US2341864A - Pneumatic counterbalance for well pumps - Google Patents

Description

| GRUMBAUGH 2,341,864

PNEUMATIC COUNTERBALANCE FOR. WELL .PUMPSl Filed Aug. 21, 1942 5 sheets-sheet 1 Feb. 15, 1944.

Feb. 15, 1944. GRUMBAUGH PNEUMATICy COUNTERBALANCE FOR WELL PUMPS Filed Aug. 21, 1942 3 Sheets-Sheet 2 i bine/Zivi' le@ 'rmazgk.

BMM) fr S Feb. l5, 1944. L. GRUMBAUGH 2,341,864

l PNEUMATIC COUNTERBALANCE FOR WELL 4PUMPS Filed Aug. 21, 1942 3 'sheets-sheet 5 *Suf-n Patented F eb. 15, 1944 ,UNITED STATESA PATENT OFFICE Lee GrunibaugmLong Beach, Calif., assignor to Vernon Tool Co. Ltd., Los Angeles, Calif., a corporation of California Application August 21, 1942,- Serial No. 455,662

15 Claims. '(Cl. 10B-206) This invention relates generally to pneumatic counterbalances for well pumps and is more particularlyv concernedwith such counterbalances wherein there is incorporated the use of an accumulator or air reservoir in communication with the equalizing or compression chamber.-

The invention is applicable to both mechanical and hydraulic types of pumping engines.

It is the principal object of theinvention to provide a counterbalance whereby the general eillciency of pumping mechanisms is materially improved, particularly in the senses that pump rod reciprocation is smoothed out and that the load requirements on the prime mover are substantially evenly distributed, thus avoiding wide variations in the power input to the prime mover; and it is a further object to accomplish this by means which, in normal times, would be of significance enough, but, in these abnormal times 'of material and workman scarcity, is of the utmost signicance.

As to this last point, advantage is taken of materials already at hand in every pumping installation, to supplant and improve upon elements which formerly had to be specially provided.

The general advantages of the pneumatic over the mechanical type of counterbalance, are well known. It has likewise been recognized that in the pneumatic type of counterbalance there is inherently present one troublesome factor. That factor is the tendency to build up increased air pressure during the vdown stroke of the pump rods, which increased pressure imposes additional load on and additional power consumption by the prime mover, and, during the upstroke of the pump rods, the decreased pressure results in relatively underloading the prime mover. These load variations on the prime mover naturally decrease the operating eiliciency of the mechanism.

It has been recognized that this disadvantageous factor may be considerably reduced by the pump rods, will not take the entire burden the use of an accumulator or pressure reservoir of this upward movement and will therefore not excessively underload the prime mover.

In designing a counterbalance for any given installation, various factors are taken into account as follows, though we will, for the present, disregard the factors of inertia and, in the case of the walking beam type of pumping mechanism, the acceleration and deceleration factors. The total load during the up stroke of the rods is the sum of the rod weight and the weight of the plunger-carried oil column. During the down stroke of the rods, the fluid load is assumed by the standing valve of the pump barrel, and the total load on the pumping mechanism is the weight of the pump rods. Thus the difference in load between the up and down stroke of the pump is the weight of the fluid column supported by the pump l plunger.

Then, during the upstroke of the rods, the uny equalized load to be lifted by the input power from the prime mover will be equal to the sum of the Weight of the rods and supported i'luid minus the effective lifting force of the air under pressure. During the down stroke of the rods, the power requirement will be that necessary to move them down against the lifting power of the air under pressure, which will -be equal to the unequalized load lifted by the prime mover during the upstroke. Thus, the power factors for both the up and down strokes would be equalized and full emciency would be had, were it not for the following consideration.

Assume the lifting force of the air to be of X value in order to answer the above desideratum of equalizing the weight oi the-rods and one-half the weight of the supported fluid column. Then.. as the rods descend, the pressure within the compression chamber is increased to K+ value, and the prime mover is relatively over-loaded to the extent of the plus value. Then, at the beginning of the up stroke of the pump rods there is X+ lifting force applied by the air under pressure,

. and the plus value is a measure of the subsequent relation to the displacement volume, the less will be the differential between the pressure at the top and the bottom of the pump rod strokes, and the less the differential, theA more nearLv will be approached the ideal counterbalancing situation-that is, the more constant will be the lifting eil'ect oi' the counterbalancing air, the more nearly constant will be the load on the prime mover, and the smoother will be the pump rod reciprocation. V

Accordingly, accumulators of relatively large size have been manufactured and put into use, but practical considerations of cost, material, and space economy have heretofore prevented the use ot accumulators or reservoirs of a volumetric capacity that would closely approach the ideal condition.

On the other hand, I have devised an arrangement whereby the volumetric capacity of the accumulator may approach much more nearly that which will give ideal results, and I have accomplished this end in a manner which dispenses with the pre-fabrication of a separate accumulator and utilizes in its stead structures which are already present in any producing well-namely, the annularly spaced pipes which surround the pump tubingand which have been set in place during the well drilling operations.

How this is accomplished, as well as other objects and features of the invention will be made apparent from the following detailed description, reference being had to the accompanying drawings, wherein:

.'lg.l l is a side elevation showing an embodiment of my invention in connection with a pumping unit of the walking beam type, but showing only the upper part of my improved accumulator;

Fig. 2 is an enlarged section through the upper partof the accumulator shown in Fig. 1 and showing. in addition, the lower part of the accumulator;

Fig. 3 is an enlarged, longitudinal contracted section through the compression assembly or displacement cylinder of the mechanism; and

Fig.- 4 shows an `embodiment of my invention as applied to an hydraulic type of pumping mechanism.

As has been said, my invention is applicable to both mechanical and hydraulic types of pumping mechanism and I will therefore first describe the features which are common to both types, namely the well bore installation generally indicated at I and more particularly disclosed in Fig. 2. Except for particular adaptations utilized in connection with my improved system, as will be later described, the showing of the structural elements of Fig. 2 may be considered as typical of wellf-bore installations. The showing is also to be considered as conventional, since the precise type of casing head, and the precise type and number vof pipe strings will vary according to the particular characteristics of individual wells and the practices of individual drilling operators.

Placed in pit or cellar |I over the relatively 1am surface bm n.1 amm; need la 'met is connected to the upper end of surface casing" or conductor pipe I4. Surface casing is usually from 500' to 1000 in length, though these gures are not limitative. Pipe I4 is annularly spaced from the wall of formation bore l2, as at I6, the lower end of space I6 being closed oi! by a cement "shoe" Il during the initial cementing operation, shoe |6 being subsequently drilled out at I1 to leave an annular ilange I6 projecting partially across the lower end of the bore of the pipe.

Supported by casing head slips I6 is a pipe 26, usually known as a "water string, which is annularly spaced as at 2| from surface pipe |4 and annularly spaced as at 22 from the bore of diametrically opposite ports 21 and 26 open through the head to this space. Valve fittings 29 and 30 are provided for ports 21 and 28, respectively, which valves are adapted to take pipes 3| and 32, respectively.

The top plate 23 of head I3 supports tube 34 which is, in eilect, an extension of water string 26, its cap 35 supporting the upper end of pump,

tubing 36 and the pipe fitting 31, which latter carries stuiling box 36 and oil delivery pipe 33. Tubing 36 is annularlyspaced at 31 from tube 34 and water string 20, a valved outlet 36 leading from space 31'.

Polish rod 40 extends upwardly into connec-. tion. with the pump actuating mechanism, and downwardly into connection with pump rods 4I. Rods 4| extend into connection with a vertically reciprocatory pump plunger (not shown) in a pump barrel (not shown) at the bottom of tubing 36. Tha pump barrel, plunger, travelling and standing valves. etc., may be of any suitable type, it being unnecessary to show or describe them here since their structure and operation are well understood and the particularities thereof are not at all controlling on the present invention.

It need merely be stated that on the down stroke of rods 40, 4| and the plunger, the standing valve supports the fluid column thereabove while the fluid between the standing and travelling valves is admitted to the barrel above the plunger, and on the up stroke of the pump rods the fluid column above the plunger is lifted to deliver a commensurate quantity of oil through pipe 39, while a new charge of oil is drawn in between the ascending plunger and the standing valve. It follows that, during the down stroke of the plunger, the total load applied to the load ciprocated by any suitable mechanism. For instance, in Figs. 1 and 3, I have shown this mechanism Ias being of the walking beam type, wherein walking beam 42 is pivoted at 48 on Samson post 44, with the work end of the beam pivotally connectedthrough any suitable fitting 45 with polish rod 40. The power end of the beam is connected by pitman 46 to crank 41 on shaft 48, the latter being rotated by any suitable prime mover (not shown). It is obvious that crank shaft rotation oscillates or rocks beam 42 and thus vertically reciprocates rods 40, 4| and the pump plunger to accomplish the pumpingoperation.

The pneumatic equalizing or compression pis- A pair of sleeves 5| and 52, either of which maybe considered the piston and the other the cylinder, are fitted for relative longitudinal telescopic movement'. The upper end of sleeve 5| is closed by detachable head 53, and the lower end of sleeve 52 is closed by detachable head 54 which is formed with a rocker base 55 and an apertured false bottom or plate 58. The sleeves and heads thus make up what may be considered a telescopic cylinder, thecomposite bore 51 forming a compression or displacement chamber.

The upper head 53 is suitably pivoted at 58 to walking beam 42, while rocker base 55 rests in the cradling recess 59 in stationary pillow 60. Integral, external studs 6| on head 55 are loosely embraced by hold-down straps 62 to prevent bodily displacement of the lower end of cylinder 50, and one of the studs is bored out as at 63 to provide a port opening from chamber 51 tothe exterior of the cylinder.

Reciprocation of beam 52 alternately telescopivcally extends and collapses the compression cylinder 50 and thus alternately enlarges and reduces the volumetric capacity of chamber 51. As will presently appear, chamber 51 is in communicaf tion with an accumulator kor pressure reservoir and the air in chamber 51 andthe accumulator is to be held substantially at a predetermined pressure value which is well above that of the atmosphere. During operation of the mechanism, a portion of the air within chamber 51 is alternately displaced and returned, the displacement being into the accumulator, and consequentlyv the common pressure within chamber 51 and the accumulator varies, but the variance is held within a predetermined pressure range. In order to hold the pressure up to predetermined value in spite of leakage losses which are bound to occur,

it is highly desirable to provide an automatically* acting air replenishing device. y

While, broadly, any suitable replenishing means, operated in any suitable manner, may be employed, I have devised and have here shown a particularly effective means. walking beam reciprocation and, by reason of its peculiar location and nature, much 0f the complication and expense of usual replenishing means is avoided. By reason of this replenlshing provision, it is possible to reduce, to a marked degree, the cost and complications of compression cylinder 50, for it becomes unnecessary to provide usual close fits 'or pressure sealing means between sleeves 5| and 52. In other words, the

It is actuated byv 1-5, check valve 18 and pipe 16.

design of the main telescopic cylinder 50 may be such that it is fully to be expected that leakage will occur, but the auxiliary pump or replenishing means constantly compensates for the leakage losses. and insuring usual snug piston-and-cylinder flt between sleeves 5I and 52 by providing piston rings or liquid seals .(which provisionsl have been necessary heretofore in order to hold the pres'- sures up to predetermined values) these sleeves may be formed -of ordinary pipes which need merely be machined on their opposed peripheral faces to vgive working fit withl relatively large clearance tolerances.

The replenishing pump generally indicated at '84 k(Fig. 3) is made up of cylinder 65, attached at 66 to the center of head 53, and hollow piston 61 secured through hollow fitting 68 to the center of base plate 56. The composite bore 69 'of members 65 and 81 Ymakes up the compression chamber of the replenishing pump, it being obvious that the volumetric capacity of this chamber is varied by reason of alternate telescopic extension and collapse of members 65 and 61 as accomplished by corresponding telescopic movement of cylinder 50 under the influence of walking beam oscillation.

Pump 64 has inlet and outlet ports 10 and 1|, respectively, inlet port 10 being connected by pipe 12, which extends through and to the exterior of sleeve 55, to an air filter and lubricant container 13, there being a check valve 14 in line 12. to prevent the back flow of air during the compression stroke of the replenishing pump. Outlet 1| is connected by pipe 15, which extends through and to the exterior of sleeve 52, to a pipe 16 which returns and opens to chamber 51, there being a pressure release valve 11 and a check valve 18 in line 16, the check valve pre-` venting flow of air from chamber 51 to chamber 69 during the up stroke of the replenishing pump.

During the up stroke of walking beam 42, the volumetric capacity of chamber 69 is increased and air at atmospheric pressure flows into this chamber through member 13, check valve 14, and pipe line 12. On the down stroke of the Walking beam, the volumetric capacity of chamber 69 is decreased and a certain amount of the air within that chamber is displaced and is forced under pressure into chamber 51 through pipe The air thus forced into chamber 51 against the pressure already ycontained in that chamber and in the accumulator connected thereto, will compensate for leakage losses in all parts of the pneumatic system, that is, in the compression or displacement cylinder 50, the line leading from that chamber through pori'l 63 to the accumulator and in the accumulator itself. With the'vmaxi# mumy pressure within chamber 51 and the vaccumulator having been predetermined for agiven installation, pressure release valve 11 is' regulatedto exhaust to the atmosphere any pressure in excess of that amount, it being realized that since the chamber 51 and the accumulator are y in communication, valve 11 serves to predeter.

mine the maximum pressure in both.

Returning now to Fig. 2, it has been said that in usual well bore installations the annular space bore 24 to prevent or control the ingress' of Thus, instead of using cast cylinders ,following will give an example from which one may readily understand how other beginning situations may be treated to accomplish the same Fundamentally, the preparatory step consists in creating a closed air chamber within space 2|, this space to be defined annularly by pipes I4 and 20, to be defined at its upper end by casing head I3 or its packer 2B, and to be defined at its lower end by whatever substance be left in that annular space.

Assuming the space 2| is initially filled with mud and water, the mud is at least partially pumped out, for instance through ports 21 and 28, the remaining mud then being allowed to settle to the bottom, as indicated at M. Then a rubber tube may be introduced through one of the ports 21 or 28 and lowered into the water body above mud M. By then applying air pressure through the opposite port, the water may be ietted out through the hose until the remaining water is at a predetermined level. vIn a typical situation, this letting was Acontinued until the level L of water W was lowered to a depth around 200 ft. Water W, backed up by mud M and, finally, by cement 25, forms an end wall for the air spacell which, in eil'ect, becomes the accumulator or pressure chamber. In certain instances it may be desirable to improve the bottom seal by depositing weighted mud B such as Baroid on top of mud M.

With space 80 thus created, the letting tu is removed, pipe 3| is connected by'flexible hose 8| to port 63 of cylinder head 54 and, with valve 29 open, the pressure of the air within accumulator 80 and chamber 51 is raised to the desired degree by the application of a pump to pipe 32, for instance. When the pressure is built up to the predetermined value, valve 30 is closed and,

assuming the pumping mechanism is started im? in any given well and, in part, upon the calculations which have been made to counterbalance a given pumping unit. Assuming a given volumetric capacity is desired for the accumulator and knowing the effective cross sectional area thereof as determined by the diameters of the defining pipes, the preparatory steps will include the establishment of a water level L which will give the proper effective length to the accumulator or pressure chamber 80. 'I'his may involve pumping out mud and water as described above, or, in some instances it may involve the addition of water to raise -the level L. Again, during the operation of the device. it may be determined that greater or less capacity should be given to theaccumulator,inwhichcaseitiaeithershort ened by the addition of water or. lengthened by the expulsion of water.

any event there is available by reason of the annular space between the surface casing and water string, a spacev of relatively unlimited length which may be put to use as an accumulator, and it only requires comparatively simple operations to vary-thisv size to give any desired volumetric capacity. ,For instance, it is perfectly feasible to lower the water level'L to an extent which will give space Il a volumetric capacity many times greater than the displacement f capacity of cylinder 5l. In one installation the ratio was in the order of 50 to l, but the differential may, in some installations, be much greater.

It will be perfectly obvious that it is utterly unfeasible to provide an accumulator having such relatively great capacity if that accumulator be in the form of a usual groundsurface tank. If this ratio were to be even approached by the provision of a ground surface,tank, such a tank would be prohibitively expensive and bulky-and, during current times, would be absolutely unavailable. By virtue of my invention, this exceedingly favorable and hitherto unobtainable ratio has been secured by utilizing materials already at hand and necessary to the drilling of the well, rather than calling for new or enlarged equipment. 'I'he savingeifected is obvious, and,

in this connection, considerable saving can be ef.. fected by utilizing space 2| as an accumulator, even though for some reason it be determined that it be only of the volumetric capacity of a usual ground surface accumulator.

With the system connected as has been described and with the loads and volumetric capacities estimated. it can be predetermined as to what air pressure should be maintained beneath cylinder head 53 (of given effective area) in order to counterbalance the load requirements on the prime mover, all as set forth above. The pressure initially introduced to the accumulator chamber 80 and compression chamber l1 will be built up approximately to that value and pressure relief valve 'l1 will be set to relieve the pressure if, through over-delivery of pump 64, that pressure becomes excessively high. However, replenishment pump 64 may be designed so it will just about compensate for leakage losses and therefore the relief of excess pressure through valve 11 will occur infrequently, if at all.

In any event, with the predetermined pressure existing in chambers 5'! and 80 at the top of the walking beam stroke, it will be seen that as the walking beam descends and there is displacement of air from cylinder 50, the pressure within chambers 51 and 80 necessarily will be built up. And on the upstroke of the Walking beam, the pressure will diminish as chamber 51 increases in volumetric capacity. However, the volumetric capacity of accumulator chamber 80 is so great with relation to the displacement volume of compression chamber Bl that there will be a relatively little pressure change in the chambers (or, expressed otherwise, the balance pressure range is small) and therefore the alternate overloading and underloading of the prime' mover incidental to these changes in pressure will be of a relatively low order, particularly as compared with the overloading or underloading of a prime mover where the accumulator is relatively small. With the potential size of the accumulator practically unlimited, as it is when space 2| is utilized for this purpose, tnedifrerensioi between the volumetric capacity of the accumulator and of the displacement chamber may be increased to a point where the pressure changes are negligible. As has been said, this reduction in pressure variation is directly and favorably reflected in the smoothness of rod reciprocation and prime mover efficiency.

The system may not only be adjusted by varying the static pressure within chambers 51 and 80 or by changing the water level L. but `it may also be regulated to a certain extent by manipulation of valve 29 to create lesser or greater restriction to the flow of air between chambers B1 and 80.

' Usually, chamber 80 will be of such volumetric capacity that there will be a measurable, though slight, increase in chamber pressure during the down stroke oi' the walking beam. Though, with the use of the large accumulator, the differential is reduced to an extent which gives the advantageous results spoken of above, it still may play a part in compensating for other operating conditions such as pumprod inertia and acceleration and deceleration characteristics. For instance, in the walking beam type of pumping mechanism the'crank movement drives the walking beam in simple oscillatory harmonic motion and gives to the pump rods simple vertical harmonic motion. During the period of acceleration in the down stroke of the walking beam, a relatively great load is imposed on the prime mover but less resistance is offered by the compression of the air in chambers 61 and 80 than during the immediately following period of deceleration when there is less load on the prime mover. During the period of acceleration in the upstroke of the walking beam, increased load is placed on the prime mover, but the lifting effect of the com- Dressed air is greater than it is during the subsequent period of decelerationwhere there is less 10aa on the prlme mover. Thus the variations in air pressure compensate at least partially for the variation in load requirements on the prime mover cylinder 92 by a pump generally indicated at 93 and driven by any suitable prime mover P. Pump. 93 has two branch lines 94 and 95 which lead to the reversing valve 96. Pipe 91 leads from one side of valve 9B to the lower end of cylinder 92, While pipe 98 leads from the other side oi' the reversing valve to receiver or surge tank 99. Actuating uid stands in tank 99, but its level is always suiliciently low tov provide a space |00 which constitutes the counterbalancing or equalizing compression chamber of the system. An open-ended stand pipe |0| extends vertically through receiver 99 to a level above the highest level ever reached Iby fluid F, the lower end of `the line being connected by pipe 3| a to valve 30,

the stand pipe |0I and pipe 3|a thus putting chambers 80 (Fig. 2) and |00 into communication.

Disregarding for the time beingcertain of the details of water and air replenishment, it will .be seen that the volumetric relation between chamber |00 and chamber 80 is approximately the same as between chamber 51 andchamber 80. It will also be seen that chambers |00 and 80 may be considered together as a single closed air chamber, the volumetric capacity of which may be varied by increasing or decreasing the amount of actuating fluid in receiver 99. It follows that all which has been said of the system as generated by the acceleration and deceleration vthe same as that used in connection with the walking beam type of mechanism except thatthe connecting line between the accumulator and compression chamber is taken'from valve 30 instead of valve 29. Therefore Fig. 2 may be considered as an enlarged downward 'extension of Fig. 4 and the description of Fig. 2 may be taken as a description of the well -bore installation shown fragmentarily in Fig. 4. All comments as topreparation, nature and functions of the Well bore installation previously given, are to be taken as applying likewise to the installation of Fig. 4.

Here, polish rod 40 extends into connection with piston rod 90 carrying piston 9| which is adapted to reciprocate through A,vertical power cylinder 92. The showing of the hydraulic pumping engine and accessories, is to be taken as typical of such devices and, since their construction and operation are well known, the showing of Figure 1 may be said of the system of Fig. 4, except for the remarks regarding acceleration and deceleration of the crank-generated movement. l

With the piston 9| and hence pump rods 4| at upper stroke limit (Fig. 4) the reversing valve 96 is automatically put in condition to cause pump 93 to drive the water or actuating fluid in the direction of the full line arrows a. Water is thus drawn from beneath piston 9| in cylinder 92 and driven into receiver or surge tank 99. Pump rods 4| descend of their own weight and thus accomplish the down stroke of the pump plunger. This movement of the actuating fluid into r"- ceiver 99 reduces the volumetric capacity chamber |00. Theair'in this chamber |00 as well as in chamber 5l will preliminarily have been4 built up to a pressure which is calculated in the same manner as that described in connection with Fig. 1 and therefore the flow of water into receiver 99 is resisted by this built up pressure,

` which thus acts as a counter-balance for the pump rods; the proportioning of parts and pressures being such that the effective resisting force of the air is approximately equal to the weight of the rods plus one-half the weight of the oil column above the pump plunger.

When piston 9| reaches the bottom of its stroke, valve 96 is automatically shifted sothe pump circulates the actuating fluid in the direction of the dotted line arrows b, the fluid being drawn from receiver 99 and being forced into cylinder 92 below piston 9|, thus driving the piston and rods 4I through their up stroke. The compressed air within chamber |00 acts against the actuating iiuid in receiver 99 with an effective force approximately equal to that required to lift the weight of the 4pump rods plus one-half the Weight of the column of oil above the pump is conventional and the operation thereof will 'not be described in detail.

Actuating fluid F, such as water, is alternately admitted to and drawn from the lower end of plunger, and that force is effective to aid the pump in lifting the load.

If the pressure within chambers 80 and |00 is at the predetermined value when piston 9| is at the top of its stroke, th'e'pressure in those chambers will be slightly increased as the piston 9| descends. but, due to the relatively large volu- 4 been described in connection with the description of the operation of the pumping mechanism of Fig. 1. Likewise, level L may be raised or lowered to vary the diiferential, as previously described.

It will be seen that if the system is to be maintained in any predetermined condition, approximately the total amount of actuating fluid F must be maintained in the system and that the pressure in chambers 80 and |00 must be maintained approximately constant, except for variations due to fluctuation of the fluid level in receiver or surge tank 99 as caused by normal pump action. I therefore provide replenishing means to compensate for air losses through leakage and for returning to the surge tank such actuating fluid as may leak from various parts of the flow line. For these purposes, I provide a vacuum tank through pipe |06 with a replenishing' pump |01, there being a check valve |08 in pipe |08 to prevent the back iiow of iluid from pump |01 to tank |05. Pump |01 is belt-driven at |09 from pump shaft I so, in eiect, the prime mover for the main pump 93 also drives the auxiliary or replenishing pump |01.

At the discharge side of pump |01 is pipe ||I adapted to deliver fluid into chamber |00, pipe being providedwith a check valve ||3 which prevents back ilow of fluid from chamber |00 to pump |01. A pressure relief valve I I2 is lprovided for chamber |00.

Vacuum tank |05 is provided with a vacuum relief valve Ill which opens into the top of the tank. while from the bottom of the tank a pipe 5 leads to a catch basin H6, there being a check valve ||1 in pipe ||5 to prevent the back ilow of iiuid from tank |05 to basin IIS. There-is also a pipe ||8 leading from trap H9 at the upper part of cylinder 92 to the upper part of vacuum tank |05 so that actuating fluid which nds its way above piston 9| may be delivered to the vacuum tank.

Pipes and |2I conventionally represent lines for delivering to catch basin H8 such iluid as may leak from various parts of the pumping engine or from chambers to which the actuating uid may flow during valve-change periods and thus be temporarily removed from the pump actuating line. Pump 01 draws a depression within tank |05 (to an extent determined by the setting of valve ill) and thus draws into that tank water. which has collected in basin I6. This water is then picked up by pump |01 and returned to tank 99 through lpipe thus restoring the fluid to the actuating line. Pump |01 will also force such air as it draws from the vacuum tank (the supply of such air being periodically replenished through the opening of valve ||4 when the pressure in tank |05 reaches a predetermined negative value) and delivers such air, at times along with actuating fluid, to chamber |00 through pipe Pressure relief valve ||2 is set to exhaust this replenishing air to the atmosphere in the event the pressure within chambers |00 and 80 approaches an excessive value.

|05 which is connected at its bottom Thus, the amount of actuating fluid and the pressure of the air within the system are kept substantially uniform, to the end that the performance will be substantially uniform.

While I have shown and described preferred embodiments oi my invention, it will be understood that various changes in design, structure and arrangement may be made without departing from the spiritl and scope ofthe appended claims.

I claim:

1. A-pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within tubing which extends downwardly through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers defining the endsof a pressure chamber which is annularly defined by said pipes, Dump reciprocating mechanism including a reciprocating member at the ground surface. means for reciprocating the member, pump rods extending from said member to said plunger, fluid pressure means for counterbalancng said rods and comprising a compression chamber, a compressible iiuid in the compression chamber, a iluid-compressing medium adapted to act on the 'compressible fluid, a force transmitting medium between the member and the compressing medium. all in a manner whereby descension of the meinber and rods is against the pressure within the compression chamber, va connection between said compression chamber and said pipe deilned pressure chamber for putting them into communica'- tion, and means for maintaining pressure insaid chambers.

2. A pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within tubing which extends downwardly through a piping system which includes a water string annularly spaced from an outer casing, vertically spaced barriers defining the ends of a pressure chamber which is annularly defined by said casing and water string, pump reciprocating mechanism including a reciprocating member at the ground surface. means for reciprocating the member, pump rods extending from said meinber to said plunger, fluid pressure means for counterbalancng said rods and comprising a compression chamber, a compressible fluid in the compression chamber, a fluid-compressing medium adapted to act on the compressible fluid, a force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the member and rods is against the' pressure within the compressionl chamber, a connection between said compression chamber and said casing-and-string defined pressure chamber for putting them into communication,a and means. for maintaining pressurein said chambers.

3. A pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within tubing which extends downwardly through a piping system which includes a pair oi annularly spaced pipes, vertically spaced barrlers defining the ends of a pressure chamber which is annularly dened by said pipes, means for shifting at least one of the barriers vertically to vary the eiective capacity of said pressure chamber, pump reciprocating mechanism includ-f ing a reciprocating member at the ground surface, means for reciprocating the member, pump rods extendingfrom said member to said plunger, iluid pressure means for counterbalancing said rods and comprising a compression chamber. a

compressibie uid in the compression chamber, a

fluid-compressing medium adapted to act on the compressibie fiuid, a force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the 4. A pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within .tubing which extends downwardly through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers'defining the ends of a pressure chamber which is -annularly defined by said pipes, pump reciprocating mechanism including a reciprocating member at the ground surface, means for reciprocating the member, pump rods extending from said member to said plunger, fiuid pressure means for counterbalancing said rods and comprising a compression chamber, a compressibie fluid in the compression chamber, a fiuid-com pressing medium adapted to act on the compressible fiuid, a force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the member and rods is against thev pressure within the compression chamber, a valved connection between said compression chamber and saidl pipe defined pressure chamber for putting them into communication, and means for maintaining pressure in said chambers.

for reciprocating the member, pump rods extendr ing from said member to vsaid plunger, fluid pressure means for counterbalancing said rods and comprising a compression chamber, a compressi; ble fluid in the compression chamber, a fluidcompressing medium adapted to act on the compressible liuid, a force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the member and rods is against the pressure Within the compression chamber, a connection between said compression chamber and said pipe defined pressure chamber for putting them into communication, and means for maintaining pressure in said chambers. i

6. A pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within tubing which extends downwardly through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers defining the ends of a pressure chamber which is annularly defined by said pipes, the upper barrier comprising a head connecting the two pipes at the ground surface, and the lower barrier comprising astationary .filler between the two pipes and a body of liquid on top the filler, pump reciprocating mechanism including a reciprocating member at the ground surface,

means for reciprocating the member, pump rods extending., from said member to said plunger, fluid pressure means for counterbalancing said rods and comprising a compression chamber, a compressibie fluid in the compression chamber, 'a fluid-compressing medium adapted to act on the compressibie fluid, a force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the member and rods is against the pressure within the compression chamber, a connection between said compression chamber and said pipe defined pressure chamber for putting them into communication, and means for maintaining pressure in said chambers.

7. A pumping system for oil wells wherein a. vertically reciprocating pump plunger is disposed within tubing which extends downwardly through a piping system which includes a pair of' annularly spaced pipes, vertically spaced barriers defining the ends of a. pressure chamber which is annularly defined by said pipes, pump reciprocating mechanism including a reciprocating member at the ground surface, means for reciprocating the member, pump rods extending from said member to said plunger, fluid pressure means for counterbalancing said rods and comprising a compression chamber, a compressible fiuid in the compression chamber, a fluid-compressing medium adapted to act on the compressible fluid, a. force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the member and rods is against the pressure within the compression chamber, a connection between said compression chamber' and said pipe defined pressure chamber for putting them into communication, and means for introducing fluid under pressure from an external source to one of the chambers. y

8. A pumping system for oil Wells wherein a vertically reciprocating pump plunger is disposed wthin tubing which extends downwardly through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers deflningthe ends of a pressure chamber which is annularlydeiined by said pipes, pump reciprocating mechanism including a reciprocating. member at the rground surface, means for reciprocating the member, pump rods extending from said member to said plunger, fluid pressure means for counterbalancing said rods and comprising a compression chamber. a compressibie fluid in the compression chamber, a fluid-compressing medium adapted to act on the compressibie fiuid, a force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the member and rods lis ag-ainst the pressureiwithin the compression chamber, aconnection between said compression chamber and said pipe defined pressure chamber for'putting them into communication, and auxiliary pump means for holding the 9. A pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within tubing which extends downwardly through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers defining the ends of a pressure chamber which is annularly defined by said pipes, pump reciprocating mechanism including a reciprocating member at the ground surface, means for re- -ciprocating the member, pump rods extending from said member to said plunger, fluid pressure means for counterbalancing said rods and comprising a compression chamber.'a compressible fluid in the compression chamber, a iluid-comany given stage of the pumping cycle, and pressure release means for exhausting fluid from the chambers when the pressure within the chambers exceeds said given value.

10. A pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within tubing which extends downwardly through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers deilning the ends of a pressure chamber which is annularly defined by said pipes, pump reciprocating mechanism including a reciprocating member at the ground surface, means for reciprocating the member, pump rods extending from said member to said plunger, fluid pressure means for counterbalancing said rods and comprising a compression chamber, a compressible fluid in the compression chamber, a uid-compressing medium adapted to act on the compressible iiuid, a force transmitting medium between the member and the compressing medium, all in a manner whereby descension of the member and rods is against the pressure within the compression chamber, a connection between said compression chamber and said pipe denned pressure chamber for putting them'into communication, and vauxiliary pump means operated by reciprocation of said member for holding the pressure within the chambers up to a given value at any given stage of the pumping cycle.

11. A pumping system for oil wells wherein a vertically reciprocating. pump plunger is disposed within tubing which extends downwardly sure Awithin the chambers up to a given value at l assises pressure means for countcrbalanclng said .rods and comprising a substantially vertically arranged cylinder and piston assembly secured against substantial vertical movement at its lower end and applied at its upper end to the beam at a point between its fulcrum and the point of rod application. a connection between said chamber' and the cylinder of the assembly for putting them into communication, and means operated by walking beam reciprocation for supplying iluid A plunger, means for reciprocating the beam; fluid through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers defining the ends oi' a pressure chamber which is annularly deilned by said pipes, pump reciprocating mechanism including va walking beam, pump rods applied to the work end of the beam and extending into connection with said plunger, means for reciprocating the beam; iluid pressure means for counterbalancing said rods and comprising a substantially vertically arranged cylinder and piston assembly secured Vagainst substantial vertical movement at its lower end and applied at its upper end to the beam at a point between its fulcrum and the point of rod application, a connection between said chamber and the cylinder of the assembly for putting them into communication, and means for maintaining pressure in said chamber and cylinder.

12. A pumping system for oil wells wherein-a vertically reciprocating pump plunger is disposed within tubing which extends downwardly throughl a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers defining the ends of a pressure chamber which is annularly defined by said pipes, pump reciprocating mechanism including a walking beam, pump rods applied to the work end of the beam and extending into connection with said plunger, means for reciprocating the beam; uid

pressure means for counterbalancing said rods and comprising a substantially vertically arranged, closed-ended telescopic cylinder secured against substantial vertical movement at its lower end and applied at its upper end to the beam at a point between its fulcrum and the point of rod application, a connection between the cylinder and said chamber for putting them into communication, and a pump within said cylinder and operated by walking beam'reciprocation, an

inlet duct for said pump and adapted to admit air from a point external of the cylinder, and a discharge duct from the pump to the interior of the cylinder, and a check valve in the discharge duct to prevent return ilow from the interior oi.' the cylinder to the pump.

14. A pumping system for oil wells wherein a vertically reciprocating pump plunger ls disposed within tubing which extends downwardly through a piping system which includes a pair of annularly spaced pipes, vertically spaced barriers defining the ends of a pressure chamber which is annularly denned by said pipes, pump reciprocating mechanism including a piston adapted to be reciprocated through a cylinder, pump rods operatively connecting the piston and plunger whereby the plunger is moved upwardly by virtue oi piston movement in one direction and whereby downward movement oi the plunger and rods move the piston in the opposite direction, a closed container for actuating fluid and connected to the cylinder at one side of the piston, there being an air chamber within the container above the actuating fluid, means for alternately applying the actuating fluid under pressure and for relieving the pressure of said fluid to and from, respectively, one side of the piston to alternately move the rods and plunger upwardly and to allowthem tognove downwardly, a connection between said chambers for putting them into communication, and means for maintaining pressure in said chambers.

15. A pumping system for oil wells wherein a vertically reciprocating pump plunger is disposed within tubing which extends downwardly A' ,2,341,804 9 by virtue oi. piston movement in one direction and whereby downward movement of the plunger and rods move the piston in the opposite direction, a

" closed container for actuating uid and connected to the cylinder at one side of'the piston, there being an air chamber withinthe container above the actuating iiuid, means for alternately applying the actuating uid under pressure and for relieving the pressure of said iiuid to and from,

respectively, one side of the piston to alternately move the rods and plunger upwardly and to allow them to movecdownwardly, a connection between said chambers for putting them into communication, a flow control valve in said connection,

and means for maintaining pressure in said chambers.

LEE GRUMBAUGH.

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