Title:
Apparatus for measuring well depths and well strings
United States Patent 2166212
Abstract:
This invention relates to well depth measurement and particularly to apparatus for measuring the depths of wells and the lengths of well strings by measurement of the linear movements of a drilling or other well string Inserted in the well bore. In the drilling of wells, particularly oil wells,...


Inventors:
Hayward, John T.
Application Number:
US18179837A
Publication Date:
07/18/1939
Filing Date:
12/27/1937
Assignee:
Hayward, John T.
Primary Class:
Other Classes:
73/152.43, 175/45, 377/24
International Classes:
E21B47/04
View Patent Images:
Description:

This invention relates to well depth measurement and particularly to apparatus for measuring the depths of wells and the lengths of well strings by measurement of the linear movements of a drilling or other well string Inserted in the well bore.

In the drilling of wells, particularly oil wells, exact knowledge of the depth of the well at all stages of the drilling operation is extremely important. This is particularly true In the case of wells being drilled by the rotary method, wherein the sub-surface position of the oil producing formation being sought is calculated beforehand, ordinarily, by correlation with the same or other formations in adjacent wells, or is determined by geologic or geophysical measurements. As the drilling fluids conventionally used in the drilling operation tend to obscure the evidence of oil when the producing formation is penetrated by the drill, it is highly important that the depth of the well and the position of the drill be known at all times in order that the approach of the drill to the desired formation may be carefully regulated and controlled. Otherwise, the drill may pass entirely through the desired formation and cause a complete loss of the well, or at best, will result in additional expense of "plugging-back" and of special "cleanout" operations and the like.

The extreme imporance of exact measurements is graphically illustrated in the case of certain wells drilled in the Gulf Coast region of Texas and Louisiana, where the oil producing formation is only six feet thick and lies at a depth of over ten thousand feet below the surface of the ground. In other words, an error of only six one-hundredths of one percent in the measurement of the total depth of such a well could cause the driller to miss the producing formation altogether. The failure of such a well will result In tremendous financial loss as the cost of drilling wells of such great depth ordinarily is considerably more than $100,000.00.

At the present time, well depths are measured by measuring the length of the drill pipe as the drilling proceeds. This is done by measuring with a steel tape each section of drill pipe as it is added to the drilling string, the cumulative length being taken as the maximum depth of the well. As each section is measured before being added to the string, the "stretch" produced in the sections by the great weight of the drill pipe itself and of the drilling tools attached thereto, cannot be measured exactly and is ordinarily calculated and allowed for on the basis of previously determined tensile characteristics of the drill pipe. Such a more or less empirical calculation may result in an error In measurement of the total length of the drilling string, which will be sufficient, in wells of great depth such as those noted above, to cause the driller to miss the producing formation entirely. Other sources of error in this method of measurement arise through the fact that the drilling is never continuous and uninterrupted. The drill bit must be repaired or replaced frequently, which operations require the complete withdrawal of the entire drilling string for each repair or replacement operation. As the drilling string must be removed in sections, very often, many of the sections must be discarded lue to defects, and must be replaced by others, the measurements of which are different from those removed because of the lack of exact uniformity of length of standard drill pipe sections. Each section removed and each new section added, therefore, must be individually measured and the full length of the new string recalculated and corrected for any changes so made, and when it is considered that in the drilling of a very deep well, the entire drilling string mayjbe removed from the well and re-introduced from fifty to one hundred times before final completion of the well, the factor of human error, particularly, becomes increasingly great and may oftentimes be disastrous to the success of the drilling operation.

Another method of measurement is that wherein a weighted line is lowered into the well until the weight on the end of the line strikes the bottom of the well and the line measured 85 by means of a calibrated measuring wheel as It descends or is pulled from the well. This method has several disadvantages. One is that the drilling operation must be stopped completely every time the measuring line is run. Also, as the weight must ordinarily descend through a column of relatively viscous drilling mud, difficulty is often experienced in running the line. Again, the weight may lodge against an obstruction in the drill pipe or well bore and produce an erroneous result. Stretch of the very long measuring line when the well depth is great is an additional factor which complicates, and often adversely affects, the accuracy of this method of measurement. To eliminate.the several difficulties and errors experienced with conventional methods and apparatus for measuring well depths and well strings, this invention contemplates, primarily, the measurement of the linear movements of a well string and only when the string Is suspended in the well bore and in motion linearly therein.

Briefly this method of measurement is accomplished by attaching a measuring line to the conventional traveling block from which the drilling or casing strings are normally suspended as they are run in and out of the well, and measurIng the linear movements of the measuring line, by means of a conventional calibrated measuring wheel, as the line follows the upward and downward movements of the block between the crown and floor of the derrick in raising or lowering the well string. For recording the movements of the measuring line, an automatic duplex-type counter Is provided in cooperation with the measuring wheel. One portion of the counter adds together the measurements of only the progressive downward movements of the measuring line, when the string is supported by the block, and visibly records, non-reversibly, the total of these measurements, this total giving the maximum depth of the well, irespective of subsequent or intermediate upward movements of the well string. The other portion of the counter adds W algebraically the measurements of all the upward and downward movements of the measuring line when the block supports the well string and visibly records this total The algebraic sum thus obtained, gives the length of the string remaining 09 in the well after any number of reciprocating movements of the string. A means Is provided to disconnect the counter from the measuring wheel when the string Is not in movement linearly In the well. This method and means of measure85 ment automatically provides the driller with continuous and exact information as to the maximum depth of the well, and the position, i. e., the length, of the string in the well at any time, all as will be more fully described hereinafter. Therefore, it sl a principal object of this Invention to provide apparatus for measuring well depths by measuring the linear movements of a well string in a well Another object is the provision of apparatus for automatically measuring well depths while the well Isbeing drilled.

A further object is the provision of apparatus for measurement of drilling strings,' whereby linear measurements of the progressive down0o ward movements of the drilling string are selectively- and: non-reversibly added together to thereby obtain the maximum depth of the well, and in addition; the algebraic sum of the measurements ot all of the linear movements of said a5 string in the well is continuously obtained to thereby measure the length of the string in the well: at any-particular period in the drilling operation;An additionakobject Isthe provision of appaso ratus: suitable- for successfully practicing the method:qt thisinvention Other iand more specifle objects will become apparent fronithe following detailed descrption. taken: in conjunction with the accompanying 0s drawings:which-itllustrate several modifications of apparatumt:iaccordance with this invention.

Inthe-drawingsa FIlr 1 shows the cooperative arrangement of various: part of a conventional rotary drilling rigr Ftg. 2 showr izenlarged detail the cooperative arrangement ot a conventional rotary table with a drilling:strng: supported from a conventional travelin: block- together with measuring apparatus In-accordance with this invention Pig: 3 is a view similar to Fig. 2 showing the relationship of parts of the apparatus when the drilling string is supported directly on the rotary table.

Fig. 4 is a cross-sectional view of the meas- uring wheel according to this invention as taken along line 4-4 of Fig. 2.

Fig. 5 is a longitudinal sectional view of the measuring wheel taken along line 5-5 of Fig. 4.

Fig. 6 Is a detail of electri al connections included In certain of the apparatus in accordance with this invention.

Figs. 7, 8 and 9 are details of various modifications of apparatus in accordance with this invention. Referring to Fig. 1, particularly, it will be seen that a conventional rotary drilling rig is herein illustrated. The principal parts shown consist of a derrick I, mounted on a floor 2, a crown block pulley 3 from which a conventional travelIng block is suspended by means of the ordinary wire cables 5 terminating in the hoisting or drilling line 6, movement of which about crown pulley 3 controls the raising and lowering of traveling block 4. Mounted on derrick floor 2 is the usual rotary table 1 through which the usual drilling string indicated at I extends into the well bore 3. Drilling string I consists of a rotary drive member or kelly 10 attached by a swivel II to a hook 12 suspended from traveling block 4, hollow drill pipe 13 connected by a coupling 14 to the kelly and a drill bit II attached to the lower end of the drill pipe.

Some of the principal parts of rotary table 7 are shown in somewhat greater detail in Pigs. 2 s5 and 3. As illustrated, the table comprises a rotary cylinder II about the upper edge of which is mounted a bevel gear It, which is adapted to be rotatively driven in the conventional manner by a geared shaft, not shown. Cylinder IS is rotatably mounted on roller bearings 18 which roll in a race I, and the entire assembly is supported on a base member 28 which is in turn spacedly'supported from derrick floor 2 by beams 21. A hollow master bushing 22 is supported within cylinder I on shoulders 23 and the upper section of the interior of bushing 22 is cut away to form a square seat 24 adapted to receive a square rotary bushing 21 which slidably receives kelly II. A section of the interior of master 60 bushing 22 below seat 24 is provided with a downwardly tapering conical surface, generally termed a slip-bowl 28, adapted to receive toothed slips 27 (Fig. 3) into wedging engagement with the drill pipe 13 for purposes to be more fully 5s described hereinafter.

A measuring device for measuring the vertical movements of traveling block 4 consists of a measuring line a2, which is attached to traveling block 4 and is led vertically therefrom to a point (., near the top of the derrick where it is passed over a pulley 20 supported from the top of the derrick, thence over a second pulley 30 to a measuring wheel SI.

Measuring line 21 is constructed preferably of metal of the typi of piano wire, having high tensile strength and a relatively low coefcient of expansion with respect to temperature changes.

Measuring wheel 31, Illustrated in greater detail in Fgs. 4 and 5, comprises a drum 32, the circumference of which is calibrated ordinarily, so that one turn of measuring line 21 thereon will be equivalent to one foot qf the line, or in other words, one turn of line 28 about drum 32 will represent one linear foot of vertical movement of traveling block 4. Of course, the dimensions of the drum 32 may be varied for calibration to other lengths of the measuring line. Drum 32 is rigidly mounted on a shaft 33 by means of a key 4 and shaft 33 is journalled on a supporting frame 35 which is fixedly attached to any suitable support, such as a leg of derrick I, as shown n Fig. 1. A portion of the drum about shaft 33 is hollowed out to form an annular space 36 in which is mounted a coil spring 31 surrounding shaft 33. One end of spring 31 is fixedly attached to shaft 33 and the other to frame 35.

Spring 31 cooperates with drum 32 and frame 35 to hold tension on measuring line 28 at all times. Measuring line 28 is of at least sufficient length to follow block 4 from its highest position in the derrick to its lowest position therein, and the peripheral surface of drum 2 is of sufficient area to properly accommodate this length of line. Fixedly mounted on one end of shaft 33 is clutch member 38 which is adapted to engage a cooperating clutch member 39 which is mounted on a shaft 40 of a registering counter 41. Shaft 40 is slidably supported in a bearing 42 and a coil expansion spring 43 surrounds shaft 40, and has one end attached to bearing 42 and the other to clutch member 39, and is adapted to hold clutch member 39 normally in engagement with clutch member 383.

A spline connection 44 (Fig. 3) is provided for slidably connecting shaft 40 to counter 41 in order that shaft 40 will be in driving engagement with counter 41, at all times, while permitting axial movement of the shaft. A solenoid 45 surrounds a portion of the shaft 40 between bearing 42 and counter 4', and an iron core 45a is fixedly attached to this portion of shaft 40 so that when current is applied to the solenoid, it acts to draw core 45a in the right hand direction and thereby cause shaft 40 to move in the direction of counter 41 against the resistance of spring 43 and to pull clutch member 39 out of engagement with clutch member 38, thus disengaging counter 41 from measuring wheel 31. Suitable current leads 46 and 41 are connected to solenoid 45, lead 46 leading to a ground connection while lead,41 leads to one terminal of a suitable current source. such as a battery 43.

Electrical connections are provided in rotary table 7 for completing a circuit including solenoid 45 and battery 48. Referring to Figs. 2, 3 and 8 particularly, the form of connections shown include a contact pin 49, which is reciprocably mounted in an opening 50 in the wall of slip bowl 53 26 and is provided with a rounded end normally adapted to protrude into the bowl. The opposite end of contact pin 49 forms an electrical contact point 49a and is fixedly attached to one end of a resilient member such' as a leaf spring 51, which oo is an electrical conductor having it3 other end fixed to the inner side of the wall of the slip bowl, and in conducting contact therewith. Spring 51 cooperates with pin 49 and the wall of slip bowl 26 to normally cause pin 49 to protrude into the S5 bowl. A contact switch arm 52 is mounted within master bushing 22 and is positioned in registration with pin 49, so that when pin 43 is depressed or pushed inwardly from the interior of slip bowl 26, and assumes the position shown in dotted outline in Fig. 6, contact point 49a will make contact with switch arm 52. Switch arm 52 is attached to a slip ring 53 mounted in the lower face of master bushing 22. Slip ring 53 is made of a suitable electrical conductor metal and is suitably insulated from the metal body of mastei bushing 22 by insulation 64. Mounted in base member 20 and insulated therefrom by insulation 55a, is a brush 55, which is in registration with slip ring 53, and is held in continuous electrical contact therewith by means of a spring 56, which makes electrical contact with brush 55 and is connected by a lead 51 to the other terminal of battery 48. A lead 58 connects a portion of the rotary table, such as race 19, to ground, although the provision of such a lead to ground is ordinarily unnecessary since the rotary table is generally thoroughly grounded through direct metal-tometal contact with the metal structure of the derrick.

When contact pin 49 is pressed itno contact with switch arm 52, in a manner to be more fully described hereinafter, the circuit, which includes the several parts of the rotary table, and the solenoid 45, will be closed, and current from battery 48 will flow to the solenoid and actuate core 45a to effect the above described movements of shaft 40.

Counter 41 comprises generally a duplex-type counter having two sets of counting wheels. For purposes of clarity, one of these will be designated a progressive counter and is indicated generally by the numeral 60, and the other, an algebraic counter, designated by the numeral 61.

The construction of the counters is more or less conventional. Algebraic counter 61 is an ordinary revolution counter which is directly connected to shaft 40 and adds all the revolutions of the shaft in nondirection and subtracts when reversed, thus always recording the algebraic sum of all the revolutions of the shaft. Progressive counter 63 is a maximum revolution counter, and is also connected to shaft 40, but is adapted to count revolutions of the shaft rotating in one direction only. When the rotation of shaft 40 is reversed, the reading on counter 60 will remain unchanged, and counter 60 will not be actuated again to register additional revolutions until the reading of counter lI has returned to that appearing on counter 60. Thus counter 60 will count only those revolutions of shaft 40 which are progressively in one direction only, while counter 61 will count all the revolutions of the shaft in either direction of rotation and will always record the algebraic sum of these revolutions. 5o The apparatus above described is utilized for the measurement of well depth and the length of the well string in the following manner: Referring to Figs. 1 and 2 in particular, which show the more or less conventional arrangement of a rotary drilling string suspended from traveling block 4 and extending through rotary table 1 into the well I being drilled, the measuring operations will be described in connection with the measurement of the movement of a single section o0 of drill pipe during the drilling operation, and it will be readily understood that the method of measurement described will be equally applicable to the movements of the drill pipe throughout the entire drilling operation. In conventional rotary drilling, the drilling operation will be conducted more or less continuously until a depth of well equal to the length of a section of drill pipe 13 will have been drilled, whereupon the entire drilling string will be drawn upwardly from the bottom of the well by drawing e traveling block 4 upwardly through the medium of drilling line 5, until the end of the drill pipe section next.below kelly 10 Is above rotary table r 1. Rotary bushing 25 will be removed from master bushing 22 and will be replaced by slips 21 (Fig. 3) which will support the well string while the kelly is unscrewed therefrom. A new section of drill pipe is then connected to the , upper end of the drill pipe in the well. The slips are then removed, and the weight and support of the entire drilling string again transferred to traveling block 4 which will lower the string until the bit is again near the bottom of the. well. ] The kelly will now be connected again to the upper end of the drilling string, whereupon drilling will be resumed for another interval of depth equal to the length of the kelly.

For the purposes of this description, it will be assumed that the drill bit is resting on the bottom of the well, and that a new section of drill pipe has been added to the drilling string, thereby again placing traveling block 4 at about its highest normal position in the derrick, and that o2 drilling is about to be resumed. At this point, progressive counter 60 will register a measurement which is that of the depth of the well as measured from the bottom of the well to the point just above the rotary table, conventionally considered as the top of the well, and known as the "measuring point". All measurements are made relative to this point. Since the drill bit is resting on the bottom, the length of the drilling string from the bottom of the well to the measuring point will be equal to the depth of the well and therefore equal totals will be registered on both the algebraic counter 61 and progressive counter 60.

The rotary drilling motion of the drilling string is begun and drilling continued until a distance has been drilled which is substantially equal to the full length of the kelly, and at this point, the upper end of kelly 10 and traveling block 4 will be at about the position illustrated in Fig. 2. As traveling block 4 descends from its high position to its lower position above the rotary table in following the downward movement of the drilling string, both counters will register the length of the downward travel of the block through the medium of measuring line 28 and measuring pulley 31. As the downward distance moved by the block is now in addition to the sum of the preceding downward movements, the new measurement recorded on progressive counter 60 will be the 0 new depth of the well and likewise, the new figure appearing on algebraic counter S1 will represent the new length of drilling string in the well, and both measurements will still be equal.

To continue drilling, it is now necessary to add 5o still another section of drill pipe. To do this, the rotary table is stopped, rotary bushing 25 removed from the table, and the entire drilling string pulled upwardly from the well by block 4 through pulling force applied to drilling line 5, until the upper end of the drill pipe section next below the kelly appears above the rotary table in about the position shown in Fig. 3. The upward movement of the traveling block in effecting this withdrawing operation will be measured by meas05 uring wheel 31, which will rotate, however, in the reverse direction, as measuring line 28 is automatically reeled thereon through the action of spring 37. The reverse rotation of measuring wheel 31 will reverse algebraic counter I1 and the reverse measurement so obtained will be subtracted from, i. e. algebraically added to, the measurement previously appearing on counter I1 and the final figure will represent the original length of the drilling string minus the length withdrawn from the well, and will thus represent the length of the drilling string remaining In the well. Since progressive counter 60 is unaffected by reverse rotations of measuring wheel 31, the measurement recorded thereon will remain unchanged and will continue to show the full depth of the well. Therefore, at the completion of the described withdrawal operation, counter 41 will register two figures, one the depth of the well and the other the length of the drilling string remaining in the well. Of course, algebraic counter 11 will continuously and automatically register the changing length of the drilling string in the well as the string is drawn upwardly in the derrick, and the drill operator will be supplied with continuous information as to the depth of the well and the amount of drill pipe in the well at any instant during the upward or downward movement of the drilling string.

As noted, the drilling string has now been drawn upwardly from the bottom of well to the position shown in Fig. 3 preparatory to addition of another section of drill pipe, and rotary bushing 25 has been removed. Slips 21 are now dropped into place in slip bowl 26 to supportingly erigage the drill pipe, and the entrance of the slips into the slip bowl will act to push contact pin 49 and its electrical contact point 49a against switch arm 52 and thereby close the circuit which includes the rotary table and solenoid 45. Closing of this circuit will cause current to flow from battery 48 to the solenoid which will be energized thereby to cause disengagement of clutch members 38 and 39 and thus disconnect the counters from the measuring wheel. No movements of traveling block 4 can now affect the counters, and the traveling block may be utilized in the conventional manner to assist in disconnecting the kelly from the drilling string, drawing into the derrick a new section of drill pipe, swinging the newly connected section into position over the end of the drill pipe protruding aboVb the rotary table, and in connecting the new pipe section and the kelly into the drilling string.

The new pipe section is now made up into the drilling string and the traveling block, which is now attached directly to the upper end thereof, is moved upwardly very slightly to take the full weight of the drilling string and permit the removal of the slips preparatory to lowering the drilling string back into the well. The removal 60 of the slips will permit the return of contact pin 49 to its normal position and thus break the solenoid circuit, causing the counters to be reconnected to the measuring wheel. The kelly is again connected into the drilling string which is now lowered into the well by the traveling block until the bit is again on bottom, and this downward movement will be registered on algebraic counter 61. Since at this point, the drilling string will move downwardly exactly the same distance it Go was previously raised, the measurement of the length of the drilling string which will -now appear on algebraic counter 61 will be the same as that previously registered, and will be equal to the depth of the well as recorded on progressive 05 counter 60, which, of course, will remain unaffected, since It does not change until after the figures on the algebraic counter are the same as those on the progressive counter.

Drilling is again resumed and both counters begin again to register the descending movement of the traveling block as the drill moves deeper into the earth, and when the downward movement of the drill has again progressed a distance equal to the length of the new section of drill pipe, 76 both count~rs W'il record the new well depth and the new length of the drilling string below the measuring point. Drilling is again halted and the previously described operations for adding a new drill pipe section repeated and the movements of the traveling block which are significant with respect to well depth and drilling string measurements, recorded as described.

By conducting the measuring operations as above described, from the beginning of the drilling operation and continuing them through the entire drilling operation, progressive counter 60 will continuously record, non-reversibly, only the progressive downward movements of the drilling string, while algebraic counter 61 will record the algebraic sum of all the upward and downward movements of the drilling string and the counters will thus provide, automatically, a continuous record of the well depth and of the length of the drilling string remaining in the well at every stage of the drilling operation.

It will be evident from the foregoing description, that the method of the inventior comprises the measurement of well depths and of well strings by measuring the linear displacement of a well string support, moving in a zone extending vertically above the well, and selectively measuring those movements of the support when a well string is movably supported thereby in the well. The invention additionally contemplates the steps of adding together cumulatively the measurements of only the downward movements of the support when the well string is movably supported thereby in the well, and adding to:i5 gether algebraically all of the upward and downward movement of the support when the well string Is movably supported thereby in the well.

By this method of measurement, the several errors arising in former measuring methods are eliminated. For example, the factor of "stretch" of the drilling string is automatically compensated for and Included in the measurements recorded, for, in order to actuate the counters after each addition of a pipe section, the traveling block must lift the entire drilling string upwardly in order to free the slips and thereby break the circuit to the solenoid. As the weight of the drilling string is taken on the traveling block, the new section of pipe will begin to stretch in accordance 60 with the weight of the string suspended therefrom, and this will require the traveling block to be moved upward a distance equal to the maximum extent of the resulting stretch before the slips, can be fully released. Therefore, at the instant the slips are fully released and the counters actuated, the traveling block will be spaced vertically above the rotary table, a distance, which will be equal to the original length of the pipe section, plus the amount of the stretch. Then as the traveling block descends with the subsequent downward movement of the drilling string, the counters will record a downward movement of the block which will be equal to the stretched length of the new pipe section, and thus the measurements recorded on both counters will be in terms of the full length of the drilling string.

By the method and apparatus of this invention, every vertical movement of the traveling block when it supports the well string in the well is automatically meAsured and recorded, and since, normally, th' drilling string cannot be moved vertically in the well except when it is movably supported by the traveling block or similar movable support member, it will be evident ;3 that no vertical movement of the drilling string which is of significance In the measurement of the well depth or of the length of the string in the well, can escape the measuring and recording apparatus, and the factor of human error is thus largely eliminated. It will also be evident that the measurements may be, and are, made while the drilling operation is in progress, for the rotary movement of the drilling string does not effect the measuring apparatus in any way and since every increment of downward or upward movement of the drilling string is reflected in an equal movement of the traveling block, every increment of downward or upward movement of the drilling string will be automatically measured and recorded by the counters.

Furthermore, since only the vertical movements of the traveling block are measured and since these movements are limited in length by the vertical distance between the crown and floor of the derrick, only a relatively short measuring line is required, and since the measuring line is not required to support any substantial weight, errors due to stretch of the measuring line are eliminated for all practical purposes. In the foregoing description, this invention has been applied to the measurements of well depths and well strings during a conventional rotary drilling operation. However, it will be evident that the invention may be applied equally ad- g0 vantageously to the measurement of casing or tubing strings as they are run into and out of a well in the usual manner. * Frequently casing or tubing strings are run into the well through the rotary ,able and the slips 85 and slip bowl previously described will be utilized, as described, to hold the string while new sections are added to or removed from the string and the measurements of the strings will be obtained in exactly the same manner as in the case of drilling strings. At other times, the master bushing 22 may be removed from the rotary table and the slips and slip bowl therein will be replaced by a conventional tubing or casing spider 62, which is mounted on the rotary table In the manner illustrated in Fig. 7. The measuring operations are conducted in exactly the same way as previously described though the electrical connections are changed slightly by mounting the switch, consisting of contact pin 48 and switch arm. 52, on spider 62 rather than'in the rotary table.

Fig. 8 shows another modification of apparatus for disconnecting the counters from the measuring wheel when there is no vertical movement of the well string In the well. In this modification, the counters are dis-connected from the measuring wheel when the weight of the well string is brought to bear on the rotary table, as when the slips 21 support the well string while the travel- so ing block may be engaged in other operations.

The same electrical circuit and the.same general form of switch are employed as described above In the principal modification, .but the position of the switch is changed by placing contact pin 49 in one of the beams 21 and. allowing it to protrude slightly above the upper surface of the beam. The rotary table is spaced slightly above beams 21 and normally out of contact with pin 49 and is supported in this position by means of springs 63, which are adapted to be compressed when a load greater than the normal weight of the rotary table is applied thereto. Thus, when the weight of the well string is brought to bear on the rotary table, and normally such circumstance will occur only when there will be no Immediate further vertical movements of the well string in the well, the rotary table will be depressed against springs 63 and base member 28 Swill depress contact pin 46 into contact with switch arm 52, thereby closing the solenoid circuit and dis-connecting the counters from the measuring wheel. Upon the lifting of the weight of the well string from the rotary table, which 1o action must necessarily occur before the well string can be moved vertically in the we4 the springs 63 will lift the rotary table from beams 21 and allow the contact pin to return to its normal position, thereby breaking the solenoid cir1 cult and permitting reconnection of the counters to the measuring wheel.

In still another modification, the conventional weight indicator devices, which are actuated by the pull applied to drilling line I by the weight of the well string suspended therefrom, may be employed to connect or disconnect the counters from the measuring wheel. In this case, when the weight of the well string is taken on the slips in the rotary table, the pull on the drilling line will be reduced sharply, and the resulting movement of the weight Indicator mechanism will be applied to effect disconnection of the counters.

Immediately upon reapplicltion of the weight of the well string to the drilling line, when the so string is lifted from the slips, the opposite movements of the weight indicator, corresponding to the increase in the pull on the drilling line, will be utilized to re-connect the counters to the measuring wheel.

SStraight mechanical devices, such as hydraulic tubes and plungers may be used in place of the electrical circuit and magnetic clutch heretofore described, for actuating the axial movements of shaft 48 in disconnecting the counters from the measuring devices.

The connections from measuring wheel 31 to counter 41 may be modified in various ways. One modified arrangement is shown in Fig. 9, which illustrates an arrangement wherein a self-synchronous, transmisslon system, commonly known 4as a "Sel-syn" system, is substituted for the direct mechanical connection, such as shaft 13, from measuring wheel 31 to clutch member, .3 . In this arrangement, pulley 23, over which measuring line 21 Is run, is calibrated to serve in place o0 bo measuring wheel 3I for measuring the movements of the line, and the armature of one Selsyn motor 4 Is connected directly to the shaft of pulley -2. The armature of the other Sel-syn motor IN is connected directly to shaft 33. By this- arrangemen, every revolution of pulley 21 will be transmitted electrically through leads ltl to shaft 3, Just as: thoughahaft 33 were connecteddirectly to.pilley. S2, In accordance with Go the well: known unctione of a Sel-syn system.

Also la thisarratement, a weight member t6 Is attached to the free end of the measuring line and: substituted for the spring reel action of measuringwhee I3 for holding tension continu0g ously on measuring line 2 By use- of the Bel-syn system, the described magnetic clutcharrangement may be eliminated.

This may be done by connecting the two armstures of the Sel-syn motors In the circuit with 7U the contact switch -In the rotary table and by varying the switch details slightly so that when it is desired to measure movements of the well string, the circuit through the Sel-syn motors will , be closed when the well string is moving vertically In the well and opened when ther is no movement.

In will be understood that the method of this invention may be applied in connection with operations other than well drilling operations and particularly to those wherein the linear distance to which a linearly moving elongated member extends beyond a fixed point cannot ordinarily be measured directly with suitable accuracy.

When applied generally, the method of this invention may be said to comprise, indirectly measuring the linear distance to which one end of a linearly moving elongated member extends beyond a fixed point by measuring directly the linear movements of the opposite end of the member on the opposite side of said fixed point.

Numerous modifications and alterations may be made In the size, form and arrangement of the details of apparatus in accordance with this invention without departing from the scope of the invention as defined in the appended claims.

SWhat I claim and desire to secure by Letters Patent is: 1. In apparatus for registering movements of objects relative to a well, a relatively fixed support member adjacent a well and having an opening therein registering with the well, a register for registering movements of objects relative to said well, an electro-magnetically releasable clutch member normally placing said register in movement-registering connection with said objects, a normally open electrical circuit connecting said clutch member .with said support member, and circuit-closing means positioned in said support member to close said circuit to thereby release said clutch member, said circuit-closing means comprising a normally open switch member positioned adjacent said opening and adapted to be closed by a compressive force laterally applied from within said opening, and means removably insertable In said opening for applying lateral compression therein for closing said switch member.

2. Ii an apparatus for registering movements of objects relative to a well, a rotary table adja- 40 cent the top of said well, a register for registering movements of objects relative to said well, an electromagnetically releasable clutch member normally placing said register in movementregistering connection with said objects, a slip bowl in said rotary table, slips insertable in said slip bowl, an electric circuit connecting said clutch member with said slip bowl, and normally open switch means in said circuit positioned in said alip bowl, said switch means being adapted to be g closed uponthe insertion of said slips in-said slip bowl to thereby close said circuit and release said clusch member.

3. In apparatus for registering movements of objects relative to a well, a rotary table adjacent 00 the top of said well, a register for registering movements of objects relative to said well, an electro-magnetically releasable clutch member normally placing said register in movementregistering connection with' said objects, a slip 5 bowl in said rotary taole, slips insertable in said slip bowl, an electro' circuit connecting said clutch member with said slip bowl, and normally open switch means In said .circuit positioned in said slip biwl, said switch means being adapted to  closed upon Insertion of said slips in said slip bowl to thereby close said circuit and release said clutch member, said circuit including a slip ring and brush connection to said slip bowl 1g to maintain electrical connection therewith while the rotary table is in motion.

4. In apparatus for registering movements of objects relative to a well, a rotary table adjacent the top of said well, a slip bowl mounted in said rotary table and having an opening therein registering with the bore of said well, a register for registering movements of objects relative to said well, an electro-magnetically releasable clutch member normally placing said register in movement-registering connection with said objects, a normally open electrical circuit connecting said clutch member with said slip bowl, and circuitclosing means positioned in said slip bowl to close 1said circuit to thereby release said clutch member, said circuit-closing means comprising a normally open switch member mounted in said slip bowl and having one contact arm thereof yieldably projecting into said opening and adapted to be urged into circuit-closing contact with the other contact arm of said switch member, and slips insertable in said opening in the slip bowl to urge said one contact arm into circuit-closing contact with said other contact arm of the switch n5 member.

5. In apparatus for registering movements of objects relative to a well, a rotary table adjacent the top of said well, a slip bowl mounted in said rotary table and having an opening therein registering with the bore of said well, a register for registering movements of objects relative to said well, an electro-magnetically releasable clutch member normally placing said register in movement-registering connection with said objects, a normally open electrical circuit connecting said clutch member with said slip bowl, and c'rcuit-closing means positioned in said slip bowl to close said circuit to thereby release said clutch member, said circuit-closing means comprising a normally open switch member mounted in said slip bowl, said switch member including a first contact arr yieldably projecting into said opening, a second contact arm in circuit-closing relationship to said first contact arm, a slip ring carlied in said slip bowl and connected to said second contact arm, a fixed brush member in said circuit positioned externally of said slip bowl and in electrical contact with said slip ring, and slips insertable in said opening in the slip bowl to urge said first contact arm into circuit-closing contact with said secpnd contact arm. JOHN T. HAYWARD.