US2596361A - Displacement indicating apparatus - Google Patents

Description

y 1952 D. w. BLANCHER ,596,

DISPLACEMENT INDICATING APPARATUS Original Filed Jan. 25, 1950 2 SHEETSSHEEIT l INSULATION 87 4 ELEME RECORDING ILLOGRAPH RECEIVER 245 a INVENTOR D. 14/. B/ancher ATTORNEY y 1952 D. w. BLANCHER DISPLACEMENT INDICATING APPARATUS 2 SHEE'iS-SHEET 2 Original Filed Jan. 23, 1950 INVENTOR 0. 1 14 B/anc/zer ATTORNEY com @963 oh @253 zoFSQoE 2. an

Patented May 13, 1952 DISPLACEMENT INDICATING APPARATUS Donald W. Blancher, North Hollywood, Calif., as-

signor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Original application January 23, 1950, Serial No. 140,128. Divided and this application March 19, 1951, Serial No. 216,429

3 Claims. 1

This invention relates broadly to the art of telemetering and specifically, in part, to the telemetering up a well bore of data on the operating characteristics of a pump in the well, particularly data on the stress in and the motion of the pump rod at the pump- Pumps in deep wells, usually oil wells, are commonly reciprocated by a sucker rodextending up through the well to a pumping jack at the surface. In deep wells the long sucker rod has considerable stretch and distributed inertia. Because of this, its motion at the pump end may be radically different from that imparted to it at the upper end, and may be quite unpredictable, particularly at high pumping speeds. It is desirable to be able to ascertain just what stresses and motion are induced at the lower end of the sucker rod and their relation to the stresses and motion at the upper end.

A general object of the invention is to provide a practicable and accurate system for continuously telemetering operating data from the bottom of a well to the surface.

Another object is to provide a particularly effective apparatus for translating relatively long stroke motion of a pump plunger in a well into an electrical value that can be transmitted to the surface.

Other more specific objects and features of the invention will become apparent from the description to follow.

This is a division of my application Serial No. 140,128, filed January 23, 1950, for Telemetering System for Wells, to which reference is made.

Broadly, in accordance with the invention, the stress in and motion of a pump rod in a well are translated into electrical values which are trans mitted up the well to the surface and there converted into readings, the time delay between subsurface and surface data being negligible.

More specifically, a first carrier wave is generated in the well and frequency modulated in accordance with the stroke of the pump, and a second carrier wave is generated in the well and frequency modulated .in accordance with the stresses developed in the pump rod. These two.

rated by two filter circuits, and separately detected to produce direct currents of magnitude varying in accordance with the frequency modulations but independent of any variation in amplitude resulting from attenuation during transmission. These direct currents are preferably fed into a recording oscillograph. It is desirable to simultaneously record along with subsurface data the stresses and motion at the surface end of the sucker rod, but since equipment for doing this is in existence and does not require the use of the present invention, it will not be described in detail.

A complete understanding of the invention may be had from the following detailed description, with reference to the drawing, in which:

Fig. 1 is a schematic diagram showing the general arrangement of apparatus in a system in accordance with the invention;

Fig. 2 is a vertical sectional view showing the portion of the apparatus of the invention that is located in the well;

Fig. 3 is a vertical sectional view showing a portion of the apparatus of Fig. 2 drawn to larger scale; and

Fig. 4 is a schematic circuit diagram of the transmitter of the system.

Referring first to Fig. 1, there is shown a well having the usual well casing l0 extending from the surface to the bottom thereof. Positioned within the well casing I0 is the usual production tubing I I having the usual pump barrel [2 at the lower end thereof. The pump barrel llcontains the usual standing valve l3 and aplunger l4 containing the usual traveling valve IS. The plunger I4 is actuated by the usual pump rod 16 which is connected by a strain rod 33 (Fig. 2) to the usual sucker rod I! that extends up through the production tubing to the surface and is connected at its upper end (within the production tubing) by a coupling l9 to the usual polished rod 18 which extends through a packing joint in the well head to any desired reciprocating mechanism, which in this instance is shown as a pumping beam 20, the polished rod being shown connected to the beam by a cable 2|.

With the exception of the strain rod 33, the

' apparatus so far described is in accordance with the usual practice. The present invention resides in the addition to the usual apparatus of equipment responsive to the motion and stresses at the pump rod to produce frequency modulation of alternating currents, and transmit them to the surface where they are detected in a receiver I01 and recorded by an oscillograph 81.

The apparatus in the well is, in part, contained in a fluid-tight housing 22 and comprises additional elements including a torque tube 23 and a helix tube 24 positioned below the housing 22 and above the pump barrel I2, the helix tube 2t being mounted on the pump barrel l2. For reasons which will appear later, the pump rod must not rotate with respect to the pump barrel I2 and the helix tube 24, and for that reason it is preferably of non-circular cross section (hexagonal as shown in the drawing, Fig. 2)

and passes through a similar non-circular opening in the upper end of the pump barrel.

As previously indicated, the readings to be transmitted to the surface are:the stroke and the stress at the pump rod 16.- The stress is measured by means of a condenser 25 (Figs. 2 and 3) the capacitance of which varies with stretch in a short section of the strain rod 33. The way in which this condenser 25 is mechanicallyinserted in the system will nowbe described with reference to Figs. 1, 2 and 3.

Referring first to Fig. 1, as there shown, the lower end of the sucker rod I1 is connected by a screw coupling 29 to a coupling member 21 (Fig. 2) which consists of a head 21a 0n the lower end of a stem 272), the upper end of whichstem is threaded into the coupling 23. The head 21a is secured to the upper end member 29 of the housing 22. The sucker rod is used in combination with the production tubing as a coaxial electrical transmission line, and is electrically insulated from the housing 22. To this end, the head 2": and lower portion of the stem 211) are enclosed with insulating material 39, such as fibre glass, to electrically insulate it from the housing top 29. The head 27a is secured to the housing top 29 by a screw cap 32 which is threaded onto the top 29. In this way the insulating material 39 has only to resist compressive forces.

The housing top 29 has threaded into its lower end the upper end of the strain rod 33 which extends down through the housing 22, and through the torque tube 23, and is secured to the upper end of the pump rod I6 by a coupling 34 which also functions as a centering device for centering the strain rod with respectv to the helix tube 24;

Referring now to Fig. 3, the condenser 25 consists of a pair of plates 39 and 31 of flat annular shape which are separated from each other by a resilient dielectric member 33 which is positioned therebetween. The condenser plates 36 and 31 arepressed together by a pair of insulating blocks 39 and. 40 positioned on opposite sides thereof and having central apertures slideably fitting the strain rod 33. The lowerinsulating block 39 rests on'a clamp 4| that is rigidly clamped as by bolts 42 to the strain rod 33. The clamp may have an annular groove in its inner periphery engaging a snap ring 44 which is also engaged in an annular groove in the outer surface of the strain rod 33, the object being to fix the clamp rod 4| to the strain rod for movement therewith. Restingon the top of the upperinsulating block 40 is a pressure plate 45 which has an upwardly extending, externally threaded. neck 45a which is screwed into the lower end of a sleeve 59. The upper end of this sleeve is locked to the strain rod by a split clamp 41 and a snap ring 48 which engages grooves in the strain rod and split clamp respectively. The split clamp 4! is fitted in a counterbore in the upper end of the sleeve 46 and is locked in place by a lock nut E9, to force the-sleeve 49 to move with the strain rod. The construction described causes the insulating blocks 39 and 49 to move apart, in response to elongation of the strain rod 33, thereby permitting the resilient dielectric 38 to separate the condenser plates 36 and 31, and forces the plates together, compressing the dielectric 38, when the strain rod contracts. The condenser 25 constitutes one of the frequency determining elements of an oscillating circuit of an electronic unit, which will be described later.

In addition to performing the mechanical function of causing the plates 35 and 31 to follow the movements of the blocks 39 and 40, the resilient dielectric 38 performs the important function of increasing the capacity between the plates 38 and 3i; Suitable rubberlike materials havinga dielectric constant of about 5 are available for this use;

For convenience in illustration, in Fig. 2 the electronic unit is indicated as located within an annular container 50 within the housing 22, and the leads from the condenser 25 areshown entering this container. Actually, the elementsof the electronic unit are physically distributed within the housing 22 because of the limited space therewithin.

The resilient dielectric 38 cf the condenser 25 is preloaded to a desired value so that under the greatest elongation of the strain rod 33, the dielectric 38 will still have an expansive force to separate the condenser plates. This preloading adjustment is made by loosenin a lock nut 45b on the stem 35a and rotating the pressure plate @5 with respect to the sleeve 43 until the desired pressure is obtained, after which the lock nut 351) is tightened.

The stroke-measuring portion of the apparatus will next be described. The stroke of an oil well pump is relatively great, varying from 3 feet to 20 feet, and it is desirable. to apply a shorter movement to the electrical pick-up unit which effects the modulation of the electric current. This stroke reduction is effected by means of the helix tube 24 and the torque tube 23 in conjunction with a traveller 5| which is threaded on the upper end of the torque tube 23. As clearly shown in Fig. 2, the helix tube 24 is secured as by screws 24a to a neck i2a on the upper end of the pump barrel, and extends upwardly therefrom. The helix tube 24 contains a continuous helical groove formed in two sections 52 and 53. The two sections are of different pitch, the upper section 52 being of relatively high pitch whereas the bottom sectionfiS is of much lowerpitch. The torque tube 23 whichextends down into the helix tube 24 has a cam follower 54, in the form of a roller, which extends radially therefrom into the helical groove. The torque tube 23 is supported on the strain rod 33 for vertical movement therewith but for free rotation therearound. To thisend, it is shown secured betweentwo thrust collars 5S and 57 which are locked to the strain rod in any desired manner. As the strain rod 33 is reciprocated, the cam follower 54 and the helical groove into which it extends forcerotation of the torque tube. When the cam follower 54 is in the upper section 52 of the helical groove, the rotation of the torque tube in response to vertical movement of the strain rod is relatively small, whereas it is much more rapid during movement of the cam follower 5 through the groove 53 of lower pitch. The purpose of this will be described later.

The rotation of the torque tube 23 in response to vertical movement of the strain rod produces a lesser vertical movement of the traveller 5!, because the threads 2312 on the torque-tube'23 and the cooperating threads on the traveller 5| are of very low pitch as compared to that of the grooves 52 and 53. The traveller 5| is restrainedfrom rotation by tongues 5|ia thereon which register with vertical grooves 60 in a downwardly extending skirt 220 on the housing 22.

The traveller 5| actuates the core or plunger 6| of a variable inductance element 62, and also a rod 66 that actuates a switch 64 for energizing and de-energizing the electronic unit.

The plunger BI is fixed rigidly to the traveller 5| so that it is always moved thereby. However, the inductance element 62 is only utilized during that portion of the stroke of the strain rod corresponding to movement of the cam 54 in the high pitch groove 52. The switch 64, on the other hand, is intended to be actuated only in response to movement of the strain rod near its lower limit and below the normal lower limit of the stroke during a pumping operation. It is to insure suflicient movement of the traveller 5| to engage the head 65 on the lower end of the switch-actuating rod 66 in response to a relative- 1y limited movement of the strain rod below the lowermost pumping stroke limit that the low pitch groove 53 is employed. This causes a relatively large downward movement of the traveller 5| after the cam 54 gets into the low pitch groove 53.

The push rod 66 for actuating the switch 64 extends through the end wall 22a of the housin 22 with a seal fit, the seal being indicated at 61 in Fig. 3, since the interior of the housing 22 is maintained at atmospheric pressure and must be maintained dry because of the equipment it contains. The plunger 6| associated with the inductance element 62 is surrounded by a closedtop sleeve 69 of non-magnetic material which extends into the inductance element 62 and is fluid tight. Where this sleeve 69 extends through the lower end wall 22a of the housing 22 it is sealed with a conventional seal 22b. The sleeve 69 is preferably of non-magnetic non-conductive material, such as plastic, its sole purpose being to provide for free motion of the plunger 6| into and out of the inductance winding 62 while preventing entrance of pressure fluid into the housing 22.

The switch 64 is of a common type which opens in response to one actuation and closes in response to the next actuation. Downward movement of the traveller 5| sufficient to engage the head 65, withdraws the push rod 66 and permits the switch button 64a to move outwardly by virtue of a spring within the switch 64. On the next upward movement of the traveller 5|, the push rod 66 is forced upwardly by the oil pressure in the production tubing H and the switch is reset, 1. e. if it was in open position before. it is closed, and if it was in closed position before, it is opened. The result is that the apparatus can be lowered into the well with the switch in open position, and the switch then actuated by first lowering the sucker rod all the way until the cam 54 is in the lower end of the helical groove 53, and then lifting the sucker rod to carry the cam 54 upwardly through the cam section 53. In an actual apparatus in which the useful stroke of the pump is 10 feet, the distance travelled by the cam 54 while traversing the lower groove section 53 may be only 3 feet. However, because of the difference in pitch of the helical groove section 53 as compared to that of the groove section 52, the traveller 5| will move a sufficient distance to insure posi tive actuation of the switch 64 despite the fact 6': that the vertical movement of the strain rod 33 that is utilized to produce the switching action is relatively short as compared to the normal pumping stroke.

A plurality of brush elements 10 are preferably provided on the upper end of the helix tube 24 for bearing against the production tube H and insuring good electric contact therewith to complete the electrical return circuit from the electronic equipment, since the production tubing is used as one element of the coaxial line over which the electrical currents are transmitted to the surface. A wiper or brush II is also provided on the upper end of the neck |2a of the pump to bear against the pump rod 6 and insure good electrical contact therewith. The circuit from the electronic unit 56 to the production tubing may be traced in Fig. 2 from the electronic unit 50 to the-strain rod. by means of a bonding clamp 1'2, down the strain rod through the coupling 34 to the pump rod Hi, from the pump rod l6 through the wiper 1| to the pump head In. thence through the helix tube 24, which is directly secured to the pump neck, and thence through the brush 10 to the production tubing Connection from the electronic unit 50 to the sucker rod may be traced over a conductor I4 to a slip ring 15 supported on an insulating partition 15a, thence through a brush 16, which is insulated from the housing top 29 by an insulator TI, and thence over an insulated conductor 18 to a projection 19 on the head 21, which in turn is connected through the coupler 26 to the sucker rod.

The conductor 18 is in fluid sealing relation with the housing top 29 so as to prevent the entry of pressure fluid from the well into the housing 22.

Referring to Fig. 1, the sucker rod H which extends up through the well must be maintained in spaced relation with the production tube I to prevent it from being electrically shorted" thereagainst. To this end, spacing and insulating elements 80 of rubber or the like, are distributed along the sucker rod at sufficiently close intervals to insure against contact between the sucker rod and the production tubing.

At the well head, the polished rod I8, which constitutes a continuation of the sucker rod I'I, passes through an insulating bushing 8| to maintain it insulated from the production tubing, and the upper end of the polished rod I8 is mechanically connected to the hanger cable 2| by an insulating connector 82.

In practice, it is highly desirable, in order to utilize the present invention to its fullest extent, to simultaneously record the stroke motion and stress in the sucker rod at the surface, so that these values can be compared with the stroke and stress at the bottom of the well. To this end, the polished rod I8 would ordinarily be equipped with a strain gauge 84 of any known design, and a stroke-measuring device 85 would be connected to the polished rod, the devices 84 and 85 being shown connected to the recording oscillograph 81 into which the readings from the bottom of the well are also fed, so that all four readings can be recorded simultaneously with respect to time.

As previously indicated, the stroke at the bottom of the well is converted into an electrical value by means of the variable inductance 62 having the movable plunger 6| moving in synchronism with and proportional to the pump plunger. This causes the inductance of the element 62 to vary in accordance with the movement of the pump rod. It has also been pointed out that the stress applied to the pump rod in the well amass-r is -m'easuretl by the variations in capacity of the condenser 25'shown in Fig. 3, the'capacity varying:

inaccorda nce with the stretch of the strain rod 33 between the rings 44 and 48.

Referring now to Fig, 4, which indicatesschematically thecircuit ofthe electronic equipment located in the well and previously identified with the container .itLthe condenser 25 is shown connected to an inductance element 90 and forming therewith the frequency determining circuit of an oscillator tube 9i. Stabilizing capacitors 92 and 93 are-connected between the cathode" and anode, and between the cathode and control grid of the'tube 9| to stabilize its operatiornand-a blocking condenser EM is connected between'the cathode andthe center tap of the inductance 90. The oscillator'9i oscillates continuously whenever it is energized byolosureof the-switched to the filament energizing battery 95.- Thea'node of 'tube 9| is coupled through a condensers? to the control grid of an amplifier tube 528, the anode ofwhich is coupled by an output transformer 99 to-the coaxial line consisting of the sucker rod and the production tubing for transmission to the surface.

The inductance element 62 having the movable core-6| constitutes, with a pair of condensers lei) and H, the frequency controlling circuit of a second oscillator tube H32, the anode of which is coupled througha coupling condenser 5533 with the grid of an amplifier tube his, the anedeof which is connected, in parallel with the anode'of tube 98-, to the output transformer 99.

I find it desirable in practice to so choose the constants of the circuit associated with the tube 9! that its normal oscillating frequencyi about 50 kc. and so choose the constants of the frequency determining circuit of the tube 32 that its normal operating frequency is about 10 kc., these two frequencies being transmitted simultaneously'up the well to the surface. The variations in capacity of the condenser 25 produced by variations in stress applied to the pump plunger produce a total frequency variation of about 2 kc. Likewise, the variations in the inductance of the inductance elements 82 produced by movement of the plunger 6| in response to the stroke movement of the pump plunger produce a frequency variation of about 2 kc.

At the surface, the two frequency-modulated waves transmitted over the coaxial line consisting of the sucker rod and production tubing are appliedover conductors I95 and H36 to the receiver It! where they are separately detected and applied to the recording oscillograph to produce curves showing the stress in, and the stroke of. the pump rod.

The characteristic, or surge, impedance-ofa coaxial line consisting of the'produ-ctiontubing and sucker rod of a well, is about'50 ohms, and the output transformer SS'matches the'rela-tively high impedance of thetubes 98'and Hi l tothe relatively low impedance of the line.

Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and clescribedobvious modifications will occur to a person skilled in the art,and I do not desireto be limited to the exact details shown and described.

I claim:

1. Apparatus for indicating-the-stroke characteristics of apump plunger in a well comprising: a rod extending from said plunger; a first pair of cooperating screw elements; means securing one'of said elements to' said rod for reciprocation therewith and free rotation with'respect thereto; the other of said screw elements-being stationary for rotating said one screw element through a predetermined angle proportional to the stroke of the rod; 2. second pair of cooperating screw elements one of which is fixed to said one screw element of said first pair; means securing the other screw element of said second pair to said rod for rotation therewith and free reciprocation with respect thereto; said second pair of screw elements having a lesser pitch than said first pair of screw elements, whereby said other screw element of said second pair reciprocates in unison with said rod but through a stroke'proportional to but less than the stroke of the rod, and means for indicating the position of said other screw element of said second pair relative to said rod.

2. Apparatus according to claim 1 in which said first pair of screw elements have a main thread section of high pitch and an auxiliary thread section of low pitch at one end of said main section, said main thread section'operating during the pumping stroke of said rod, and said auxiliary thread section operating in response to downward movement of said rod beyond the lower end of the pumping stroke, whereby movement of said other screw element of said second pair relative to the rod movement is amplified when the rod is moved beyond its pumping stroke range.

3. Apparatus according to claim I in which said indicating means includes a control element for rendering it operative or non-operative, and means for actuating said control element in re sponse to movement of saidother screw element of said second pair into one end position beyond its stroke range during pumping. I v v DONALD W. BLANCHER.

No references cited.

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