US2157219A - Hydraulic pumping jack - Google Patents

Description

3 Sheets-Sheet 1 l HJIIU 'IIIIIIIIIIIIA May 9, 1939- H. M. SALENTINE HYDRAULIC PUMPING JACK Filed Dec. 27, 1955 fit-25597 M SAM/v77:

May 9, 1939'. H. M. SALENTINE 2,157,219

HYDRAULIC PUMPING JACK I Filed Dec. 2'7, 1935 3 SheetsSheet 2 hfsesrer M Sqzawmr y H. M. SALENTINE 2,157,219

HYDRAULIC PUMPING JACK Filed Dec. 27, 1935 3 Sheets-Sheet 5 TIME 8 3 62 A STRETCH y 85 9 L Z 1 z .91 89 6'6 6 Fra gwucm/tom M79555? M jazz/mm:

Patented May 9, 1939 UNITED STATES PATENT OFFICE- 5 Claims.

My invention relates to hydraulic pumping jacks and to methods of pumping wells. This application is a continuation in part of my copending application for Oil well pumping systems, Serial No. 605,916, filed April 18, 1932, now Patent 2,073,809, as to common subject matter.

The characteristic production cycle of an oil well begins with a flush period in which the oil flows by reason of subterranean pressure, gradually subsiding until it is necessary that the well be placed on the pump. As the life of the well progresses, the quantity of oil obtained decreases and its quality deteriorates. Usually more and more water is brought in with the oil; also, as the pressure on the oil decreases, the lighter fractions change to gas and escape so that the remaining oil increases in viscosity with the result that its flow into the well bore is slower. By reason of the increased viscosity and surface tension of the oil, the tendency for sand to enter the well bore is increased.

In each well there are a number of variables which in their various combinations provide an infinite variety of conditions. For example, the fluid level and also the rate of flow into the well bore, which in itself has several contributing variables, changes the viscosity of the oil and the formation pressure whether due to gas or water urge.

These several variables are increasingly im-' portant as the well reaches its final stage of production. Naturally, as the cost of production per barrel oil increases, the yield is low; therefore, the ability of the pumping apparatus to meet the particular conditions existing becomes increasingly important. These various factors cannot readily be determined before the pumping apparatus is installed but require, first, installation of the apparatus, and then adjustment to meet ,the conditions.

Within the pumping apparatus itself, it is necessary to maintain a pressure difierence tending to urge the oil into the pumping apparatus, but this pressure diiference should be as low, and preferably as nearly constant as possible. The reason for this is that as the pressure diminishes, dissolved gases in the oil are freed, and back pressure differences materially exceeding the average, although existing for short intervals,

have a tendency to liberate the dissolved gases which do not readily redissolve when the pressure difference drops; thereby decreasing the volumetric efficiency of the pumping apparatus, and further increasing the viscosity of the oil.

In consideration of the problem as outlined above, among the objects of my invention are:

First, to provide a hydraulic pumping jack which is adapted to operate well pumps of comparatively shallow wells, such as those requiring a lift from a few hundred to two or three thousand feet.

Second, to provide a hydraulic pumping jack which is particularly designed for "stripper wells; that is, wells which are in the last stages of production.

Third, to provide a pumping jack of this character in which special provision is made for a wide range of adjustment to meet the manifold variations of pumping conditions determined by the rate of flow of oil into the well; the viscosity and specific gravity of the oil; the amount of deleterious matter present, such as water or sand; the crooksdness of the well bore; and the pumping depth.

Fourth, to provide a pumping jack which incorporates a cushion means operable at the end of the down stroke, and means whereby the cushioning effect may be varied to'meet well conditions.

Fifth, to provide a hydraulic pumping jack which incorporates means whereby the initial interval of the up stroke may be rapid, as compared to'the remainder of the up stroke, so that a minimum of time is lost in restretching the sucker rod string prior to beginning the up stroke of the pump plunger attached to its lower end, and a maximum of the total cycle may be devoted to the pumping stroke.

Sixth, to provide a pumping jack which may be installed on wells in which the derrick and other surface equipment has been removed.

Seventh, to provide a hydraulic pumping jack which may be operated with or without pro vision for counterbalancing of the sucker rods, depending upon the depth of the well.

Eighth, to provide a hydraulic pumping jack wherein counterbalancing means for the sucker rods may be incorporated with only superficial changes in the jack; such changes being in the natureof additions whereby a single Jack design may be used for both uncounterbalanced and counterbalanced installations.

Ninth, to provide a hydraulic pumping jack wherein the jack cylinder may be supported directly upon the well casing in centered relation thereover, thereby eliminating need for other support.

Tenth, to provide a hydraulic jack which is particularly compact and which provides a unitary jack cylinder base and a control valve housing so arranged as to minimize extraneous pipe.

Eleventh, to provide a hydraulic pumping jack which incorporates a novel sealing means through which the polish rod extends, and from which any leakage is drained into the return or low pressure side of the operating fluid circuit.

Twelfth, to provide a hydraulic jack which is particularly durable, eflicient in its action, and capable of withstanding long and continued use without deterioration.

with the above and other objects in view as may appear hereinafter, attention is directed to the drawings, in which: i

Fig. l is a fragmentary elevational view of my hydraulic pumping jack, showing substantially diagrammatically the operating fluid circuit ineluding the pump and storage tank.

Fig. 2 is an enlarged, fragmentary, sectional view of the hydraulic jack taken through 2-2 of Fig. l, with parts and portions shown in elevation, illustrating the base of the jack cylinder, and showing particularly the cushioning means and the arrangement whereby the cushioning effect may be varied.

Fig. 3 is a similar, fragmentary, sectional view through 3-3 of Fig. 2, showing particularly the control valve in the position for delivering operating fluid into the jack cylinder.

Fig. 4 is a fragmentary sectional view of the control valve similar to Fig. 3 but showing the valve in the position for permitting discharge of fluid from the jack cylinder as well as by-passing fluid from the pump back to the strage tank, and indicating further by dotted lines the manner in which discharge from the jack cylinder may be throttled.

Fig. 5 is a fragmentary sectional view similar to Fig. 3 but illustrating a modified form of cushioning means which also incorporates an arrangement whereby rapid movement may be obtained during the initial part of the up stroke.

Fig. 6 is an enlarged, fragmentary, sectional view showing the upper portion of the jack cylinder, the trip rod retaining means, and the manner in which the polish rod projects above the jack cylinder.

Fig. 7 is a partially elevational, partially transverse sectional view through 1--1 of Fig. 6.

Fig. 8 is a fragmentary, partially diagrammatical view of the pressure pump in which a pressure tank and a pressure maintaining means is substituted for the storage tank, and the operating fluid circuit is maintained under a pressure to counterbalance partially the weight of the sucker rods.

Fig. 9 is a composite graph illustrating representative stroke characteristics obtainable with the hydraulic jack, and showing for comparison the stroke characteristic of the conventional Walking beam and pitman drive.

My hydraulic pumping jack comprises generally a jack piston and cylinder means i, a combined cylinder base and valve housing 2, a valve operating mechanism 3, a pump 4, and a storage chamber 5. The jack cylinder base 2 has a modifled form indicated by 6 in Fig. 5, and the storage chamber 5 may be substituted by a pressure tank I and pressure maintaining means 8, as shown in Fig. 8.

The combined jack cylinder base and control valve housing 2 is in the form of a casting having an externally threaded lower end adapted to screw into a coupling A, or other fitting, forming the upper end of the oil well tubing, not shown.

The base 2 is provided with a bore l2 therethrough which receives a polish rod It. The lower end of said here is provided with a packing gland i4. Above the packing gland ll, the bore i2 is provided with an enlargement I! which is adapted to be connected with the low pressure side of the operating fluid circuit, as will be brought out hereinafter. "jAbove the enlargement ii, the polish rod ll flts snugly, though slidably, within the bore so that the amount of fluid entering the enlargement i5 is minimized. With this arrangement, the packing gland I4 is not subjected to the pressures existing in the jack piston and cylinder means.

The upper end of the base member 2 is provided with a socket l6 which is annular at its lower portion so that the upper part of the bore i2 is within a hollow boss H. The upper end of the base 2 receives the lower end of the jack cylinder l8 forming part of the piston and cylinder means i. The jack cylinder I8 is a length of pipe or tubing, the upper end of which is screw-threaded into a cylinder head l8, shown best in Fig. 6.

The cylinder l8 receives a piston 20 mounted on a piston sleeve 2|. The piston sleeve 2i receives the polish rod i3, and both of these members project through the cylinder head I 9. Air relief ports 22 may be provided in the cylinder head, as shown in Fig. 6. The upper end of the piston sleeve, however, carries a pacldng gland 23 which fits around the projecting end of the polish rod to seal the annular space between the sleeve and polish rod.

The projecting end of the polish rod is adapted to receive a clamp 24 to prevent downward movement thereof relative to the sleeve 2|. With this arrangement, the position of the polish rod may be adjusted after the pumping jack has been in stalled without dismantling or otherwise disturbing the pumping jack.

At one side of the base member 2 there is provided an enlargement which forms a valve housing, as shown best in Figs. 1, 3, and 4; said housing is provided with a cylindrical valve chamber 25 which extends horizontally or at right-angles to the bore l2 and is provided with a jack cylinder port 26 which extends laterally and intersects the lower end of the socket l6. Below and parallel with the valve chamber, is an intake passage 21' which has upwardly extending ports 28 intersecting the valve chamber at either side and below its horizontal axis. Similarly, above the valve chamber 25 and in parallel relationship therewith, is a discharge passage 2Q having ports 31] extending downwardly and intersecting the valve chamber at either side and above its horizontal axis.

The valve chamber 25 receives an oscillatable valve 3i having at its side adjacent the jack chamber port 26 a recess 32 which, depending upon the position of the valve member, connects the jack chamber port with either or both the intake passage .21 and exhaust passage 29 by means of their corresponding ports 28 and 3%. On the opposite or outer side, the valve member 3! is provided with an areuate channel 33 which forms between its points of intersection with the periphery of the valve member a sealing bar 34. When the recess 32 connects the jack cylinder with the intake passage 21, the sealing bar seals communication between this passage and the exhaust passage 29, as shown in Fig. 3. When the jack cylinder port 26 is connected with the discharge passage 29, the passage 33 also connects the intake passage 21 with said discharge passage 29. The valve member is so arranged that the communication between jack cylinder port 26 and the discharge passage 29 may be throttled, and in certain positions some of thefluid from the intake port may be diverted therethrough so that the rate of discharge of fluid from the jack cylinder may be. varied by adjusting the corresponding extreme position oi the valve member.

The valve member 3| is provided with a stem which extends through one end of the valve housing and receives the lever 35 which extends toward the main part of the base .2, as shown in Fig. 1. The lever is connected to a yoke 35 in which is 15 threaded the lower end of a trip rod 31, there being provided a locknut for adjustably securing the trip rod in the yoke member 36. The trip rod 31 adjustably receives a spring cup 38 which may be threaded thereon and also secured by a locknut. The spring cup 38 receives an adjustable spacer sleeve 39 and a spring 40, as shown best in Fig. 2.

A second spring cup 4| is slidably mounted upon the trip rod 31 and is likewise provided with an adjustable stop sleeve 42 and spring 43. The spring cup 4| is provided with a laterally extending lug 44 which adjustably receives the lower end of a connecting rod 45. The trip rod 31 and connecting rod 45 extend upwardly in contiguous relation to the Jack cylinder and head IS. The upper end of the head I 9 is reduced in section to receive a collar 46 having a guide bracket 41 extending laterally there-from, and through which project the trip rod 31 and connecting rod 35 The upper end of the piston sleeve 2| below its packing gland 23 supports a collar 48 having a laterally extending arm 49, the extremity of which receives the upper end of the connecting rod 45 so that the connecting rod is raised and lowered with movemnt of the piston 20 and its sleeve.

The upper end of the trip rod 31 which projects through the guide bracket 41.is provided with a cam collar 50 having flat faces which converge downwardly, and other faces converging upwardly which are engaged by similarly shaped cam riders 5| supported by leaf springs 52 which extend upwardly from the bracket 41, as shown best in Figs. 1 and 6.

The lower end of the piston sleeve 2|- is provided with an inverted cup 53 which is adapted to fit over and coact with the boss IT to form a dashpot for cushioning the down stroke of the piston at its extremity. The extent of the cushioning or dashpot action is dependent upon adjustment of the spring cup 38, for the piston moves downwardly until the spring cup 4| engages the spring 40 and its cup 38 with sufficient force to reverse the valve; that is, move the valve from the position shown in Fig. 4 to that shown in Fig. 3. The effect of this dashpot action is discussed more in detail hereinafter.

Mounted on the side of the base 2, above and below the lever 35, are set screws 54 and 55. Set screw 54 limits downward movement of the lever and consequently the port opening between the jack cylinder port 26 and the intake passage 21, and thereby determines the position of the valve shown in Fig. 3. The set screw 55 similarly controls the port between the jack cylinder port 26 and the exhaust passage 29, as shown in Fig. 4. Usually the communication between the intake passage 21 and the jack cylinder port 25, as determined by set screw 54, iswide open so that the As shown in Fig. 1, the intake passage 21 is connected by a pipe 56 to the discharge end of the pump 4; while the discharge passage 29 is connected by a pipe 51, preferably larger than pipe 56, with the storage tank 5 and a suitable pipe 53 which may include in part the pipe 51 and which provides communication between the storage tank 5 and the intake of the pump 4.

A small pipe 59 may extend between the enlargement l5 and the outlet or exhaust passage 29, or at any suitable point of the return circuit of the operating iluid- Similarly, a tube 611 communicates between the head l9 and the return circuit. Thus, any fluid escaping through the bore |2' or through the enlargement or pocket l5, or working past the piston 2|! is returned to the storage tank.

Attention is now directed to Fig. 5 in which is' illustrated a modified cylinder base and control valve housing 6. This structure is in most respects similar to the base 2; like characters designating the similar parts. In place of the recess IS, the jack cylinder base 6 is provided with a recess 5| at its upper end equal in diameter to the inside of the jack cylinder l8 and extending a short distance below. Beneath recess 5|, is provided a smaller recess or socket 62, below which is the bore |2. The jack cylinder port 26 of the control valve intersects the bottom of the socket 52. I

In place .of the inverted cup member 53, the lower end of the piston sleeve 2| is provided with a ram sleeve 63 through which extends the polish rod 3. The ram 63 forms a snug sliding fit within the socket 62 when the piston approaches the lower end of its stroke.

A by-pass 54 extends from the recess 5| to the socket 52; said by-pass is provided with a check valve 65 for preventing flow from the socket 62' to the recess 6|, and a needle valve or other suitable throttling valve65 which determines the rate of discharge from the recess 6| and jack cylinder into the socket 52.

In addition to the by-pass 64, a second and preferably larger by-pass 61 is provided between the recess 6| and the exhaust or outlet passage 29 of the control'valve. Said by-pass 61 is provided with a check valve 68 which permits flow from the outlet passage 29 into the jack cylinder whenever the pressure in the cylinder is less than that in the discharge passage.

With the arrangement shown in Fig. 5, the downward movement of the piston 2| is cushioned and retarded when the ram 63 enters the socket 62, inasmuch as the fluid from under the piston may now flow only through the by-pass 54. However, the ram 63 may be so arranged that a certain amount of leakage may occur during its initial movement into the socket 62; which leakage gradually decreases as the ram enters its socket, thereby providing a gradual checking in the -downward movement of'the piston. At the beginning of the up stroke, the operating fluid coming through port 26 acts only upon the ram 63. Because the diameter of this ram is smaller than the piston, a given amount of fluid causes a more rapid movement thereof. During this initial movement, the check valve 68 prevents the formation of a negative pressure below the piston 20 and maintains the recess ul completely full of liquid; thus when the ram clears the socket 82, the force of the operating fluid is applied against the entire under-surface of the piston; and inasmuch as the area of the recess 8| and jack cylinder i8 is larger than the socket 82, the remaining upward movement of the piston is at a lower rate than its initial movement. The effect or this is shown in Fig. 9 and is discussed in more detail hereinafter.

The structures so far described do not provide for any counterbalancing of the sucker rods, and such counterbalancing is unnecessary in the shallower wells. As the depth of the fluid level increases, counterbalancing becomes more and more necessary in order to maintain efllcient operation. The practical depth of a well pump operated by the apparatus may be increased by maintaining a pressure in the storage tank 5. This can be readily accomplished inasmuch as the fluid circulating system is a closed one. In the event that back pressure is maintained, the force of such back pressure on the piston i8 is of course less than the weight of the rods, so that such excess weight of the rods may be utilized to cause return movement of the'piston. Such counterbalancing may be accomplished by means of the pressure tank 1 which is substituted for the storage chamber 5. Said pressure tank I comprises a. base H and a cylinder 72 in which is mounted a floating diaphragm or piston 13 which divides the cylinder 12' into an upper or air chamber 14 and a lower or operating liquid chamber 15. The pressure maintain-- ing means 8 is formed within a housing 80 which may constitute the head of the cylinder 12. Within said housing 80, there is formed a major cylinder 8i and a coaxial minor cylinder 82 which receive a dual piston 83 comprising a major piston element 86 and a minor piston element 85. Said piston elements fit into the cylinders BI and 82 respectively.

The chamber formed in the major cylinder between the major piston element 84 and the minor cylinder is connected with the air chamber of the pressure tank I through a port 86, and in addition, is provided with a spring 81 tending to urge the dual piston in a direction which withdraws the minor piston element from cyli'l. The chamber. formed in the opposite side of the major piston element is connected by a pipe 89 to a suitable point in the pressure side of the operating fluid circuit; the pressure, in which, drops when the pump 4 delivers back into the return line.

The cylinder 82 is connected by a port 90 through an intake check valve 9| to the atmosphere, and through an outlet check valve 92 to the interior of the counterbalancing chamber 8.

With each cycle of operation of the hydraulic jack, the dual piston 83. reciprocates and pumps a quantity of air into the upper or air chamber 14 of the pressure tank, A relief valve 93 may be incorporated in the pressure maintaining means to relieve the pressure in the air chamber should it exceed a predetermined value.

The purpose of the diaphragm 13 is to separate the cushioning air within the chamber 14 from the liquid circulating system in order to prevent dissolving of the air into the liquid. The liquid within the circulating system is, therefore, substantially free of gas and, substantially thereiore, incompressible; thereby eliminating any loss of time which might otherwise be consumed in compressing a compressible medium. It is possible with this arrangement to maintain the liquid in the circulating system under considerable pressure although the pressure difference on opposite sides of the pump may be kept with a reasonable value. This enables the hydraulic Jack to operate a well pump at a deeper level than is feasible without counterbalancing.

As stated hereinbefore, each well has characteristics diiferent from all others; consequently, in order that my hydraulic jack may be installed to meet most effectively the conditions existing at a particular well and also to facilitate experimenting with and testing of the well to determine just what will prove the most efficient pumping cycle and rate, a number of adjustable elements are provided. Thus, the set screws 54 and 55 regulate the extent of movement of the valve element Si; by so doing, it is possible to regulate independently the up stroke and the down stroke of the jack, as well as the rapidity of the pumping cycle as a whole.

Inasmuch as high pressure pumps, such as the pump 4 used to circulate the operating fluid, operate most efficiently within a particular speed range, it is preferable that, for continuous operation, the port to the jack cylinder be wide open during the intake stroke. First, however, it is necessary to determine what quantity of fluid per minute should be delivered to the jack cylinder. Therefore, during initial testing of the well and determining of the variable factors thereof, the set screw 54 is particularly useful. After the test is completed, the proper size pump 4 may be installed, if need be, for permanent operation, and the set screw backed down to provide full opening of the valve.

The set screw 55 likewise serves particularly during the testing period of the well, and is locked once the desired rate of discharge from the jack cylinder is determined. However, as the delivery from the well gradually subsides, quite likely with increase in viscosity of the oil, the set screw 55 may be adjusted to increase the duration of the down stroke and consequently the period of the entire cycle commensurate with the reduced quantity of oil available.

The duration of the down stroke, as well as the cushioning effect, may also be regulated by adjustment of the spring cup 38 which determines the position of the piston 28 and dashpot element 53, as shown in Fig. 2. With the arrangement shown in Fig, 5, either or both the cup 38 and valve 88 may be utilized for this purpose.

Inasmuch as the length of stroke of the jack is determined by the stroke for which the well pump is designed, plus the stretch in the sucker rods which is dependent upon the depth of the well, the collar 31a on the trip rod 31 provides a ready and convenient adjustment of the stroke length to meet this variable.

The springs 43 and 48 are first compressed until the valve starts to change its position and then expand to force the valve to complete its movement, thus insuring full movement of the valve. It should be here noted that the passage 33 through the valve member 3i is smaller at its end communicating with the outlet or return passage 29 than with the intake passage 21. Therefore, the valve member is urged upwardly by hydraulic pressure, particularly when in the position shown in Fig. 3; thus facilitating proper sealing of the outlet passage 29 from the intake passage 21 during delivery of fluids to the jack cylinder. With this arrangement, leakage due to Wear 01 thevalve member is minimized.

Attention is now directed to Fig. 9. The upper chart, designated A, indicates a conventional pumping cycle of the crankpin type" as obtained by a walking beam and pltman drive. Chart B illustrates the typical cycle obtained by my hydraulic pumping jack as arranged in Fig. 2; while chart illustrates the typical cycle obtained with the arrangement shown in Fig. 5.

In each chart, the upper or solid line represents the movement of the polish rod, while the lower or dotted line represents the movement of the well pump plunger which carries the traveling valve. The distance between the two lines indicates the rod string stretch, while the slope of the lines indicates the velocity.

Several factors should be borne in'mind; first, the quantity of gas which is capable of going into solution with aliquid such as crude oil varies inversely as the pressure; second, the space occupied by the dissolved gas in a liquid varies inversely as the pressure; third, when the pressure on the liquid exceeds the critical pressure of the normally gaseous substance, such substance is in solution as a liquid. Thus, as-the pressure on crude oil is lowered, gas is freed and the remaining liquid increases in viscosity.

The greater the pressure drop, whether between the formation and well bore or elsewhere, the greater is the amount of gas freed; also the rate of fiow into the well bore is increased. This tends to increase the amount of sand and other deleterious matter carried into the well bore by the oil and is due not only to increased velocity but also to the increased viscosity and surface tension of the oil under its lowered pressure.

The fluid level in a well bore at which the most efficient recovery may be had in view of the above factors is termed the "critical fluid level", and a certain amount of experimentation and testingof a particular well is necessary in order to determine this level. There is a focalpoint at which the effect of gas being liberated due to decrease in fluid pressure becomes particularly noticeable, and this is in the intake chamber of the well pump between the standing and traveling valves. The greater the velocity of the traveling valve during the intake stroke of the pump, the greater the pressure drop between the fluid in the well bore and that within the intake chamber. Increase in the pressure drop means a lower pressure withinthe intake chamber, resulting in an increased liberation of gas. This both reduces the volumetric efliciency of the pump and increases the viscosity of the liquid. Even though the minimum pressure reached in the intake chamber is of short duration, gasis liberated which requires both time and agitation to redissolve. Inasmuch as the pressure on the liquid continues to diminish as the liquid reaches the surface through the production string, very little, if any, of the released gas redissolves.

With the crankpin cycle, as shown in chart A, it will be noted that while the polish rod moves in a 50-50 cycle, the well pump plunger, due to the taking up of the sucker rod stretch during the down stroke and re-stretching of the rods during the initial up stroke, must accomplish its up stroke in less than 50% of the cycle. This means that the plunger velocity during the up or intake stroke is faster than the polish rod.

In addition, the peak velocity of the plunger, represented by the tangent line X, is greater than the average or straight line velocity represented by the line Y.

On the other hand, even the average velocity represented by line Y is too fast for a given pumping cycle. With the cycle obtainable by my hydraulic jack, not only may the intake velocity of the well pump be substantially constant, but it may be materially slower than that possible with the crank-pin cycle at the same pumping rate. As shown in charts B and C, the up stroke of the well pump plunger may occupy 70 to 80 percent, or more, of the total cycle. With the hydraulic jack, the downstroke of the polish rod need occupy only a sufficient proportion of the total cycle to insure dropping of the well pump plunger and the sucker rod string by the action of gravity as modified by the character of the n being pumped, the

straightness or crookedness of the hole, and,

other frictional factors. The polish rod, because of frictional resistance to movement of the well pump plunger, is free to drop faster than the plunger. For this reason, it is desirable to cushion materially the otherwise sudden reversal of the polish rod, as indicated by the chart B, and still obtain the greatest possible up stroke duration. In other words, a substantially fixed time is required for the plunger to drop back to its lower position, and this time may be utilized in any manner to provide for the most desirable movement of the polish rod in order to minimize excessive loads on the various parts of the pumping apparatus.

Due to the fact that the sucker rods are relatively long and are stretched by their own weight, the weight of the plunger, and, during the up stroke, the weight of fluid above the plunger, they are in effect an elongated spring. This causes a certain amount of lost time in the pumping cycle whether by the crankpin cycle, as shown in chart A, or by the special cycle shown in chart B. This lost time may be materially reduced by. rapidly raising the polish rod during its initial up stroke as shown in chart C. The duration of the rapid portion of the up stroke is adjusted so that the normally slower portion of the up stroke begins'before the well pump plunger starts on its up stroke.

While at first it may appear that the rapid down stroke comparatively rapid reversal of movement might set up undue stresses in the sucker rods, such is not the case. The greatest load occurs during the up stroke when the weight of the fluid is added to the weight of the sucker rods and plunger. With the crank pin cycle, the velocity either maximum or average during the up stroke is materially greater than with my special cycle, so that the stresses on the rods are necessarily greater with the crankpin cycle.

A further advantage is obtained with my special cycle which is particularly noticeable when the pumping rate may be only a few strokes per minute, as is the case with stripper wells. Because of the relatively long, slow, and uniform up stroke and the quick down stroke, it is impossible to set up surging in the well bore. With the crankpin cycle at slow speeds, a periodic impulse is applied to the fluid within the well bore. If this impulse approximates the natural fre-' quency of fluid oscillation, the fluid may be caused to surge up and down from its critical fluid level. This results in increased pressure difference between the well bore and the formathen cushioning its downward movement as it reaches the lower end of its stroke, the duration of the entire downward stroke of the polish rod being approximately equal to or less than the interval required for the plunger of the well pump piston to reach its bottom position under the influence of gravity as modified by frictional resistance; then slowly raising the polish rod at a substantially uniform rate. In order to.minimize the interval required to re-stretch the sucker rods and increase the relation of the up stroke time to the down stroke time. the method is modifled by starting the up stroke of the polish rod before the sucker rods have been re-stretched by their own inertia and weight, rapidly raising the polish rod until the sucker rods have been re-stretched, and thereafter slowly raising the polish rod until it completes its up stroke.

In the event that the sucker rod string is partially counterbalanced, such counterbalancing effeet is sufilciently below the weight of the sucker rod string that the pumping cycles shown in chart B and C may be obtained. V

Though I have shown and described certain embodiments of.my invention and certain methods of operation, I do not wish to be limited to the precise disclosure herein made, but desire to include in the scope of my invention the constructions, combinations, and arrangements substantially as set forth in the accompanying claims.

I claim:

1. In a hydraulic pumping jack having 9. cylinder and a piston therein, said piston arranged to be raised by hydraulic pressure and to be lowered by the load on said jack; piston speed control means comprising: a plunger of reduced diameter projected downwardly from said piston; a socket in the lower head of said cylinder arranged slidably to receive said plunger; 9. channel arranged to permit the escape of hydraulic fluid from the lower end of said socket; a second channel arranged to permit the escape of hydraulic fluid from the annular space between said plunger and the wall of said cylinder; a regulating valve interposed in said second channel, and means for introducing hydraulic fluid under pressure into the lower end of said socket to move said piston upwardly at a relatively rapid rate until said plunger emerges from said socket and thereafter at a lower rate.

2. In combination with a hydraulic pumping jack and a pressure creating pump for actuating said jack, load counterbalancing means comprising: a substantially closed storage tank arranged to supply jack actuating fluid to the suction side of said pump during the power stroke of said jack and to receive said fluid during the return stroke, and means for maintaining automatically a substantially constant superatmospheric pneumatic pressure on the liquid supply within said tank.

3. In combination with a hydraulic pumping Jack and a pressure creating pump for actuating said jack; load counterbalancing means comprising: a substantially closed storage tank arranged to supply actuating fluid to the suction side of said pump during the power stroke of said Jack and to receive said fluid during the return stroke, and means actuated by fluctuations in fluid pressure in said jack for maintaining a substantially constant superatmospheric pneumatic pressure on the liquid supply within said tank.

4. In a hydraulic pumping jack for a well having a casing therein: a unitary housing structure supported by said well casing, said housing structure including a jack cylinder receiving socket disposed coaxially with said well casing; a valve chamber formed within said housing; a channel for the passage of pressure fluid between said chamber and said socket; an axial bore.

through said housing for the passage of a recipr0- eating rod from said socket into said casing; a packing gland arranged to surround said rod, and means formed on the lower end of said housing for attaching said housing to the upper end of said casing coaxially therewith.

5. In a hydraulic pumping jack assembly including a cylinder, a piston reciprocating therein, said piston arranged to be raised by hydraulic pressure and lowered by the load on said jack, a reservoir for hydraulic fluid, and pressure creating means adapted continuously to deliver a stream of hydraulic fluid of constant volume; valve means comprising: a valve chamber rigidly aflixed to said cylinder; 9. cylinder port connecting said chamber with the lower end of said cylinder; an exhaust port connecting said chamber with said reservoir ;a pressure port connecting said chamber with said source of pressure fluid; a valve member within said chamber, said member having two independent passages within its body arranged to connect said cylinder port with said pressure port while closing said exhaust port and alternatively to connect both said cylinder port and said pressure port with said exhaust port, and means responsive to the movement of said piston to reciprocate said valve member a1- ternately to make said connections.

HERBERT M. SALENTIN E.

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