US2456456A - Oil well pump control system - Google Patents

Description

Fim-1015i 0R 54569456 Dec. 14, 194s. A, SMH 2,456,456 /-.f

OIL WELL PUMP CONTROL SYSTEM 2 Sheets-Sheet 1 Dec. 14, 1948. A, SMWH 2,456,456

oIL WELL PUMP CONTROL SYSTEM Filed Jan. 4, 194e 2 sheets-sheet 2 Power nvenorl rafon A. SmJrh B5 his momes-@amm Patented Dec. 14, 1948 gaeta OIL WELL iUMP CONTROL SYSTEM Grafton A. Smith, Tulsa, Okla., assigner to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application January 4, 1946, Serial No. 639,117

5 Claims. (Cl. 10S-25) l This invention pertains to a system for recording and/or controlling the operation of oil well pumps, and relates more particularly to an automatic system for the control of electrically driv-' en pumps in wells producing small quantities of fluid.

In many wells, especially during the later stages of their exploitation, the quantity of fluid entering the borehole from the formation is often less than that which can be readily handled by the pumping equipment, that is, the volumetric capacity of the pumping equipment installed at the well is such that a sustained operation thereof results in pumping the well off or dry. Under these conditions, it is usual to produce such wells by intermittent pumping, so that the uid is permitted to accumulate in the borehole during pump shut-down periods, and is exhausted from the well during alternate pump operation periods.

Such intermittent operation of the well pumping equipment may be controlled either manually, whereby the pump is started and stopped by hand for each operating period, or automatically, whereby the pump is started and stopped at predetermined set intervals by a time-responsive mechanism, such as an electrically or spring driven clock.

The disadvantages of manual pump control methods, involving the hazards of the human element, are obvious. The dispadyraptages of automatic time-resgphsve ,methQgs/ofontrgl muws. he length `of Qfhapafficular tin'peoddring which a wellusiehgt.

mtlhe m-Qper amount of 011 to,

accumulate thereinJfand the ratiognjhiswtidme periodTo '"tlwat'during wlch the pump is opweg; ated to el'ect'a complte depletion of the 71511,

A'cli/the time-responsive.punipmcpngfn mechanism often rgsultswinxhrpgeiime griods being selectedl whereby the oyer-all eiicienuynQL-lhe Ellllllllmeratiglysgaly lowered.

Thus, a well which'was pumped/daily in two 2 duced 9.12 barrels of oil per day, whereby the pump eniciency was raised to 64.4%.

It is therefore an object of this invention tc provide wellmlgpgnnrstim lielilalie. duration of the gmping and shut-down pgxjgdl be correctl o indications secur,e d a n recorded i n QpelatngSaiiLSystem;J

"/I't is also an object o this invention to provide a wel- Mm: wherein the opjgtipln 0f. eeingglwa C. alliitgiwmhe @id in the borehole is dllllii- It is another object of this invention to provide a system wherein each pumping period is started by an automatic time-responsive device, and is terminated by an automatic device responsive to well conditions.

It is another object of this invention to pro-` vide a system wherein the operation of the pump may be automatically stopped at any time when abnormal conditions develop in the pumping installation.

These and other objects of this invention will be understood from the following description taken with reference to the attached drawings, wherein:

Fig. 1 is a diagrammatic sketch showing the general arrangement of the component. parts of the present system;

Fig. 2 is a perspective diagrammatic view of the controller and recorder elements of the present system;

Fig. 3 shows an alternative arrangement of the circuit of the controller 2U of Fig. 2;

Fig. 4 illustrates a type of circular record chart obtained by means of the present system;

Fig. 5 is a three-phase circuit diagram of another embodiment of the circuit of the present invention;

Fig. 6' is a detail view of a magnetic mercury switch used at 61 in Fig. 1.

Referring to the drawings, the presentsystem is described by way of illustration with regard to an electrically driven reciprocating pump,

although it obviously can be used in installationscomprising pumps of the centrifugal or other types.

As shown in Fig. 1, a pump located in a well I is actuated by means of a sucker rod stringi,

the uid lifted to the surface being directed to storage through a pipe 5. The sucker rod string- 3 is reciprocated in the well by the oscillating motion of the walking beam l, which is driven,"

through a pitman 9, crank ll and reducing mechanism i3, by an electric motor l5, receiving its power through lines l'l and I9. Although the present system is described for simplicity with regard to a. single phase power supply, it is understood that the following description applies equally well to three-phase systems.

The operation of the motor I5 is started by the closing of the normally open magnetic switch 2|. whose electrical circuit is energized from the lines l1 and I9, connected to the electric power supply, and comprises lines i4 and IB and a hand-operated switch I8, such as a single pole switch, whereby said circuit may be closed through either or both of two branch circuits connected thereto in parallel: the time-responsive control circuit 2, and the work-responsive control circuit 20.

The control circuit 2 comprises a normally open switch 23, adapted to be closed by a timeresponsive device such as an electric or spring driven clock mechanism 25 of any desired type. For simplicity, this mechanism is shown in Fig. 1 asvcomprisinga rotating wheel or disk 21 provided with a segment 29 adapted to close the switch 23 by contact therewith. It will be seen that the time at which the switch 23 is closed and opened can be accurately pre-set or controlled by suitably adjusting the speed of rotation of the disk 21 and the size of the segment 29.

The control circuit 20 comprises any desired number of resistances connected in series in one of the lines supplying power to the motor l5, for example, line i9. For purposes of illustration, four such resistors are shown at 3|, 33, 35 and 31. These resistors are preferably made in the form of at coils and are placed adjacent to a desired number of spirally wound bi-metallic strips or coils such as shown at 4| and 43, said lai-metallic elements being electrically insulated from the `strips 4| and 43 are attached to a rotatable shaft.

49 passing through the center of said coils. The shaft 49 carries an arm 5| adapted to describe an arc upon the rotation of the shaft 49. At-

tached to the arm 5| is a friction belt or string z 53, passing over a pulley 55 rotatable about a shaft .or bearing 59. Fixedly carried by the pulley 55 is a magnet 6I adapted to rotate together with the pulley between stops 83 and 65. Arranged in the proximity of one of these stops, for example, stop 63, is a switch 61, such for example asmall mercury switch diagrammatically shown in Fig. 6 and comprising a glass envelope E2, a body of mercury 64 and a magnetically movable pivoted element 65, the switch being adapted to open when the magnet 5| rests against the stop 63 and pulls the element 6B out of contact with the mercury. The switch 61 serves to open or to close that branch of the circuit of the magnetic switch 2l which forms part of the controller 20.

As shown in Fig. 2, the rotatable shaft 49 may have attached thereto, in addition to the arm 5l, a second arm 1I carrying a pen 13, whereby the motion of the shaft 49 may be recorded on a strip or disk type chart 15, for purposes to be described hereinbelow, said chart being actuated by an electrically or spring driven clock mechanism 11.

It is understood that instead of being connected to the same shaft 49, the arm v5l and. the.

pen-arm ll may be connected to separate shafts, each responsive to a separate set of bi-metallic coils and resistors connected in series into the circuit of the motor l5, as shown in Fig. 3 with regard to pen arm Ill, shaft |49 and elements |3|-I31, |41 and |43.

With the above organization of the .present system in mind, its opera-tion is as follows:

The speed of the clock-work mechanism 25 is regulated so as to start pumping periods at desired predetermined time intervals. For example, if the pump is capable of depleting the well in three hours, and the well then requires another four hours to accumulate sufficient fluid for the next pumping period, the timing mechanism is adjusted for a time interval of seven hours between the starting of two consecutive pumping periods. For example, the wheel 21 is adjusted to make one complete revolution in seven hours.

With the hand -operated switch i8 closed, the switch 23 is closed by the. -timing mechanism, which energizes the circuit of the magnetic switch 2| and closes said switch, thereby starting the motor l5 and the pumping operations.

The switch 61, which may be selected as a normally closed switch, that is, a switch tending to remain closed unless specifically controlled, is open at that time, since the magnet 6| rests against the stop 53, in the proximity of said switch, and its magnetic eifect pulls the movable electrode of the switch away from its xed electrode, or the mercury pool if a mercury switch is used. l

The electric currentactuating the motor l5 passes through the resistances 3|-31, heating said resistances, which transmit the heat to the adjacent bi-metallic coils 4| and 43. The heating of the coils 4| and 43 causes these coils to develop, in well known manner, a torque effect which is applied to the shaft 49, thus rotating said shaft and the arm 5I, for example, in clockwise direction. The pulley string 53 transmits this rotation to the pulley 55, which moves lthe magnet 6| away from the stop 53 towards the running stop 65, thereby permitting the. switch E1 to close. the stop B5, any further rotation of the arm 5| under the effect of further increases of temperature results merely in a slipping action of the belt 53 on pulley 55, this arrangement thereby serving as a protective clutch.

Since the heating of the coils 4| and 43 proceeds quite rapidly once the motor I5 starts operating, the switch 61 closes very soon thereafter, so that by the time the branch control circuit 2 opens, for example, after the segment 29 has rotated past the switch 23 and has permitted said switch to open, the circuit of the magnetic switch 2| remains energized through the branch'of the controller 2D, holding switch 2| closed to continue supplying power to the motor 1i When, after a certain period of pumping, for example after two hours, all the :duid accumulated in the well has beenexhausted, the pump begins to pump off, that is, the motor I5 contnues to reciprocate the pump in the well at the same rate without any appreciable amounts of fluid being lifted to the surface. Since the work done is the product of a force by the distance acted through, or in the present case, a function of the product of the weight of the Well fluid by the distance through which this iluid is being lifted, it will be seen that considerably less energy will be required to operate the pumping equipment After the magnet comes against aaaese when it is pumping off than when it is working at full load. Thus, for example, if the pump required 3 1/2 kilowatts for operation at full load, it may require only about 2 kilowatts when pumplng ofi. The amount of current taken by the motor |5 being thus greatly reduced, the heating eect of the resistors 3 |-3l is likewise decreased below a predetermined minimum an the bi-metallic coils, upon cooling, reverse the torque applied to the shaft 49, and thus pull the magnet back to the stop 53, opening the switch 61 and thus stopping the motor i5 by the de-energization of the circuit of the magnetic switch 2l and the opening of said switch.

The use of the recording device of Fig. 2 in the controlling system describedhereinabove is advantageous for the following reasons.

In setting the time-responsive control circuit 2, it is important to know the length of time required by the pumping installation to deplete the Well, and the optimum time required by the well to accumulate'the required amount of oil for the next pumping period. For this purpose, the control circuits 2 and 20 may be removed or rendered inoperative in any desired manner, for example, by closing a switch 8 l, and the pumping operations |80 and |90 controlled by a magnetic switch 2|0 similar to switch 2|. The lines |10, |80 and |00 are provided with transformers |13, |03 and |93, whereby three phase current is supplied to a control system 200, comprising resistors 23|, 233, and 235 fed by said transformers, a bi-metallic' 4coil 243, or a plurality of such coils, a rotatable shaft 25| and magnet 25|, similar to these described with regard to Fig. l.

It is known that a three phase motor will con-I tinue to run as a single phase motor infcase of failure in one of the lines supplying the current.

i Such condition is, however, bad as tending to may then be controlled manually by means of the u switch i8 while recording the performance of the pump by meansv of the devices shown of Fig. 2 or 3.

A typical record chart for a period of 24 hours is'shown in Fig. 4. This chart shows that the pump was started at noon (point A) and operated at full power for approximately one hour. At B,.

the well became depleted and the pump operated at reduced power for the next ve hours, raising merely a trickle of oil. The operation of the pumps was therefore manually stopped at C. After leaving the well shut down for three hours, pumping was resumed and continued for two hours. As shown at D in the diagram, practically no oil was produced during the second hour of vthis period. The well was then shut down for four hours, and again pumped for two hours, as shown at E. The production results being substantially the same as at D, the pumping system was thereafter adjusted for automatic control, pumping being started every four hours by the controller 2, and being automatically stopped ap- 1proximately one hour after the start of each pumping period by the controller 20, the performance of the pumping equipment being checked if desired by recording diagrams similar to these shown in Fig. 4. In some cases, the optimum length of the pumping and shut-down period being very accurately determined by the above procedure, it may sometimes be found possible to control thereafter the pumping installation by manual control.

Although the present system has been described for simplicity with regard to a single phase motor, it is understood that it is fully applicable to three-phase operation. It is further understood overheat the motor. With the arrangement shownin Fig. 5, a change in the amount of heat supplied by the resistors 23|-235 to the bi-rnetallic strip 243 occurring upon the motor |50 changing from three-phase to one-phase operation, causes the magnet 25| to swing toward the switch 267. and to open said switch, thus operating the magnetic switch 2|0 and stopping the motor |50.

The motion of the magnet towards or away from switches El to 251 has been described hereinabove with regard to Figs. l and 5 in a purely illustrative manner and without limiting in any way the scope of the present invention, it being understood that the direction of said motion is determined in every case by the particular type of swit 3h used, such as a normally open or normally closed switch, the object being in every case to effect a proper actuation of the circuit controllingr the supply of power to the pump motor.

it `is further understood that each of the circuits shown in Figs. l and 5 is susceptible of use with all the features shown in either figure, but omitted for brevity in the other. such as time controllers, recorders, transformers, switches,

' pulleys, etc.

I claim as my invention:

1. In a well installation comprising a pump for lifting a iiuid tc the surface, an electric motor to drive said pump, and a power circuit for energizing said motor, a branch circuit connected to said power circuit, a switch in said branch circuit, time responsive control means ror closing said switch at predetermined time intervals, a second branch circuit connected to said power circuit in parallel with said iirst branch circuit, a switch in said circuit, and control means responsive to a decrease of the current owing in the power circuit for opening said second switch.

2. In a well installation comprising a pump for lifting a iiuid to the surface, an electric motor to drive said pump, and a power circuit for energizing said motor, a branch circuit connected to said power circuit, a switch in said branch circuit, time responsive control means for temporarily closing said switch at predetermined time intervals, a second branch circuit connected to said power circuit in parallel with said first branch circuit, a switch in said circuit, control means responsive to a decrease of the current flowing in the power circuit for opening said second switch, and switch means ln the power circuit adapted to be maintained in a closed position when at least one of said two branch circuit switches is closed, and to be maintained in an open position when both said branch circuit switches are open.

3.` In a well installation comprising a pump 'for lifting a uid to the surface, an electric motor to drive said pump, and a power circuit for energizing said motor, a control circuit connected to said power circuit, said control circuit comprising a magnetically operable switch, a magnet adapted to move with regard to said switch, thereby closing and opening said switch, a rotatable shaft adapted to move said magnet, bimetallic coil means having one xed end and one end attached to said shaft, resistor means connected in the motor power circuit, said resistor means being positioned adjacent to said bilmetallic coil means, whereby the torque exerted by said coil means on said rotatable shaft is varied in accordance with the heat developed by the current passing through said resistors and transmitted to s aid loi-metallic coil means.

4. In a method for intermittently pumping a well producing small quantities of fluid, the steps of pumping a well throughout a time period longer than that necessary for the pumping equipment to deplete the iiuid in the well, recording the rate of energy consumption by the pumping equipment throughout said period, determining from said record the exact length of that effective portion of said period during which the fluid was heing pumped fromthe well with a 'high rate of energy consumption, shutting the well down for an arbitrary period of time, repeating and recording the pumping andrshut-down operations, determining from the record the optimum length of the shut down period necessary for the well to accumulate the desired quantity of fluid, and adjusting the well for automatic pumping operation wherein said well is started for consecutive pumping operation periods at intervals of time equal to the sum of an effective pumping period and an optimum shut down period.

5. In a method for intermittently pumping a well producing small quantities of fluid, the steps of pumping a well througl'lout a time period longer than that necessary for the pumping equipment to deplete the fluid in the Well, recording thel rate of energy consumption by the pumping equipment throughout said period, determining from said record the exact length of that eiective portion of said period during which the uid was being pumped from the well with a high rate of energy consumption, shutting the well down for an arbitrary period of time, repeating and recording the pumping and shut-down operations, determining from the record the optimum length of the shut down period necessary for the well to accumulate the desired quantity of uid, and adjusting the well for automatic pumping operation wherein said well is started for consecutive pumping operation periods at intervals of time equal to the sum of an eiective pumping period and an optimum shut down period and is stopped REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,473,441 Perry Nov. 6, 1923 1,492,844 Hall May 6, 1924 1,892,631 Quigg Dec. 27, 1932 1,896,358 Gutrnan Feb. 7, 1933 2,180,400 Coberly Nov. 21, 1939 2,279,958 McKay Apr. 14, 1942 2,306,810 Jones Dec. 29, 1942 2,329,614 Holmes Sept. 14, 1943 2,334,943 Miller et al. Nov. 23, 1943 2,441,851 Sperow May 18, 1948

Images