This application claims priority of U.S. provisional patent application serial no. 61/231,266 filed August 4, 2009 and hereby incorporates the same provisional application by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to reciprocating pumps and more particularly to downhole pumps for oil and gas wells. BACKGROUND OF THE INVENTION

Artificial lift methods play an important part in the oil and gas industry. With the higher costs to operate aging oil and gas wells producers, diminishing reserves of so called easy oil and gas, need for de-watering of the gas wells and development of new technologies such as Steam Assisted Gravity Drainage (SAGD) processes, the need for artificial lifting equipment is greater than ever.

Typical oil and gas wells can range in depth from approximately 200 ft to more than 20,000 ft and require pumps that are unique in their configuration and capabilities. The pumps must be placed downhole and therefore their outside dimensions are limited because they must fit within the casing of the well. Additionally, these pumps are installed as close as possible to the bottom of the well in order to achieve the maximum possible drawdown of often multiphase fluid in the well. The output pressure required of the pump varies directly with the depth that the fluid must be lifted. For example, to compensate for the lift required and the fluid friction in the tubing, a 10,000 ft well might require a 4,000 lb/in ² pump. Pumps that are currently used in the oil and gas industry include positive displacement pumps. These positive displacement pumps, in contrast to rotodynamic pumps, can pump gases as well as liquids so they are suitable for very high gas fractions. They can also give high discharge pressures. However, positive displacement pumps work with small clearances and so are more susceptible to sand and corrosion. These small clearances also affect their applicability in high temperature applications such as e.g. are Steam Assisted Gravity Drainage (SAGD) processes.

One type of positive displacement pump is the hydraulic reciprocating pump. Several prior art designs of hydraulic reciprocating pumps for multiphase fluids are available, including double acting, balanced-design and single acting pumps. Although, there is no standardization of design among the various manufacturers, and the various models are quite diverse, they typically have the same basic structure consisting of an engine piston and engine cylinder with an engine-reversing valve, along with a pump barrel and plunger. These are assembled into one unit, and a polished rod connects the engine piston and the engine-reversing valve to the pump plunger so the three reciprocate together. In all of these designs the engine module, engine-reversing valve module and the pump module are separated from each other, connected together by the polished rod. Thus, to increase the stroke of the pump it is necessary to increase not only the stroke of the engine but also to increase the stroke of the engine-reversing valve. As a result, to, increase the pumping rate of the pump by increasing its stroke by e.g. 1 foot, the overall length of the pump may have to be increased three-fold by 3 feet.

SUMMARY OF THE INVENTION

It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings wherein like reference numerals indicate similar parts throughout the several views, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:

Fig. 1 is a schematic illustration of a pump in a fast aspect;

Fig. 2 is a schematic illustration of the pump in Fig. 1 , during an intake stroke by a top piston;

Fig. 3 is a schematic illustration of the pump of Fig. 1, with .a reversing sleeve shifting while the top piston is at a bottom of an intake stroke;

Fig. 4 is a schematic illustration of the pump of Fig. 1 during a discharge stroke of the top piston;

Fig. 5 A is a top. schematic illustration of the pump of Fig. 1 in one aspect;

Fig. 5B is a bottom schematic illustration of the pump in Fig. 5 A;

Fig. 6 is a schematic illustration of a reversing device in a first aspect, to reverse the direction of the pistons in the pump;

Fig. 7 is a schematic illustration of the reversing device shown in Fig. 6, during operation of the reversing device;

Fig. 8 is a schematic illustration of reversing device shown in Fig. 6-with biasing devices to reset the reversing device after use;

Fig. 9 is a schematic illustration of a reversing device in a second aspect; Fig. 10 is a schematic illustration of the reversing device shown in Fig. 9, during the operation of the reversing device;

Fig. 11 is a schematic illustration of a reversing device in a third aspect;

Fig. 12 is a schematic illustration of the reversing device shown in Fig. 11, during the operation of the reversing device;

Fig. 13 is, a schematic illustration of a reversing device in a fourth aspect;

Fig. 14 is a schematic illustration of the reversing device shown in Fig. 13, during the operation of the reversing device;

Fig. 15 is a schematic illustration of a pump in a further aspect;

Fig 16 is a schematic illustration of the pump of Fig. 15, during a discharge stroke by a top piston;

Fig. 17 is a schematic illustration of the pump of Fig. 15, during a changing of direction of motion by the top piston;

Fig. 18 is a schematic illustration of the pump of Fig. 15, during a reversal of motion;

Fig. 19 is a schematic illustration of the pump of Fig. 15., during an intake stroke by the top piston;

Fig. 2OA is a schematic illustration of a pump being installed in a parallel free configuration;

Fig. 2OB is a schematic illustration of the pump in Fig. 2OA installed in place in the casing;

Fig. 2OC is a schematic illustration of the pump in Fig. 2OA being retrieved from the casing; Fig. 21A is a schematic illustration of a pump installed in a casing free configuration;

Fig. 21B is a schematic illustration of a pump installed in a further aspect of a casing free configuration;

Fig. 22 is a schematic illustration of a number of pumps configured in parallel to form a cluster;

Fig. 23 is a schematic illustration of a number of clusters of parallel pumps installed in a series;

Fig. 24 is a schematic illustration of a prior art reciprocating pump operating in a seal-less configuration;

Fig. 25 is a schematic illustration of centering mechanism;

Fig. 26 is a schematic illustration of a prior art reciprocating pump operating in a seal configuration;

Fig. 27 is a schematic illustration of a reciprocating pump operating in a seal configuration;

Fig. 28 is a schematic illustration of a porting mechanism of a pump having a groove;

Fig. 29 is a top view of the groove in Fig. 28;

Fig. 30 is a side view of the groove in Fig. 28;

Fig. 31 is a schematic illustration of a porting mechanism with a second port in an open position;

Fig. 32 is a schematic illustration of the porting mechanism of Fig. 31 with a sealing ring over a first port; and Fig. 33 is a schematic illustration of the porting mechanism of Fig. 31 with a first port in an open position.

DESCRIPTION OF VARIOUS EMBODIMENTS

Figs. 1-4 are schematic illustrations of a pump 1 with a first end 3 and a second end 4, in a first aspect. Pump 1 has an outer housing 2, with an inner housing

5 provided within the outer housing 2. The inner housing 1 contains a first compression chamber HA having a first piston 1OA and a second compression chamber 1 IB having a second piston 1OB. The first piston 1OA and the second piston

1OB are connected together with a connecting rod 7 so that the first piston 1OA and second piston 1OB are forced to move in conjunction by the connecting rod 7.

The outer housing 2 may be a bottom portion of the tubing or coiled tubing, i.e. the tailpipe, or may define a device connected to the tail pipe (or-other-lower point) of the wellbore string (not shown). In Figs. 1-4, the outer housing 2 is shown connected to a power fluid conduit 30 that supplies high-pressure power fluid to a power fluid supply conduit 24 that runs between the outer housing 1 and the inner housing 5 and supplies power fluid to drive the pump 1. The power fluid can be a gas or liquid.. A target fluid intake conduit 27 and a target fluid discharge conduit 22 are provided within the outer housing 2, but outside the inner housing 5. The target fluid intake conduit 27 is provided with an opening 21 at the second end 4 of the housing 3 so that it can be placed in contact with a target fluid to be moved with the pump 1 (e.g. formation fluid down a well bore the pump 1 is placed in). The target fluid intake conduit 27 directs target fluid from the opening 21 to the first compression chamber HA and second compression chamber 1 IB, where the target fluid will be drawn in by the first compression chamber HA and second compression chamber 1 IB, respectively, before it is discharged to a target fluid discharge conduit 22. Figs 5A and 5B are top and bottom schematic illustrations of the pump 1 in one aspect. The power fluid supply conduit 24, target fluid intake conduit 27 and target fluid conduit 22 are all defined by the annulus formed between the outer housing 2 and the inner housing 5. The annulus between the outer housing 2 and the inner housing 5 is divided into different sections by partitions 32 to form the power supply conduit 24, target fluid intake conduit 27 and target fluid conduit 22.

Referring again to Figs. 1-4, the first compression chamber HA is provided with an intake valve 15 A, between the target fluid intake conduit 27 and the first compression chamber 1 IA, and a discharge valve 14A, between the first compression chamber 1 IA and the target fluid discharge conduit 22. During an intake stroke of the first piston 1OA, with the first piston 1OA moving towards the second end 4 of the pump 1 (as shown in Fig. 1), the intake valve 15 A is open and the discharge valve 14A is closed causing target fluid from the target fluid intake conduit 27 to be drawn into the first compression chamber HA through the open intake valve 15 A. During a discharge stroke of the first piston 1OA, with the first piston 1OA moving towards the first end 3 of the pump 1 (as shown in Fig. 4), the discharge valve 14A is open and the intake valve 15A is closed, causing target fluid that was drawn into the first compression chamber 1 OA during the previous intake stroke of the first piston 1 OA to be discharged out the discharge valve 14A into the target fluid discharge conduit 22 where it will eventually exit the pump 1.

In a similar manner, the second compression chamber HB is also provided with an intake valve 15B, between the second compression chamber HB and the target fluid intake conduit 27, and a discharge valve 14B, between the second compression chamber HB and the target fluid discharge conduit 22. Through the opening and closing of the intake valve 15B and the discharge valve 14B, the second compression chamber 1 IB pumps target fluid. During an intake stroke of the second piston 1OB (as shown in Fig. 4), target fluid is drawn into the second compression chamber HB from the target fluid intake conduit 27 and then discharged from the second compression chamber 1 IB during a subsequent discharge stroke of the second piston 1OB (as- shown in Fig. 1), discharging the target fluid in the second compression chamber HB to the target fluid discharge conduit 22 where the target fluid will eventually exit the pump 1.

In this manner, both the first compression chamber 11A and second chamber 1 IB act to pump the target fluid with both the first piston 1OA and second piston 1OB acting as pumping pistons, drawing in and expelling target fluid in a reciprocating manner.

In an aspect, the intake valves 15 A, 15B and the discharge valves 14A, 14B are one-way valve ball valves that operate with pressure differentials. When the pressure of fluid in the first compression chamber HA is lower than the pressure of the target fluid in the target fluid intake conduit 27, by an amount sufficient to overcome a bias of the valve, the intake valve 15 A opens. When the pressure of the fluid in the first compression chamber 1 IA is greater than the pressure in the target fluid discharge conduit 22, by an amount sufficient to overcome the bias of the valve, the discharge valve 14A opens. Similarly, when the pressure of fluid in the second compression chamber HB is lower than the pressure of the target fluid in the target fluid intake conduit 27 by an amount to overcome a bias of the valve, the intake valve 15B opens and when the pressure of the fluid in the second compression chamber HB is greater than the pressure in the target fluid discharge conduit 22 by an amount to overcome a bias of the valve, the discharge valve 14B opens. In addition to the first piston 1OA and second piston 1OB operating as pumping pistons, the first piston 1OA and second piston 1OB also operate as engine pistons to drive the pump 1. A first chamber 12A is provided adjacent to the first piston 1OA on an opposite side of the first piston 1OA from the first compression chamber 1 IA. A second chamber 12B is provided adjacent the second piston 1OB on an opposite side of the second piston 1OB from the second compression chamber 1 IB. By introducing power fluid into the first chamber 12A, the power fluid acts on the first piston 1 OA, on an opposite side of the first piston 1 OA from the first compression chamber HA, driving the first piston 1OA in a discharge stroke. By introducing power fluid into the second chamber 12B, the power fluid acts on the second piston 1OB, on an opposite side of the second piston 1OB from the second compression chamber 1 IB, driving the second piston 1OB in a discharge stroke.

By altering the size of the connecting rod 7 and thereby the volume of the first chamber 12A and second chamber 12, the operating parameters, such as pumping output can be altered. The change in outside diameter dimension of the connecting rod 7 has an effect on the ratio of the supplied power fluid to the volume of discharged target fluid and the power fluid pressure requirements.

A reversing sleeve 6 is provided, slidably mounted in the inner housing 5 between the first piston 1OA and the second piston 1OB with a bumper 29 provided to limit the range of motion of the reversing sleeve 6. The reversing sleeve 6 operates to reverse the direction of motion of the first piston 1OA and second piston 1OB when the first piston 1OA and second piston 1OB are at the end of either an intake stroke or a discharge stroke. The reversing sleeve 6 separates the first chamber 12A and the second chamber 112B. Through the positioning of the reversing sleeve 6, power fluid is routed into either the first chamber 12A or the second chamber 12B to drive the pump 1. With power fluid being directed into the first chamber 12A the first piston 1OA is driven through a discharge stroke, as shown in Fig. 4. With power fluid directed to the second chamber 12B, the second piston 1OB is driven through a discharge stroke, as shown in Fig. 1. Because the first piston 1OA and second piston 1OB are connected by the connecting rod 7, when the first piston 1OA is driven through a discharge stroke towards the first end 3 of the pump 1 , the connecting rod 7 pulls the second piston 1OB through an intake stroke and when the second piston 1OB is driven through a discharge stroke by the power fluid, the connecting rod 7 pulls the first piston 1OA through an intake stroke.

Power fluid is introduced to the first chamber 12A through a power fluid inlet port 8A passing into the power fluid supply conduit 24 and to the second chamber

1OB through a second power fluid inlet port 8B passing into the power fluid supply conduit 24. Both the first housing inlet port 8A and the second housing inlet port 8B, passing through the inner housing 5.

A first housing exhaust port 9A and a second housing exhaust port 9A are provided passing through the inner housing 5 to the target fluid discharge conduit 22 where fluid vented from the first chamber 12A and second chamber 12B, respectively, will mix with the target fluid being discharged from the pump 1 , although a person skilled in the art will appreciate that a separate exhaust fluid conduit could be used to keep vented exhaust fluid from co-mingling with the target fluid being moved by the pump 1.

A first reversing sleeve exhaust port 19A is provided in the reversing sleeve 6, positioned so that when the reversing sleeve 6 has been moved towards the first piston 1OA, during an intake stroke of the first piston 1OA (as shown in Fig. 1), the first reversing sleeve exhaust port 19A aligns with the first housing exhaust port 9A causing the first chamber 12A to be in fluid communication with the target fluid discharge conduit 22, venting fluid from the first chamber 12A to the target fluid discharge conduit 22, where the vented fluid will commingle with the target fluid being discharged from the pump 1. The second chamber 12B is vented with a second reversing sleeve exhaust port 19B provided in the reversing sleeve 6 and positioned so that second reversing sleeve exhaust port 19B aligns with a second housing exhaust port 9B, in fluid communication with the target fluid discharge conduit 22, when the second piston 1OB is in an intake stroke, as shown in Fig. 4.

Referring to Fig. 1, during a discharge stroke of the second piston 1OB, the reversing sleeve 6 has been moved towards the first end 3 of the pump 1 until the reversing sleeve 6 has been stopped by the bumper 29. In this position, the reversing sleeve 6 is exposing the second power fluid inlet port 8B placing the second chamber 12B in fluid communication with the power fluid supply conduit 24, allowing power fluid to enter the second chamber 12B. At the same time, the reversing sleeve 6 is blocking the second housing exhaust port 9B, preventing fluid in the second chamber 12B from being vented to the target fluid discharge conduit 22. The power fluid being introduced into the second chamber 12B, from the power fluid supply conduit 24, through the second power fluid intake port 8B, drives the second piston 1OB through the discharge stroke causing the second compression chamber 11 B to discharge target fluid from the second compression chamber HB through the discharge valve 14B into the target fluid discharge conduit 22.

At the same time the second 1OB is traveling through the discharge stroke, the first piston 1OA is being pulled through an intake stroke by the connecting rod 7. During the intake stroke of the first piston 1 OA, the reversing sleeve 6 blocks the first power fluid inlet port 8 A in the inner housing 5, preventing power fluid from entering the first chamber 12A from the power fluid supply conduit 24. At the same time, the first power fluid inlet port 8A is being blocked by the reversing sleeve 6, the first reversing sleeve exhaust port 19A is aligned with the first housing exhaust port 9 A allowing fluid in the first chamber 12A to be vented from the first chamber 12A, as the first piston 1 OA travels through the intake stroke, decreasing the size of the first chamber 12A and displacing fluid in the first chamber 12A out through the first reversing sleeve exhaust port 19A and the first housing exhaust port 9A, where the fluid will be discharged into the target fluid discharge conduit 22 to co-mingle with the discharged target fluid. As the first piston 1OA moves through an intake stroke, target fluid is drawn through the inlet valve 15 A from the target fluid intake conduit 27 into the first compression chamber 1 IA.

Referring to Fig. 4, during a discharge stroke of the first piston 1OA, the reversing sleeve 6 has been moved towards the second end 4 of the pump 1 until the reversing sleeve 6 has been stopped by the bumper 29. In this position, the reversing sleeve 6 is exposing the first power fluid intake port 8A, placing the first chamber 12A in fluid communication with the power fluid supply conduit 24, while at the same time blocking the first housing exhaust port 9A and preventing the venting of fluid from the first chamber 12A. The high-pressure power fluid being introduced into the first chamber 12A from the power fluid supply conduit 24, through the first power fluid intake port 8 A, drives the first piston 1OA through a discharge stroke causing the first compression chamber HA to discharge target fluid through the discharge valve 14A to the target fluid discharge conduit 22. At the same time, the first piston 1OA is traveling through the discharge stroke; the second piston 1OB is being pulled through an intake stroke by the connecting rod 7. The reversing sleeve 6 is blocking the second power fluid inlet port 8B in the inner housing 5, preventing power fluid from entering the second chamber 12B and the second reversing sleeve exhaust port 19B is aligned with the second housing exhaust port 9B allowing fluid in the second chamber 12B to be vented as the second piston 1OB is pulled along the intake stroke by the first piston 1OA, decreasing the size of the second chamber 12A and displacing fluid in the second chamber 12A out through the second reversing sleeve exhaust port 19B and the second housing exhaust port 9B, where the fluid is exhausted to the target fluid discharge conduit 22 to co-mingle wit the target fluid being discharged. The intake stroke of the second piston 1OB draws target fluid from the target fluid inlet conduit 27 through the intake valve 15B into the second compression chamber 1 OB which will later be expelled by a subsequent discharge stroke of the second piston 1OB.

When the first piston 1 OA and second piston 1 OB have reached the end of an intake stroke/discharge stroke or discharge stroke/intake stroke, the direction of motion of the first piston 1 OA and the second piston 1 OB must be reversed so that the pump 1 continues to operate. The reversing sleeve 6 is moved so that it reverses the direction of motion of the first piston 1OA and the second piston 1OB. To instigate the movement of the reversing sleeve 6, a first reversing device 4OA and a second reversing device 4OB are provided to shift the reversing sleeve 6.

The first piston 1OA and the second piston 1OB have a first boss 54A and a second boss 54B, respectively. The first boss 54 A is provided on the first piston 1OA extending into the first chamber 12A. The first boss 54A and a first end 6OA of the reversing sleeve 6 are sized so that an outer surface 58A of the first boss 54A mates with an inner surface 55 A of the first end 6OA of the reversing sleeve 6 as the first piston 1 OA approaches the a bottom of an intake stroke.

Fig. 2 illustrates the first piston 1OA approaching the bottom of an intake stroke. The mating of the outer surface 58A of the first boss 54A with the inner surface 55A of the first end 6OA of the reversing sleeve 6 partitions the first chamber 12A into a first boss annulus 16A and a first sleeve annulus 17A. To reverse the direction of the pump 1 , the first reversing device 4OA increases the pressure of the fluid in the first boss annulus 16A, forcing the sleeve 6 towards the second end 4 of the piston 1, until the reversing sleeve 6 is stopped by the bumper 29, as shown in Fig. 3. With the sleeve 6 moved towards the second end 4 of the pump 1 until the reversing sleeve 6 has contacted the bumper 29, power fluid begins to enter the first chamber 12A because the reversing sleeve 6 has uncovered the first power fluid inlet port 8 A, with the power fluid initially entering the first boss annulus 16 A. At the same time the shifted reversing sleeve 6 is allowing power fluid to enter the first chamber 12A, fluid in the second chamber 12B is exhausted through the aligned second exhaust port 19B and second housing exhaust port 9B. This reverses the direction of motion of the first piston 1OA and the second piston 1OB, causing the first piston 1OA to travel through a discharge stroke while the second piston 1OB travels through an intake stroke.

In a similar manner, the second boss 54B on the second piston 1OB extends into the second chamber 12B. The second boss 54B and the second end 6OB of the reversing sleeve 6 are sized so that an outer surface 58B of the first boss 54A mates with an inner surface 55B of the reversing sleeve 6 as the second piston 1OB approaches a bottom of an intake stroke partitioning the second chamber 12B into a second boss annulus and a first sleeve annulus. To reverse the direction of the pump 1 when the second piston 1 OB has reached the end of an intake stroke, the second reversing device 4OA operates in the same manner as the first reversing device 4OB, increasing the pressure of the fluid in the second boss annulus 16B and in turn forcing the reversing sleeve 6 towards the first end 3 of the pump 1 , until the reversing sleeve 6 is stopped by the bumper 29. In this position, the second chamber 12B is placed in fluid communication with the power fluid supply conduit 24, while the first chamber 12A is exhausted, driving the second piston 1OB into a discharge stroke while the first piston 1OA is pulled through an intake stroke.

First reversing device 4OA and second reversing device 4OB are housed in opposite ends of the connecting rod 7 and operate independently from each other, so that there is no communication between the first reversing device 4OA and the second reversing device 4OB. In this manner, the connecting rod 7 can be extended to any practical length to extend the strokes of the first piston 1OA and the second piston

1OB, without impacting the performance of the first reversing device 4OA and the second reversing device 4OB. This allows the length of the stroke to be set to meet the applications requirements, e.g. to prevent gas locking.

The operating temperature of the pump 1 can be altered based on the temperature of the power fluid being provided to the pump 1. Because the power fluid comes in contact with both the first piston 1OA and second piston 1OB, the temperature of the power fluid can affect a substantial portion of the pump 1.

Figs. 6 and 7 illustrate an implementation of the first reversing device 4OA, in one »aspect. Although only the first reversing device 4OA is illustrated, second reversing device 4OB is substantially the same as first reversing device 4OA and operates in the same manner on the second boss annulus 16B. A person skilled in the art will be able to readily duplicate the operation of first reversing device 4OA in implementing the second reversing device 4OB.

In this aspect of the first reversing device 4OA, hydraulic multiplication is used to boot the pressure of the fluid in the first boss annulus 16A. This increased pressure of the fluid in the first boss annulus 16A acts on a first end 6OA of the reversing sleeve 6, shifting the reversing sleeve 6 and reversing the direction of motion of the first piston 1 OA and the second piston 1 OB at the bottom of an intake stroke of the first piston 1OA.

A booster 128 is provided in a booster chamber 132 in the connecting rod 7. On an end of the booster 128, proximate the first piston 1OA, is a booster small piston 135 and on an other end of the booster 128 is a booster large piston 134. The booster small piston 135 defines a small piston chamber 148 located in the connecting rod 7 and having a booster chamber passage 155 placing the small piston chamber 148 in fluid communication with the first boss annulus 16A when the first piston 1OA has partitioned the first chamber 12A into the first boss annulus 16A and the first sleeve annulus 17A. A booster passage 136 is also provided passing through the booster small piston 135 and the booster 128 and ending in the booster chamber 132. The booster passage 136 places the small piston chamber 148 in fluid communication with the booster chamber 32 and the first chamber 12A through an internal vent port 50, when the first, piston 1OA is not at a bottom of an intake stroke, and therefore allowing fluid in the first boss annulus 16A and the small piston chamber 148 to be vented.

The booster big piston 134 defines a big piston chamber 147 on one side of the booster big piston 134 and the booster chamber 132 on an other side of the booster big piston 134. The internal vent port 50 places the booster chamber 132 in fluid communication with the first chamber 12A and the first sleeve annulus 17A when the first piston 1OA is partitioning the first chamber 12A into the first boss annulus 16A and the first sleeve annulus 17A.

A pilot port 137 and a high-flow port 138 are provided passing into the connecting rod 7 and into the big piston chamber 147. A high-flow valve 129 is placed at the end of the high-flow port 138, blocking the high-flow port 128 when the high-flow valve 129 is not open.

Referring to Fig. 6, before the first reversing device 4OA is in operation, the booster large piston 134 rests against a ridge 133 and the high-flow valve 129 is blocking the entry of power fluid from the second chamber 12B through the high-flow port 138. A booster large piston annulus 145 is defined by the booster large piston

134 and the ridge 133, which the pilot port 137 opens into.

As the first piston 1 OA travels towards a bottom of an intake stroke, the first chamber 12 A becomes partitioned into the first boss annulus 16A and the first sleeve annulus 17A. Fluid in the first sleeve annulus 17A is vented from the first sleeve annulus 17A through the first reversing sleeve exhaust port 19A and the first exhaust housing port 9B as the first sleeve annulus 17A decreases in volume. Fluid in the first boss annulus 16A is also being vented as the volume of the first boss annulus 16A decreases. The fluid in the boss annulus 16A is vented by passing into the small piston chamber 148 through the booster chamber passage 155 and then to the first sleeve annulus 17A through the booster passage 136, where it is vented through the first reversing sleeve exhaust port 19A and the first housing exhaust port 9A from the first sleeve annulus 17A.

Meanwhile, as the first piston 1OA reaches a bottom of an intake stroke, the high-flow port 138 exits the reversing sleeve 6 and passes into the second chamber 12B coming into contact with high-pressure power fluid in the second chamber 12B. However, the high-flow valve 129 initially prevents the power fluid from entering the big piston chamber 147 through the high- flow port 138. As the first piston 1OA continues toward the bottom of the intake stroke, the pilot port 137 passes out of the reversing sleeve 6 and becomes exposed to the high-pressure power fluid in the second chamber 12B. Some of this power fluid enters the pilot port 137 where it is directed to the booster large piston annulus 145, formed between the booster big piston 134 and the ridge 133. In the booster large piston annulus 145, the power fluid acts against the booster large piston 134, forcing the booster large piston 134 away from the ridge 133. With the booster large piston 134 forced away from the ridge

133, the power fluid can pass by the ridge 133 and come into contact with a top surface 131 of the high-flow valve 129, moving the high-flow valve 129 downwards until the high-flow valve 129 contacts a high-flow valve bumper 130, exposing the high-flow port 138 to the booster big piston 147. With the high-flow port 138 opened, power fluid from the second chamber 12B gains entry into the big piston chamber 147 through the high-flow port 138 and acts against the booster big piston

134. The pressure of the power fluid against the booster large piston 134 forces the booster large piston 134 upwards and, in conjunction, the booster small piston 135 upwards.

Referring to Fig. 7, as the booster small piston 135 and the booster large piston

134 move upwards, propelled by the high-pressure power fluid acting on the booster large piston 134, the booster passage 136 becomes cut off from the booster chamber 132 and therefore the sleeve annulus 17A, preventing fluid in the first boss annulus 16A and the small piston chamber 148 from being vented. As the booster small piston 135 continues to move upwards, pushed by the booster large piston 134, the volume of the small piston chamber 148 is decreased.

Because the booster passage 136 is now blocked from communicating with the first reversing sleeve annulus 17 A, the fluid in the small piston chamber 148 is displaced through the booster chamber passage 155 and into the first boss annulus 16 A, as the small piston chamber 148 decreases in volume. The displaced fluid from the small piston chamber 148 applies a force to a top surface 61 A of the first end 6OA of the reversing sleeve 6, shifting the reversing sleeve 6 towards the second end 4 of the pump 1 until the reversing sleeve 6 contacts the bumper 29, preventing the reversing sleeve 6 from moving any further.

The differential in the surface area of the booster large piston 134 and the surface area of the booster small piston 135 causes the resultant pressure in the small piston chamber 148 to be greater than the pressure of the power fluid supplied to the pump 1. This higher pressure of the fluid in the first boss annulus 16A acting against the reversing sleeve 6 overcomes the force of the lower pressure power fluid acting against the reversing sleeve 6 in the opposite direction, resulting in the reversing sleeve 6 shifting away from the first boss annulus 16A and into the second chamber 12B. The increase in pressure generated in the small piston chamber 148 by the booster 128 must be sufficiently greater than the pressure of the power fluid to overcome the force applied on the reversing sleeve 6 by the power fluid in the second chamber 12B and cause the reversing sleeve 6 to shift towards second end 4 of the pump 1. The desired pressure magnification can be achieved by the appropriate surface area ratio between the booster large piston 134 and booster small piston 135.

With the reversing sleeve 6 moved towards the second end 4 of the pump 1 until the reversing sleeve 6 has contacted the bumper 29, the second reversing sleeve exhaust - port 19B becomes aligned with the second housing exhaust port 9B and the second power fluid intake port 8B becomes blocked by the reversing sleeve 6, as shown in Fig. 7. With the second power fluid intake port 8B blocked, power fluid no longer enters the second chamber 12B and, in turn, no longer enters the large piston chamber 145 through the high- flow port 138. With the reversing sleeve 6 in this position, the first inlet port 8 A is once again exposed to the first chamber 12A, initially to the first boss annulus 16A. The power fluid entering into the first boss annulus 16A passes into the small piston chamber 148 through the booster chamber passage 155. This power fluid then acts on the booster small piston 135 forcing it towards the second piston 1OB - which in turn forces the booster large piston 134 towards the second piston 1OB, until the booster large piston contacts the ridge 133.

Fig. 8 illustrates the first reversing device 4OA with a number of biasing devices to reset the booster 128 after the reversing sleeve 6 has been shifted and the direction of motion of the first piston 1OA and the second piston 1OB reversed. A boost return biasing device 241 and flow valve return biasing device 242 are used to reset the booster 128. The boost return biasing device 241 biases the booster 128 towards the second piston 1OB and in one aspect is a spring. The flow valve return biasing device 242 biases the high-flow valve 129 towards the ridge 133 and in one aspect is a spring. When high-pressure power fluid is acting on the booster big piston 134 and the top surface 131 of the high-flow valve 129, the force imposed on the booster 128 and the high-flow valve 129 overcome the biasing force imposed by the boost return biasing device 241 and the flow valve return biasing device 242, respectively. However, when the high-pressure power fluid is no longer acting on the booster big piston 134 and the high flow valve 129 because the reversing sleeve 6 has shifted reversing the direction of the first piston 1OA and second piston 1OB, the boost return biasing device 241 and the flow valve return biasing device 242 place force on the booster 128 and high-flow valve 129, respectively, resetting the booster 128 and the high-flow valve 129 back to their initial positions.

In an aspect, a bumper shock auxiliary device 243 is provided between the first piston 1OA and the reversing sleeve 6 to decrease the shock between the first piston 1OA and the reversing sleeve 6 at the bottom of an intake stroke of the first piston 1OA. In one aspect, the bumper shock auxiliary device 243 could be a spring.

Referring to Figs. 9 and 10, in a further aspect of the first reversing device 4OA, hydraulic amplification is used and in shifting the reversing sleeve 6. In some applications the booster 128 alone may be insufficient to shift the reversing sleeve 6 and create the reciprocating motion of the pump 1, (e.g. dimensional restrictions). In a further aspect, the first reversing device 4OA comprises a high-pressure chamber 344 and a low-pressure chamber 345 in addition to the booster 128.

Although Figs. 9 and 10 illustrate only the first reversing device 4OA, second reversing device 4OA can be implemented in substantially the same manner as the first reversing device 40, operating in the same manner on the second boss annulus

16B. A person skilled in the art will be able to readily duplicate the operation of the first reversing device 4OA in implementing the second reversing device 4OB.

The booster 128 works as previously described to increase the pressure in the small piston chamber 148, which in turn increases the pressure of the fluid in the first boss annulus 16A acting against the top surface 61 A of the first end 6OA of the reversing sleeve 6. Additionally, the high-pressure chamber 344 is provided with the bumper 29 providing one side of the high-pressure chamber 344, while the reversing sleeve 6 provides another. A high-pressure passage 350 passes through the reversing sleeve 6 and into the high-pressure chamber 344. A high-pressure internal passage 352 connects with the pilot port 137. The high-pressure passage 350 and the high- pressure internal passage 352 are arranged so that high-pressure chamber 344 is in fluid communication with the pilot port 137.

The low-pressure port 345 is in fluid communication with a low-pressure passage 360 and a low-pressure internal passage 362 is provided in the reversing sleeve 6 venting into the first chamber 12A. The low-pressure passage 360 and the low-pressure internal passage 362 are arranged so that the low-pressure passage 360 and the low-pressure internal passage 362 align when the first piston 1OA is near a bottom of an intake stroke; causing the low-pressure chamber 345 to be in fluid communication with the target fluid discharge conduit 22 through the first chamber

12A.

Referring to Fig. 9, when the first piston 1OA nears a bottom of an intake stroke and the pilot port 137 becomes exposed to the high-pressure power fluid in the second chamber 12B, high-pressure power fluid enters the connecting rod 7 through the pilot port 137, where some of the high-pressure power fluid is directed to the booster large piston annulus 145, starting the booster big piston 134 moving towards the first end 3 of the pump 1 and some of the high-pressure power fluid is directed through the high-pressure passage 350 and the high-pressure internal passage 352 to the high-pressure chamber 344. In the high-pressure chamber 344 the high-pressure power fluid acts on the reversing sleeve 6 forcing it away from the bumper 29 and towards the second end 4 of the pump 1 , increasing the volume of the high-pressure chamber 344. At the same time, fluid in the low-pressure chamber 345 is in fluid communication with the target fluid discharge conduit 22 where it can be exhausted from the pump 1. The fluid in the low-pressure chamber 345 can exit the low- pressure chamber 345 through the first chamber 12A. As high-pressure power fluid continues to be introduced to the high-pressure chamber 344 forcing the reversing sleeve 6 towards the second end 4 of the pump 1, fluid escaping from the low pressure chamber 345 allows the low pressure chamber 345 to decrease in volume.

The force exerted on the reversing sleeve 6 by the high-pressure chamber 344 acts in conjunction with the force placed on the top surface 61 A of the first end 6OA of the reversing sleeve 6 by the operation of the booster 128 increasing the pressure of the fluid in the first boss annulus 16A. As a result of these forces, the reversing sleeve 6 shifts towards the second piston 1OB, until the reversing sleeve 6 contacts the bumper 29 (as shown in Fig. 10), blocking the second inlet port 8B and preventing power fluid from entering the second chamber 12B, while at the same time exposing the first inlet port 8A, allowing power fluid to be introduced into the first boss annulus 16A and subsequently the entire first chamber 12A as the first boss 54A moves out of the first end 6OA of the reversing sleeve 6, as the first piston 1OA moves through a discharge stroke. At the same time, the shifting of the reversing sleeve 6 causes the second chamber 12B to be vented to the target fluid discharge conduit 22, allowing fluid to exit the second chamber 12B, while the first housing exhaust port 9A is blocked from the first chamber 12A, preventing fluid in the first chamber 12A from escaping.

The high-pressure chamber 344 and low-pressure chamber 345 will not have to be reset, because the reversing sleeve 6 will be shifted back into the initial position shown in Fig. 9 by the operation of the second reversing device 4OB and the movement of the reversing sleeve 6 at the end of the discharge stroke of the first piston 1OA. The booster 128 will be reset as described above, with the aid of the boost return biasing device 241 and the flow valve return biasing device 242. Referring to Figs. 11 and 12, in a further aspect of the first reversing device 4OA a pressure equalization spool 432 is provided in the connecting rod 7 that works in conjunction with the high-pressure chamber 344 and low-pressure chamber 345 to shift the reversing sleeve 6, changing the direction of motion of the first piston 1 OA and second piston 1OB. The pressure equalization spool 432 has a central passage 410, a pressure equalization shutter 452, a pressure equalization piston 451 and a pressure equalization port 449. Although only the first reversing device 4OA is illustrated in Figs. 9 and 10, second reversing device 4OA is substantially the same as first reversing device 40 and operates in the same manner on the second boss annulus 16B. A person skilled in the art will be able to readily duplicate the operation of first reversing device 4OA in implementing the second reversing device 4OB.

A venting passage 455 places the first boss annulus 16A in fluid communication with the central passage 410 of the pressure equalization spool 432, which is initially vented to the target fluid discharge conduit 22 through the internal vent port 50, the first chamber 12A and the first reversing sleeve exhaust port 19A and the first exhaust housing port 9 A during an intake stroke of the first piston 1OA. Initially, the high-pressure chamber 444 is isolated from the central passage 410 because it is blocked by the pressure equalization spool 432. The low-pressure chamber 345 is in fluid connection with the internal vent port 50 which places the low-pressure chamber 345 in fluid communication with the target fluid discharge conduit 22 through the first reversing sleeve exhaust port 19A and the first exhaust housing port 9B during an intake stroke of the first piston 1OA.

As the first piston 1OA continues through the discharge stroke, the high-flow port 138 in the connecting rod 7 passes into the second chamber 12B. Initially, the high-flow port 138 remains closed because of equalized pressure across the pressure equalization shutter 452.

Referring to Fig. 11, when the pilot port 137 passes out of the reversing sleeve 6 into the second chamber 12B, the pilot port 137 comes into contact with the high- pressure power fluid in the second chamber 12B. Some of this high-pressure power fluid in the second chamber 12B enters the pilot port 137, where it acts on the pressure equalization piston 451 forcing the pressure equalization spool 432 towards the first piston 1 OA.

Referring to Fig. 12, as the pressure equalization spool 432 is moved towards the first piston 1 OA, a number of things occur: the pressure equalization shutter 452 uncovers the high-flow port 138; the pressure equalization port 449 aligns with the high-pressure internal passage 352 and the high-pressure passage 350 leading to the high-pressure chamber 344; and, the equalization spool 432 covers the internal vent port 50.

By uncovering the high-flow port 138, the pressure equalization shutter 452 allows high-pressure power fluid to enter the central passage 410. From the central passage 410, the power fluid can enter the first boss annulus 16A through the venting passage 455 and the high-pressure chamber 344, however, the power fluid in the central passage 410 can not exit through the internal vent port 50 because the internal vent port 50 is now blocked by the pressure equalization spool 432.

The reversing sleeve 6 is shifted towards the second piston 1 OB through forces exerted on the top surface 61 A of the first end 60A of the reversing sleeve 6 and the pressure exerted by the power fluid in the high-pressure chamber 344. Power fluid routed to first boss annulus 16A acts on the top surface 61 A of the first end 6OA of the reversing sleeve 6 placing a force, in the direction of the second piston 1OB, on the reversing sleeve 6. Power fluid entering the high-pressure chamber 344 helps shift the reversing sleeve 6 towards the second piston 1OB. Because the low-pressure chamber 345 is in fluid communication with the target fluid discharge conduit 22 through the internal vent port 50, the first chamber 12A, the first reversing sleeve exhaust port 19A and the first exhaust housing port 9A, the low-pressure chamber 345 decreases in volume allowing the increase in volume of the high-pressure chamber 344 driven by the power fluid. The expansion of the high-pressure chamber 344 causes the reversing sleeve 6 to shift towards the second end 4 of the pump 1.

Referring to Fig. 12, when the reversing sleeve 6 has been shifted towards the second end 4 of the pump 1 until the reversing sleeve 6 has contacted the bumper 29, the power fluid inlet port 8B is cut off from the second chamber 10 preventing additional high-pressure power fluid from entering the second chamber 10 and thereby the central passage 410 through the high-flow port 138 and preventing a force acting on the pressure equalization piston 451, forcing it towards the first end 3 of the pump 1. With the pressure equalization spool 432 no longer being forced towards the first piston 1OA, a pressure equalization bias device 431 resets the pressure equalization spool 432 by returning the pressure equalization spool 432 to its initial position (as shown in Fig. 11). In one aspect, the pressure equalization bias device can be a spring. In the embodiment of the first reversing device 4OA shown in Figs. 13 and 14, the pressure of the fluid in the first boss annulus 16A acting on a top surface 61 A of the first end 6OA of the reversing sleeve 6 is equal to the pressure of the power fluid, because the power fluid is allowed to pass directly into the first boss annulus 16A from the central passage 410 through the venting passage 455. In the embodiment of the first reversing device 4OA shown in Figs. 13 and 14, a plunger equalization spool 532 is provided. The plunger equalization spool 532 has a central passage 510, a plunger 553, a pressure equalization shutter 552, a pressure equalization piston 551 and a pressure equalization port 549.

Although only the first reversing device 4OA is illustrated in Fig. 13 and 14, the second reversing device 4OA is substantially the same as first reversing device

4OA and operates in the same manner on the second boss annulus 16B. A person skilled in the art will be able to readily duplicate the operation of first reversing device 4OA in implementing the second reversing device 4OB.

Similar to the aspect of the first reversing device 4OA shown in Figs. 12 and 13, initially the high-pressure chamber 344 is isolated from the central passage 510 because it is blocked by the plunger equalization spool 532. The low-pressure chamber 345 is in fluid connection with the internal vent port 50 which places the low-pressure chamber 445 in fluid communication with the target fluid discharge conduit 22 through the first reversing sleeve exhaust port 19A and the first exhaust housing port 9A during an intake stroke of the first piston 4A.

The plunger equalization spool 532 has a plunger 553 provided with the plunger 553 defining a plunger chamber 548. A venting passage 555 places the first boss annulus 16A in fluid communication with the plunger chamber 548. The plunger chamber 548 is initially vented to the first chamber 12A through an internal plunger passage 536, the internal vent port 50, the first chamber 12A and the first reversing sleeve exhaust port 19A and the first exhaust housing port 9 A during an intake stroke of the first piston 1OA.

In operation, as the first piston 1OA approaches a bottom end of an intake stroke, the first chamber 12A is partitioned into the first boss annulus 16A and the first sleeve annulus 17A. When this first occurs, fluid displaced from the first sleeve annulus 17A can initially be exhausted from the plunger chamber 548 through the internal plunger passage 536 and eventually through the first chamber 12A to the target fluid discharge conduit 22.

As the first piston 1OA continues to travel along towards the bottom end of the intake stroke, the high flow port 138 in the connecting rod 7 passes into the second chamber 12B. Initially, the high flow port 138 remains closed because of equalized pressure across the pressure equalization shutter 552. As the first piston 1OA continues through the intake stroke, the pilot port 137 passes out of the reversing sleeve 6 into the second chamber 12B coming into contact with the high-pressure power fluid in the second chamber 12B. Some of this high-pressure power fluid in the second chamber 12B enters the pilot port 137 where it acts on the pressure equalization piston 551 forcing the plunger equalization spool 532 towards the first piston 1OA. As the plunger equalization spool 532 moves towards the first piston 1OA, the pressure equalization shutter 552 uncovers the high-flow port 138 and the pressure equalization port 549 aligns with high-pressure passage 352 and the high- pressure internal passage 350 leading to the high-pressure chamber 344.

By uncovering the high-flow port 138, the pressure equalization shutter 552 allows high-pressure power fluid to enter the central passage 510. With high-pressure power fluid entering the central passage 510, the power fluid acts on the plunger 553, moving the plunger 553 towards the first piston 1OA. As the plunger 553 moves towards the first piston 1OA, the plunger passage 553 is blocked from the first chamber 12A preventing fluid in the plunger passage 553 from being exhausted to the target fluid discharge conduit 22. The decreasing volume of the plunger chamber 548 as the plunger 553 is moved towards the first piston 1OA displaces fluid out of the plunger chamber 548 through the venting passage 555 and into the first boss annulus 16 A where the pressure of this fluid will act on the top surface 61 A of the first end 6OA of the reversing sleeve 6 creating a force on the first end 6OA of the reversing sleeve 6 towards the second end 4 of the pump 1.

The force of the fluid, pressurized by the plunger 532, on the top surface 61 A of the first end 6OA of the reversing sleeve 6, in conjunction with the force excited on the reversing sleeve 6by power fluid entering the high-pressure chamber 344, shifts the reversing sleeve 6 towards the second piston 1OB, reversing the direction of motion of the first piston 1OA and the second piston 1OB.

Referring to Fig. 14, when the reversing sleeve 6 has been shifted towards the second piston 1OB until the reversing sleeve 6 has contacted the bumper 29, the second housing inlet port 8B is cut off from the second chamber 12B preventing additional high-pressure power fluid from entering the second chamber 12B and thereby the central passage 510 through the high flow port 138. With the plunger equalization spool 532 no longer being forced towards the first piston 1OA, a pressure equalization return biasing device 531 is used to reset the plunger equalization spool

532 by returning it to its initial position (as shown in Fig. 13). In one aspect, the pressure equalization return biasing device 531 can be a spring.

The size of the plunger 535 in comparison to the central passage 510 causes a resultant pressure magnification in the fluid in the plunger compression chamber 548 as power fluid acting in the central passage 510 moves the plunger 535 towards the first piston 1OA. This higher pressure of the fluid in the first boss annulus b6A acting against the reversing sleeve 6, in conjunction with the force acting on the reversing sleeve by the power fluid in the high-pressure chamber 344, overcomes the force of the lower pressure power fluid acting against the reversing sleeve 6 in the opposite direction, resulting in the reversing sleeve 6 shifting towards the second end 4 of the pump 1. The desired pressure magnification can be achieved by the sizing of the plunger 553 in relation to the central passage 510.

Figs. 15-19 are schematic illustrations of a pump 601 in a further aspect.

Pump 601 has a first end 603, a second end 604, an outer housing 602, and an inner housing 605 provided within the outer housing 602. The inner housing 605 contains a first compression chamber 61 IA having a first piston 610A and a second compression chamber 61 IB having a second piston 610B. The first piston 610A and the second piston 610B are connected together with a connecting rod 607 so that the first piston

610A and second piston 610B are forced to move in conjunction by the connecting rod 607.

The outer housing 602 maybe a bottom portion of the tubing or coiled tubing, i.e. the tailpipe, or may define a device connected to the tail pipe (or other lower point) of the wellbore string (not shown). In Figs. 15-19, the outer housing 602 is shown with a power fluid supply conduit 624 that runs between the outer housing 601 and the inner housing 605 and supplies power fluid to drive the pump 601. A target fluid intake conduit 627 and a target fluid discharge conduit 622 are provided within the outer housing 602, but outside the inner housing 605. The target fluid intake conduit 627 is provided with an opening 621 at the second end 604 of the pump 601 so that it can be placed in contact with a target fluid to be moved with the pump 601 (e.g. formation fluid down a well bore the pump 1 is placed in). The target fluid intake conduit 627 directs target fluid from the opening 621 to the first compression chamber 61 IA and second compression chamber 61 IB, where the target fluid will be drawn in by the first compression chamber 61 IA and second compression chamber 61 IB, respectively, before it is discharged to the target fluid discharge conduit 622. The first compression chamber 61 IA is provided with an intake valve 615A, between the target fluid intake conduit 627 and the first compression chamber 61 IA, and a discharge valve 614A, between the first compression chamber 61 IA and the target fluid discharge conduit 622. During a discharge stroke of the first piston 610A, with the first piston 610A moving towards the first end 603 of the pump 601 (as shown in Fig. 15), the discharge valve 614A is open and the intake valve 615 A is closed, causing target fluid that was drawn into the first compression chamber 610A during the previous intake stroke of the first piston 610A to be discharged out the discharge valve 614A into the target fluid discharge conduit 622 where it will eventually exit the pump 601. During an intake stroke of the first piston 610A, with the first piston 610A moving towards the second end 604 of the pump 601 (as shown in Fig. 19), the intake valve 615 A is open and the discharge valve 614A is closed causing target fluid from the target fluid intake conduit 627 to be drawn into the first compression chamber 61 IA through the open intake valve 615A.

In a similar manner, the second compression chamber 61 IB is also provided with an intake valve 615B between the second compression chamber 61 IB and the target fluid intake conduit 627 and a discharge valve 614B between the second compression chamber 61 IB and the target fluid discharge conduit 622. Through the opening and closing of the intake valve 615B and the discharge valve 614B, the second compression chamber 61 IB pumps target fluid. During an intake stroke of the second piston 610B (as shown in Fig. 15), target fluid is drawn into the second compression chamber 61 IB from the target fluid intake conduit 627 and then discharged from the second compression chamber 61 IB during a subsequent discharge stroke of the second piston 610B (as shown in Fig. 19), discharging the target fluid in the second compression chamber 61 IB to the target fluid discharge conduit 622 where the target fluid will eventually exit the pump 601.

In this manner, both the first compression chamber 61 IA and the second chamber 61 IB act to pump the target fluid with both the first piston 610A and second piston 610B acting as pumping pistons, drawing in and expelling target fluid in a reciprocating manner.

In addition to both the first piston 610A and second piston 610A acting as pumping pistons, they also operate as engine pistons to drive the pump 601. A first chamber 612A and a second chamber 612B are provided, with the first chamber 612A positioned adjacent the first piston 610A, on an opposite side of the first piston 610A from the first compression chamber 61 IA, and the second chamber 612B positioned adjacent the second piston 610A, on an opposite side of the second piston 610B from the second compression chamber 61 IB. Power fluid is directed alternatingly into the first chamber 612A and the second chamber 612B to drive the pump 610. To drive the first piston 610A through a discharge stroke, power fluid is directed into the first chamber 612A and to drive the second piston 610B through a discharge stroke, power fluid is directed into the second chamber 612B.

The reversing spool 657 has a position piston 658 and a balancing pressure piston 659. The balancing pressure piston 659 equalizes forces acting on the reversing spool during operation of the pump 601, exerting a force on the reversing spool 657 acting in an opposite direction to the force exerted by power fluid on either the first end 670A or the second end 670B of the reversing spool 657. A first balancing pressure piston passage 671 and a second balancing pressure piston passage 672 are provided in the reversing sleeve 606. Based on the position of the reversing sleeve 606, either the first balancing pressure piston passage 671 or the second balancing pressure piston passage 672 is placed in fluid communication with power fluid supply conduit 624 to supply power fluid one of the sides of the balancing pressure piston 659. If the reversing sleeve 606 is positioned so that the first balancing pressure piston passage 671 is provided in fluid communication with the power fluid supply conduit 624, the power fluid passing through the first balancing pressure piston passage 671 to the balancing pressure piston 659 exerts a force on the balancing pressure piston 659 towards the second end 605 of the pump 601. If the reversing sleeve 606 is positioned so that the second balancing pressure piston passage 672 is provided in fluid communication with the power fluid supply conduit 624, the power fluid passing through the second balancing pressure piston passage 672 to the pressure balancing piston 659 exerts a force on the balancing pressure piston 659 towards the first end 603 of the pump 601.

Power fluid in either the first chamber 612A of the second chamber 612B applies a force to first end 670A of the reversing spool 657 or the second end 6703 of the reversing spool 657, respectively. The balancing pressure piston 659 exerts a force on the reversing spool 657 in an opposite direction from the force exerted by the power fluid in either the first chamber 612A or the second chamber 612B. By adjusting the surface area of the first end 670A and the second end 670B of the reversing spool 657 with the surface area of the balancing pressure piston 659, the forces placed on the reversing spool 657 can be substantially balanced, with the pressure balancing piston 659 substantially counteracting the forces placed on the reversing sleeve 657 by the power fluid in either the first chamber 12A or the second chamber 12B.

With the force exerted on either the first end 670A of the second end 6703 of the reversing spool 657 substantially counteracted by the balancing pressure piston 659, the reversing spool 657 is held in place by the position piston 658. Power fluid from the power fluid supply conduit 624 is routed to either side of the position piston 658 to hold the reversing spool 657 in place. A first fluid supply passage 662 A is provided in the inner housing 605 in fluid communication with the power fluid supply conduit 624. A second fluid supply passage 662B is provided in the reversing sleeve 606 that aligns with the first fluid supply passage 662A. A first slot 667A and a second slot 667B are provided on the position piston 658 to route power fluid from the fluid supply 662A and the fluid supply 662B to either side of the position piston 658, depending on the position of the reversing spool 657. By altering the surface area of the position piston 658, the amount of force requires to shift the reversing spool 657 can be adjusted.

In this manner, the pressure balancing piston 659 counteracts the forces on the reversing spool 657 from the first chamber 612A and the second chamber 612B, with the position piston 658 holding the reversing spool 657 in position and determining how much force is required to shift the reversing spool 657.

A reversing sleeve piston 664 is provided to shift the reversing spool 657.

Referring to Fig. 15, the pump 601 is shown during a discharge of the first piston 610A and an intake stroke of the second piston 610B. The reversing sleeve 606 is initially positioned towards the second end 604 of the pump 601, exposing the power fluid inlet port 608 A to the first chamber 612A, placing the first chamber 612 A in fluid communication with the power fluid supply conduit 624, while blocking the exhaust port 609A. At the same time, the reversing sleeve 606 is exposing the second exhaust port 609B to the second chamber 612B while blocking the power fluid inlet port 608B from the second chamber 612B. With power fluid entering the first chamber 612A adjacent the first piston 610A and fluid being vented from the second chamber 612B adjacent the second piston 610B, the first piston 610A is driven through a discharge stroke while the second piston 610B, pulled along by the connecting rod 607, follows along through an intake stroke.

During the discharge stroke of the first piston 610A, the power fluid exerts a force on the first piston 610A as well as a first side 670A of the reversing spool 657 and a first side 680A of the reversing sleeve 606. The force exerted on the first side

670A of the reversing spool 657 by the power fluid in the first chamber 612A is substantially counteracted by the force exerted on the reversing spool 657 by the pressure balancing piston 659 with the position piston 658 exerting a force on the reversing spool 657 towards the second end 604 of the pump 601 and pressing the reversing spool 657 against the reversing sleeve 606. The reversing sleeve 606 is pressed against a bumper 629 in the inner housing 605.

When the top piston 610A reaches a top of the discharge stroke, the reversing sleeve 606 and the reversing spool 657 act in conjunction to reverse the direction of motion of the first piston 610A and the second piston 610B. Referring to Fig. 16, as the first piston 610A reaches an end of the discharge stroke, a bottom of the second piston 610B comes into contact with the second end 670B of the reversing spool 657. Because of the balancing of the forces on the reversing spool by the balancing pressure piston 659, the second piston 1OB only has to exert a force on the reversing spool 657 to overcome the force exerted on the reversing spool 657 towards the second piston 1OB by the position piston 658. With the second piston 610A overcoming the force placed on the reversing spool 657 by the position piston 658, the reversing spool 657 is shifted by the second piston 1OB towards the first end 603 of the pump 601. Referring to Fig. 17, with the reversing spool 657 shifted towards the first end 603 of the pump 601, power fluid is directed to the other side of the position piston 658 causing the force exerted on the reversing spool 657 by the position piston 658 to act in the direction of the force exerted on the reversing spool 657 by the second piston 1OB. The shifting of the reversing spool 657 moves the first slot 682A away from the reversing sleeve piston passage 685 and places the second slot 682B in fluid communication with the reversing sleeve piston passage 685 which routes power fluid from the power fluid supply conduit 624 to the other side of the reversing sleeve piston 664. The force exerted on the other side of the reversing sleeve piston 664 drives the reversing sleeve 606 towards the first end 603 of the piston 601, shifting the reversing sleeve 606, as shown in Fig 18.

Referring to Fig. 19, when the reversing sleeve 606 has been shifted towards the first end 603 of the piston 601 until the reversing sleeve 606 has been stopped by the bumper 629, the reversing sleeve 606 exposes the second power fluid inlet port 608B, which allows power fluid to enter the second chamber 612A, while at the same time aligning the first housing exhaust port 619A with the exhaust port 609 A, allowing fluid in the first chamber 612A to be vented. With power fluid now entering the second chamber 612B and the first chamber 612A being vented, the second piston 610B is driven by the power fluid in the second chamber 612B through a discharge stroke, while the first piston 610A is pulled through an intake stroke by the connection rod 607.

When the second piston 610B reaches a bottom of the intake stroke, the reversing sleeve 606 and the reversing spool 657 act in conjunction to change the direction of motion of the first piston 610A and the second piston 610B. Pump 1 shown in Figs. 1 -4 or pump 601 shown in Figs. 14-18 can be adapted to be deployed in the wellbore using known installation techniques for conventional downhole pumps.

In an aspect, the pump 1 or pump 601 can be installed in a parallel free configuration where a U-tube arrangement is used with one of the legs of the U-tube supplying power fluid and the other leg directing pumped target fluid back up to the ground surface. Figs. 2OA, 2OB, 2OC are schematic illustrations of a pump 701 being installed, operated and retrieved from a well bore 710. The pump 701 could be a pump 1 as shown in Fig. 1-4 or a pump 601 as shown in Fig. 15-19. Fig. 2OA illustrates the pump 701 being installed in casing 710 lining a well bore. Fig. 2OB illustrates the pump 701 in position and during operation. Fig. 2OC illustrates the pump 701 being retrieved.

A first tubing string 702 and a parallel second tubing string 704 are used to install the pump 701 in the casing 710. The second tubing string 704 is connected to the first tubing string 702 near a far end 703 of the first tubing string 704. A standing valve 708 is provided at the far end 703 of the first tubing string 702 to seal the far end 703 of the first tubing string 702 when the pump 701 is not in place proximate the far end 703 of the first tubing string 702. A seal 709 is also provided in the first tubing string 702 to seal the pump 701 in place when it is located proximate the far end 703 of the first tubing string 702.

Referring to Fig. 2OA, to install the pump 701 in place down the casing 710, the first tubing string 702 and the second tubing string 705 are inserted down the casing 710. The pump 701 is inserted in the first tubing string 702 and the first tubing string 702 and a cap 712 is provided at a top end 705 of the first tubing string 702 to seal the first tubing string 702. Power fluid is then forced down the first tubing string 702 behind the pump 701 and then back up the second tubing string 704 to force the pump 701 down the first tubing string 702.

Referring to Fig. 2OB, when the pump 701 reaches the far end 703 of the first tubing string 702, the pump 701- contacts the standing valve 708. The pump 701 and the standing valve 708 are configured so that the pump 701 engages a seat on the standing valve 708. The standing valve 708, along with the seal 709 forms a seal with the pump 701. With the pump 701 no longer moving downwards, power fluid can be forced into the pump 701 (such as with the use of an elastomer seal on the top of the pump 701 to reduce or prevent power fluid from entering the pump 701 until it reaches the far end 703 of the first tubing string 702).

With power fluid now entering the pump 701, the pump 701 begins pumping target fluid. Target fluid is drawn through the standing valve 708 into the pump 701 and forced by the pump 701 up the second tubing string 704.

Referring to Fig. 2OC, to retrieve the pump 701, power fluid can be forced down the second tubing string 704, to force the pump 701 upwards in the first tubing string 702. When the pump 701 is forced to a top end 705 of the first tubing string

702, it can latch into the cap 712 so that the pressure in the first tubing string 702 can be bled off, allowing the cap 712 to be removed and the pump 701 to be retrieved.

In another aspect, the pump 1 or pump 601 can be installed in a casing free configuration. Fig. 21 A is a schematic illustration of a pump 721 configured in a casing free configuration. The pump 721 (such as pump 1 or pump 601) is provided near a bottom of a tubing string 722 with openings 725 in the tubing string 722 where the pump 721 exhausts target fluid being pumped. To install the pump 721 in the casing 720 the tubing string 722 is lowered down the casing 722 and a packer 726 is used to seal the tubing string 722 to the casing 720 just below the pump 721. In this manner, an annulus 727 is formed between the tubing string 722 and the casing 720.

To operate the, pump 721, power fluid can be forced down the tubing string

722 into a first end 728 of the pump 721 to drive the pump 721. A second end 729 of the pump 721 is in fluid communication with the target fluid to be lifted up the casing

720 with the pump 721 (such as oil in an underground formation). Target fluid drawn and expelled from the pump 721, along with spent power fluid is exhausted out the opening 725 in the tubing string 722 and up the annulus 727 formed between the tubing string 722 and the casing 720. In this manner, power fluid can be forced down the tubing string 722 from the ground surface to drive the pump 721 and target fluid and exhausted power fluid can be forced by the pump 721 up the annulus 727, formed between the tubing string 722 and the casing 720, to the ground surface.

Fig. 21 B illustrates a variation of the installation of pump 721 in a casing free installation where power fluid exhausted by the pump 721 is not mixed with the target fluid being pumped to the ground surface. A first tubing string 731 and second tubing string 732 are used to install the pump 721 in the casing 720. The pump 721 is provided inside the first tubing string 731 near a bottom of the first tubing string 731 with the second tubing string 732 connected to the pump 721.

Power fluid is forced down the second tubing string 732 and into the pump 721, where the power fluid drives the pump 721. Target fluid is drawn into the pump

721 where it is exhausted to a first annulus 727 formed between the first tubing string 731 and the casing 720. The spent power fluid, rather than being mixed with the target fluid being pumped up to the ground surface, is directed back up a second annulus 735 between the first tubing string 731 and the second tubing string 732. In this manner, the spent power fluid can be kept separate from the target fluid being pumped.

In a further aspect, the spent power fluid might be exhausted directly into a formation the from which the target fluid is being taken, instead of bringing it up to the ground surface as shown in Figs. 21 A and 2 IB.

A person skilled in the art will appreciate that there are various other configurations in which a pump could be installed downhole, in addition to those described herein.

In some implementations it may be desirable to use more than one pump 1 (or pump 601). Fig. 22 illustrates an aspect where three pumps IA, IB and IC are installed in parallel in a casing 750 of a well to form a pump casing 752. Spacings 748 in between the pumps IA, IB and IC can be used as fluid conduits for the supplied power fluid, exhausted power fluid and the pumped target fluid.

In this manner, a failure by one of the pumps IA, IB or 1C will decrease the amount of target fluid being pumped, but will not stop the flow of pumping target fluid completely.

Fig. 23 illustrates a further aspect, where a number of clusters 752A, 752B and 752C, of parallel pumps IA, IB and IC, are placed in series in a casing 750. This can be done to increase the total output of pumped target fluid or to provide redundancy.

Extremely high temperature applications (such as e.g. Steam Assisted Gravity Drainage processes or SAGD processes) and hostile environments require seal-less designs for reciprocating pumps. Fig. 24 illustrates a schematic illustration of a prior art reciprocating pump 801 in a seal-less configuration. The pump 801 has a pumping piston 803 contained in a pumping cylinder 804 and an engine piston 805 contained in an engine cylinder 806. The pump piston 803 divides the pump cylinder 804 into a first chamber 814 and a second chamber 815. Power fluid is alternately routed to either side of the engine piston 805 to drive the pump 801, with power fluid being routed to the engine cylinder 806 above the engine piston 805, to drive the engine piston 805 in a downstroke and then below the engine piston 805, to drive the engine piston 805 in an upstroke.

A connecting rod 807 connects the pumping piston 803 to the engine piston 805. As the engine piston 805 is driven through either an upstroke or a downstroke by the power fluid, the pumping piston 803 is forced into a corresponding downstroke or upstroke, respectively. With the pumping piston 803 driven through upstrokes and downstrokes, the pumping piston 803 draws in target fluid and then expels this target fluid from the pump cylinder 804 on both sides of the pumping piston 803. When target fluid is being drawn into the pump cylinder 804 on one side of the pumping piston 803 because of the movement of the pump cylinder 804, target fluid is being expelled from the pump cylinder 804 on the other side of the pump piston 803.

Because the pump 802 is seal-less, annular gaps 811, 812 are present. The annular gap 811 is present between the pump piston 803 and the pump cylinder 804 and the annular gap 812 is present between the engine piston 805 and the engine cylinder 806. These gaps 811, 812 allow some fluid to by-pass the pump piston 803 and the engine piston 805.

Not only is the by-pass of some of the fluid unavoidable, but it is often necessary. Fluid passing between the pump piston 803 and the pump cylinder 804 and passing between the engine piston 805 and the engine cylinder 806 provides sealing and hydraulic self-centering of the pump piston 803 and engine piston 805. The hydraulic self-centering is meant to prevent the pump piston 803 and engine piston 805 from sticking to the pump cylinder 804 and engine cylinder 806, respectively, as well as reducing friction.

The power fluid in the engine cylinder 806 is relatively "clean", however, with the pump cylinder 804, the target fluid is often "dirty" (i.e. containing solid contaminants). These solid contaminants can affect the operation of the pump piston

803 by increasing the friction between the pump piston 803 and the pump cylinder

804 and even damaging the pump cylinder 803 as some of the dirty target fluid bypasses the pump piston 803.

Fig. 24 illustrates the pump piston 803 in a discharge stroke where target fluid is being discharged from the pump cylinder 804 above the pump piston 803. The movement of the pump piston 803 increases the pressure of the target fluid in the first chamber 814 defined by the pump piston 803 while causing the pressure of the target fluid in the pump cylinder 804 in the second chamber 815 defined by the pump piston 803 to be decreased as the pump piston 802 travels through the downstroke. The pressure gradient between the first chamber 814 and the second chamber 815 causes some of the target fluid to migrate towards the second chamber 815 through the gap 811 between the pump piston 803 and the pump cylinder 804. Any solids or abrasives in this target fluid can also be forced by the pressure into this gap 804.

When the pump piston 803 changes its direction of motion, and starts traveling though an upstroke, the pressure gradient reverses and target fluid from the second chamber 815 can now be forced into the gap 811, which can cause a buildup of solids and abrasives in the gap 81 1 between the pump piston 804 and the pump cylinder 804. Because the gap 811 often has very small clearances, the pump 901 can be especially susceptible to small particles of solids like sand. For reciprocating pumps that operate in a similar manner to pump 801, when the target fluid that will be pumped is "dirty" (i.e. containing solids and abrasives) the pump has to be retrofitted with additional flushing systems. However, this adds complexity to the pump and in some cases it is not always possible to add a flushing system to a reciprocating pump.

Referring to Figs. 1-4, the pump 1 does not require an additional flushing system to be operated in a seal-less configuration where the target fluid contains solids and abrasives because the pump 1 provides flushing as a result of the design.

Power fluid is introduced to the first chamber 12A and second chamber 12B during the operation of the pump 1. Target fluid is drawn into the first compression chamber HA and the second compression chamber HB during the operation of the pump 1. The power fluid is clean (free from solids, abrasives and other contaminants) and is under a higher pressure in the pump 1 than the target fluid causing the pressure gradients between the first chamber 12A and the first compression chamber HA and the second chamber 12B and second compression chamber 1 IB to always be positive moving towards the first chamber 12A and the second chamber 12B. This results in a continuous flush of clean power fluid around the first piston 1 OA and second piston 1OB towards the first compression chamber 12A and the second compression chamber 12B, respectively.

In this manner, some clean power fluid is continuously flushing past the first piston 1OA and second piston 1OB into the first compression chamber 12A and second compression chamber 12B, sweeping away any solids and providing a built-in flushing action for the pump 1.

The same flushing of power fluid will occur in pump 601 shown in Figs 14-18 when pump 601 is operated in a seal-less configuration. Fig. 25 illustrates centering mechanisms 1120 that can be provided on the outside surface of a piston 1110 to help center the piston 1110 when a pump 1101 is operated in a seal-less configuration. The pump 1 101 can be a pump similar to pump

1 shown in Figs. 1-4, pump 601 shown in Figs. 14-18 or some other similar pump being operated in a seal-less configuration.

A number of centering mechanisms 1120 can be provided on the outside surface of the piston 1110 with each centering mechanisms 1120 having a slot 1122 and a recess 1125. The slot 1 122 can be a relatively shallow depression in the piston that can direct fluid passing through the gap between a bore 1115 of the pump 1101 and the piston 1110 to the recess 1125 of the centering mechanism 1120. The recess 1125 can form a much larger depression in the piston 1110 that can be sized and configured based on the amount of lateral force desired to center the piston 1110.

The centering mechanisms 1120 can operate on the hydrostatic bearing principal. When the piston 1110 is displaced from a concentric position in the bore 1115 of the pump 1101, a rise in the mean pressure at the region of decreased clearance between the piston 1110 and the bore 1115 of the pump 1101 can occur as a result of fluid being directed into the centering mechanisms 1120. Additionally, a fall in the mean pressure at the region of increased clearance between the piston 1110 and the bore 1 115 can also occur. This increase in pressure at the region of decreased clearance and corresponding decrease in pressure at the region of increased clearance can cause an overall centering force on the piston 1110 tending to center the piston 1 110 in the bore 1115 of the pump 1101.

This centering of the piston 11 10, aided by the centering mechanisms 1120 can help to prevent the contact of the piston 1110 with the bore 1115, reduce friction acting on the piston 1110, reduce leakage (bypass) of the fluid past the piston 1110, etc.

Referring again to Figs 1-4, when the pump 1 is used in a "seal" configuration, the pressure gradient between the first compression chamber HA and the first chamber 12A and the pressure gradient between the second compression chamber

HB and the second chamber 12B in pump 1 can be beneficial to the seals. These same pressure gradients are present in the pump 601 shown in Figs. 15-19.

Fig. 26 is a schematic illustration of a prior art reciprocating pinup 901. An engine piston 905 is provided in an engine cylinder 906. A pump piston 903 in a pump cylinder 904 defines a first pump chamber 914 and a second pump chamber 915. The pump piston 903 reciprocates in the pump cylinder 904 to alternately draw in and discharge target fluid from the first pump chamber 914 and the second pump chamber 915 to pump the target fluid. A seal 909, which is typically an elastomer seal, is provided around the pump piston 903 to fluidly separate the first pump chamber 814 and the second pump chamber 815. When target fluid is being discharged from the first pump chamber 814, the pressure of the target fluid in the first chamber 814 acts against the seal 909 and places a force on the seal 909 acting away from the first pump chamber 814 because the pressure of the target fluid in the first chamber 815 will be significantly greater than the pressure of the target fluid in the second chamber 815. Additionally, a friction force also acts on the seal 909 in the same direction as the force acting on the seal 909 by the pressure of the target fluid in the first chamber 814. When the pump piston 803 reverses direction, a force is applied to the seal 909 in an opposite direction by the pressure of the target fluid in the second chamber 815 and a friction force is also applied to the seal 909 in the same direction as the force applied by the pressure of the target fluid in the second chamber 815. The force from the pressure of the target fluid and the force of friction act in the same direction resulting in combined forces acting in a single direction on the seal 909 that is opposite to the direction of movement of the pump piston 903. This combination of forces in a single direction opposite to the direction of motion of the pump piston 903 can cause the seal 909 to be dragged between the pump piston - 803 and the pump cylinder 904 (extruded) reducing the life and compromising the reliability of the seal 909.

Although the forces are not as great, the same effects can occur for the seal 908 encircling the engine piston 905.

Fig. 27 is a schematic illustration of a pump 1001 during the discharge of target fluid from the first end 1003 of the pump 1001. Pump 1001 is shown with similar element to pump 1 shown in Fig. 1-4, however, a person skilled in the art will appreciate that pump 601 shown in Figs. 15- 19 could also be used with seals. The pump 1001 has a first piston 101 OA and a second piston 101 OB. The first piston 101 OA divides a first compression chamber 101 IA from a first chamber 1012A and the second piston 101 OB divides a second compression chamber 101 IB from a second chamber 1012B. A first sealing ring 1009A is provided encircling the first piston 101 OA and a second sealing ring 1009B is provided encircling the second piston 1010B. When the first piston 101 OA is being driven through a discharge stroke, the pressure exerted on the first seal 1009 A by the target fluid in a first compression chamber 101 IA is less than the pressure exerted on the first seal 1009A by the power fluid in the first chamber 1012A because the pressure of the power fluid driving the first piston 101 OA is higher than the pressure of the target fluid being discharged from the first compression chamber 101 IA. The force acting on the first sealing ring 1009 A as a result of the higher pressure of the power supply fluid acts in the same direction as the motion of the of the first piston 101 OA. The same forces occur on the second seal 1009B when the second piston 101 OB is being driven through a discharge stroke.

In this manner, the pressure differential between the first compression chamber 1 IA and the first chamber 12A or the second compression chamber 1 IB and the second chamber 12B during a discharge stroke of the first piston 1OA or second piston 1OB, acts in the direction of movement of the piston, reducing the likelihood of the first seal 1009 A or second seal 1009B being extruded or damaged during operation of the pump 1001.

Fig. 28 through 30 illustrate a porting mechanism that can be used to selectively allow and prevent a flow of fluid from passing around a sealing ring. A pair of sealing rings 1212, 1214 can be provided in conjunction with a groove 1220. As shown in Fig. 29, the groove 1220 can, in one aspect, have a side profile wherein the groove 1220 is wider at the top of the groove 1220 tapering narrower towards the bottom of the groove 1220. In one aspect, the edges of the groove 1220 can be slightly rounded as the groove 1220 tapers towards a bottom of the groove 1220. As shown in Fig. 30, the groove 1220 can have ends 1222, 1224 that converge into narrower widths, with a middle section of the groove 1220 having the widest width. In one aspect, a gear cutter can be used to form the grooves 1220.

The groove 1220 can be used to allow a fluid entering through a inlet port

1230 to by-pass one of the sealing rings 1212 as shown in Fig. 28. When one of the sealing rings 1212 is slid over the groove 1220 as shown in Fig. 28, fluid can pass around the sealing ring 1212 by entering the groove 1220 and passing around the sealing ring 1212. The other sealing ring 1214, which is not shown placed over the groove 1220 in Fig. 28, will block the flow of fluid past the other sealing ring 1214. The sliding of the sealing ring 1212 over the groove 1220 can reduce or avoid the shearing force that is placed on sealing rings when sealing rings are slid across a more conventional cross-drilled port, rather than the groove 1220.

Referring to Figs. 1-4, the reciprocating movement of the reversing sleeve 6 is accompanied by the opening and closing of the housing inlet ports 8A, 8B and the housing outlet ports 9 A, 9B. Housing outlet ports 9 A, 9B open when they align with the reversing sleeve exhaust ports 19A, 19B, respectively. A groove 1220, as shown in Figs. 28-29, could be used with the these ports or other ports in the various pumps discussed herein.

Additionally, grooves, similar to grooves 1220 shown in Figs. 29 and 30, can be used to equalize pressure across a sealing ring as the sealing ring is moved across a port and before the sealing ring reaches the other side of the port. Figs. 31-33 illustrate grooves 1320 being used to equalize pressure across sealing rings 1312, 1314 as the sealing rings 1312, 1314 move across first and second ports 1342, 1344 connected to the grooves 1320.

A fluid introduced through a first inlet 1330 can be directed to either a first port 1342 or a second port 1344 depending on the position of a spool 1350. When the second port 1344 is open, the sealing rings 1312, 1314 can be placed on either side of the second port 1344, allowing fluid from an inlet port 1330 to flow into the second port 1344, as shown in Fig. 31. As the spool 1350 moves, moving the first port 1342 towards the inlet port 1350, the sealing rings 1312, 1314 can slide across the outer surface of the spool 1350. Rather than simply crossing over a cross-drilled port, when one of the sealing rings 1312 reaches the first port 1342 with a groove 1320 provided at the opening of the port 1342, the sealing ring 1312 can pass over the groove 1320. When the sealing ring 1312 is positioned substantially over the groove 1320 and the first port 1342, as shown in Fig. 32, fluid from the inlet port 1330 can enter the groove 1320. Some of the fluid that enters the groove 1320 can then enter the port 1342, while some of the fluid can pass around the sealing ring 1312 through the groove 1320 to try and equalize the pressure on either side of the sealing ring 1312. As the spool 1350 continues to move, the sealing ring 1312 will eventually cross over the first port 1342 and the groove 1320 and the first port 1342 will not be fully opened, with the sealing rings 1312 preventing fluid from passing around it. Directing the fluid from the inlet port 1330 into the fist port 1342.

Again, these grooves 1320 can be used with a number of suitable pumps. In one aspect they can be used with pump 1 shown in Figs. 1-4, pump 601 shown in Figs. 14-18 or any other suitable pump.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article "a" or "an" is not intended to mean "one and only one" unless specifically so stated, but rather "one or more". All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those or ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.