High torque and high capacity rotatable center core and floatable sealed body assemblies with universals ram applications and method

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of my application filed Nov. 26, 2001 and bearing Ser. No. 09/994,161.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The system of the present invention relates to high torque and high capacity rotatable center core and floatable seal body assemblies with universal ram applications and the method of undertaking same. More particularly, the present invention relates to an apparatus that would allow one to pick up the entire weight of the drill string tubing or pipe which would allow one to rotate from the top and have the torque completely through it while rotating.

2. General Background of the Invention

In undertaking wireline work utilizing a side entry device in the present state of the art, the device includes a packoff assembly or grease seal assembly at the entry to the side entry port or top entry port which provides for protection against blowouts while the device is in use. However, while wireline is being lowered through the device, there must be an additional method to seal off the passageway while the wireline is in place. Therefore, there are provided blowout preventors positioned below the wireline packoff on the side entry device which may be manually or hydraulically closed to seal oft the wireline in case of a blowout. Such blowout preventors are manufactured by, for example, Bowen Inc. under the name.

However, it would be beneficial to have such a blowout preventor located in the drill string itself, above the rig floor, which would allow the wireline to be sealed off below the swivel. In that manner, when the drill string below the swivel needs to be rotated to provide torque, the blowout preventors would simply rotate with the drill string. However, in the case of a blowout, or in the event work needed to be done above the swivel above this side entry device, while the well is under pressure, the blowout preventors could be closed off. The type of blowout preventors currently used, as discussed above, manufactured by Bowen Inc., would not have the capability of being placed within the drill string, since the device could not withstand the enormous weight of the drill string below the preventors. So, there is a need for a type of blowout preventors that can be positioned below the swivel, within the drill string, that can be maintained open, and allow to rotate freely with the string, but in the event work needed to be done above the device, the blowout preventors would be closed, and the well, although under pressure would not be capable of blowing out during the curative work. The system of the present invention solves many problems in the art.

BRIEF SUMMARY OF THE INVENTION

An apparatus for use in a drill string is disclosed. The apparatus comprises an inner core assembly having a first and second transverse bore, and has a shoulder formed thereon. A first outer core assembly is slidably disposed about the inner core assembly and rests on the shoulder. The outer core assembly has a first and second transverse bore that is aligned with the first and second transverse bore of said inner core assembly.

The apparatus further comprises a first piston means, disposed within the first and second transverse bore of the outer core assembly, for closing an internal longitudinal bore of the inner core assembly. The apparatus further comprises a ring inserted into an indentation on the inner core assembly, with the ring abutting a top surface of the outer core assembly. A pin means for maintaining the inner core assembly in line with the first outer core assembly may also be included. In one of the preferred embodiments, the inner core assembly is connected at one end to a drill string and at the other end to a swivel.

In one embodiment, the first piston means comprises a first piston member disposed within the first transverse bore of the outer core assembly, a second piston member disposed within the second transverse bore of the outer core assembly, and means for moving the first and second piston member into the internal longitudinal bore of the inner core assembly in order to close seal the internal bore. The first piston member may include a first sleeve disposed within the first transverse bore of the outer core assembly; and the second piston member may include a second sleeve disposed within the second transverse bore of the outer core assembly.

In one of the embodiments, the apparatus further comprises a third and fourth transverse bore positioned within the inner core assembly and a third and fourth transverse bore positioned within the first outer core assembly that is aligned with the third and fourth transverse bore of the inner core assembly. A second piston means, disposed within the third and fourth transverse bore of the outer core assembly, is included for closing the internal longitudinal bore of the inner core assembly.

In another embodiment, a second outer core assembly is slidably disposed about the inner core assembly and rests on a first outer surface of the first outer core assembly, and wherein the second outer core assembly has a third and fourth transverse bore that is aligned with a third and fourth transverse bore located within the inner core assembly. With this embodiment, a second piston means, disposed within the third and fourth transverse bore of the second outer core assembly, is included for closing the internal longitudinal bore of the inner core assembly. In this embodiment, the first and second piston means comprises: a first piston member disposed within the first transverse bore of the first outer core assembly; a second piston member disposed within the second transverse bore of the first outer core assembly; a third piston member disposed within the third transverse bore of the second outer core assembly; a fourth piston member disposed within the fourth transverse bore of the second outer core assembly; and, means for moving the first, second, third, and fourth piston members into the internal longitudinal bore in order to close the internal longitudinal bore.

A method of sealing off flow in a work string is also disclosed. The method comprises providing an apparatus containing an inner core assembly having a first and second transverse bore, and a shoulder formed thereon; a first outer core assembly slidably disposed about the inner core assembly and resting on the shoulder, the outer core assembly having a first and second transverse bore that is aligned with the first and second transverse bore of the inner core assembly; first piston means, disposed within the first and second transverse bore of the outer core assembly, for closing an internal longitudinal bore disposed through the inner core assembly.

The method further comprises connecting the work string to the inner core assembly and transmitting the weight of the drill string to the inner core assembly. Next, the work string is rotated so that a torque is created, and the torque is transmitted through the inner core assembly. The rotation of the work string is terminated. The first piston means is closed in order to close off the internal longitudinal bore of the inner core assembly. Next, the first piston means is opened thereby opening the internal longitudinal bore.

A concentric work string, such as wireline, is provided within the internal longitudinal bore. The concentric work string may have attached thereto a down hole assembly. The concentric work string is run down the work string with the down hole assembly. Next, the first piston means is closed about the wireline within the internal longitudinal bore. Curative work may be performed on the wireline above the first piston means. Next, the first piston means is opened so that the internal longitudinal bore is unsealed. The concentric work string can then be pulled from the work string.

In another embodiment, at least one blowout preventor is positioned within the drill string, above the rig floor, between a swivel and a length of drill pipe below. The apparatus includes an outer core assembly (sometimes referred to as a principal body portion) having a central bore for accommodating an inner core assembly (sometimes referred to as a central assembly), having a first end attached to the lower end of the swivel, and a lower end attached to the drill pipe below. The inner core assembly would include a central bore for accommodating the passage of fluid, tubulars and/or wireline therethrough; there is further provided a pair of transverse bores which would be aligned with the pair of traverse bores in the outer core assembly so as to provide a piston within the bores, capable of moving into the central bore of the inner core assembly to seal the cental bore from flow therethrough; there is further provided a sleeve slidably engaged within the transverse bores for aligning the bores of the body and the inner core assembly; the inner core assembly would provide an annular shoulder around its lower portion so that the outer core assembly would rest upon when the transverse bores are aligned; there would be provided an upper ring in the wall of the inner core assembly to maintain the outer core assembly in place between the shoulder and the upper ring; further, there are provided sealing rings to prevent fluid in the pistons of the apparatus from seeping into other parts of the assembly. There may be provided a plurality of the blowout preventors stacked one upon the other, which would allow multiple sealing off of the wireline, or other small pipe as wash pipe or coiled tubing, but would not be interconnected so as to avoid potential stretching when the inner core assembly must take the weight of the drill string down hole.

The apparatus and method involved would allow one to pull on a center core and have the block with the rams without exerting any pull on the outside body of the block, which would allow one to rotate the drill string without having the torque on the outer core assembly exerted. By using a separate outer core assembly in the system, if the inner core assembly would have stretch and torque, the outer core assembly would be spared from the same stretch and/or torque.

This system could be used when the wire of a wireline unit balls up under the pack off or grease head flow tubes. The operator could close off the apparatus and perform the curative work desired above the apparatus. If an unexpected pressure is exerted on the well, in order to correct the problem, one will close the rams in order to seal off the pressure; then the operators would bleed off above the rams. If one has a pump down tool below the rams, this would allow one to pump fluids downhole if one would need to kill the well.

A method of sealing off flow in a tubular string while using a concentric work string is also disclosed. The concentric work string can be a coiled tubing string. The method comprises providing a sealing apparatus having an inner core assembly and an outer core assembly. The method includes connecting the tubular string to a first end of the inner core assembly and connecting a swivel to a second end of said inner core assembly. Next, the weight of the tubular string is transmitted to the inner core assembly, and the coiled tubing is lowered into the tubular string and through the internal bore of the inner core assembly, and wherein the coiled tubing disposed within the tubular string creates an annular space.

The method further includes rotating the tubular string so that a torque is created, and transmitting the torque through the inner core assembly. Rotation of the tubular string is terminated and the piston means is closed about the coiled tubing in order to seal off the annular space. Next, a fluid is pumped through a side entry sub located below the apparatus, the fluid being pumped into the annular space.

The method further comprises opening the piston means so that the annular space is unsealed and running into the well bore with the coiled tubing to a desired depth. Next, the piston means is closed about the coiled tubing thereby closing the annular space. The method may further comprise opening the piston means so that the annular space is opened and pulling force may be exerted on the tubular string. The weight of the tubular string is transmitted through the outer core assembly. Rotation of the tubular string creates torque which is transmitted to the outer core assembly. Rotation may be stopped and the coiled tubing is pulled out of the tubular string.

It is a principal object of the present invention to provide a blowout preventor system above the rig floor within the drill string to allow sealing off of downhole pressure in order to do work on a side entry or top entry device above the swivel.

It is a further object of the present invention to provide a blowout preventor system in the drill string above the rig floor which can withstand the weight of the drill string without damage to the blowout preventors.

It is a further object of the present invention to provide a blowout preventor system in the drill string above the rig floor which would allow for a plurality of separate outer core assemblies aligned in sequence. This embodiment allows the apparatus to withstand the weight of the drill string but avoid the outer core assembly from being damaged.

It is a further object of the present invention to include a method and apparatus, which would provide a blowout preventor type of seal assembly in the drill string that would allow one to pick up the entire weight of the drill string tubing or pipe and still be able to rotate from the top and have the torque completely go through the apparatus in order to rotate the pipe below it.

It is a further object of the present invention to provide a system which would allow tools or pipe to enter down the center bore of the apparatus, and would allow the apparatus to be closed to control downhole well pressure in the event any tools or pipe above it would need to be worked or changed. Thus, curative work could be performed while controlling well pressure below the apparatus.

It is a further object of the present invention to provide a system for use on chemical cutting or regular logging applications where you can use with high pressure tubing connections or high pressure connections that includes a grease head on top to control well pressure. This would allow one to eliminate the Bowen quick connections which are normally used without elevators and would not have pulled on the tubing below.

It is a further object of the present invention to provide a system which is applicable when doing many types of applications, for instance, the operator is able to pull while chemical cutting the pipe below with heavy loads and still have the availability to rotate the pipe. Prior art blow out preventors cannot rotate or withstand heavy loads. The present invention solves these problem.

An advantage of the High Torque and High Capacity Rotatable Center Core and Floatable Sealed Body Assemblies with Universal Ram Applications and Method is that in the present state of the art, there are no drill pipe blow out preventors (BOP) with seal assemblies that would allow one to pick up the entire weight of the drill string, tubing or pipe without damaging the apparatus. Furthermore, there are no current BOP assemblies which would enable one to rotate from the top and have the torque completely go through the BOP assembly to rotate the pipe below the assembly. The apparatus of the present invention will rotate with the pipe. It could be used when the wireline strands in the grease head and on the pack off assembly have a leak or any of the connections above the assembly within the lubricator are leaking. With the use of the apparatus of the present invention, one would be able to hold the load of the drill string and seal off on any items such as wireline that the seals are installed to fit, and in turn, the operator could correct the problems above the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements.

FIG. 1A

is a cross-section view of the apparatus, which is one of the preferred embodiments of the present invention.

FIG. 1B

is a partial cross-section view of the apparatus seen in FIG.

1

A.

FIG. 2

is a perspective view of the outer core assembly of the apparatus seen in

FIGS. 1A and 1B

of the present invention.

FIG. 3

is a cross-section view of the outer core assembly taken from line

3

—

3

of FIG.

2

.

FIG. 4

is a perspective view of the pistons of the apparatus engaging a wireline.

FIG. 5

is a cross-section view of a second embodiment of the apparatus having a composite double outer core assembly.

FIG. 6

is a cross-sectional view of the pistons of the double core assembly from

FIG. 5

engaging a wireline.

FIG. 7

is a cross-sectional top view of the view of the top pistons taken along line

7

—

7

of

FIG. 6

engaging the wireline.

FIG. 8

is a schematic illustration of the single apparatus of the present invention seen in

FIG. 1

positioned below a swivel for use during wireline work in the drill string above the rig floor.

FIG. 9

is a schematic illustration of a third embodiment of the apparatus having a pair of outer core assemblies positioned below a swivel for use during wireline work in the drill string above the rig floor.

FIG. 10

is a schematic illustration of the apparatus below the swivel and above a side entry sub above the rig floor.

FIG. 11

is a schematic illustration of outer core assemblies positioned below the swivel but above a side entry sub in the drill string above the rig floor.

FIG. 12

is a cross-sectional view of the preferred embodiment of the trap door assembly.

FIG. 13

is a cross-sectional view of the trap door assembly taken from line

13

—

13

of FIG.

12

.

FIG. 14

is a cross-sectional view of the trap door assembly taken from line

14

—

14

of FIG.

12

.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-14

illustrate the preferred embodiments of the apparatus and system of the present invention as would be utilized in a work string, such as a drill string. Referring to

FIG. 8

, the apparatus

10

a

, which may be referred to as a high torque floatable seal body assembly, would be threadedly connected to a drill string

16

below a locking or regular swivel

14

. In effect, the high torque floatable seal body apparatus

10

a

would be an apparatus for use as a blowout preventor within the drill string

16

above the rig floor

18

, as seen in FIG.

8

.

Prior art blowout preventors were placed below a packoff

20

of a side entry device

22

.

In operation, the apparatus could be utilized as a single apparatus as seen in

FIGS. 1A and 1B

; or, a pair of outer core assemblies, positioned atop one another, as seen in

FIG. 9

; or, as a composite double outer core assembly as seen in FIG.

5

. In each configuration, the operation of the apparatus would be to carry out the same function.

Reference is made to

FIG. 1A

where is seen a cross section view of the single apparatus

10

a

which includes the outer core assembly

30

a

, and an inner core assembly

32

a

having a threaded portion

34

on its upper end and a male threaded portion

36

on its lower end. The upper threaded end

34

would connect to the lower end of the swivel, for example,

14

, as seen in

FIG. 8

, and the lower end

36

of the inner core assembly

32

a

would attach to the section of drill pipe

16

, as illustrated in FIG.

8

.

The inner core assembly

32

a

includes a continuous longitudinal bore

38

therethrough, as seen in

FIGS. 1A and 1B

, for allowing the flow of fluids or other concentric items such as coiled tubing or wireline therethrough as it is inner-connected between the swivel and the length of drill pipe as is appreciated by those of ordinary skill in the art. It should be noted that like numbers appearing in the various figures refer to like components.

As seen in

FIG. 1A

, the inner core assembly

32

a

would also include a radial transverse bore

40

a

extending across its entire width which would intersect the vertical bore

38

therethrough. Transverse bore

40

a

would house piston

70

a

therein as would be described further. A second bore

40

b

and second piston

70

b

are disposed within the apparatus

10

a.

The inner core assembly

32

a

further provides a substantial shoulder portion

42

, as seen in

FIG. 1A

, for allowing the outer core assembly

30

a

to rest thereupon, as will be discussed further, during use of the apparatus

10

a

. Further, there is noted an annular indentation

44

around the wall of inner core assembly

32

a

which would house a ring

45

(sometimes referred to as sleeve

45

) which would maintain the outer core assembly

30

a

to rest on shoulder

42

, again as will be discussed further.

As further seen in

FIG. 1A

, expanded shoulder

42

would hold the outer core assembly

30

a

in line by pin members

47

a

,

47

b

that will maintain the outer core assembly

30

a

and allow rotation with the inner core assembly

32

a

. Pin members

47

a

,

47

b

are inserted into apertures

47

c

,

47

d

in the shoulder

42

and corresponding apertures

47

e

,

47

f

in outer core assembly

30

a

. The pin members

47

a

,

47

b

will allow slight longitudinal movement up and down as the weight of the drill string creates a certain amount of stretch. The pin members

47

a

,

47

b

are large enough to keep the inner core assembly

32

a

and the outer core assembly

30

a

rotating together and keeps the entire apparatus

10

a

in line. The pin members

47

a

,

47

b

may be attached to the shoulder

42

by conventional means such as thread engagement.

The ring

45

slides on the upper portion of the inner core assembly

32

a

and would be locked as seen in FIG.

1

B. The ring

45

will keep the outer core assembly

30

a

in line with inner core assembly

32

a

so that under heavy loads, although inner core assembly

32

a

may have stretch, the ring

45

will allow inner core assembly

32

a

to stay in line. When the apparatus

10

a

is required to be activated i.e. closed, the pistons

70

a

,

70

b

will properly seal since there is no bending motion or torque on the outer core assembly

30

a

. The pistons may be referred to as rams.

Turning to

FIGS. 2 and 3

, there is illustrated the outer core assembly

30

a

which in the preferred embodiments is either a substantially cubical shape but can also be a circular shaped block. The outer core assembly

30

a

seen in

FIG. 2

contains a first vertical bore

52

, the bore

52

having an interior diameter substantially equal to the exterior diameter of inner core assembly

32

a

. The inner core assembly

32

a

will be disposed within the bore

52

. There would further be provided transverse bores

54

a

,

54

b

extending through each end

55

of the outer core assembly

30

a

which would be in communication with the bore

52

.

FIG. 3

depicts a cross-sectional view of the outer core assembly

30

a

seen through line

3

—

3

of FIG.

2

.

Referring again to

FIG. 1A

, the two bodies

30

a

and

32

a

work in combination. That is, the outer core assembly

30

a

would be slidably engaged upon the upper end of inner core assembly

32

a

in the direction of arrow

60

seen in

FIG. 1A

, so that the outer core assembly

30

a

would then come to rest upon the upper surface of shoulder

42

. When coming to rest on shoulder

42

, the transverse bores

54

a

,

54

b

of outer core assembly

30

a

would be in alignment with transverse bore

40

a

,

40

b

respectively in the inner core assembly

32

a

, and would be maintained in line by the pin members

47

a

,

47

b

as described earlier. It should be noted that bores

54

a

,

54

b

would be aligned with bores

40

a

,

40

b

respectively. When that particular alignment is complete, there would then be provided the ring

45

which as seen in

FIG. 1A

, placed into the groove

44

in the wall of inner core assembly

32

a

, so as to maintain the outer core assembly

30

a

between the shoulder

42

and the ring

45

so that the outer core assembly

30

a

would minimally move up and down during use.

In

FIG. 1A

, outer core assembly

30

a

is illustrated resting on shoulder

42

with the transverse bores

54

a

,

54

b

of block

30

a

aligned with bore

40

a

,

40

b

of inner core assembly

32

a

. In order to assure the proper alignment and to ensure that the pistons

70

a

,

70

b

which would be operated within the bore

54

a

and

54

b

are properly engaged, there would be included a sleeve

57

a

,

57

b

, cylindrical in nature, which would slide within each of bores

54

a

and

54

b

and terminate within the notched area

31

a

,

31

b

in the body wall of inner core assembly

32

a

. When both sleeves

57

a

,

57

b

have been disposed within bores

54

a

,

54

b

, and engaged into the notches

31

a

,

31

b

, it is therefore assured that the bores

40

a

,

40

b

and bores

54

a

,

54

b

are properly aligned.

FIG. 1A

further illustrates the outer core assembly

30

a

disposed about the inner core assembly

32

a

with piston members

70

a

,

70

b

having been inserted into each of the bores

54

a

,

54

b

of the outer core assembly

30

a

. The piston member

70

a

, as illustrated, would be threaded through a cap

71

a

which would be threaded into the bore

54

a

and sealed therein with O-rings. Piston

70

a

would be secured to the end of a threaded shaft

73

a

threaded through cap

71

a

, so that rotation of shaft

73

a

would move piston

70

a

in or out of bore

54

a

as needed. Piston

70

b

is similarly constructed with cap

71

b

and shaft

73

b.

Reference is now made to

FIG. 4

, where the pistons

70

a

,

70

b

are seen in isolated view being moved inwardly to grasp the wireline

77

to prevent fluid flow past that point. It should be noted that the pistons

70

a

,

70

b

may also be referred to as rams

70

a

,

70

b

. The pistons

70

a

,

70

b

move inwardly, as denoted by arrow

81

a

. For instance, rotation of shaft

73

a

moves piston

70

a

inward.

Returning to

FIG. 1A

, the sleeves

57

a

,

57

b

in the bores

54

a

,

54

b

would also be sealed with O-rings to assure that any pressure which would be contained within the apparatus

10

a

(and which is generated by the well) would be sealed therein. The numerous O-rings provided with the apparatus

10

a

are denoted by the letter “O”. The details of the operation of the pistons are not novel in the sense that the pistons used would be the same pistons that are used quite commonly in the industry on such tools as the Bowen blowout preventors, commercially available from Bowen Oil Tools Inc. under the name Blowout Preventor. Additionally, details of the operation of the O-rings are well known in the art. O-rings are commercially available from Industrial Products Inc. under the name Viaton.

Reference is now made to

FIG. 5

which illustrates a second embodiment of the apparatus, denoted as

10

b

, having a composite double outer core assembly

32

b

.

FIG. 5

depicts an inner core assembly

32

b

having a bore

38

therethrough, an upper thread engagement

34

and a lower thread engagement

36

. Unlike the inner core assembly

32

a

seen in

FIG. 1A

, this particular inner core assembly

32

b

would include a pair of lower transverse bores

40

a

,

40

b

and a pair of upper transverse bores

40

c

,

40

d

so as to accommodate two sets of pistons, namely

70

a

,

70

b

and

70

c

,

70

d

. As with the embodiment as seen in

FIG. 1A

, the apparatus

10

b

of

FIG. 5

would include the pin members

47

a

,

47

b

which would function in the same manner. Again, there is also included the shoulder member

42

and the upper ring

45

. As seen in particular in

FIG. 5

, the composite double outer core apparatus

30

b

comprises a lower

54

a

,

54

b

and an upper set of transverse bores

54

c

,

54

d

, which has been slidably engaged in the direction of arrow

60

onto the inner core assembly

32

b

. There is illustrated sleeves

57

a

,

57

b

,

57

c

,

57

d

of the type that would be slidably engaged into the bores

54

a

,

54

b

,

54

c

,

57

d

, respectively, of the block assemblies and would be latched within notches

31

a

,

31

b

,

31

c

,

31

d

. The double outer core apparatus

30

b

would accommodate a pair of pistons therein, namely top pistons

70

c

,

70

d

and bottom pistons

70

a

,

70

b

. This particular embodiment constitutes a more effective mode to be able to maintain a double seal via double pistons

70

a

,

70

b

and

70

c

,

70

d

against the wireline

77

.

FIG. 6

depicts a cross-sectional view of the pistons of the double core apparatus

30

b

in the closed position. As illustrated in

FIG. 6

, the double seal is seen with the upper set

70

c

and

70

d

and lower set of pistons

70

a

,

70

b

grasping the wireline

77

to effect a more effective seal than a single set of pistons

70

a

,

70

b

as was seen with the embodiment of FIG.

4

. As seen in

FIG. 6

, the piston member

70

c

is connected to shaft

73

c

which may be operated either hydraulically or manually. Depending on the rotation of shaft

73

c

, the pistons move either interiorly or exteriorly relative to the outer core assembly

30

b

. Pistons

70

a

,

70

b

are moved inwardly as denoted by arrows

81

a

,

81

b

. Pistons

70

c

,

70

d

are moved inwardly as denoted by arrows

81

c

,

81

d

. Once pistons

70

a

,

70

b

, and pistons

70

c

,

70

d

are in place, they would seal against, for example, a wireline

77

which is disposed through the bore

38

in order to sealingly engage therein.

FIG. 7

illustrates a partial cross-sectional top view of the top pistons

70

c

,

70

d

taken along line

7

—

7

of

FIG. 6

moved inward engaging the wireline

77

. Therefore, should there by any problem with wireline use, the positioning of the apparatus

10

b

below the locking or regular swivel

14

, one would simply engage the pistons

70

a

,

70

b

, and pistons

70

c

,

70

d

to close off the bore

38

and sealingly engage wireline

77

which in turn prevents any fluid flow and/or pressure flow through the bore

38

above the apparatus

10

b

. In the event that the embodiment of the outer core assembly

30

b

and inner core assembly

32

b

has to take a very heavy load of the work string, there is a chance that the inner core assembly

32

b

will have some stretch due to the load. Should this occur, the transverse bores

54

a

,

54

b

, and bores

54

c

,

54

d

will become slightly misaligned with the bores

40

a

,

40

b

and

40

c

,

40

d

of the inner core assembly

32

b

, which could affect the ability of the pistons

70

a

,

70

b

and pistons

70

c

,

70

d

from moving in and out of the inner core assembly

32

b

. It should be noted that this misalignment would also be similar for the single embodiment seen in

FIGS. 1A

,

1

B.

Therefore, in some cases it may be preferred to employ multiple points of sealing against the work string (i.e. pistons

70

a

,

70

b

and

70

c

,

70

d

) with multiple outer core assemblies

30

a

of the type illustrated in FIG.