipe joins the stuck portion may be accurately located.

It will be apparent that under some conditions, the location of the stuck portion of the pipe may be determined by a single pass of the inclinometer, either with the pipe in a relaxed condition, or under the tension produced by an upward pull on the string. It will also be seen that the amount of upward pull exerted on the string need not be suicient to place the entire length of the free portion of the pipe in tension, since the method ofthe invention does not depend upon the tension or compression to which the pipe is subjected, but only upon the change in inclination resulting from a change in the downward force exerted on the pipe.

rThe invention is disclosed herein connection with a certain specific embodiment of the apparatus employed and procedure in carrying out the method, but it will be understood that these are intended by way of illustration only and that various changes may be made in the construction and arrangement of the parts of the apparatus as well as in the particular steps of the method, within the spirit of the invention and the scope off the appended claims.

Having thus clearly shown and described the invention, what is claimed as new and desired to secure by Letters Patent is:

l. The method of locating the stuck portion of a well pipe Strick in a well bore in which the free portion of the pipe above the stuck portion is in a condition of stress causing inclination of said free portion of the pipe above the stuck portion comprising, measuring variations in the inclination of the pipe along the pipe, and concurrently measuring the depth at which said measurements are made whereby the stuck point can be located as lbeing that portion of the pipe below which no variations in the inclination of the pipe are noted.

2. The method of locating the stuck portion of a well pipe stuck in a well bore comprising, placing the pipe above the stuck portion in a stress causing inclination of the free portion of the pipe above the stuck portion, measuring variations inthe inclination of the pipe along the pipe, and concurrently measuring the depth at which said measurements are made whereby the stuck portion can be located as Ibeing that portion of the pipe below which substantially no variations are measured.

3. The method of locating the stuck portion of a well pipe stuck in a well bore comprising, measuring the variations in the inclination of the pipe along the pipe while the pipe is one condition of stress, concurrently recording the depth at Iwhich the inclination measurements are taken, applying a force to the pipe suf'ricient to cause the free portion of the pipe above the stuck portion to assume inclinations different from those existing when the first measurements are made, again measuring the variations in the inclination along the pipe while concurrently recording the depth at which the secc-nd inclination measure- `ments are taken, and comparing the first and second measurements whereby the stuck portion is located as being the portion below which no change of inclination occurred in either measurement.

4. The method of claim 3 wherein the step of applying a force to the pipe includes the steps of applying a longitudinal 'force to the pipe.

5. The method `of claim 3 wherein the step of applying a force to the pipe includes the step of applying a torque to the pipe.

6. The method of locating the upper stuck point of the stuck portion of a Well pipe stuck in a well bore comprising, measuring variations in the inclinationy of the pipe along the pipe While the pipe is in one condition of stress, concurrently recording the depth at which the inclination measurements are taken, applying at the surface a force to the pipe sufficient to cause the free portion of the pipe above the stuck point to assume inclinations different from those existing when the lirst measurements are taken, again measuring the variations in inclination along the pipe while concurrently recording the depth at which the second inclination measurements are taken, and comparing the first and second measurements whereby the upper stuck poin-t is located las being the point below which no change in inclination of the pipe occurred between the rst and second measurements.

7. The method of substantially neutralizing the stress in a tool joint of known position above the stuck portion of a well pipe stuck in a well bore preliminary to disconnecting the tool joint comprising, placing an inclinorneter in the pipe adjacent said tool joint, and applying =a force to the pipe to remove the stress from the pipe at the tool joint until the inclination of the pipe changes thereby indicating that the stress in the tool joint is substantially removed.

8. The method of substantially neutralizing the longitudinal stress in a tool joint of known position above the stuck point in a well pipe stuck in a well bore preliminary to disconnecting the tool joint comprising, placing an in clinometer in the pipe adjacent said tool joint, applying a llongitudinal `force to the pipe in a direction to remove the `longitudinal stress `from the pipe at the tool joint until the inclination of the pipe changes thereby indicating the longitudinal stress in `a tool joint is substantially removed.

9. The method of locating the position of variations in the internal diameter or" a pipe comprising, moving an inclinometer through and in contact with the pipe thereby measuring the inclination of the pipe, concurrently measuring the position of the inclinometer in the pipe, and noting the variations of the inclination of the inclinorneter with reference to the variations of the inclination of the pipe thereby locating the positions of the variations in the internal diameter of the pipe.

10. The method of locating the positions of variations in the internal diameter of a pipe in a well bore comprising, moving an inclinometer through an in contact with the pipe, concurrently measuring variations in the inclination of the pipe, concurrently measuring the position of the inclinometer in the pipe, and noting the variations of the inclination of the inclinometer with reference to the variations `of the inclination of the pipe thereby locating the positions of variations in the internal dameter of the pipe.

References Cited in the file of this patent UNITED STATES PATENTS 2,078,426 Sweet Apr. 2,7, 1937 2,190,901 Wilcox et `al Feb. 20, 1940 2,686,039 Bender Aug. 10, 1954 2,746,550 Mitchell May 22, 1956 2,761,218 Bielstein Sept. 4, 1956 2,814,019 Bender Nov. 19, 1957 2,847,808 Gieske Dec. 24, 1957 2,851,784 Flatow Sept. 16, 1958 2,905,437 Bell et al Sept. 22, 1959 2,936,411 Doty May 10, 1960

Images