Double acting linear electrical submersible pump and method for its operation

Abstract

The invention relates to reciprocating piston pumps, in particular, to a reciprocating double acting well pump driven by a linear submersible permanent magnet motor. The essence of the claimed invention lies in the fact that the upper pumping plunger pair of a pump module of a double acting linear electric submersible pumping unit is configured to intake a double volume of a borehole fluid sufficient for one operating cycle and contains delivery traveling and inlet fixed valves with a directional pusher, closing by straight oncoming flow of the borehole fluid. Also a separator of downward and upward flows of the borehole fluid with low and high-pressure passages is installed above a cylinder of the pumping plunger pair. Wherein the low-pressure passages are performed in fluid communication with a borehole fluid delivery port from an annulus, containing a filtration and gravitational gas separation zone.

Claims

1. A double acting linear electrical submersible pump, comprising: a pump module with a traveling valve (8), a reversing valve (4) and an inlet valve (5), wherein said pump module comprising a pair of successively mounted plungers (6, 7) that forms an upper plunger (6) and a lower plunger (7), wherein said pair of plungers (6, 7) are connected to a movable part of a linear drive (2) and configured to displace an internal volume of a fluid of said pump module by means of a reciprocal motion of the linear drive, wherein the upper plunger (6) is equipped with the traveling valve (8) and said inlet valve (5), wherein said upper plunger (6) forms a first annular cavity (9) with a pump module enclosure, wherein a cylinder (11) of the upper plunger (6) is configured to collect a double volume of the fluid which is sufficient for one operating cycle of the pump module, wherein the cylinder (11) is installed under a separator (15) of a downward flow of the fluid (16) and an upward flow of the fluid (17), wherein the separator (15) comprising a low pressure channel (18) and a high pressure channel (19), wherein said low-pressure channel (18) is arranged in fluid communication with a fluid delivery channel (20) of the pump module, wherein said delivery channel (20) has a filtration zone (21) and a gravitational gas separation zone (22), wherein a volume of the gravitational gas separation zone (22) is greater or equal to the volume of the cylinder (11), wherein a plunger rod (10) of the lower plunger (7) is partially located inside of the cylinder (11) of the upper plunger (6) to form a second annular cavity (12), wherein said lower plunger (7) is designed as a labyrinth sealing of the movable part of the linear drive, wherein the pump module enclosure (3) contains a lower borehole fluid filtration zone (23), wherein said lower borehole fluid filtration zone (23) is arranged around a cavity (24) formed between the lower plunger (7) and the pump module enclosure (3), wherein the lower plunger (7) and the linear drive (2) are connected to each other within the cavity (24) formed between the lower plunger (7) and the pump module enclosure (3).

2. The double acting linear electrical submersible pump according to claim 1, wherein the first annular cavity (9) is arranged between the pump module enclosure (3) and an outer surface of the cylinder (11), wherein the second annular cavity 12 is formed around the plunger rod (10) of the lower plunger (7) under the upper plunger (6), wherein said first annular cavity (9) and second annular cavity (12) are connected by a common volume (14) arranged between the pair of successively mounted plungers (6,7).

3. A method of operation of a double acting linear electrical submersible pump comprising: a) lowering a pump module (1) connected to a linear drive into a well; b) filling said pump module (1) with a fluid, and displacing the fluid subsequently into a tubing string cavity by reciprocating an upper plunger (6), wherein the upper plunger (6) is connected to a lower plunger (7) to form a pair of plungers and is equipped with an integrated traveling valve (8) and a fixed inlet (5) valve, wherein the lower plunger (7) is connected to a movable part of the linear drive within a cavity (24) formed between the lower plunger (7) and a pump module enclosure (3), wherein both plunger strokes of said pair of plungers (6,7) are operating, wherein the radial dimensions of said pair of plungers (6, 7) provide approximately equal volumes of the fluid to be displaced during an upward stroke and a downward stroke of one operating cycle; c) performing a fluid intake from an annular space during the downward stroke with the open inlet valve (5) and the closed traveling valve (8) of the upper plunger (6), filling a double volume of a cylinder (11) of the upper plunger (6) required for one operating cycle; d) pushing the fluid through a filtration zone (21) and a gravity gas separation zone (22), wherein a volume of the gravity gas separation zone (22) is larger or equal to the volume of one operating cycle of the pump module, separating gas particles from the fluid during the motion through the gravity gas separation zone (22); e) simultaneously during the downward stroke of the linear drive: filling the cylinder (11) and displacing the fluid from a second annular cavity (12) into a first annular cavity (9), pushing the fluid towards high-pressure channels 19 arranged within a separator (15) of a downward flow of the fluid (16) and an upward flow of the fluid (17), the separator (15) being installed above the cylinder (11), pushing the fluid through a reversing valve (4) into the tubing string; f) simultaneously during the upward stroke of the linear drive: creating a pressure within the cylinder (11) with closed inlet valve (5) and opened traveling valve (8) of the upper plunger (6), displacing the fluid under an influence of the pressure created within the cylinder (11) towards a common volume (14) located between the pair of plungers (6,7); g) during the upward stroke and downward stroke of the linear drive filtering the fluid within the cavity (24) formed between the lower plunger (7) and the pump module enclosure (3).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The essence of the claimed invention is explained, but is not limited to the following images:

(2) FIG. 1 is a functional diagram of the pump module during the upward stroke;

(3) FIG. 2 is a functional diagram of the pump module during the downward stroke.

(4) FIG. 3 shows the first variant of pumping module valve.

(5) FIG. 4 shows the second variant of pumping module valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(6) FIGS. 1, 2 show pump module 1 of the double acting linear electrical submersible pump installable into a wellbore and driven by means of the linear drive executed as a movable part (slider) 2 of a linear submersible permanent magnet electric motor (not shown on the illustration).

(7) Pump module 1 contains enclosure 3 of a high pressure and of a cylindrical form with a reversing valve 4 and an inlet valve 5. A pair of plungers 6, 7 are arranged on-line inside of the enclosure, driven by the linear drive capable to force out the internal volume of the borehole fluid due to the reciprocal motion of the linear drive. Upper pumping plunger 6 contains delivery traveling gravity or spool valve 8 and inlet fixed gravity or spool valve 5 installed in the upper portion of its cylinder, equipped with the pusher rod, and both of said valves are closed by the oncoming flow of the borehole fluid. Also the upper plunger 6 forms a first annular cavity 9 with the pump module enclosure. Stroke of the pump module plungers in both directions is operational.

(8) Upper plunger 6 with integrated traveling delivery valve 8 and fixed inlet valve 5 is connected to a lower plunger 7 of a smaller diameter by means of plunger rod 10. The mentioned plunger 7 is also designed as the labyrinth sealing to prevent losses of the borehole fluid and protect the linear drive from abrasive wear due to mechanical impurities effect and allows to increase the plunger stroke of the upper plunger with increasing the pump module productivity.

(9) Lower plunger 7 is connected to linear drive 2, and its plunger rod 10 partially located inside of the cavity of cylinder 11 of upper plunger 6 with forming a second annular cavity 12 under its plunger rod 13. Herewith said second annular cavity 12 is executed in fluid communication with the first annular cavity 9, arranged between the pump enclosure and outer surface of the upper plunger cylinder 11 by means of common volume 14, arranged between the pair of plungers 6, 7. Flow separator 15 of downward flaw 16 and upward flaw 17 of the borehole fluid with low-pressure channel 18 and high-pressure channel 19 respectively is installed above the cylinder of upper plunger 6. Wherein the low-pressure channel is executed in fluid communication with a delivery channel 20 of borehole fluid feed from the annulus, that includes filtration zone 21 with arranged filters.

(10) A volume of gravitational gas separation zone 22 is greater or equal to the volume of one operating cycle of pump module 1. The volume of one operating cycle is determined by the volume of fluid displaced during a single upward and downward stroke of plungers of the pumping module. Additional reversing valve 4 preventing a drain back of the borehole fluid from the oil well tubing is installed at an output of the pump module in a place of its connection to the oil well tubing string (not shown on the figures). Traveling valve 8, inlet valve 5 and reversing valve 4 are executed as valves with a pusher rod 25 and are capable to be closed instantaneously by straight oncoming flow of the borehole fluid, which provides reliable operation of the section isolation valves. Consequently, it is possible to significantly simplify the design of the pump module and avoid losses of the borehole fluid as against utilization of gravity valves, used in corresponding patents.

(11) Borehole fluid filtration zone 23 is arranged around the lower plunger 7 for filtration of the borehole fluid, periodically filling a cavity 24 in the pump module enclosure. Wherein said cavity 24 is formed by the difference in radial dimensions of plunger rod 10 and linear drive 2 connected to each other.

(12) It should also be noted that the radial dimensions of pair of plungers 6 and 7 are assorted in a manner for providing approximate equality of the fluid volumes pumped (displaced) during upward stroke and downward stroke.

(13) According to said invention named traveling valve 8, inlet valve 5 and reversing valve 4 are equipped with directional pusher rod 25 which contacts with locking element 26 and closed by the straight oncoming flow of the borehole fluid.

(14) Pump module valves (FIG. 3) comprise cylindrical body 27 with locking element 26 inside of the cylindrical body, said locking element 26 is made in form of a ball. A motion of locking element 26 is enabled by means of pusher rod 25 with a plurality of recirculation holes 28 crossing a body of the pusher rod with an angle to a central axis of the pusher rod. Said embodiment providing that an area of increased hydraulic resistance is arranged within the pusher rod cavity 29, which creates a hydraulic pressure necessary for a translation movement of the pusher rod.

(15) According to another variant of invention (FIG. 4), pump module valves comprise a cylindrical body 30 with locking element inside of the cylindrical body, which made in form of directional neck 31 with sealing cone 32, closing by a straight oncoming flow of the borehole fluid, named locking element is made in solid-metal form and consists on parts with a variable radial cross section.

(16) The locking element inside of the cylindrical body is made of materials with variable hardness. For example, locking element 26 is made of a material, hardness of which is greater than a hardness of pusher rod 25 in preferred variant of implementation (FIG. 3). In both said variants (FIG. 3 and FIG. 4), the pusher rod 25 or directional neck 31 are made or covered with inert, corrosion-resistant and friction material.

(17) The method for operation of the Double Acting Linear Electrical Submersible Pump utilizing the pump module of the described design involves lowering of the said pump module together with the installation into a well and filling it with the borehole fluid with its subsequent displacement into the oil well tubing string cavity by means of reciprocal motion of plungers 6, 7 connected to movable part of linear drive 2, while both plunger strokes are operational.

(18) The borehole fluid intake from the annulus is conducted during the downward stroke (FIG. 2), with upper plunger inlet valve 5 open and traveling valve 8 closed, while filling the double-volume of the cylinder 11 of the upper plunger 6 that is sufficient for one operating cycle. Herewith the borehole fluid is being pushed through the filtration zone 21 with installed filters and gravitational gas separation zone 22, arranged within the borehole fluid delivery channel 20 of the pump module. A volume of gravitational gas separation zone 22 is executed to be greater or equal to the volume of one operating cycle of the pump module, which provides effective separation of gas particles from liquid particles and brings them out to the annulus, as shown in FIG. 2. Simultaneously, during the downward stroke the fluid is pushed out from the second annular cavity 12 under plunger rod 13 of upper plunger 6 by means of common volume 14 arranged between the pair of plungers and the first annular cavity 9 connected to the common volume 14. Wherein the fluid is pushing out from the second annular cavity 12 towards high-pressure channels 19, arranged within separator 15 of downward and upward flows of the borehole fluid and further through reversing valve 4 into the oil well tubing string. The flow separator 15 is installed above cylinder 11 of upper plunger 6. During the return upward stroke (FIG. 1) with pumping plunger pair inlet valve 5 closed and traveling valve 8 open, under the effect of pressure created in cylinder cavity 11. The borehole fluid flow is spread towards common volume 14 located between the pair of plungers and, from analogy of the downward stroke (FIG. 2), is fed towards the oil well tubing string.

(19) Also during the upward and downward strokes constant circulation of the borehole fluid is performed within lower plunger 7 (as shown in FIG. 1 and FIG. 2) by means of periodical filling of cavity 24 located in the pump module enclosure formed by a difference in radial dimensions of plunger rod 10 and linear drive 2 connected to each other. The borehole fluid filtration zone 23 with a set of filters is arranged in order to provide protection of the linear drive from mechanical impurities.

(20) An embodiment of the claimed invention contributes to achievement of the mentioned technical result by providing simplification of the design while increasing the productivity of the pumping unit utilization by using the set of valves with absence of a complex system of channels for borehole fluid passage, which allows to regulate the fluid motion within the pump module cavity without losses even with its horizontal positioning in a well. Also the arrangement of filtration and gravitational gas separation zones provides possibility of protection from harmful effect of gas and mechanical impurities, containing in the borehole fluid.

(21) The claimed method provides various options and alternative forms of embodiment. A particular embodiment is disclosed in the description and illustrated by means of the given graphic materials. Described embodiment of the invention is not limited to a particular disclosed form and may encompass all possible embodiments, equivalents and alternatives, within the limits of essential features disclosed in the claim.