Sealing and matching integrated device

Abstract

The utility model discloses a sealing and distributing integrated device, and belongs to the technical field of oilfield water injection. The device is provided with an upper joint, an inner inserting pipe and an upper connecting sleeve connected to the lower part of the upper joint, the inner inserting pipe is sleeved with the center pipe, the center pipe is connected to the bottom end of the upper connector, and the lower connector is arranged at the bottom end of the center pipe. The sealing assembly and the piston are sequentially connected to the lower portion of the upper connecting sleeve. The inner wall of the piston is hermetically connected with the outer wall of the lower joint; the sealing assembly is provided with a supporting pipe, the outer wall of the supporting pipe is sleeved with a rubber sleeve capable of being extruded by axial force to deform, and a locking mechanism is arranged at the bottom end of the supporting pipe. In the working state, under the driving of the central pipe, the piston moves upwards to generate axial force to extrude the rubber sleeve to seal an oil sleeve annulus in a diameter expanding mode, the rubber sleeve is locked through the locking mechanism, the rubber sleeve can be kept in the sealing state, and the sealing and matching integrated device can meet the purpose of effectively packing a water injection well section in a shaft.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of oilfield water injection, especially to an interlayer packoff and effective water distribution packoff integrated device for a concentric two-pipe (or three-pipe) fine water injection process. BACKGROUND

[0002] After an oilfield with sandstone reservoirs enters a development stage, in order to maintain the production capacity of the oil layer, high-pressure water is injected into the oil layer to maintain sufficient energy and meet the efficient production of the reservoir crude oil. Due to the differences in the physical and chemical properties of the corresponding layers of the injection well section and the water absorption capacity, if the water injection volume and injection speed are not reasonably adjusted, it may lead to excessive water injection in some formations and insufficient water injection in other formations, affecting the overall development effect.

[0003] At present, the existing surface separate injection and water distribution process of each oilfield can at most realize two-section (layer) separate injection. If three-section (layer) separate injection is intended, a set of water distribution device needs to be installed in each corresponding water injection well section. If the injection volume or injection speed of a certain well section (or a certain layer) needs to be changed, a special operation team needs to perform fishing operation to replace the water nozzle, which is complex and increases the operation cost, and valuable water injection time and formation pressure are lost.

[0004] In addition, the existing separate section (layer) water injection has the following common problems and difficulties:

[0005] 1) The separate section (layer) water distribution process is complex, uses many tools, and increases the difficulty of separate section water injection.

[0006] 2) Due to the complex downhole conditions such as casing corrosion, wellbore sand production, and scaling, the downhole tool may be stuck in the downhole and cannot be pulled out. INVENTION CONTENTS

[0007] The utility model aims at overcoming the defects in the prior art and providing an interlayer packoff and water distribution packoff integrated device for fine water injection of an oilfield, which can at least solve the problems of complex three-pipe water injection construction process and high operation cost caused by the complex concentric double-pipe separate injection process.

[0008] In order to achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[0009] The interlayer packoff and water distribution packoff integrated device comprises:

[0010] an upper joint, an inner sleeve, an upper connecting sleeve connected to the lower part of the upper joint, and

[0011] a central pipe sleeved on the outer part of the inner sleeve and connected to the bottom end of the upper joint, and a lower joint installed at the bottom end of the central pipe; and

[0012] A sealing assembly and a piston connected to the lower part of the upper connecting sleeve in sequence;

[0013] The inner wall of the piston is sealingly connected with the outer wall of the lower joint;

[0014] The sealing assembly has a support tube, the outer wall of the support tube is sleeved with a rubber tube capable of being extruded and deformed by axial force, and the bottom end of the support tube is provided with a locking mechanism;

[0015] In the working state, the piston goes up under the driving of the central tube, generates axial force to extrude the rubber tube to expand the annulus of the oil jacket, and is locked through the locking mechanism, so that the rubber tube can maintain a sealed state.

[0016] Further, the outer wall of the upper joint and the inner wall of the upper connecting sleeve form a liquid passage, the side wall of the upper joint is provided with a circulation through hole communicating with the liquid passage, and the inner sleeve of the inner sleeve is sealingly connected between the upper joint and the inner sleeve. The inner sleeve sealing sleeve is used to block the circulation through hole.

[0017] Further, the upper joint and the bottom end of the inner sleeve sealing sleeve, and the connection position of the upper joint and the top end of the upper connecting sleeve are provided with shear nails.

[0018] Further, the sealing assembly further comprises an upper rubber cylinder seat and a lower rubber cylinder seat sleeved on the outside of the support tube, and the rubber cylinder is arranged between the upper rubber cylinder seat and the lower rubber cylinder seat.

[0019] Further, the end of the rubber cylinder is in contact with the end of the upper rubber cylinder seat and the lower rubber cylinder seat through the rubber cylinder shoulder.

[0020] The rubber cylinder comprises a plurality of rubber cylinders, and a rubber cylinder spacer is arranged between adjacent two rubber cylinders.

[0021] Further, a cavity is formed between the inner wall of the lower rubber cylinder seat and the outer wall of the central tube, and a first through hole is formed in the side wall of the lower rubber cylinder seat and communicates with the cavity.

[0022] Further, the locking mechanism comprises a lock ring seat, the top end of the lock ring seat is connected with the support tube, the bottom end of the lock ring seat is provided with a lock ring clamping block, the outer part of the lock ring clamping block is sleeved with a lock ring, and the lower rubber cylinder seat of the sealing assembly is provided with a lock ring sleeve matched with the lock ring.

[0023] Further, the lock ring seat and the lower rubber cylinder seat of the sealing assembly are connected with a locking shear nail.

[0024] Further, it further comprises an upper joint sub connected sealingly with the upper joint and the central tube, and a stable nail connected between the top end of the upper joint sub and the upper joint.

[0025] Further, the piston comprises an upper piston and a lower piston abutting against the upper piston;

[0026] The center pipe bottom end is fixedly connected with a center short pipe, and the outer wall of the center short pipe is in sealing connection with the upper piston and the lower piston;

[0027] The upper piston top end is in sealing connection with the outside of the center pipe;

[0028] The lower piston inner wall is in sealing connection with the outer wall of the lower joint.

[0029] In the above technical solution, the sealing and spacing integrated device has the beneficial effects that:

[0030] The sealing and spacing integrated device is installed on the concentric pipe column, and the rubber tube of the sealing assembly is expanded in diameter to seal the oil jacket annulus under the axial force, and is locked by the locking mechanism, so that the rubber tube can maintain the sealing state, and the sealing and spacing integrated device can meet the purpose of effectively sealing and spacing the water injection well section in the wellbore;

[0031] Secondly, the concentric pipe insertion technology is adopted, so that the number of segmented water injection sections (layers) can be increased to three sections (layers), and the purpose of sealing and spacing integration is achieved.

[0032] In addition, once the injection channel is found to be blocked, the reverse well washing operation can be performed to unblock the injection channel, without using professional operation teams to perform the downhole fishing nozzle operation, so that the injection stop time is reduced, the labor intensity of workers is reduced, and the comprehensive cost of water injection operation is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below, and obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0034] Figure 1 is a schematic diagram of the overall structure of the sealing and spacing integrated device disclosed by the present application;

[0035] Figure 2 is an enlarged view of the upper half of the sealing and spacing integrated device disclosed by the present application;

[0036] Figure 3 is an enlarged view of the lower half of the sealing and spacing integrated device disclosed by the present application.

[0037] EXPLANATION OF REFERENCE NUMERALS:

[0038] 1, upper joint; 2, inner tube; 3, unsealing shear pin; 4, inner tube sealing sliding sleeve; 5, upper connecting sleeve; 6, inner tube sealing sliding sleeve shear pin; 7, stabilizing pin; 8, upper joint; 9, central tube; 10, upper rubber cylinder seat; 11, rubber cylinder shoulder; 12, rubber cylinder; 13, rubber cylinder spacer ring; 14, middle rubber cylinder; 15, rubber cylinder support tube; 16, lower rubber cylinder seat; 17, locking shear pin; 18, locking ring seat; 19, locking ring clamping block; 20, locking ring; 21, upper piston; 22, central short tube; 23, lower piston; 24, lower joint;

[0039] 100, liquid passage; 101, circulating through hole;

[0040] 200, locking ring sleeve;

[0041] 300, injection passage;

[0042] 400, cavity; 401, first through hole;

[0043] 500, cavity; 501, second through hole. DETAILED DESCRIPTION

[0044] In order for those skilled in the art to better understand the technical scheme of the utility model, the utility model will be further described in detail below in combination with the drawings.

[0045] Referring to Figures 1-3 as shown;

[0046] The utility model sealing and matching integrated device comprises an upper joint 1, an inner tube 2, an inner tube sealing sliding sleeve 4, an upper connecting sleeve 5, an upper joint split body 8, a central tube 9, a central short tube 22, a sealing assembly, a locking mechanism, a piston and a lower joint 24.

[0047] The upper joint 1 is located at the upper part of the sealing and matching integrated device, an oil pipe box is formed at the upper end of the upper joint 1 for connecting an oil pipe, the lower end is sealingly connected with the upper connecting sleeve 5, the inner tube 2 is inserted into the inner part of the upper connecting sleeve 5 for establishing a new injection passage 300, the upper end of the inner tube 2 is an oil pipe box for connecting with an inner tube column of corresponding size;

[0048] Referring to Figure 2 as shown, a liquid passage 100 is formed between the outer wall of the upper joint 1 and the inner wall of the upper connecting sleeve 5, and a circulating through hole 101 is formed in the side wall of the upper joint 1 and is communicated with the liquid passage 100, wherein the inner tube sealing sliding sleeve 4 for plugging the circulating through hole 101 is sealingly connected between the upper joint 1 and the inner tube 2;

[0049] The lower part of the inner tube 2 is a smooth round tube wall, the outer wall of the inner tube 2 cooperates with the inner wall of the inner tube sealing sliding sleeve 4, and the inner wall of the upper joint 1 cooperates with the outer wall of the inner tube sealing sliding sleeve 4, so that the circulating through hole 101 on the upper joint 1 is closed or opened through the closing or opening of the inner tube sealing sliding sleeve 4.

[0050] The upper joint 1 and the inner tube sealing sleeve 4 bottom end, the upper joint 1 and the upper connecting sleeve 5 top end connecting position are provided with shear nails, and the structure, the shear nail includes unsealing shear nail 3 and inner tube sealing sleeve shear nail 6, the upper joint 1 and the upper connecting sleeve 5 are circumferentially connected with unsealing shear nail 3, when the sealing and matching integrated device needs to be unsealed, the upper joint 1 and the upper connecting sleeve 5 produce tensile force or produce rotating force shear unsealing shear nail 3, unseal the seal of oil, the sleeve ring space, the inner tube sealing sleeve shear nail 6 is located on the upper joint 1, is connected in the upper joint 1 and the inner tube sealing sleeve 4 bottom end connecting place, controls the closing and opening of the upper joint 1 circulation through hole 101;

[0051] The upper connecting sleeve 5 upper part is connected with the upper joint 1, and the upper connecting sleeve 5 lower part is connected with the upper rubber cylinder seat 10 of the sealing assembly, and the inner cavity of the upper connecting sleeve 5 and the upper joint 1 form annular liquid passage 100;

[0052] Referring to Figure 2 As shown in the figure:

[0053] The sealing and matching integrated device further includes the upper joint split body 8;

[0054] The upper joint split body 8 is fixedly connected to the bottom end of the upper joint 1, and the lower end of the upper joint split body 8 is screwed with the upper end of the central pipe 9, wherein the upper end of the upper joint split body 8 is connected with the upper joint 1 through the stable nail 7, and the stable nail 7 is used to keep the upper joint 1 and the upper joint split body 8 connected firmly, so as to prevent the upper joint 1 and the upper joint split body 8 from being separated and invalid;

[0055] The central pipe 9 is located between the upper connecting sleeve 5 and the inner tube 2, the upper end of the central pipe 9 is connected with the upper joint split body 8, and the lower end of the central pipe 9 is connected with the central short pipe 22;

[0056] Referring to Figure 2 As shown in the figure:

[0057] The sealing assembly includes: the upper rubber cylinder seat 10, the rubber cylinder shoulder protection 11, the rubber cylinder, the rubber cylinder spacer ring 13, the support pipe 15, and the lower rubber cylinder seat 16;

[0058] The upper rubber cylinder seat 10 is located outside the sealing and matching integrated device, the upper end of the upper rubber cylinder seat 10 is connected with the upper connecting sleeve 5, and the lower end of the upper rubber cylinder seat 10 is connected with the support pipe 15, the rubber cylinder shoulder protection 11 is arranged at the top end and the bottom end of the rubber cylinder 12, and the rubber cylinder shoulder protection 11 is made of soft metal and is used for protecting the upper rubber cylinder 12 and the bottom rubber cylinder 12 from being deformed in the working state;

[0059] The rubber cylinder includes upper and lower rubber cylinders 12 and a middle rubber cylinder 14. The upper and lower rubber cylinders 12 are respectively located at the upper and lower ends of the sealing assembly and are key sealing elements of the sealing and integrated device for the oil sleeve annulus. The rubber cylinders are made of special rubber materials for oil fields. When the rubber cylinders are subjected to axial external force, they are deformed to seal the oil sleeve annulus. The middle rubber cylinder 14 is located at the middle position of the sealing assembly and is also a key sealing element of the sealing and integrated device for the oil sleeve annulus. When the middle rubber cylinder 14 is subjected to axial external force, it is deformed first to seal the oil sleeve annulus;

[0060] A rubber cylinder spacer ring 13 is arranged between the adjacent two rubber cylinders. The rubber cylinder spacer ring 13 can effectively isolate the rubber cylinder 12 and support and isolate the deformation of the rubber cylinder 12, so as to ensure that the rubber cylinder 12 smoothly enters the working state and effectively seals the oil sleeve annulus.

[0061] The support pipe 15 is connected to the upper rubber cylinder seat 10 at the upper end and connected to the lock ring seat 18 at the lower end. The support pipe 15 supports the oil sleeve sealing rubber cylinder. The inner cavity of the support pipe 15 and the center pipe 9 form a liquid passage 100.

[0062] The lower rubber cylinder seat 16 is located at the lower end of the oil sleeve sealing assembly. The upper end of the lower rubber cylinder seat 16 is in contact with the rubber cylinder shoulder 11, and the lower end is in contact with the upper piston 21. The inner wall of the lower rubber cylinder seat 16 and the outer wall of the center pipe 9 form a cavity 400. The side wall of the lower rubber cylinder seat 16 is provided with a first through hole 401 which is in communication with the cavity 400. A lock ring sleeve locking mechanism is designed in the cavity 400 of the lower rubber cylinder seat 16.

[0063] Referring to Figure 3 , it is shown that

[0064] The locking mechanism includes a locking shear pin 17, a lock ring seat 18, a lock ring clamping block 19, and a lock ring 20.

[0065] The lock ring seat 18 is fixedly connected to the lower end of the support pipe 15. The lock ring seat 18 is provided with a lock ring clamping block 19 at the bottom, which is used to control the precise action of the lock ring 20. The lock ring 20 is assembled on the lock ring seat 18 and can float on the lock ring seat 18. When the rubber cylinder of the sealing assembly receives axial pressure and enters the working state, the lock ring 20 cooperates with the lock ring sleeve 200 in the lower rubber cylinder seat 16 to lock the sealing assembly, so that the rubber cylinder maintains the sealing state.

[0066] The locking shear pin 17 is located at the connection between the lower rubber cylinder seat 16 and the lock ring seat 18. When the sealing and integrated device needs to be set, the locking shear pin 17 is sheared to ensure that the oil sleeve sealing assembly normally enters the working state.

[0067] Referring to Figure 3 , it is shown that

[0068] The piston includes an upper piston 21 and a lower piston 23.

[0069] The upper piston 21 is located on the upper portion of the lower piston 23, the center tube 9 is fixedly connected with a center short tube 22 at the bottom end, the outer wall of the center short tube 22 is in sealing connection with the upper piston 21 and the lower piston 23, the top end of the upper piston 21 is in sealing connection with the outside of the center tube 9, the inner wall of the lower piston 23 is in sealing connection with the outer wall of the lower joint 24, the center short tube 22 forms a sealed cavity 500 between the lower piston 23 and the upper piston 21, and the outer wall of the lower piston 23 is provided with a second through hole 501 in communication with the sealed cavity 500;

[0070] The top end of the upper piston 21 is in contact with the lower rubber cylinder seat 16, and the upper piston 21 is pushed upward by the pressure from the inside of the center tube 9, so that the axial force is transmitted to the lower rubber cylinder seat 16, and the rubber cylinder of the sealing assembly is compressed;

[0071] The lower piston 23 is connected to the lower portion of the upper piston 21 and is a power assisting mechanism of the upper piston 21, the lower piston 23 is pushed upward by the pressure from the inside of the center short tube 22, so that the axial force is transmitted to the upper piston 21, and the lower rubber cylinder seat 16 is further pushed to compress the rubber cylinder of the oil jacket sealing assembly, so that the expansion diameter of the rubber cylinder is ensured to effectively seal the annulus of the oil jacket;

[0072] The lower joint 24 is located at the lowermost end of the sealing and matching integrated device, the upper end of the lower joint 24 is connected with the center short tube 22, and the lower end is a tubing box, which is connected with the lower tubing or downhole tool.

[0073] In the above technical scheme, the sealing and matching integrated device has the following working principles:

[0074] 1) Sealing and spacing the annulus of the oil jacket:

[0075] In the working state, the locking shear pin 17 is sheared off under the driving of the center tube 9, the lower piston 23 and the upper piston 21 are pushed upward to generate axial force, the upper rubber cylinder 12, the lower rubber cylinder 12 and the intermediate rubber cylinder 14 are extruded to be elastically deformed and expanded in diameter, so as to seal and space the annulus of the oil jacket, the two layer positions in the wellbore are spaced, the locking ring 20 of the locking mechanism is clamped and locked with the locking ring sleeve 200, the rubber cylinder can maintain the expanded diameter posture, the sealing state is maintained, and the sealing operation is completed;

[0076] 2) Staged water injection:

[0077] According to the actual needs of the water injection well, the placement position and type are determined, the sealing and matching integrated device is installed on the well column of different positions of the well section, and is combined with the corresponding matching tool and process, so that fine water injection operation can be simultaneously performed on two (or three) well sections (layer positions);

[0078] 3) When the injection channel is blocked, reverse circulation well flushing (reverse circulation well flushing is completed by injecting into the inner tube from the annulus);

[0079] The sealing and matching integrator is installed on the well column, the inner tube sealing sleeve shear pin 6 is sheared, the circulation through hole 101 is opened, and the liquid flow passes through the circulation through hole 101, the liquid passage 100, the first through hole 401, and the annular space of the oil jacket, and then returns to the injection passage 300 of the inner tube, so that the reverse circulation well washing operation is realized;

[0080] The sealing and matching integrator disclosed by the utility model adopts axial extrusion rubber cylinders to produce deformation, so that the annular space of the oil jacket is reliably sealed; the double-channel liquid passage design, that is, the outer channel of the circulation through hole 101-liquid passage 100-first through hole 401 and the core tube passage formed by the inner injection passage 300, can realize accurate sealing and matching injection, the inner tube of different sizes is designed and combined with the tool, two-stage (layer) or three-stage (layer) simultaneous water injection can be realized, the size of the water nozzle of the ground intelligent water distribution device matched with the sealing and matching integrator is adjusted, accurate control of the injection amount of each water injection well stage (layer) is realized, the water injection effect is improved, professional operation teams are not needed for downhole fishing operations, the injection time is reduced, the labor intensity of workers is reduced, the comprehensive cost of water injection operations is reduced, the development benefit is improved;

[0081] 2) Acidizing fluid is injected through the water injection passage 300 to realize acidizing and plugging removal, improve the water injection development effect, reduce the labor intensity of workers, effectively reduce the cost of water injection operations, and further reduce the cost of crude oil per ton, and improve the overall development benefit of the oilfield;

[0082] 3) The liquid flow direction of the injection passage 300 is changed, that is, after the inner tube sealing sleeve 4 is moved downward, the liquid passage 100 is opened, the liquid flow passes through the liquid passage 100 from the circulation through hole 101, and then returns to the annular space through the first through hole 401, and then returns to the innermost oil tube, that is, the injection passage 300, realizes reverse circulation well washing of the annular injection core tube, cleans the wellbore of the water injection well, prolongs the maintenance cycle of the water injection well, and improves the utilization rate of the water injection well.

[0083] The above only describes certain exemplary embodiments of the utility model in a descriptive manner, without doubt, for ordinary skilled persons in the art, the described embodiments can be modified in various ways without departing from the spirit and scope of the utility model. Therefore, the above drawings and description are illustrative in nature and should not be understood as limiting the scope of protection of the utility model claims.

Claims

1. A sealing and assembly integrated device, characterized in that, include: Upper connector (1), inner tube (2), and upper connecting sleeve (5) connected to the lower part of the upper connector (1); as well as The central tube (9) is sleeved outside the inner tube (2) and connected to the bottom end of the upper connector (1), and the lower connector (24) is installed at the bottom end of the central tube (9); it also includes A sealing assembly and a piston are sequentially connected to the lower part of the upper connecting sleeve (5); The inner wall of the piston is sealed to the outer wall of the lower connector (24); The sealing assembly has a support tube (15), the outer wall of which is fitted with a rubber sleeve that can be deformed by axial force, and the bottom end of the support tube (15) is equipped with a locking mechanism. In operation, driven by the central tube (9), the piston moves upward to generate axial force to squeeze the annular space of the rubber sleeve expansion diameter sealing oil sleeve, and is locked by the locking mechanism, so that the rubber sleeve can maintain a sealed state.

2. The sealing and assembly unit according to claim 1, characterized in that; The outer wall of the upper connector (1) and the inner wall of the upper connecting sleeve (5) form a liquid passage (100). The side wall of the upper connector (1) is provided with a circulation through hole (101) communicating with the liquid passage (100). The upper connector (1) and the inner tube (2) are sealed with an inner tube sealing sleeve (4) for sealing the circulation through hole (101).

3. The sealing and assembly unit according to claim 2, characterized in that; Cutting pins are provided at the connection positions of the upper connector (1) and the bottom of the inner tube sealing sleeve (4), and at the top of the upper connector (1) and the upper connecting sleeve (5).

4. The sealing and assembly unit according to claim 1, characterized in that; The sealing assembly also includes an upper glue tube seat (10) and a lower glue tube seat (16) sleeved outside the support tube (15), with the glue tube disposed between the upper glue tube seat (10) and the lower glue tube seat (16).

5. The sealing and assembly unit according to claim 4, characterized in that... ； The end of the rubber tube contacts the ends of the upper rubber tube seat (10) and the lower rubber tube seat (16) through the rubber tube shoulder protector (11).

6. The sealing and assembly unit according to claim 5, characterized in that... ； The rubber tubes include multiple tubes, and a rubber tube spacer ring (13) is installed between two adjacent rubber tubes.

7. The sealing and assembly unit according to claim 4, characterized in that; A cavity (400) is formed between the inner wall of the lower rubber sleeve seat (16) and the outer wall of the central tube (9), and a first through hole (401) communicating with the cavity (400) is opened on the side wall of the lower rubber sleeve seat (16).

8. The sealing and assembly unit according to claim 1 or 4, characterized in that... ； The locking mechanism includes a locking ring seat (18), the top end of which is connected to the support tube (15), a locking ring block (19) is provided at the bottom end of the locking ring seat (18), a locking ring (20) is fitted on the outside of the locking ring block (19), and the lower rubber sleeve seat (16) of the sealing assembly is provided with a locking ring sleeve (200) that cooperates with the locking ring (20); A locking shear pin (17) is connected between the locking ring seat (18) and the lower rubber sleeve seat (16) of the sealing assembly.

9. The sealing and assembly unit according to claim 1, characterized in that... ； It also includes an upper connector split body (8) that seals and connects the upper connector (1) and the central tube (9), and a stabilizing pin (7) is connected between the top end of the upper connector split body (8) and the upper connector (1).

10. The sealing and assembly unit according to claim 1, characterized in that... ； The piston includes an upper piston (21) and a lower piston (23) that abuts against the upper piston (21); The bottom end of the central tube (9) is fixedly connected to a central short tube (22), and the outer wall of the central short tube (22) is sealed to the upper piston (21) and the lower piston (23); The top end of the upper piston (21) is sealed to the outside of the central tube (9); The inner wall of the lower piston (23) is sealed to the outer wall of the lower connector (24).

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