US3742444A

US3742444A - De-synchronizing system

Info

Publication number: US3742444A
Application number: US00086915A
Authority: US
Inventors: J Lindsey
Original assignee: Sperry Sun Well Surveying Co
Current assignee: Baroid Technology Inc
Priority date: 1970-11-04
Filing date: 1970-11-04
Publication date: 1973-06-26
Anticipated expiration: 1990-06-26

Abstract

The particular embodiment described herein as illustrative of one form of the invention utilizes a circuit for desynchronizing a first synchronous motor. The motor drives a surface indicating apparatus which displays light signals in timed relation with the downhole detection of borehole parameters. Such downhole detection is accomplished with the use of a second synchronous motor driven from the same power supply as the first synchronous motor. Desynchronization of the first motor permits the display signals to be moved with respect to a scale, and thereby be more easily interpreted by an operator.

Description

O United States Patent 1 H 1 3,742,444

Lindsey June 26, 1973 [54] DE-SYNCHRONIZING SYSTEM 3,443,188 5/1969 Mortimer 318/341 3,452,264 6/1969 T rtle 318/34] [75] Invenm James Houston 3,360,713 12/1967 H owell 307/252 B 73 Assigneez Sperry s w surveying 2,476,873 7/1949 Jeffers 318/85 Company, Sugar Land, Tex. Primary ExaminerBen armn A. Borchelt [22] Flled: 1970 Assistant ExaminerH. A. Birmiel [21] APPL No; 86,915 At l0meyGeorge L. Church, Donald R. Johnson,

Wilmer E. McCorquodale, Jr. and John E. Holder [52] US. Cl. 340/18 R, 307/240, 307/2528, 57 7 ABSTRACT V V 7' V 7' 3 18/85, 318/3 10, 318/341 The particular embodiment described herein as illusg ig 'g' Gohlv 1/40 34 trative of one form of the invention utilizes a circuit for [5 1 0 2 18 desynchronizing a first synchronous motor. The motor 31 I3 5 3 drives a surface indicating apparatus which displays f light signals in timed relation with the downhole detec- [561 Re erences tion of borehole parameters. Such downhole detection UNITED STATES PATENTS is accomplished with the use of a second synchronous 2,707,261 4/1955 Prior eal. 318/341 motor driven from the same power supply as the first 3,214,666 5 C erc 1 4 3l8/341 synchronous motor. Desynchronization of the first Fruehauf et al. motor permits the signals to be moved re 21954-5 9/1960 Fonmsbec 8/85 spect to a scale, and thereby be more easily interpreted 3,478,839 l1/I969 Zemanek, Jr...... 340/l8 R by an operator 3,l49,273 9/]964 Wallace et al. 318/85 3,430,l48 2/1969 Miki 318/85 12 Claims, 4 Drawing Figures PATENTEDJUNZBISH SHEET 1 0F 2 FIG. I

96- TOOL FACE HIGH TOOL FACE OFF E A SID HIGHN2IDE h 0 SET men 5105 FIG. 2

J 92 as STROBE GENERATOR 7v ELECTRONIC 72 PACKAGE INVENTORS JAMES M. LINDSEY ATTORNEY PATENTEDJUN26 I973 3 7 2 sum 2 or 2 I I C: 4

I NVENTORS JAMES M. LINDSEY ATTORNEY DE-SYNCHRONIZING SYSTEM BACKGROUND OF THE INVENTION The present invention pertains to a desynchronizing system and more particularly a control circuit for desynchronizing a motor.

The motor control forming the invention herein is disclosed for use with a borehole instrument. When making boreholes into the earth s surface, it is often desirable for various reasons to deviate the holes from a vertical course through earth formations. The term directional drilling is applied to such operations. One example of the use of such directional drilling operations is found in the drilling of oil wells from offshore platforms. It is a common practice to build a large drilling platform which is permanently secured to the ocean floor and from which a multiplicity of wells are drilled, sometimes over forty in number. Because of the number of wells which are drilled from a single platform, it is necessary to drill the holes laterally away from the platform so that the earth formations containing petroleum reservoirs may be penetrated at distances laterally spaced from the platform. This procedure permits production from as great an area as possible from a single platform. The economics of such a system can readily be appreciated. It is also easily understood how important the maintenance of direction and dip of such boreholes is in order to penetrate particular formations at particular depths and thereby intersect the desired petroleum reservoirs.

A present technique for obtaining such information as to the direction of a borehole is to cease drilling and run a surveying instrument into the drill pipe on a wireline. Alternatively, the instrument may be go-deviled to the bottom of the drill pipe. The instrument is oriented with respect to the drill stern by means of a muleshoe located in the lower end of the drill stem. The muleshoe is simply a device for capturing the tool at the lower end of the drill stem and orienting the tool in a particular radial direction with respect to a predetermined point on the drill stem. For example, the drill stem normally used in such a directional drilling operation has what is termed a bent sub at its lower end whichangles the lower end of the stem and thereby permits angular deviation of the drill bit. The muleshoe is normally oriented with respect to the bent sub. This in turn orients the instrument which is being positioned in the lower end of the drill stem. This series of orientation techniques provides a correlation between the direction in which the drill bit is angled and the orientation tool. After the orientation tool is operated, generally by means of a timing mechanism, the tool is retrieved to the surface by means of a wireline, or by removing the drill pipe from the wellbore. Both of these operations are time consuming and costly, and in particular in offshore operations where the cost of drilling is many fold that of land operations, the negative economies of decreasing the non-drilling time is apparent. A recent development which is the subject of applicants copending application entitled METHOD AND APPARA- TUS FOR ORIENTING A BOREHOLE DEVICE" provides a means for obtaining downhole data indicative of bit orientation and transmitting such data to the surface over a single conductor cable during the drilling operation. In other systems where borehole data is transmitted to the surface, the surface read-out equipment normally includes recorders or printers for recording the data for later use. Sometimes the data is printed on charts or strips of paper in analog form for subsequent interpretation or for use in calculating unknown parameters. The above co-pending application sets forth a system for providing surface indications of the downhole data as it is detected. The system includes a downhole scanning system operated by a motor in synchronism with a motor in a surface indicator. The surface indicator motor drives a light source relative to a scale on the indicator and a light is projected onto the scale in time relation to parameters detected by the downhole apparatus. The detected parameters are in this instance indicative of the orientation direction of the drill relative to a predetermined reference. The light signals on the surface indicator bear a positional relationship relative to the scale which is indicative of this orientation direction of the drill. However, due to the nature of the equipment, such light flashes do not automatically occur on the scale in a manner making the readings readily indicative of the drill position. If the flashes themselves are oriented with respect to the scale while maintaining their timed relationship with the downhole data detection, such indications may be rendered more readily readable by an operator. By controlling the motor on the surface orientator so that it will momentarily desynchronize relative to the downhole scan motor, the light flashes may be moved relative to the scale while yet maintaining the timed relationship between the motors for determining drill orientation.

It is therefore an object of the present invention to provide a new and improved device for controlling a synchronous system.

SUMMARY OF THE INVENTION With this and other objects in view, the present invention contemplates a circuit for momentarily desynchronizing a motor system such as a motor. The circuit includes a switch means for passing power to the motor. A signal generating device provides cyclic signals to cause cyclic openings of the switch which in turn produces momentary interruptions of power to the motor. The motor is thus temporarily slowed relative to its synchronous operation.

A complete understanding of this invention may be had by reference to the following detailed description, when considered in conjunction with the accompanying drawings, illustrating embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing details of a portion of the borehole orientation instrument;

FIG. 2 is a front view depicting the face of the display apparatus for providing visual indications at the surface of parameters measured by the borehole instrument;

FIG. 3 is a side view of such surface indicating apparatus showing the mechanism for providing such indications; and

FIG. 4 is a schematic diagram of a circuit for desynchronizing a motor in the surface indicating apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Equipment utilized in well drilling operations is well known, and is not shown in this application, since it forms no part of the invention. Such equipment is shown however in the copending application referred to above. This disclosure includes reference to an orientation tool which is adapted for lowering into a drill string on the end of a conductor cable. The tool is seated in the drill pipe just above the drill and provides electrical signals to the surface which are indicative of the positional orientation of the drill. In order to pass the tool through the pipe, in a typical rotary drilling apparatus, the rotary swivel is furnished with a wireline opening boss in its upper side which enables a line wiper to be received in the upper end of the swivel. Such line wipers may be purchased from oil well drilling apparatus suppliers, and are constructed to seal off well pressure at the well head during line operations through the drill pipe. Typically such line wipers include a hydraulically actuated packing member in the interior of the wiper. The packing member is actuated by applying pressure into the apparatus by means of an external pressure line which in turn may be connected to a grease pump or the like for applying grease under pressure to the interior of the line wiper. A block is positioned on the upper end of the line wiper and is arranged to swivel about the upper end of the wiper by means of bearings. A sheave is positioned on the block for passing a conductor cable into and through the line wiper. The conductor cable is maintained on a motor driven drum which permits its play-out and take-up during the operations.

The orientation tool disclosed herein is typically used in directional drilling operations utilizing a fluid motor powered drill. A drill string for use in directional drilling operations includes a non magnetic drill collar and muleshoe orienting sub. A bent sub is positioned in the drill string between the collar and a mud motor. A rotating bit sub is positioned below the bent sub. The orienting tool is positioned within the orienting sub and is connected at its upper end with a conductor cable extending to the surface. As will be described, the orienting tool provides signals to the surface indicative of wellbore parameters. The orienting sub provides a means for establishing a predetermined orientation between the orienting tool and the bent sub, which in turn is oriented with respect to the top side of the borehole. The orienting tool houses a pendulum section, to be described hereinafter in detail, which is used for determining the bottom side of the hole by means of gravity operated elements. A lamp and photocell scanning section is located in a portion of the tool adjacent the pendulum section, and provides an electrical indication of the tools orientation for transmittal to the surface. An electronic section for coding electrical signals for transmittal to the surface is included in the tool string.

Referring to FIG. 1 of the drawings, the orienting tool referred to above is generally indicated by the reference numeral 10 and is shown having a pendulum section at its lower end including an outer cylindrical housing 11. The housing 11 has a threaded end portion 12 to accommodate reception of the housing within the tool 10. An O-ring seal 14 is received within a groove about the lower end of the housing 11 and forms a seal between the housing and the interior bore of the tool housing 16. An end portion 17 extends downwardly from the housing and has a knurled outer surface to provide a convenient means for threading or screwing the pendulum section into the tool housing. A lower mounting block 18 is positioned within the lower end of the housing 11 and an upper mounting block 19 is positioned in the upper end of the same housing. Vertical holes 21 are provided through the block 19 to pro vide means for transmitting fluids between the upper end of the upper block 19 and the interior bore of the housing enclosed by the upper and lower blocks, 18, 19. A pendulum assembly within the housing 11 includes a central core portion 22 made of a lightweight metal. A cylindrical body 23 is positioned about the central core 22. The body 23 is made of a lightweight plastic material which has a low specific gravity permitting it to be buoyant in a fluid filling the housing. On one side of the core 22, the plastic material is cut away throughout a substantial portion of its length, and a steel rod 24 is positioned in the cut away between spaced end portions of the plastic material. Upper and

lower shaft members

26, 27 are press-fitted into the ends of the central core. The

shafts

26, 27 each have

ball bearings

28, 29 respectively fitted thereon. The lower ball bearing 29 is positioned in a recess in the lower block 18. The upper bearing 28 is received within a bore 30 formed in the upper block 19. The upper shaft 26 extends upwardly through the block 19 and has a cup member 31 secured thereon by means of a set screw. The cup member has a thin peripheral wall 32 defining the outer perimeter of a hollow chamber within the cup. A slot 33 is formed in the wall of the cup and is parallel with the longitudinal axis ofthe shaft 26. A scanning assembly is positioned within the housing 16 above the pedulum section to form a scanning section. The cup member 31 on the pendulum assembly is shown in its cooperative arrangement with the scanning section. The scanning section includes the outer housing 16, having a synchronous motor 36 positioned in the housing near its upper end. The output of the motor is coupled to a speed reducer37. An output shaft 38 from the speed reducer is coupled to the upper end of a scanner shaft 39 by means of a multi-jaw coupling 41. The shaft 39 has a ball bearing 42 fitted about the shaft. The ball bearing is received within a block portion 43 positioned within the lower end of the housing 16. The bearing 42 is held in the block by retaining rings above and below the bearing. A lamp and photodetector housing 44 is positioned on the lower end of the shaft 39 and has an annular recess 46 formed on the bottom of the central portion of the housing 44 for receiving the cup shaped member 31 extending upwardly from the pendulum assembly. A cylindrical block 47 formed in the center of the recess has a lateral opening 48 sized for receiving a light sensitive device 49 such as a photocell. Appropriate passages in the block communicate with a longitudinal bore 51 in the shaft 39. The passages and bore provide a means for the passage of conduction wires to electrical devices in the housing 44. The housing 44 also has a cylindrical recess 52 extending upwardly from its lower surface near one pe ripheral edge thereof for receiving a light source 53 such as a lamp therein. A slot 54 is formed in the wall of the cylindrical recess 52 to provide a slotted opening between the lamp and the annular recess 46. The slot is arranged so that it is opposite the lateral opening 48 in the block 47 which opening also communicates with the annular recess 46. Another slot 56 is formed in the top of the cylindrical recess 52 which corresponds in a radial position on the housing 44 with the slot 54 in the inner wall of recess 52 so that the slot 56 is on the same radial spoke as the slot 54.

A longitudinal opening 57 extends through the block portion 43 for receiving a second light sensitive device 58 such as a photocell at its lower end. The lower end of the opening 57 has a closure 59 with a slot 61 therein which is positioned radially to the central axis of the housing 44. The light sensor 58 positioned in the longitudinal opening 57 will be hereinafter referred to as a case reference light sensor.

A series of collector rings 62 are positioned about the shaft 39 and are held thereon by means of upper and

lower collars

63, 64, positioned above and below the collector rings. The upper collar is held on the shaft by means of a set screw. The collector rings are insulated from the metal portions of the shaft. Slots 66 are formed in the wall of the hollow shaft 39 to permit passage of insulated wires from the collector rings to the photocell 49 and lamp 53 positioned in the housing 44 at the lowerend of the shaft. Electrical power is supplied to the scanner assembly including the synchronous motor 36 by means of a connector 68 at the upper end of the housing which connector is attached to a single conductor armored cable 69. The armored wires and cable are assembled to the connector in a well known manner for providing an electrical connection between such members, and also for permitting suspen sion of the tool housing from the armored portion of the cable.

The synchronous motor 36 positioned within the housing 16 operates at a speed of 12,000 rpm on a 400 cycle power signal. The speed reducer 37 provides a reduction of 100 to 1 so that the shaft 38 extending from the other end of the speed reducer 37 rotates 2 revolutions per'second. Thus, the scan shaft 39 and photocell and lamp 53 rotate at the same rate.

The interior bore of the housing 16 below the motor 36 is filled with a fluid which not only lubricates the moving parts therein such as bearings, but also provides a dampening effect with respect to movement of the pendulum assembly attached to the lower end of the housing. The vertical holes 21 are formed in the upper block 19 of the pendulum assembly to permit the fluid in the housing 16 to communicate with the interior bore of the pendulum housing 11. Preferably the fluid does not stand above the speed reducer so that the synchronous motor is not drowned by the fluid.

Referring next to FIGS. 2 and 3 of the drawings, surface equipment for providing a read-out of information from the pendulum and scan sections is shown. The read-out apparatus is comprised of a lower base portion 71 having a hollow interior 72 for receiving components of the system. A front panel 73 has a circular opening therein with a translucent plastic or glass face plate 74 placed over the circular opening. Indicia in the form of a radial scale is placed on the plate 74 by means of silk screening or the like. The scale is arcuate, and is marked off in radial degrees from 0 to 180 on both the right and left sides of the scale. Toggle type switches are mounted on the front panel and provide means for operating the surface recording apparatus as will be described hereinafter. A back panel 76 extends upwardly from the base 71 of the surface recorder and has a first mounting bracket 77 thereon extending rearwardly from the panel 76. Mounting bracket 77 has an opening for receiving a strobe light unit 78 including a strobe lamp 81. Electrical wires 79 connect the strobe light unit with a strobe generator 82 mounted in the hollow base 72 of the apparatus. The strobe generator and light unit may be the same as those popularly used in photographic operations; and which are produced by several manufacturers. An opening is provided in the center of the back plate for receiving a bearing 83 such as a ball bearing, which in turn rotatably supports one end of a lucite rod 84 extending through the opening. The rod 84 extends between the back and

front panel members

76, 73 respectively and is curved along its length so that its unsupported end 85 adjacent the front panel 73 is in close proximity to the scale on the plate 74. In order words, the circular path of the rod end 85 when rotated, is approximately coincidental with the arcuate scale on plate 74. A geared pulley 86 is mounted on the rod 84 near its bearing supported end, with the pulley being locked on the rod by means of a set screw or the like for rotation therewith.

On the inside wall of the rear panel 76 towards its bottom edge is mounted an L-shaped bracket 87"for supporting a synchronous motor and speed reducer 88. The synchronous motor is operated by the same power supply which operates the downhole synchronous motor 36 described with respect to FIG. 1 of the drawings. Another geared pulley 89 is mounted on an output shaft driven by the synchronous motor. The pulley 89 is aligned laterally with the geared pulley 86 on the lucite rod. A positive drive belt 92 extends around the geared pulleys for rotating the lucite rod in response to the rotation of the synchronous motor shaft. The belt has cogs which cooperate with gear teeth on the pulleys to provide a positive no-slip movement of one pulley relative to the other. The bearing supported end of the lucite rod 84 is aligned with the center of the scale plate 74 shown in FIG. 2. The other end 85 of the rod has an elongated flattened portion thereon aligned axially with lines 94 denoting radial degrees on the outer edge of the scale.

In the downhole electrical system, signals are generated by the activation of

photocells

49 and 58, and these signals are transmitted to the surface by means of the conductor cable 69. The signals may be transmitted to the surface over separate circuit paths or they may be superimposed on the power signal, thus permitting the borehole tool to operate on a single conductor cable. Such a single conductor system is disclosed in applicants co-pending application referred to above. In any event, such signals are used to drive the strobe generator 82 at the surface. Switching means in the surface equipment permits each of the downhole signals to be displayed individually or simultaneously. For example, if the toggle switch 96 is moved to the Tool Face Only" position, only signals generated by the activation of photocell 49 are passed to the strobe generator. When these signals are received by the strobe generator, the generator is operated to provide an instantaneous flash. lf switch 97 is moved to the High Side position, only signals generated by photocell 58 are passed to the strobe generator. lf switch 96 is moved to the down position marked "Tool Face and High Side," both of the signals are passed to the strobe generator. In the latter mode of operation, two flashes will appear on the face of the plate 74 during each revolution of the downhole scan system and coincidentally with each synchronous revolution of the rod 84 relative to the plate 74.

The surface indicating equipment of FIGS. 2 and 3 is operative in response to the signals received from the downhole tool in the following manner. If the

switches

96, 97 are activated together with the on switch, signals are passed from the downhole equipment to the strobe generator 82. Thereupon the strobe generator fires to momentarily light the lamp 81 on the strobe 78. Light emanating from the lamp 81 is directed onto the end of lucite rod 84 adjacent the lamp. The lucite rod conducts the light down the rod to its opposite end 85 where the light is directed onto the translucent plate 74. The end 85 of the rod is arranged so that light emanating therefrom in the form of a beam is opposite the scale which is placed about the periphery of plate 74. Because of the transparency of plate 74, the light beam is superimposed on the plate scale. The strobe lamp 81 is not continuously operated, but rather is activated only by the data signal derived from downhole equip ment. Thus the light appearing on the scale is intermittent and coincident with data signals. The lucite rod 84 from which the light beam is directed, is rotatable by means of the synchronous motor on the surface indicator. The motor and speed reducer 88 is driven by the same power supply as motor 36 in the downhole scanning system, and has an equivalent speed reduction mechanism so that the lucite rod 84 makes one revolution about the plate scale for every revolution of scan shaft 39 in the downhole scanner. Thus, if a reference correlation is made at the surface between the light beam position on the surface indicating scale and a known reference on the tool a similar correlation will exist when the tool is downhole and the orientation of such known reference can be followed at the surface. Such a technique for making this correlation will be described hereinafter with reference to the overall operation of the system.

The relation between the downhole detection and scan system relative to the surface indicator will now be described. In the downhole tool shown in FIG. 1, the weighted rod 24' in the pendulum section will seek the low or gravity side of a wellbore into which it is positioned. The pendulum is arranged to turn freely within its housing. The cup 31 which is attached by means of shaft 26 to the pendulum is free to rotate therewith. As the cup 31 rotates, a slot 33 in the wall 32 of the cup, permits light to pass therethrough. Therefore, when the scan shaft 39 turns the lamp 53 and photocell 49, the lamp and photocell periodically pass the slot 33 in the cup 31 once each revolution of the shaft 39. Since the lamp and photocell are oppositely aligned, when slot 33 passes between them, the photocell 49 is activated by the lamp 53 to provide a signal. As described previously, this signal is sent to the surface indicating equipment.

In a similar manner a reference signal is generated by rotation of shaft 39 when an opening 56 in the housing 44 permits periodic light passage from the lamp 53 onto a reference or high side photocell 58. This also generates a periodic signal upon each revolution of shaft 39. Thus, upon each revolution of shaft 39 a signal is generated by each of the photocells and passed to the surface indicating equipment.

In the operation of the well tool system thus far described, the following method is employed. At the surface before the tool string is inserted in the drill pipe, a reference mark on the tool housing is leveled with respect to the earths surface, i.e., it is placed in an up position relative to the surface. This reference mark is in the form of a slot which cooperates with a key in the orienting sub of the drill pipe so that when the tool is lowered into the drill pipe, the reference mark assumes a predetermined position with respect to the bent sub of the drill stem. This orientation technique is set forth in detail in Applicants co-pending application referred to above. The portion of the tool having the reference mark (slot) extends from the portion containing the pendulum and scan section shown in FIG. 1 and may be rotated relative thereto for purposes to be described later. I

Next, the surface recording equipment shown in FIGS. 2 and 3 is turned on and the switch marked High Side is depressed to complete a circuit for providing an indication of the high side of the tool. Such indication is in the form of a flashing light which will correspond to the activation of the case reference photocell 58 in the downhole tool, This light will appear somewhere on the scale on face 74 of the surface recording instrument. The light beam repeatedly occurs at periodic intervals at the same position on the scale. The appearance of the flashing light beam will coincide with movement of the scanner housing 44 past the lamp 53 and thus passing light on to the detector photocell 58. Since the light beam moves synchronously with the scanner, the position of the light beam occurring upon closing of the high side switch will always be relative to the position of the photocell 58 which is fixed with respect to the tool housing. Thus, when the housing is aligned with respect to vertical, and the high side switch thus activated, the position of the light beam at that time on the scale is representative of the tool housing in that particular orientation.

As will be described hereinafter, means are provided for desynchronizing the motor used to drive-the light rod on the surface indicator. This desynchronization of the motor will cause the motor to temporarily run slower and thus cause the light flash to be moved so that it occurs at the 0 position on the scale, and thus provides easier reading of the instrument. Since this 0 point on the scale is merely a reference point, it will readily be seen that the flash could occur at any position on the scale for ready reference; however, for the sake of simplicity and minimizing errors in the operation of the system, it would normally be better to place the high side light at the 0 position, which now corresponds to the reference mark on the tool housing being on top of the tool relative to the earth's surface. Upon establishing the high side light at this position, the operator turns off the highside light. The operator then operates the switch to the Tool Face Only position. Similarly, a flashing light will appear somewhere on the face scale, this light always occurring at a position which is relative to the position of the pendulum in the tool. The operator then loosens a locking collar (not shown) which separates the portion of the tool having the reference marker (slot) from the pendulum-scan section shown in FIG. 1, and turns the upper body portion of the tool (containing the pendulum and scan assemblies), making sure that the lower portion with the reference marker is maintained in its present position, i.e., in an up position. This turning of the upper portion of the tool housing is continued until the Tool Face Only" light, which is flashing now, appears at the 0 position on the scale. When the tool face light is in the 0 or other such reference position, the portions of the housing are once again locked together by tightening the locking collar. If the Tool Face and High Side switch on the surface indicator is now turned on, both light flashes will occur simultaneously at the same point on the scale. The tool system is thus calibrated and ready for lowering into the drill pipe.

In order to lower the tool into the drill pipe, the conductor cable 69 is passed over the sheave of the line block, through the line wiper and opening boss in the top of the swivel, and through the kelly. Upon emergence of the cable at the lower end of the kelly, the cable is connected to the tool string at connector 68 and the assembly is inserted into the drill pipe which is being held by means of slips on the rotary table. The kelly is then made up with the top of the pipe string, and by means of the spooling apparatus at the surface, the cable is let out whereupon the tool is lowered into the drill string. When the tool reaches the lower end of the drill string, the portion having the reference marker slot is received within the orienting sub. A muleshoe key in the sub for receiving the orienting slot has been aligned with a portion of the drill, and preferably the bent sub portion of the drill, so that it is known that the key is pointing in the direction that the drill is pointing. Thus, because the High Side light is set to occur at on the indicator whenthe reference slot is up, the high side reading now indicates the direction the bent sub and bit is pointing.

After the tool stringhas seated downhole, the High Side Only switch is activated to provide a flashing light on the scale corresponding to the signals emanating from the high side photocell. Since the tool has now in all probability been rotated from its calibrating position at the surface, the high side photocell light will no longer occur at the same position, i.e., 0 position on the scale as during the calibrating operation. Again by desynchronizing the surface indicator, the flashing light may drift on the scale until it occurs on the 0 position. When this is accomplished, the High Side Only" switch is moved to the Tool Face and High Side switch position. At this time, two flashing lights should occur on the scale, non-simultaneously. These lights will show the angular difference on the scale representing the angular difference between the slit 61 in the housing which passes light from lamp 53 to the high side photocell 58 and the slot 33 in the cup 31 at the upper end of the pendulum assembly, which slot 33 passes light to the tool face photocell 49. This in turn represents the angular difference between the direction which the drill is pointing, as a result of its being attached to the bent sub, and the high side of the hole. This occurs because the pendulous member was set initially so that the slot 33 on the cup produces a signal from the tool face photocell 49 corresponding to the reference slot which in turn, in the hole, corresponds to the direction in which the bent sub and drill are pointing. On the surface indicator scale, this angular difference can be measured in terms of degrees to the right or left at which the bit is pointing relative to the top side of the hole.

The drilling operator now knows which way the drill must be turned in order to achieve the desired direction. Based on this information, he will continue the drilling operation, periodically taking readings from the surface indicator to determine if the corrections he is applying to the drill bit movement are providing the de sired results. Means are provided in the drill stem to permit drilling fluid to bypass around the tool string while the tool string is positioned in the drill pipe. When drilling has continued to the extent that another section or stand of drill pipe need be added to the drill string, the drilling operator will then slow the circulation of mud as much as possible, whereupon the pres sure on the line wiper is released to the point that the conductor cable can be moved through the line wiper by rotating the reel at the surface. The tool is then retrieved to a position within the kelly, whereupon the tool joint between the kelly and top section of pipe is opened and another section or stand of pipe is placed in the drill string in a well known manner. Thereupon, the tool string is again lowered to the bottom of the drill string and seated in the orienting sub and the drilling operation is continued.

Referring next to FIG. 4 of the drawings, a circuit is shown for desynchronizing the synchronous motor in the surface indicating equipment. This desynchronization procedure has been described above with respect to the orientation procedure in operating the surface indicator. The circuit basically includes a variable oscillator operating a trigger which in turn is used to gate a power device such as a triac to control the application of AC current to the synchronous motor. The oscillator portion of the circuit includes a capacitor 101, which together with high and

low resistances

102, 103 respectively, form an RC time constant. The RC network in conjunction with a uni-junction transistor 104 forms the low frequency variable oscillator. The unijunction transistor 104 is open until a break-over voltage is reached, whereupon it fires and discharges the capacitor 101. The output of the uni-junction transistor is fed to another transistor 105 which amplifies the oscillator output. This amplified oscillator signal is then passed to a one shot trigger comprised of capacitor 112, resistor 107, and transistor 106 operating as a trigger. The trigger 106 is normally conducting because it is biased in the on condition by the base resistor 107. When the oscillator is pulsing, a signal is passed through the ca pacitor 1.12 and pulses the normally conducting transistor 106 out of conduction. The output of the trigger 106 passes through a current limiting diode 108 which eliminates the positive DC voltage coming from AC components in the system, which might forward bias the collector emitter junction of the trigger 106. The output of the trigger through the current limiting diode is fed tothe gate of the power device or triac 109. A triac is a bi-directional triode thyristor, shortened to the word triac, and serves as a bidirectional switch adaptable for the control of power to any equipment being operated directly from AC power lines. The triac has a break-over voltage level, which when exceeded in either polarity causes the triac to conduct. At the breakover voltage of the device, the triac switches from a high impedance state to a low impedance state. The current can then be increased through the triac with only a small increase in voltage across the device. The triac remains in the on state until the current through the main terminals drops below a value called the holding current, which cannot maintain the breakover condition. The triac then reverts again to the high impedance or off state. If the voltage across the main terminals of the triac is reversed, the same switching action occurs, thus the triac is capable of switching from the off state to the on state for either polarity of voltage applied to the main terminals. When a trigger current is applied to the gate terminal, the break-over voltage is reduced. After the triac is triggered, the current flow through the main terminal is independent of the gate signal, and the triac remains in the on state until the principle current is reduced below the holding current level. During this short period, at zero voltage level plus or minus a small voltage, the triac does not conduct if a so-called off pulse from the trigger 106 is available. That is, if the triac gate is not receiving an on pulse during this period, then the triac wont conduct as long as the gate is off. The triac can be turned on by applying a positive pulse to the gate at any time in the cycle. Thus, if the off pulse from the trigger occurs randomly at the same time that the triac is below the holding current level, then the triac will fail to conduct until a positive pulse is received from the trigger 106. These intermittent and random pulses occurring from the trigger in coincidence with such non-conductive level of the triac will cause the triac to cease conduction for a short period and thereby cease the passage of current to the motor 88.

In the operation of the circuit described above, if the oscillator is in the off position, that is, if the switch 111 is in the position shown in FIG, 4, the triac trigger 106 provides a constant voltage to the triac keeping it turned on, and therefore running the motor at a synchronous speed. If the oscillator is started by movement of the switch 111 to either of the circuit paths incorporating the

resistors

102, 103, pulse signals are out-putted from the oscillator, and every such pulse momentarily turns the trigger 106 off. This turning off of the trigger will randomly turn the triac off and thereby slow the operation of the motor 88. The frequency at which such turn offs occur will be in proportion to the oscillator frequency. The faster the period of oscillation, the move frequently pulses are passed to the trigger and the slower the motor 88 runs. The variable feature of the oscillator is provided by the large and

small resistances

102, 103 for controlling the voltage to the oscillator. It is readily seen that a device could be employed which would give an infinitely variable resistance control and oscillator frequency output to the system.

Thus, when the operator of the tool system depresses the toggle switch marked Set High Side, the circuit of FIG. 4 is activated for desynchronizing the motor 88 which in turn drives the light rod on the surface indica tor. This desynchronization of the motor will cause the motor to temporarily run slower and thus cause the light flash to move with respect to the scale, since the motor 88 is no longer being operated synchronously with the motor 36 in the tool housing. When the light flashes have moved about the scale so that they occur at the 0 position on the scale, the depressed toggle switch is released to deactivate the circuit of FIG. 4 and permit the light flash to maintain its repeated appearance at that point on the scale. Since this zero point on the scale is merely a reference point, it will readily be seen that the flash could be placed at any position on the scale for ready reference. However, for the sake of simplicity and minimizing errors in the operation of the system, it sould probably be better to place the light at such zero position, which now corresponds to the reference mark on the tool housing being on top of the tool relative to the earths surface. This is because the high side light has been set during calibration to occur at 0 on the indicator when the reference slot is up. At this time, by depressing the tool face and high side switch, flashing lights should occur at two positions on the scale non-simultaneously. These lights will show the angular difference on the scale representing the angular difference between the slit 61 in the housing which passes light from lamp 53 to the high side photocell 58 and the slot 33 in the cup 31 at the upper end of the pendulum assembly, which slot 33 passes light to the tool face photocell 49. This in turn represents the angular difference between the direction which the drill is pointing as a result of its being attached to the bent sub and the high side of the hole. At the surface, this angular difference can be measured on the indicator scale in terms of degrees to the right or left at which the bit is pointing relative to the top side of the hole. The desynchronizing operation merely permits the high side only light to be rotated until it occurs in the zero position so that this angular difference may be conveniently read to the right or left of the 0 position on the scale and thereby indicate to the operator that the bit is pointing to the right or left so many degrees from the high side of-the hole.

Although the invention described herein is shown for use with a particular borehole tool, it is readily seen that the desynchronizing system would have many other usesin the control of synchronous systems. Therefore, while particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects, and therefore, the air in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. An apparatus for adjusting the phase of a synchronous electric motor including: circuit means for supplying uniform current to the motor thereby providing non-varying motor phase; an electronic switch device in said circuit means for controlling the motor phase by regulating the relationship between motor speed and current level; and selectively operable automatic means for periodically shutting off said switching device for a precisely timed portion of the motors rotational cycle to thereby cease the passage of current to said synchronous motor, said electronic swithcing device being a solid state, gated, power device which is operated to pass current on the application of a voltage if a predetermined level to the gate of said power device, shutting off means including trigger means normally operable to pass said voltage of a predetermined level to said power device.

2. The apparatus of claim 1 wherein said shutting off means also includes means for periodically applying blocking voltage pulses of constant duration to said trigger means to cease the operation of said trigger means.

3. The apparatus of claim 2 wherein said blocking voltage applying means is an oscillator.

4. The apparatus of claim 3 and further including means for varying the output frequency of said oscillator.

5. The apparatus of claim 4 wherein said output varying means is a variable resistance means.

6. in an apparatus for operating in a borehole: first synchronous motor means for performing a downhole operation; second synchronous motor means for providing a surface indication of the downhole operation; power supply means for operating both of said motors synchronously; and selectively operable means for periodically ceasing the supply of power to one of said synchronous motors.

7. The apparatus of claim 6 wherein said selectively operable means includes switch means for passing power to said one of said synchronous motors and means for cyclically ceasing the operation of said switch means.

8. The apparatus of claim 7 wherein said switch means is a solid state bi-directional gated switch and further including a trigger for operating the gate of said switch and oscillator means for operating said trigger.

9. The apparatus of claim 8 wherein said oscillator means includes means for varying the output frequency of said oscillator.

10. In a borehole tool for detecting a downhole parameter and passing signals indicative of such detected parameter to the surface: downhole ineans for detecting a parameter, said downhole means including a first synchronous motor for operating such detecting means; surface means for providing a visual display of the detected parameter in time relation to its downhole detection; at second synchronous motor for operating said surface means; common power supply means for operating said first and second synchronous motors in time relation; and means for intermittently ceasing the operation of said second synchronous motor.

11. The apparatus of claim 10 wherein said visual display means includes a light flash means for projecting a light flash onto a scale with said synchronizing motor moving said light flash means relative to said scale.

12. The apparatus of claim 10 wherein said ceasing means includes a gated bi-directional solid state switch for passing power to said second synchronous motor and selectively operable oscillator means for periodically opening said gated switch.

Claims

10. In a borehole tool for detecting a downhole parameter and passing signals indicative of such detected parameter to the surface: downhole means for detecting a parameter, said downhole means including a first synchronous motor for operating such detecting means; surface means for providing a visual display of the detected parameter in time relation to its downhole detection; a second synchronous motor for operating said surface means; common power supply means for operating said first and second synchronous motors in time relation; and means for intermittently ceasing the operation of said second synchronous motor.