US2934728A - Method of and apparatus for working an oil well - Google Patents

Description

April 26, 1960 F. w. PLEUGER 2,934,728

METHOD OF AND APPARATUS FOR WORKING AN OIL WELL Filed Jan. 2, 1958 2 Sheets-Sheet l w 9 24 L J9 J4 40 i a 5 JJ I .72 4/ 25 27 20 26 J6 .70 J 7 J/ INVENTOR ATTORNEYS April 26, 1960 Filed Jan. 2, 1958 F. w. PLEUGER METHOD OF AND APPARATUS FOR WORKING AN OIL WELL 2 Sheets-Sheet 2 ATTO R N EY6 United States Patent P METHOD OF AND APPARATUS FOR WORKING AN OIL WELL Friedrich Wilhelm Pleuger, Hamburg, Germany Application January 2, 1958, Serial No. 706,770

- Claims priority, application Germany January 7, 1957 8 Claims. (Cl. 338-38) This invention relates to the working of oil wells and is especially concerned with the working of wells where it is desirable or necessary to employ intermittently operating pumps. The objects and advantages of the invention will be better understood and more fully appreciated if the following description of present practices is first considered.

In the method currently in use it is customary from time to time to take measurements in the field of the height of the oil column in the individual bore holes and then to drive the individual pumps at greater or lesser capacity as may be indicated by the results of the measurements or even to completely shut down the pumps temporarily if it is found that the oil level has dropped excessively. However, the method just described has certain inherent disadvantages in that, whenever the pump output is not precisely matched to the quantity of oil that flows into the bore hole per unit of time, the pumps have to operate at a constantly increasing or decreasing load which, of course, prevents their being utilized at anything nearly approaching their maximum efficiency. A further disadvantage of present practice is that any excessive pumping of the oil can be just as detrimental to the flow of the oil coming in from the oil bearing stratum as an excessively high oil column. This is particularly troublesome when the output of a well contains large proportions of water.

With the foregoing factors in mind, the principal object of my invention resides in providing a method of and equipment for operating the pump in a manner such that it is started and stopped according to the height of the oil column in. the bore as determined by remote measurement of the pressure involved. Furthermore, my invention makes it possible to start and stop the pump entirely automatically by means of a relay system which is directly actuated by the measuring apparatus.

My invention yields a number of, important advantages, the attainment of which constitutes some of the objects of the invention. For instance, with my invention I am enabled to greatly increase the economical utilization or exploitation of a well. The invention also enables me to obtain a greater rate of flow from a Well than might otherwise be expected. These objectives are attainable because, with my invention, it is possible to consistently maintain the column of oil in the bore at the height which yields optimum results not only from the standpoint of the quantity of oil to be obtained from a given well but also from the standpoint of What is best for the long term usefulness of any given wellf Another object of the invention resides in the provision of a method of and apparatus for exploiting a well by means of which the pump is prevented from running idle in the event that the oil column falls below the pumping level.

As an additional feature of the invention, in order to determine the pressure which is proportional to the height of the oil column, a remote resistance-type sounding or 2,934,728 Patented Apr. 26, 1960 detecting device is used whose resistance is altered by the pressure proportional displacement of a mercury column, the resistance being measured above ground with a crossed coil or parallel coil instrument.

For visual readings and for the control of the pump motor, as will further appear, it is advantageous to use a resistance type measuring instrument whose indications are sensed by a drop-ring or drop-hanger arm because such a movable part can be readily availed of as a means for initiating or discontinuing the operation of the motor which drives the pump. However, such readings can be sensed in an inertialess manner by electronic or optical means and in any event, the sensing mechanism can cooperate with adjustable limit or prescribed value markers whereby the circuit can be engaged or disengaged when deflections occur which correspond to or run beyond the pre-set markers.

In accomplishing the purposes of my invention, I prefer.

to use a resistance type sounding or detecting device in which the resistance is placed in exposed manner in an axial bore of the measuring apparatus housing, which housing is massively constructed of conductive material and contains a mercury chamber or reservoir having a movable wall or membrane as will appear more fully hereinafter.

' How all of the foregoing objects and advantages are attained will now be described in connection with the accompanying drawings wherein:

' Figure l is an axial section of a temperature and pressure transmitter or detector uesd in connection with my invention;

Figure 2 is a partial axial section similar to that of Figure 1 but on an enlarged scale and illustrating only the lower half of a modified temperature and pressure transmitter; and

Figure 3 is a schematic circuit diagram of an installation for using the method of my invention.

Referring first to the showing in Figure 3, it will be seen that I have illustrated a motor 51 for driving the pump of an oil well. The pump is not specifically illusis exposed to the oil pressure in the bore hole.

but its motor 51 can be placed either above ground in shallow wells and connected with the bore hole by a suction pipe or can be installed directly in the bore hole itself at a point below the'surface of the oil so as to force the oil up through a pipe and out at the top in a manner well understood in this art. The pump motor 51 may be started or stopped, i.e., connected to or cut off from a power supply line 54 by means of a switch 53 under the control of a relay coil 52, the relay to be operated in the manner to be described hereinafter so that the oil is pumped out while the oil column height remains at a substantially constant level. When referring to a substantially constant level, i mean to include either a relatively fixed level or one which includes a short range of possible variation, say several meters by way of example. In order to measure the height of the oil column, a resistance-type sounding or detecting device 55 is lowered into the bore hole the structure of which device, as will further appear, is of a nature such that its resistance will change according to the height of the oil column above it. This sounding device 55 contains a mercury reservoir which communicates with an expansion tube and which is sealed off at the bottom with a plastic membrane'or movable wall, the outer side of which Within the expansion tube of this sounding device 55, there is a resistancerod which, when the membrane on the mercury reservoir is forced inwardly to a greater or lesser extent by the ambient pressure, can be partially short circuited tothe ground by the mercury rising in the ex pansion' tube. In this manner, a resistance change can be brought about which is proportional to the pressure changes of the oil column and hence to the height of the oil column. Depending upon the design, the resistance can change linearly or otherwise according to the height of the oil column.

The amount of resistance in sounding device 55, which thus is an accurate representation of the height of the oil column above the sounding device, is measured with a crossed coil or parallel coil instrument 56. The crossed coil instrument 56, which is placed above ground, is powered from a source of direct current 57. With this instrument, the changing resistance of sounding device 55 is compared with a standard resistance 58, measuring instrument 56 being so calibrated that it indicates the height of the oil column in the bore hole directly upon a scale 59. When it is necessary to make very accurate measurements or when greatly varying temperatures pre vail in the sounding device, the standard resistance 58 may also be installed in the sounding device so that it is exposed to the same temperatures. In this last case, however, three conductors leading to the sounding device are required instead of two.

The crossed coil instrument 56- drives indicator 60 across scale 59 in accordance with the changes in the height of the oil column. Now, in order to turn pump motor 51 on and off according to the instrument deflections, i.e., according to the varying height of the oil column, the position of indicator 60 of measuring instrument 56 is sensed according to the drop-hanger principle in a manner known per se. A beam of light or some electronic means can also be used for inertia-less sensing of indicator 60. On the scale, two independently adjustable limit-value or prescribed- value markers 61 and 62 are provided, which establish those values of the oil column height which are not to be exceeded. In this manner, an operator can set an interval measured in meters, within which the height of the oil column is permitted to vary. By means of a circuit arrangement which is not shown in detail, but which is constructed in a common fashion, the drop-hanger or other sensing member of the measuring instrument brings it about that, as soon as the indicator of the measuring instrument reaches the one limit marker, switch 63 is closed, and when it reaches the other limit marker, switch 63 is re-opened. Switch 63 controls the power supply 64 to the energizing circuit of relay coil 52 which opens and closes switch 53.

Of course, it will be understood that instead of the above described two point control between the two oil column heights established by the limit setting device 61 and 62, a single point control may be provided in which switch 63 is closed when a certain oil column height is exceeded and opened when the oil column drops below that same height. This, of course, would be a somewhat more exact type of control, but the principle involved is just the same and the accompanying claims are intended to include within their scope either the two point or the single point control.

In the case of single-point control the pump can be shut off either when the oil level drops below a certain predetermined height, or after a certain period of time which can be predetermined by a time switch. For the permanent supervision of the output of an oil well it is particularly advantageous to record the pumps running and idle time with an automatic recording apparatus.

For the sake of economy, a plurality of resistance-type sounding devices installed in various bore holes can be associated with a common measuring and controlling ap paratus and be connected to the meter mechanism in sequence by a periodically operating switching mechanism, the meter mechanism performing the adjustment for each one in turn.

The sounding device preferred for the application of this method consists substantially, as shown in Fig. 1, of a massive metal tube 1 which is provided with an axial bore'2. Axial bore 2 communicates with a chamber 3 filled with mercury. At its outside end, mercury chamber 3 is sealed off by a membrane 4, preferably made of plastic. A perforated membrane holder 5, which is forced against corresponding membrane clamping surfaces of housing 1 by threaded member 6, serves to fasten membrane 4 in place. Above the threaded member 6, which is bored through the center, membrane 4 is in contact with the fluid enveloping the sounding device. In order that fluid inlet openings 7, which are drilled slantwise, may be freed of any dirt particles that may enter them, cap 5; is provided on threaded member 6 and can be unscrewed for cleaning purposes.

A resistance rod 9 made of graphite is inserted into axial bore 2 so as to be exposed on all sides. At its lower end, rod 9 is supported on an elastic support 10 of open construction, which is clamped into mercury chamber 3. At the other end of rod 9, a metal block 11 is mounted in a corresponding opening in housing 1, with layers of insulating material 12 between it and said housing. This metal block 11 is secured in its position by means of a head 13 which is screwed into the upper end of housing 1 in order to seal the latter. Block 11 has in its center a conductive centering projection 14 which extends into axial bore 2 without touching it and serves to center and make electrical contact with the upper end of resistance rod 9 in the manner of a point suspension.

To seal head 13 against the housing 1, a stufiing box system is used, with a gland 14 and packing 15. An insulated conductor 16 is placed coaxially in head 13 in a hole bored for the purpose, and serves to establish the connection. with resistance rod 9. The stripped end 17 of conductor 16 is fastened into metal block 11, by welding or soldering, for example. In order to prevent electrical contact between the stripped conductor end 17 and the metal head 13, the face of head 13 is recessed at 18. A gland 19 which presses packings 20 concentrically about the periphery of conductor 16 serves to seal the latter against the head.

By means of a coupling 21, which is provided with a tapered thread 22 and can be screwed onto head 13 by a thread 23, the entire sounding device can be fastened to a drill rod. Conductor 16 is led out of coupling 21 through a hole 24. When the apparatus is placed in an oil well, the pressure of the fluid at the point of measurement causes membrane 4 to yield. Membrane 4 in turn forces the mercury contained in chamber 3 into the axial bore 2 and thus to a greater or lesser extent short-circuits the resistance rod 9 to housing 1. The restoring force for forcing the mercury back out of axial bore 2 is provided by the volume of air present in bore 2. The change,

of the resistance in the sounding device can be read overground with a crossed-coil instrument or the like, which is connected on the one hand to conductor 16 and on the other hand to the drill rod coupled to the metal housing of the sounding device.

Since the precise resistance of the conductors, i.e., conductor 16 and the drill rod, must be known in order to achieve a precise measurement, resistance 9 is by-passed by a safety fuse, according to a preferred embodiment, so that the precise electrical resistance of the drill rod may first be measured before operation is started. Safety fuse 25 is fastened in an axial hole in head 13, said hole being lined with insulating material. This axial hole in head 13 opens into a cross-hole 27 into which an insulated sleeve 28 is screwed. A sharp-pointed contact screw is inserted into this insulated sleeve 28, said contact screw being able with its sharp point to penetrate through the insulation of the conductor 16 and create an electrical contact therewith. The radial cross-hole 27 is sealed off externally by a seal screw 30 and a gasket 31. As may be seen from the drawing, the bottom end of safety fuse 25 rests against contact screw 29, so that the fuse has a direct electrical connection with conductor 16. At its top end, safety fuse 25 makes contact through a spring 3 2 with a seal screw 33. This seal screw, which is made of metal, creates the contact between the one end of the safety fuse and the ground, i.e., with the drill rod.

The safety fuse described above by-passes resistance rod 9, so that the resistance of the drill rod can be determined by an initial measurement between the upper end of the drill rod and conductor 16, the resistance of conductor 16 being known. When the resistances are thus known, the measuring instrument placed above ground can be adjusted. After the measuring instrument is adjusted, safety fuse 25 can be destroyedby an overcurrent, so that the electrical connection between conductor 16 and the ground of the sounding apparatus is again broken and the variable resistance 9 is in circuit.

If the measuring system is to be used in conjunction with a non-metallic or poorly conductive drill rod, an additional conductor 34 is connected to seal screw 33 and secured in place by a set screw 35. It is to be understood that the double system shown in the drawing is not necessary, and that it suflices either to connect a conductor 34 electrically to the coupling screw 33, or to associate the safety fuse 25 with the drill rod.

If in addition to the pressure the temperature at the point of measurement is also to be determined, using the above-described system, a temperature-dependent resistance, an NTC resistor 37, for example, is placed in an additional'axial hole in head 13, which is lined with insulating material 36. This resistance 37 is electrically connected at its one end, through a spring 38, with the head 13, while the other end is connected to a separate conductor 39. Conductor 39 leads in the same manner as conductor 16, and conductor 34, if used, to the instruments placed above ground. The variations of resistance 37 can be measured between conductor 39 and the electrical ground of the drill rod or conductor 34 and be compared with a standard resistance by a crossed-coil instrument in the same manner as resistance 9, in order to observe the temperature variations. The axial hole for the temperature-dependent resistance 37 is sealed in the same manner as conductor 16, by a gland 40 which tightly presses packing rings 41 against the walls of the hole and the conductor.

In order to assure against the intrusion of oil at very great depths, all the cavities in the sounding apparatus except those serving for the expansion of the mercury may be filled with oil.

If the sounding device must operate with great accuracy, even when greatly varying temperatures are encountered, it is possible that erroneous readings will be provoked due to the difference in the thermal behavior of the mercury and of the air in bore 2 and chamber 3. In order to counteract such errors, a compensating device can be provided in the above ground instruments. By connecting and disconnecting resistance, for example, said compensating device corrects the inidcating circuit according to the temperature registered by the temperaturesensitive resistor 37 in such a manner that an accurate reading is produced.

Magnets can be mounted on the sounding device to hold it in place at the desired height, instead of using coupling 21. If the sounding device according to the invention is to measure the gas pressure above the oil level instead of the oil or water pressure in the oil-bearing stratum, the entire sounding device can be placed on a float in such a manner that openings 7, through which membrane 4 is actuated, are kept out of the liquid.

Instead of connecting the sounding device with an above ground indicating instrument by means of conductors, a radio transmitter can be installed on top of head 13, if desired, and if it is economically feasible, said transmitter being powered by a battery likewise installed in the sounding device andtransmitting the resistance changes from the petroleum bore hole to a receiver placed above ground.

Another embodiment is represented in Fig. 2, in which the external pressure is transmitted by a metal bellows 42.

This form of embodiment is used preferably in wells with a large gas content or where high temperatures prevail, particularly for the measurement of high pressures.

The use of metal membranes is possible only for small pressure ranges, since the ability of a metal membrane to yield is only slight compared with plastic membranes. In order to create a sufficiently great membrane movement at high pressures, the metal membrane must therefore be replaced by a metal bellows.

The use of plastic membranes is impossible where the gas content and the temperatures are high, due to the permeability of plastics to gases and due to their limited ability to withstand heat.

Otherwise, the construction of the model according to Fig. 2 corresponds to that of the embodiment in Fig. 1, and in both figures the parts which correspond with one another are marked with the same reference numbers. A guard tube 43 serves to protect the bellows 42.

It is also pointed out that, instead of the conductors which connect the resistance-type sounding device to meter 56, the pipe through which the oil is pumped to the surface may be used, providing the electrical resistance of this pipe is known.

It will be appreciated that the fully automatic control of the oil level made possible by my invention results in more economical utilization of the well and, generally, makes it feasible to obtain a greater rate of flow than would be possible otherwise. Furthermore, the invention has the additional advantage in that the pump is prevented from running idle should the oil in the bore fall below the pumping level. It should also be noted that, since the method of the invention makes it possible not only to control the pumping of the well butalso to measure the actual height of the oil column, the sounding device can be constantly observed and the regulator readjusted according to conditions in the well. Furthermore, recording the running time of the pump makes it possible to supervise the operation of the sounding device without continually observing the meter.

I claim:

1. A pressure responsive control device for use in controlling the pump operation of an oil well, comprising an electrically grounded housing adapted to be inserted in a well and having an axial bore therein; a resistance element of substantial section in said bore but spaced from the walls thereof; a mercury chamber below the resistance element in communication with said bore;

said mercury chamber having a movable wall exposed to when the pressure falls below a desired value.

2. Apparatus according to claim 1 characterized in that the resistance element is an elongated rod formed of graphite.

3. Apparatus according to claim 2 wherein the end of the resistance rod adjacent the mercury is secured to an openly constructed elastic carrier member mounted in the mercury chamber.

4. A pressure sensitive device for use in sensing the pressure of the oil in an oil well, comprising an elongated and massively constructed housing made of an electrically conductive material and adapted to be inserted into the Well in upright position, the housing including a chamber in the lower portion thereof, said chamber having a movable wall exposed to the pressure outside of the housing,

the housing further including an axial bore communicating at its lower end with said chamber, mercury filling the chamber and rising in the axial hole in proportion to the pressure applied to the movable wall, a straight unitary resistance rod of substantial cross section extended in said axial hole, the cross section of the rod being less than that of the axial hole, means for mounting the rod centrally in the axial hole, a first electricalv conductor connecting the upper end of the resistance rod with a circuit including a source of electric power, and a second electrical conductor connecting the housing with said circuit.

5. A construction according to claim 4 in which the means for mounting the resistance rod includes an elastic support member extended between the walls of the chamber, said elastic support member being configured to permit the passage of mercury from the chamber upwardly toward the axial hole around the edges of the support member.

6. A construction according to claim 4 and further including means for determining the resistance of said first electrical conductor comprising, a fuse interconnecting the housing and said first electrical conductor at a point adjacent the resistance rod.

7. A construction according to claim 4 and further including an electrically conductive head mounted above the housing and arranged to seal off the upper end of the axial hole, the head including electrical conductor means passing therethrough but insulated therefrom,-the lower end of the electrical conductor means being in electrical contact with the upper end of the resistance rod, and a fuse mounted in an insulated bore in the head, one end of the fuse being electrically connected to the head by a screw cap adapted to seal one end of the fuse bore, and the other end of the fuse being electrically connected to a contact screw having a contact point adapted to pierce the insulation surrounding the electrical conductor means passing through the head and make electrical contact with said conductor means.

8. A construction according to claim 4 in which the resistance rod is formed of graphite.

References Cited in the file of this patent UNITED'STATES PATENTS 1,822,203 Collins Sept. 8, 1931 1,942,241 Duhme Jan. 2, 1934 2,180,588 Henze Nov. 21, 1939 2,398,375 Heenan Apr. 16, 1946 2,399,129 Malone Apr. 23, 1946 2,656,444 Du Bois Oct. 20, 1953 2,690,713 Urmann et al Oct. 5, 1954 2,743,340 Zoltanski Apr. 24, 1956 2,769,070 Donald Oct. 30, 1956

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