US3807902A

US3807902A - Control of well fluid level

Info

Publication number: US3807902A
Application number: US00272549A
Authority: US
Inventors: B Laney; D Grable
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-07-17
Filing date: 1972-07-17
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30

Abstract

The rate of the displacement of a main drive effecting stroking of a sub-surface well pump is automatically controlled in response to changes in the level of a sub-surface column of well fluid to be pumped, and one objective is to reduce the power required to operate the main drive.

Description

United States Patent [191 Grable et al.

[ Apr. 30, 1974 L wnm WW 0 r AB 35 66 99 ll 2 1 0672 2696 7556 572 9 7 333 [731 Assignees: Donovan B. Grable, Long Beach;

Bi Laney, Torrance both of Przmary Examiner-William Freeh Calif Attorney, Agent, or FzrmW1ll1am W. Haefliger [22] Filed: July 17, 1972 Appl. No.: 272,549

ABSTRACT 41 /46 The rate of the displacement of a main drive effectin [52] US. Cl. g [51] Int. F04b 49/00 stroking of a sub-surface well pump is automatically [58] Field of Search 417/36, 38, 12, 362, 53, controlled in response to changes in the level ofa sub- 417/46, 47 surface column of well fluid to be pumped, and one objective is to reduce the power required to operate the main drive.

References Cited UNITED STATES PATENTS 2,180,400 Coborly................................ 417/46 15 Claims, 4 Drawing Figures PATENTEDAPR 30 m4 SHEET 2 BF 2 CONTROL OF WELL FLUID LEVEL BACKGROUND OF THE INVENTION This invention relates generally to the pumping of wells such as oil wells. More particularly it concerns the control of pumping of an oil well in such manner as to automatically control the fluid level in the well.

Oil production engineers everywhere are aware that the machinery being used by the oil producing industry to raise fluid from the well bore to the surface is far from being efficient, and the cost of raising a barrel of fluid to the surface is a factor they all have to reckon with. An efficient pumping operation is one that has the proper size surface lifting machinery and power source along with the right size down hole pump and the right tubing and rod string to keep the fluid pumped down to the pump shoe depth, the fluid column and the rod string counterbalanced at the surface to effect a minimum of power consumption. This type of operation is almost impossible to accomplish with the surface lifting machinery that is currently being used on many thousands of wells, unless there is a constant reading on the depth of the fluid in the well bore and a constant changing of counterbalances on the units and constant changes of the strokes per minute, all of which changes are extremely difficult or too costly to implement.

It would be safe to say there are no 100% efficient pumping operations with beam-type, counterbalanced pumping units, the reasons being the following:

If a well counterbalanced polish rod load is raising fluid from the pump shoe depth and it is not pounding fluid and the bottom hole pump is operating at 100 percent efficiency, the operation would be efficient until the first pump wear would start. A bottom hole pump is subject to wear from the first stroke it makes, so that after a few strokes the pump starts to lose some of its efficiency. Fluid in the well bore will start to accumulate over the pump, decreasing efficiency; and to capture the fluid over the pump the counterbalanced unit must be speeded up in its number of strokes per minute, or the stroke must be lengthened. lf the power source is a combustion engine, speeding up the unit is quite simple; however if the power source is electrical, a lengthy operation of changing the pulleys on the electric motor is required. If the well is a large volume producer, 4 or 5 hours down time will cause fluid accumulation over the pump that may require many days and even weeks in order to pull the fluid down to the pump shoe level. In the meantime, the pumping operation is out of balance and causing excessive power consumption and useless wear and tear on surface and down hole equipment. This description would characterize an under pumping operation.

ln order to overcome the above mentioned problems, some production men go to oversized surface and down hole equipment that has the capacity of keeping the fluid pumped down to the shoe depth at all times. This type of operation will recover the fluid; however, there can be no greater damaging force to surface and down hole equipment than over pumping a well. Raising a column of fluid along with the weight of a rod string and dropping it back on a void or a semi-void is the direct cause of many surface and down hole equipment failures. For an example, if the polish rod load weighs 10,000 lbs. and the unit is making strokes a minute, in a years time this load is dropped back on to the tubing string 5,256,000 times. Tubing, rod strings, down hole pumps, and surface machinery pay a big price for this type of pumping operation as well as oil cleaning chemical costs to demulsify the fluid pumped from the well. There can be little doubt that this type of over pumping operation is the cause of rod wear and fatigue tubing wear and collar leaks, excessive wear especially to balls and seats in the bottom hole pump, and it is safe to state that if a fluid log reading shows over a long period of time that the fluid is at the shoe, the well is being over pumped.

Many of the problems of under pumping and over pumping can be overcome by causing the pumping unit to either speed up or slow down at the command of the fluid column in the well bore i.e., the fluid level in the bore controls the operation of the surface machinery that pumps the well. If the fluid is at the pump shoe, the control causes the unit to slow down; and if there is a fluid column over the pump, the control system causes the unit to speed up. If the fluid is surging in the well bore, the control system will speed up and slow down with the surge.

SUMMARY OF THE lNVENTlON It is a major object of the invention to provide a system of improved design that will operate to control reversing of the main drive for the pumping unit as well as its rate of displacement in response to changes in the weight of the column of well fluid pumped upwardly by the sub-surface pump, in order to obviate the problems of under and over pumping as referred to above. In this regard, the system is designed to automatically change the rate of well pumping to maintain the level of the unpumped column of well fluid within a predetermined depth range in order that minimum power can be required to operate the pumping system. Once the desired depth range has been determined and the control apparatus set for that desired level (as for example by counterweight selection, as will be seen), the pumping system after activation will in effect sense the difference between the desired well fluid level depth range and the actual fluid level. The system will then increase or decrease its pumping rate to permit the actual fluid level to stabilize itself within the predetermined or selected depth range.

With the above in mind, the system incorporates, in combination with a reversible main drive the output displacement of which effects vertical stroking of a subsurface well pump, the following elements:

a. first control means for reversing the main drive at predetermined limits corresponding to upper and lower limits of the well pump stroke, and

b. second control means for controlling the rate of such displacement of the main drive in response to changes in the level of the sub-surface column of well fluid.

More specifically, the main drive may typically include a reversible hydraulic motor or torque converter and supply means to supply hydraulic fluid to the hydraulic motor or torque converter at a rate controlled by the referenced second means, and characterized in that the supply rate increases as the level of fluid standing in the well increases above a preset level, and conversely the supply rate decreases as the fluid level in the well decreases below the present level. For this purpose, the first control means may include a flow regulator movable to proportionally control the rate of hydraulic fluid supply to the motor via the supply'means, and the second control means may control movement of the regulator in response to changesin the pressure of supply fluid delivered to the hydraulic motor or converter. Further, the second control means may include,

geously sample the supply fluid pressure only during Additional objects include the provision of a counterbalancing assemblyconnected with the main drive to counterbalance weight imposed by the well pump, rod string and well fluid being lifted.

Also, the stroke of the well pump may be very simply controlled or adjusted by shifting the positions of. pins on a rotordriven in synchronism with the main drive, the pins controlling reversing of a valve through which pressure is'su'pplied to an actuator'for displacing the regulator, as referred to. l 1

These and other objects and advantages of the invention, as well as the details of an illustration embodiment, will be more fully understood from the following FIG. 2 is adiagramshowing-elements of the control system; I

FIG. 3 isa diagram showing sub-surface pump speed during its cycling; and i -FIG. 4 is a-fragmentary section showing flow control porting. I

' DETAlLED DESCRIPTION Referring to FIG. 1'', the typical oil well illustrated has: outer casing 10 and production tubing 11 extending therein. Carried within the lower extent of the tubing 11 is a pump means 13 which is vertically reciprocable in response to up and down travel of the cable.l4and rod string 12; The pump may comprise 'a-piston or swab selected ranges for the well pump. See in this regard U.S. Pat. No. 3,516,762.

Reservoir 24 is connected by cable 27 with the drive 21 as via a drum 28 also connected with shaft 22, the direction of spooling of cable 27 on drum 28 being opposite to that of cable 14 on drum 20. The quantity of counterweight material in reservoir 24 may be adjusted in weight compensating relation to variations in the load to be lifted in the well by cable 14, that load including the weight of the rod string, bottom hole pumping means 13, and the weight'of the column of production fluid in the tubing 11'. Any adjustable and measurable counter-weight material may be employed, the objective being to provide a predetermined counterbalancing force which thereby in effect establishes the pre-set surface level of the column 110 of production fluid in the well corresponding to minimum energy output of the main drive operated at the surface to capture the fluid entering the well bore to pump the well, and due to system balance,

Referring now to FIG. 2, it shows one form of system which, in accordance with the invention, is operable to adjust the pumping ofthe well to control the produc- I a'pump 41 driven by prime mover 42, either'to deliver operable to elevate a column of production fluidv toward flow. line 16 extending from the casing head 17.

The cable 14 extends upwardly of the casing head to spool on winding drum 20 driven alternately in oppo-v site directions by drive means such as beam type pump-.

ing unit gearbox 21, with output shaft 22. I

Adjustable weight structure may be provided to exert torque on the drum 20 in counterbalancing relation to the weight suspended by the wire' line and exerting suspension torque on that drum. Such structure may include a counterweight reservoir positioned to be moved upwardly and downwardly as cable 14 moves 7 sufficient to permit maximum travel corresponding to fluid via-lines 43 and 44- to the motor (with return flow via lines 146 and 45) to'the pump for clockwise operation of the motor,- or -to'- deliver fluid via

lines

45 and 146 tothe motor (with return flow via

lines

44 and 43 to'the pump), for counterclockwise operation of the motor. i

' Within'the above environment, first control means is provided for reversing the main drive at predetermined limits corresponding to upperand lower limits of the well pump stroke; and there is also second'control means for controlling the rate of output displacement of the main drive (ie the rate of angular displacement fluid level in the well as against the preset level. In this regard, it is characteristic of the control of hydraulic fluid supplying pump 41 by the referenced second means that the rate of hydraulic fluid supply'to the motor or converter is increased as the surface level of the production fluid column in the well increases, and

the rate of hydraulic fluidv supply to the motor or converter is decreased as the well fluid surface level decreases (as for example. occurs as the down-hole pump pumps down the column fluid faster than fluid flows into the well from the formation). For this purpose, the first control means may include a flow regulator movable to proportionally control the rate of hydraulic fluid supply to the motorvia the pump; also the second control means typically controls flow regulator movement in response to changes in the pressure of hydraulic fluid delivery to the motor or torque converter.

Merely as illustrative, FIG. 4 shows a flow regulator valve 46 movable endwise by rod 47 to proportionally control hydraulic fluid supply to one or the other of

lines

43 and 45, via port 48 in the regulator and

ports

49 and 50 in the body 51. When pressure flow is directed as shown to line 43, return flow via line 45 passes to the pump sump via

ports

52 and 53 in the regulator and body; and, similar

return flow ports

54 and 55, may communicate with line 43 when regulator port 48 registers with port 50.

The first control means may include a first actuator 57 to effect movement of the flow regulator, and the second control means may typically include an adjustable limiter 56 to limit movement of the flow regulator 46, there being a second actuator 84 to adjust the position of the limiter.

The limiter 56 is shown as a body having a delta shaped cut-out 58 receiving the pin 59 integral with rod 47, as appears in both FIGS. 2 and 4. Actuator 57 is shown to have an override connection with the rod 47, as via a lug 60 on rod 47 confined between actuating springs 61 and 62 carried by the actuator rod 63. When the actuator rod 63 is displaced to the left as seen in FIG. 4, rod 47 is also displaced to the left by spring 62, and until pin 59 engages the angled wall 58a of delta slot 58, after which the spring 62 is compressed as the actuator rod 63 completes its leftward stroke. Similarly, when the actuator rod is displaced to the right, regulator rod 47 is moved to the right until pin 59 engages angled wall 58b of the slot 58 in limiter 56. It is seen therefore, that the degree of leftward and rightward movement of the regulator valve 46 is governed and 67, and adjustable acceleration control valve 68.

Valve 65 is operated between alternate positions (to control pressure flow of auxiliary fluid through either of lines 66 and 67) by alternate engagement of a shifting finger 168 with pins 69 and 70 adjustably located on the rotor or feedback wheel 71. The latter is rotated forwardly and reversely in synchronism with the rota- 7 tion of shaft 22, as via a large ratio gear reducer mechanism 72. Thus when rotor 71 completes its rotationin one direction corresponding to completion of subsurface pump lift, pin 69 engages finger 168 to shift valve 65 to deliver auxiliary fluid pressure to one side of the piston in actuator 57 for reversing hydraulic fluid flow to the drive motor 40 (causing the motor to lower the sub-surface pump at a rate controlled by the position of limiter 56 as described) and when rotor 71 completes its rotation in the opposite direction, corresponding to completion of sub-surface pump lowering, pin 70 engages finger 168 to shift valve 65 to deliver auxiliary fluid pressure to the opposite side of the piston in actuator 57, for again reversing hydraulic fluid flow to the drive motor 40 (causing the motor to lift the subsurface pump, again at a rate controlled by the position of the limiter 56). It will be understood that the top and bottom stroke limiting pins 69 and 70 can be located anywhere along the broken line circle 73 on rotor 71, suitable holes being provided, thereby to control the length of the sub-surface pump stroke. For example, if the bottom four feet of the stroke of the subsurface pump are associated with a badly worn condition of the cylindrical surface in which the pump swab or element slides, the bottom limit of the pump stroke can be elevated out of that range by adjustment of the bottom limit pin.

Acceleration control valve 68 has an adjustable position which controls the acceleration of the sub-surface pump to maximum up and down velocity, as indicated by the slopes at 76 and 77 of the performance curve in FIG. 3. This corresponds to the rate at which the regulator 46 is shifted to its final position in either direction, by actuator 57, the rate at which actuator 57 shifts being controlled by the valve 68. Valve 68 can be adjusted in the field or fixed at the factory, and locked, to prevent tampering.

If at any time the operator wishes to shift the regulator 46 manually, he simply operates the by-pass valve 80 which by-passes fluid pressure from either one of

lines

66 and 67 to the other; this then allows him to move the rod 63 manually to shift rod 47.

The second control means may include a second actuator 84 to control the displacement of the limiter 56 as for example in directions indicated by arrows 85 in FIG. 2, thereby to control the rate at which the subsurface valve is stroked. Spring 137 resists upmovement of the limiter 56. Also included is what may be referred to as means for supplying fluid pressure to the second actuator 84 in correspondence to the pressure to supply fluid delivery to the motor or converter 40. See in this regard, the sensing valve 87 which intermittently samples the pressure in line 86, alternately connected by valve 110 with

lines

43 and 45, and also transmits that pressure via line 88 to the piston in actuator 84. The timing of such sampling is controlled by rotation of rotor 71; for example, a pin 188 on that rotor may intermittently contact a spring urged lever 89 which then shifts valve 87 for a brief interval to send the line pressure to actuator 84, the spring 90 restoring the valve 87 to a non-sampling state. Valve 87 is actuated when the rotor 71 turns counterclockwise, and at a point 91 in the lifting cycle (seen in FIG. 3) when .maximum pressure is delivered to

lines

16 and 86; however, valve 87 is not actuated when the rotor turns counterclockwise. Valve unit connected between

lines

43 and 45 bleeds-the higher pressure in either to line 86. A pressure sensor 190 is located in line 86. In regard to sampling, as described, when the'fluid level in the well deviates from the norm, established by selective counterbalancing as described, the motor or converter 40 will labor, and the pressure of the hydraulic fluid in sampling line 86 will correspondingly change (increase or decrease). It is this pressure change which is continuously sampled for operating the controls, as described.

It should be noted in FIG. 2 that when the limiter 56 is in uppermost position, the pin 59 is confined to center position against travel, the regulator 46 will be in neutral position and no hydraulic fluid will flow to the drive motor 40. When limiter 56 approaches uppermost position, it actuates limit sensor which operates a device 126 such as a relay which shuts down the entire system. This will occur at a predetermined minimal oil flow from the underground formation to the pump 13, which cannot fill the pump even at its slowest operating speed (this corresponds to a correspondingly high pressure in line 86).

An hydraulically operated brake 127 connected at 128 with line 86 will sense breakage of the cable 14, or cable 27, as by loss of pressure, and automatically apply the brake to the drive input shaft 139, thereby to prevent runaway and further damage to the equipment.

Hydraulic motor 160 in FIG. 2 is for emergency use; it will normally run at a much higher torque and lower speed than motor 40; and it is used as during maintenance or repair of the sub-surface pump or counter weighting apparatus. When so used, chain 161 is installed to couple from motor 160 to the pulley 162 on the shaft of motor 40. This requires removal and replacement of chain 141, assuring that only one motor can be operated at a time. Also, selector valve 163 must be shifted to supply hydraulic pressure to motor 160 via

lines

164 and 165 communicable with

lines

43 and 44, and to disconnect

lines

146 and 45 from the latter.

As will be appreciated, the equipment is capable of pumping the well fluid down faster than the fluid can enter the well bore from the formation; it is capable of so pumping until the fluid level in the well reaches a norm predetermined by selected counterbalancing; and it is capable, through sampling, to slow down or speed up the pumping action so as to pump only at such rate as is required to capture fluid entering the well bore. Therefore, it is the rate of fluid entry into the well bore from the formation that controls the surface equipment, all without any down-hole sensing equipment.

We claim:

1. In a system to automatically adjust the pumping of a well to control the actual level of production fluid freely standing in the well and above the pump, the

combination with a reversible main drive the output displacement of which effects vertical stroking of a subsurface well pump and of a rod string extending from the well head to the pump, of:

a. first control means for reversing the main drive atv predetermined limits corresponding to upper and lower limits of the well pump stroke, and

b. second control means for controlling the rate of said displacement of the main drive in response to changes in said actual level in the well from a predetermined level by increasing the rate of said displacement of the main drive in response to rising of said actual level above said predetermined level,

and decreasing the rate of said displacement of the main drive in response to dropping of said actual level, below said predetermined level, said main drive and said second control means located at the well head.

2. The combination of claim 1 wherein said main drive includes a reversible hydraulic motor and supply means to supply hydraulic fluid to the motor at a rate controlled by said second means and characterized in that the supply rate increases as said actual level increases, and the supply rate decreases as said actual level decreases.

3. In a system to automatically adjust the pumping of a well to control the actual level of production fluid in the well, the combination with a reversible main drive the output displacement of which effects vertically stroking of a sub-surface well pump of:

b. second control means for controlling the rate of said displacement of the main drive in response to changes in said actual level in the well from a predetermined level,

c. said main drive including a reversible motor, and supply means to supply hydraulic fluid to the motor at a rate controlled by said second means and char acterized in that the supply rate increases as said actual level increases and the supply rate decreases as said actual level decreases, and

(I. said first control means including a flow regulator movable to proportionally control the rate of hydraulic fluid supply to the motor via said supply means, and said second control means controlling the extent of movement of the regulator.

4. The combination of claim 3 wherein said first control means includes a first actuator, and said second control means includes an adjustable limiter to limit movement of the flow regulator, a second actuator to adjust the limiter, and means to supply fluid pressure to the second actuator in correspondence to the pressure of said hydraulic fluid supply to the motor.

5. The combination of claim 1 including a counterbalancing assembly connected with the main drive to counterbalance the weight imposed on the main drive by the well pump, the drive connection to the pump, and production fluid in the well. i

6. The combination of claim 4 wherein said means to supply fluid pressure to the second actuator includes a pressure line to receive the pressure of hydraulic fluid supply to the motor, and structure synchronized with the operation of the main drive to sample the pressure in said line when the well pump is stroking upwardly.

7. The combination of claim 6 wherein said structure comprises a rotor reversibly driven in synchronism with said main drive, and a pressure gating valve in said line and operated in response to turning of the rotor.

8. The combination of claim 3 wherein said first control means includes a first reversible actuator to move the regulator, ducting to supply auxiliary fluid pressure to the first reversible actuator, and a reversible valve operable in synchronism with the ope-ration of the main drive control to control auxiliary fluid pressure supply to the first actuator for reversing the displacement thereof. I

9. The combination of claim 8 wherein the first control means includes a rotor driven in opposite directions in synchronism with the main drive, and adjustable means to control reversing of the valve in response to rotation of the rotor.

10. The combination of claim 9 wherein said adjustable means comprises pins carried by the rotor for position adjustment thereon.

11. The combination of claim 3 including means to supply to the second control means the pressure of hydraulic fluid supply to the motor in either of two lines, corresponding to forward and reverse drive of the motor.

12. In a system to automatically adjust the pumping of a well to control the actual level of production fluid freely standing in the well and above the pump, the combination with a reversible main drive the output displacement of which effects vertical stroking of a subsurface well pump of:

b. second control means for controlling the rate of said displacement of the main drive in response to changes in said actual level in the well from a predetermined level by increasing the rate of said displacement of the main drive in response to rising of said actual level, and decreasing the rate of said displacement of the main drive in response to drop ping of said actual level, I i

c. there being counterbalancing structure near the well surface which counterbalances weight exerted by a column of fluid pumped upwardly in the well by said pump, the amount of counterbalance remaining fixed during operation of said first and second control means, for establishing said predetermined level.

13. In a system to automatically adjust the pumping of a well to control the actual level of production fluid freely standing in the well and above a pump being vertically stroked, the improvement which comprises a. means responsive to the fluid level in the well to control the rate of pumping of the well by controlling the vertical speed of said stroking so as to maintain said actual level near a predetermined LII level, and b. means for controlling the length of said stroking.

14. The system of claim 13 wherein the system includes pumping structure movable up and down in the well, and counterbalancing structure near the well surface counterbalancing the weight of said pumping. structure and a column of well fluid pumped upwardly in the well by said pumping structure.

15. In the method of adjusting the pumping of a well to control the actual level of production fluid freely standing in the well and above a pump and rod string said actual level near said predetermined level.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 3, o7 9 2 Dated April 30, 1974 Inverit0r(s) Donovan B. Gr'able and Bill C. Laney It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Colman 10, line 19; "speed in response to rising of sale i actlve level should read speed in response to rlslng of said actual level Signed and sealed this 19th day of November 1974.

(SEAL) Attest: I v MCCOY H. GIBSON JR. c. MARSHALL DANN Attest'ing Officer" Commissioner of Patents F ORM PO-1050 (10-69) USCOMM'DC 60376-P89 Y U.S. GOVERNMENT PRINTING OFFICE I909 O366-3$4,

Claims

1. In a system to automatically adjust the pumping of a well to control the actual level of production fluid freely standing in the well and above the pump, the combination with a reversible main drive the output displacement of which effects vertical stroking of a sub-surface well pump and of a rod string extending from the well head to the pump, of: a. first control means for reversing the main drive at predetermined limits corresponding to upper and lower limits of the well pump stroke, and b. second control means for controlling the rate of said displacement of the main drive in response to changes in said actual level in the well from a predetermined level by increasing the rate of said displacement of the main drive in response to rising of said actual level above said predetermined level, and decreasing the rate of said displacement of the main drive in response to dropping of said actual level, below said predetermined level, said main drive and said second control means located at the well head.

3. In a system to automatically adjust the pumping of a well to control the actual level of production fluid in the well, the combination with a reversible main drive the output displacement of which effects vertically stroking of a sub-surface well pump of: a. first control means for reversing the main drive at predetermined limits corresponding to upper and lower limits of the well pump stroke, and b. second control means for controlling the rate of said displacement of the main drive in response to changes in said actual level in the well from a predetermined level, c. said main drive including a reversible motor, and supply means to supply hydraulic fluid to the motor at a rate controlled by said second means and characterized in that the supply rate increases as said actual level increases and the supply rate decreases as said actual level decreases, and d. said first control means including a flow regulator movable to proportionally control the rate of hydraulic fluid supply to the motor via said supply means, and said second control means controlling the extent of movement of the regulator.

5. The combination of claim 1 including a counterbalancing assembly connected with the main drive to counterbalance the weight imposed on the main drive by the well pump, the drive connection to the pump, and production fluid in the well.

8. The combination of claim 3 wherein said first control means includes a first reversible actuator to move the regulator, ducting to supply auxiliary fluid pressure to the first reversible actuator, and a reversible valve operable in synchronism with the operation of the main drive control to control auxiliary fluid pressure supply to the first actuator for reversing the displacement thereof.

12. In a system to automatically adjust the pumping of a well to control the actual level of production fluid freely standing in the well and above the pump, the combination with a reversible main drive the output displacement of which effects vertical stroking of a sub-surface well pump of: a. first control means for reversing the main drive at predetermined limits corresponding to upper and lower limits of the well pump stroke, and b. second control means for controlling the rate of said displacement of the main drive in response to changes in said actual level in the well from a predetermined level by increasing the rate of said displacement of the main drive in response to rising of said actual level, and decreasing the rate of said displacement of the main drive in response to dropping of said actual level, c. there being counterbalancing structure near the well surface which counterbalances weight exerted by a column of fluid pumped upwardly in the well by said pump, the amount of counterbalance remaining fixed during operation of said first and second control means, for establishing said predetermined level.

13. In a system to automatically adjust the pumping of a well to control the actual level of production fluid freely standing in the well and above a pump being vertically stroked, the improvement which comprises a. means responsive to the fluid level in the well to control the rate of pumping of the well by controlling the vertical speed of said stroking so as to maintain said actual level near a predetermined level, and b. means for controlling the length of said stroking.

14. The system of claim 13 wherein the system includes pumping structure movable up and down in the well, and counterbalancing structure near the well surface counterbalancing the weight of said pumping structure and a column of well fluid pumped upwardly in the well by said pumping structure.

15. In the method of adjusting the pumping of a well to control the actual level of production fluid freely standing in the well and above a pump and rod string being vertically stroked, the steps that include a. sensing, at the surface of the well, the well pumping requirements as imposed by the actual level of fluid in the well, and b. controlling the rate of pumping by controlling the vertical speed of said stroking at the well head and in response to such sensing thereby to increase said speed in response to rising of said active level above a predetermined level and to decrease said speed in response to dropping of said actual level below said predetermined level so as to maintain said actual level near said predetermined level.