US2707440A - Oil well pump control system - Google Patents

Description

y 1955 M. v. LONG EIAL 2,707,440

OIL WELL PUMP CONTROL SYSTEM Filed July 21, 1951 2 Sheets-Sheet 1' FIG. I

AMPLIHER INVENTORSI M. v. LONG THE-JR ATTORNEY y 3, 1955 M. v. LONG HAL 2,707,440

OIL WELL PUMP CONTROL SYSTEM Filed July 21 1951 2 Sheets-Sheet 2 o IIIIIIIIIIII'IIIIIAn-n TEMP.

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M.v LONG F. c. scuuzmak BY: THE-R ATTORNEY United States Patent OIL WELL PUMP CONTRGL SYSTEM Marion V. Long and Frederick Carl Schneider, Berkeley, Calif., assignors to Shell Development Company, Emeryville, Calif., a corporation of Delaware Application July 21, B51, Serial No. 237,934

7 Claims. (Cl. 103-25) This invention relates to a system for the eificient production of oil wells and pertains more particularly to an automatic system for the control of well pumps.

In many wells, especially during the later stages of their exploitation, the quantity of fluid entering the borehole fromthe 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 oil or dry. Under these conditions, it is usual to produce such wells by intermittent pumping, so that the fluid 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 equipmcnt 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 time-consuming task for a pump operator to visit a great number of wells, as well as the hazards of the human element, are obvious. The main disadvantage of most automatic time-responsive mechanisms is that they are adjusted to shut oh. and stop the pump after a certain time interval. If the time interval is not accurately determined for each well, the pumping period may be prematurely cut off at a time when considerable oil remains in the borehole, thus lowering the efficiency of the pumping operations, or the pumping period may be cut off only long after the borehole has been pumped substantially dry, thus increasing the wear on the pumping equipment and wasting power.

Additionally, many automatic pump control mechanisms employ a swinging or reciprocating check valve in the flow line containing the production fluid. The movement of the check valve gate is utilized to actuate the pump control mechanism. However, oil, as it is produced from a well, often contains considerable quantities of sand, paraflin or asphaltic materials which rapidly tend to clog the check valve, and the associated pump control mechanism soon becomes inoperative.

It is, therefore, an object of the present invention to provide a well-pumping control mechanism which operates efiiciently irrespective of the amount of sand, paraflin or other materials present in the stream of production fluid.

It is also an object of this invention to provide a wellpumping control system wherein the duration of the pumping period is automatically adjusted to the amount of fluid available for pumping from a well during said pumping period.

It is also an object of this invention to provide a well-pumping control system wherein the operation of the 2,707,440 Patented May 3,. 1955 pump is automatically stopped when the fluid in the borehole is depleted.

Another object of this invention is to provide a system wherein each pumping period may be started either by hand or by an automatic time-responsive device, and is terminated by an automatic device responsive to well conditions.

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

Figure 1 is a diagrammatic sketch illustrating the component parts of the present system;

Figures 2, 3 and 4 are views, partly in cross-section, of the. flow or temperature-responsive device of the present system;

Figure 5 is a cross-sectional View of another form of the temperature-sensing elements of Figure 2;

Figure 6- is a detailed cross-sectional view of the tem perature element shown in Figure 4, and

Figure 7 is a typical time-temperature curve for oil produced by intermittent pumping of a well.

As shown in Figure l, a pump located in well it) is actuated in a well known manner by means of a sucker rodv string 11 the well fluid lifted to the surface being directed to storage through a pipe 12. The sucker rod string 11 is reciprocated in the well by the oscillating motion of a walking beam 13, which is driven, through a pitman l4, crank 15 and speed reducing mechanism 16, by a prime-mover 17 such as an electric motor receiving its power through leads 18 and 19. it is understood that any suitable type of motor or engine may be used as the prime mover 17, such, for example as a gas or gasoline engine having its energizing ignition current supplied through leads 18 and 19.

The control circuit of the pump motor 17 may comprise three control switches 2t 21 and 22 that are connected in parallel between the motor 17 and a power source 23. Switch 2% is a normally-open hand-operated switch which, when closed, places the pump 17 in continuous operation. Control switch 21 is normally open being adapted to be closed by a time-responsive device such as an electric or spring driven clock mechanism 24 of any desired type. For simplicity, this mechanism is shown in Figure l as comprising a rotating wheel or disc 25 provided with a segment 26 adapted to close the switch 21 by contact therewith. It will be seen that the time at which the switch 21 is closed and opened can be accurately pre-set or controlled by suitably adjusting the speed of rotation of the disc 25 and/or the size of the segment 26.

Control switch 22 is normally closed all the time that fluid is being pumped from the well borehole and through the delivery line 21. Preferably, switch 22 is small in size, such as a microswitch, or a sealed-mercury type switch. The switch 22 is mounted on, and adapted to be actuated by, a flow-responsive controller device 27 which is in turn connected to a temperature-sensing element 29 which is mounted on the pipe line 12 in such a manner that a portion of the element is immersed in the flow stream in said line 12.

As shown in Figures 2 to 4, the flow-responsive controller device 27 of Figure 1 may take many forms. In each case the controller device comprises means responsive to the temperature of the fluid flow in the pipe line for closing switch 22 upon cessation of fluid flow through said line. The device, as illustrated in Figure 2, comprises a pair of pressure bulbs 30 and 31 adapted to contain a pressure fluid or vapor. The bulbs 30 and 31 are in open communication through thermally insulated conduits 32 and 33 with a pressure housing 34. The pressure bulbs 30 and 31, conduits 32 and 33, and housing 34 constitute a closed fluid-filled system.

The housing 34 is divided into two chambers 35 and 36 by a flexible diaphragm 37. A rigid linkage arm 38 1S fixedly attached to the diaphragm 37 and movable therewith, said arm extending through a pressure-tight fitting 40 in the wall of the housing 34. The end of the arm as, outside the housing, is adapted to contact terminals 41 and 41a of the electrical switch or relay 22 thus closing or opening said relay 22 upon movement of the diaphragm 37. Leads 42 and 42a connect the relay 22 into the pump circuit shown in Figure l.

The pressure bulbs 30 and 31 are constructed or arranged in a manner so that they respond differently to changes in temperature conditions of the fluid flow stream. This is accomplished preferably by employing pressure bulbs made of materials having substantially different heat conductivities and/or capacities. For example, if one bulb is made of copper and the other of steel, any change in the temperature of the fluid flow stream will change the temperature of the copper bulb at a more rapid rate than the steel bulb.

In the flow controller device illustrated in Figure 2, bulb 30 may be a steel bulb while bulb 31 may be made of copper. With oil at well temperature flowing through the pipe line 12, the normal position of the switch 22 is in its closed position, as illustrated in Figures 1 and 2. When the well has been temporarily pumped dry and oil ceases to flow through line 12, the vapor or fluid in pressure bulb 31 will cool and decrease in volume more rapidly than that in bulb 30, causing the diaphragm 37 to move upwardly from its illustrated position. Upon movement of the diaphragm, arm 38 is also moved so that switch 22 in the pump circuit is opened, thus shutting down the pump. While the pump is shut down, additional oil will drain from the surrounding formations into the well borehole. when the pump starting mechanism 24 (Fig. 1) closes switch 21 to start the pump as previously mentioned. As the oil flows past the pressure bulbs 30 and 31, the fluid in the pressure bulb 31 will expand more rapidly than that in bulb 30, thus closing switch 22 and maintaining it in its closed position as long as oil flows past the bulbs 30 and 31. Hence, even when the segment 26 (Fig. 1) of pump starting mechanism 24 has rotated sufficiently far to open switch 21, switch 22 will remain closed and the pump will continue to operate until the well has been pumped temporarily dry.

Instead of making the pressure bulbs of different materials in order to obtain a time difference in their responsiveness to temperature changes, the pressure bulbs may be made of the same material if desired as long as the Walls of one bulb are of substantially larger cross-section than the walls of the other. The pressure bulbs 30 and 31 will also respond differently if one is lagged or covered with insulation of low thermal conductivity. While the pressure bulbs 30 and 31 are shown in Figure 2 as being axially spaced along the pipe line 12, a pair of fluidfilled pressure bulbs 43 and 44 may also be positioned one within the other as illustrated in Figure 5. In this form the two bulbs may be inserted in a single well in the pipe 12 with conduits 45 and 46 leading from the bulbs to a pressure chamber similar to the one shown at 34 in Figure 2.

Another form of a pump shut-off device of the present well control system is shown in Figure 3 wherein the flow-sensing element comprises a resistance thermometer 47 positioned in a thermometer well 48 in the pipe line 12. The resistance thermometer forms one arm of a bridge circuit having two fixed resistance arms 49 and 50 across which is connected the power source 23. The fourth arm of the bridge comprises a variable resistance 51 which may be set at a value equal to that of the resistance thermometer 47 when no oil is flowing through the pipe 12. Terminals 52 and 53 of the bridge are connected through leads to preferably an amplifier 56 and then the relay 22 in the pump circuit of Figure 1.

This oil will be subsequently removed In operation, the variable resistance 51 is set at a value about equal to the resistance of the resistance thermometer 47 when no oil is flowing through line 12. While oil is flowing through the pipe line 12 the temperature and hence the resistance of the resistance thermometer 47 is increased, unbalancing the bridge and causing a current to flow therefrom to the amplifier and the current actuated relay 22 which maintains a normally closed position as long as current is supplied to it. When the well has pumped dry and the flow through line 12 has ceased, the resistance of thermometer 47 is decreased until it equals the setting of variable resistor 51. At this time the bridge is in balance with no current output to energize relay 22. Hence, relay 22 in the pump circuit will open causing the pump to be shut down.

While the device illustrated in Figures 1 and 3 has great utility in many pumping installations, in other installations the length of time necessary for the thermometer to cool down to its operative value may prove to be undesirable. In such case a fluid flow-sensing device similar to that shown in Figure 4 may be employed. In this form of the present invention a pair of resistance thermometers 57 and 58 are positioned in the flow stream of pipe line 12, preferably in a single thermometer well 61 as shown in Figures 4 and 6.

The resistance thermometers 57 and 58 form two arms of a bridge circuit, the other two arms comprising resistances 59 and 60. The resistance thermometers 57 and 58 are differentially responsive to changes in temperature. Thus, the thermometers may be positioned in two separate thermometer wells made of materials having different thermal conductivity values, or one of the thermometers may be surrounded or covered with an insulating sheath 62, as shown in Figures 4 and 6. Hence, with a slight change in temperature of one thermometer with respect to the other, the balance of the bridge is changed thus altering the current output from terminals 63 and 64 to the amplifier 56 and relay 22.

As shown in Figure 4, a normally balanced bridge circuit may be employed together with an amplifier 65 and a spring-loaded normally-closed relay 66 which opens when the bridge becomes unbalanced in one direction. Preferably, however, the values of the fourresistance arms are arranged so the bridge circuit is normally slightly unbalanced so that, upon a drop in temperature of oil flowing past the resistance thermometers 57 and 58, the bridge becomes balanced with no current output from terminals 67 and 68 to energize relay 66.

The remainder of the circuit of pump 69 normally comprises a power supply source 70 for the various com ponents of the system, a normally-closed energized main pump switch or relay 71, and an electrically or mechanically actuated time-responsive device 76 for closing relay 71. Preferably, a time-delay relay 72 of any desired type well known to the art, is also included in the circuit of relay 71.

While the pump circuit may be arranged so that the main switch 71 automatically opens when relay 66 be comes deenergized due to a drop in temperature and a stoppage of oil flow in pipe 12, it has been found that the temperature of oil pumped from a well may fluctuate for short periods. In fact, a time vs. temperature pumping curve for many wells approximates the curve shown in Figure 7. Since there is a slight dip at X in the temperature curve shortly after the pumping of oil from a well has begun, the pump would be shut off at point X rather than at point Y where the well has been pumped dry it a time delay relay 72 is not employed.

In the operation of the pump circuit shown in Figure 4, a decrease in the temperature of the oil being pumped, as indicated by the slight dip at X in the curve shown in Figure 7, causes the bridge to become balanced and relay 66 deenergized causing its movable member 74 to contact terminal 75, closing the circuit to the time-delay relay 72 which may be of the motor-driven type. In

the well known manner, relay 72 becomes energized and opens terminals 72a and 72b after a predetermined period, say five minutes, thus deenergizing the main pump switch or relay 71 and causing it to open and shut oif the pump. When the temperature of the oil being pumped decreases only for a period shorter than that for which the time delay relay 72 is set, a further increase in the temperature of the oil, as after point X on the curve, again causes the bridge to become unbalanced, and the current output therefrom energizes relay 66 again.

Thus, it is seen that the use of a delay relay 72 in the present circuit permits the pump to operate in spite of small fluctuations in the temperature of the oil being pumped. However, a continued drop in the temperature in the pipe 12, due to the stoppage of the oil flow therein, as shown at point Y on the curve in Figure 7, energizes the time-delay relay 72 for a sufliciently long period, i. e., over 5 minutes and the pump 69 is thus shut off when the well has been temporarily pumped dry. The pump 69 is again started by closing relay 71 either manually or with a mechanical or electrical time-responsive switch closing device '76, as previously described with regard to element 24 in Figure 1. Preferably, the switch-closing device 76 is connected to become electrically actuated when the pump 69 is shut off. After a predetermined period the device 76 closes relay 71.

In the pumping of wells where a drop in temperature of the oil is not likely to occur until the well has been pumped dry, the time delay relay 72 may be left out of the circuit so that the main pump relay 71 is deenergized and opens to shut oh the pump 69 when there is no ouput current from the balanced bridge due to a drop in temperature when the oil flow stops. While in the preferred form of the invention the bridge circuit is normally unbalanced, it is understood that the elements of the pump circuit could also be arranged to employ a bridge circuit which is normally balanced when oil is being pumped and becomes unbalanced on a drop in temperature at the end of the pumping period to shut off the main switch 71 in the pump circuit.

We claim as our invention:

1. A control system for a well installation producing a well fluid at a temperature above atmospheric temperature, said system comprising a well pump, a prime mover for said pump, an energizing electric circuit for said prime mover, and conduit means for the fluid delivered by said pump, said control system comprising first and second temperature-sensing means of different thermal responsiveness to changes in temperature of the fluid flow positioned in said conduit means, means for comparing the response of said first and second temperature-sensing means, and a switch in said electric circuit operated by said comparing means to shut off the well pump when the fluid flow in said conduit means ceases.

2. A control system for a well installation comprising a well pump, a prime mover for said pump, an energizing electric circuit for said prime mover, and conduit means for the fluid delivered by said pump, said system comprising a pair of temperature-sensing means of different thermal responsiveness positioned in said conduit means, a balancing bridge circuit, said pair of temperaturesensing means forming two arms of said bridge, a pump control circuit connected to said bridge, a first relay in said circuit responsive to the state of balance of the bridge, a time delay relay in said control circuit actuated by the operation of said first relay, a normally-closed second relay in said circuit actuated by said time delay relay for shutting off said pump, and a time-responsive device positioned adjacent said second relay for actuating said second relay in the opposite direction to start said pump.

3. In a well installation comprising a well pump, a prime mover for said pump and a conduit for the fluid delivered by said pump, the combination of an energizing electric circuit for said prime mover, two resistance thermometers having diflerent rates of thermal response positioned in said conduit, a balancing bridge circuit, said two resistance thermometers being connected to form two arms of said bridge circuit, a control circuit comprising an amplifier connected to said prime-mover energizing circuit and to said bridge circuit to apply to said energizing circuit the amplified unbalance current appearing across said bridge circuit, and switch means in said encrgizing circuit actuated by said amplified current to deenergize said energizing circuit in response to a change in the balance of the bridge produced by a predetermined change of temperature of the fluid in said conduit.

4. In a well installation comprisin a well pump, a prime mover for said pump and a conduit for the fluid delivered by said pump, the combination of an energizing electric circuit for said prime mover, two resistance thermometers having difierent rates of thermal response positioned in said conduit, a balancing bridge circuit, said two resistance thermometers being connected to form two arms of said bridge circuit, a control circuit c0mprising an amplifier connected to said energizing circuit and to said bridge circuit to apply to said energizing circuit the amplified unbalance current appearing across said bridge, switch means in said energizing circuit actuated by said amplified current to deenergize said energizing circuit in response to a change in the balance of the bridge produced by a predetermined change of temperature of the fluid in said conduit, and a time delay relay connected between the amplifier and the switch means in the energizing circuit for retarding the actuation of said switch means by a predetermined time period.

5. In a well installation comprising a well pump, a prime mover for said pump and a conduit for the fluid delivered by said pump, the combination of an energizing electric circuit for said prime mover, two resistance thermometers having different rates of thermal response positioned in said conduit, a balancing bridge circuit, said two resistance thermometers being connected to form two arms of said bridge circuit, a control circuit comprising an amplifier connected to said energizing circuit and to said bridge circuit to apply to said energizing circuit the amplified unbalance current appearing across said bridge, switch means in said energizing circuit actuated by said amplified current to deenergize said energizing circuit in response to a change in the balance or" the bridge produced by a predetermined change of temperature of the fluid in said conduit, a time delay relay electrically connected between the amplifier and the switch means .in the energizing circuit for retarding the actuation of said switch means for a predetermined time, and a time-responsive device positioned adjacent said switch means for actuating said switch means and energizing said energizing circuit at predetermined intervals.

6. In a well installation comprising a well pump, a prime mover for said pump and a conduit for the fluid delivered by said pump, the combination of an energizing electric circuit for said prime mover, a resistance thermometer positioned in said conduit, a balancing bridge circuit, said resistance thermometer being connected to form an arm of said bridge circuit, a control circuit comprising an amplifier connected to said energizing circuit and to said bridge circuit to appiy to said energizing circuit the amplified unbalance current appearing across said bridge, and switch means in said energizing circuit actuated by said amplified current to deenergize said energizing circuit in response to a change in the balance of the bridge produced by a predetermined change of temperature of the fluid in said conduit.

7. A control system for a well installation producing a well fluid at a temperature above atmospheric temperature, said system comprising a well pump, a prime mover for said pump, an energizing electric circuit for said prime mover, and conduit means for the fluid delivered by said pump, said control system comprising first and second temperature-sensing pressure bulbs of different thermal responsiveness to changes in temperature of the fluid flow switch in said electric circuit actuated by movement of positioned in said conduit means, a fluidtight housing, diasaid rod means for shutting off the well pump when the phragm means dividing said housing into a pair of fluidflow of fluid from the pump ceases. tight chambers, 21 first conduit in communication between one of said pressure bulbs and one of said chambers, 21 5 References Cited in the file of this Patent second conduit in communication between the other pres- UNHED STATES PATENTS sure bulb and the other chamber, said pressure bulbs,

868,464 Mann Oct. 15, 1907 housing and conduits being filled with a pressure fluld, rod 2,550,093 Smith p 24, 1951 means connected to and actuated by said diaphragm means and extending through the wall of said housing, and a 10

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