NO146248B - DEVICE FOR LOADABLE FITTING OF AN OBJECTS, EX. A Borehole Cement Plug for a Stir-Shaped Enclosure - Google Patents

Description

The invention relates to a device for releasably attaching an object, e.g. a borehole cementing plug for a tube-shaped casing as specified in more detail in the introduction to the following main claim.

US patent 2,438,992 describes an apparatus for borehole cementing that uses two sequentially triggered cementing plugs, US patent 3,364,996 also describes an apparatus that uses two sequentially triggered cementing plugs, and US patent 3,545,542 likewise describes an apparatus that uses two sequentially triggered cementing plugs.

Problems have been encountered with the use of extraction devices for cementing plugs due to premature release of the cementing plugs. As the cementing operation for a borehole, due to its very nature, will cause the cementing plugs to be cemented in the borehole at the end of the cementing operation, it is particularly difficult to determine the cause of such premature release. However, some probable causes have been identified. One such problem is breakage of shear pins due to twisting forces on the plugs relative to the part of the drill pipe to which they are attached. Another is the pressure wave described in US patent 3,616,850 which occurs when the closing element is placed in the respective plugs.

Problems have also arisen due to failure

in releasing the cementation plugs at all. The reason for this has also been difficult to establish, because the evidence, as noted above, is cemented into the borehole or well, and must be drilled out and thereby destroyed. However, one reason has been found to be the so-called "Brinelling" or the embedding of steel balls which are used as part of normal release equipment to avoid torsional forces and pressure waves as mentioned above,

down the drill pipe. The use of such steel balls is explained in

HALLIBURTON SERVICES SALES AND SERVICE CATALOG No. 37,

page 2.404.

As multiple cementing plugs thus work very satisfactorily when these plugs are released correctly, there is a need for a more reliable release mechanism.

The device according to the invention solves these and other problems.

According to the invention, a device of the type indicated above has been provided, which is characterized by the fact that the collar arranged between the sleeve and the enclosure has an upper part attached to a retractable, outwardly extended upper ledge part which can be placed against an internal ledge in the enclosure and constitutes the said holding device and that the object is carried by an intermediate piece which is releasably attached to the collar.

The device according to the invention is described in more detail with reference to the drawings, where fig. 1 is a schematic section of a system for a cementing plug, where the device according to the invention can be used, fig. 2 is a partially cut away perspective view of a device for releasing an upper plug using the invention, fig. 2a, 2b, 2c,

2d, the right side is shown only schematically in section of the device in fig. 2 at different stages of the operation.

With reference to fig. 1 shows the main construction of an underwater borehole casing with cementing plug system 1 comprising the invention.

The system 1 comprises a rigging part 2 carried by a rigging floor 3 above the sea surface 4, an underwater part 5 between the rigging floor 3 and the seabed 6 and a part 7 which is located below the seabed 6.

The rig part 2 comprises a plug container 8, an upper release plug 9, a retractable plunger piston 11, a release ball 12, a ball channel 13, an extendable plunger piston 14, a cement inlet 15 and an upper part of a drill pipe 16. The upper release plug 9 is located inside the upper section 10 of the plug container 8. A retractable plunger piston 11 in

releasably carries the upper release plug 9. Release

the ball 12 is located inside a ball channel 13 and is T-shaped connected to the plug container 8 below the plunger piston 11 and abuts the extendable plunger piston 14. The cement inlet 15 is preferably T-shaped connected to the plug container 8 below the plunger piston 11, although this inlet 15 could be itself anywhere below the plunger piston 11 and the part 7 below the surface. The drill pipe 16 extends downwards from the plug container 8.

The underwater part 5 comprises the middle part of the drill pipe

16 and an installation tool 17 attached to the lower end of the drill pipe 16.

The subsurface part 7 comprises a well casing suspension 18, an intermediate piece 19 for the cementing head, an upper plug release mechanism 20, an inner casing 21, outer casing 22, upper cementing plug 23 and lower cementing plug 24. The well casing suspension 18 is fixed in the upper end of the outer liner 22 and the construction tool 17 are sealingly attached to the suspension 18, whereby the drill pipe is sealingly attached indirectly to the part 7 which is below the surface. The suspension 18 carries the inner liner 21 inside the outer liner 22

and forms between these the annular space 25, the intermediate piece 19 for the cementing head hangs downwards from the tool 17 and the intermediate piece 19 holds and carries the upper plug release device 20. This device 20 releasably holds the upper cementing plug 23

and this in turn releasably holds the lower cementing plug 24.

With reference to fig. 2, it will be seen that the construction of the release device 20 for the upper plug in the fully retained position comprises a casing 30, a bushing 40, a collar 50,

a sleeve 60, an upper spacer 70 for cementing plug,

a cutting element 80 and a swivel 90. In the fully fixed position shown in fig. 2, the housing 30 internally carries a bushing 40 which holds back and supports the swivel 90 inside the housing 30. The swivel 90 internally carries the collar 50, and this in turn carries the intermediate piece 70 internally. The intermediate piece 70 internally carries the sleeve 60 by means of a cutting element 80 which connects it inner surface of the intermediate piece 70 with the outer surface of the sleeve 60.

The housing 30 is a cylinder with an axial bore

31 which connects an upper end 32 with a lower end 33. Upper internal threads 34 extend from the upper end 32

down a sufficient distance in the housing 30 to make it possible to achieve a solid threaded connection of the housing 30 with the cementing head intermediate piece 19 in fig. 1. An axial recess 35 of larger diameter than the axial bore 31 extends upwardly from the lower end 33 to a central portion 36 of the housing 30 to produce an annular ledge 37. The ledge 37 may be conical if desired. Lower internal threads 38 extend upwards inside the recess a sufficient distance to ensure a solid threaded connection for the bushing 40 as described below. A set screw 39 connects the housing 30 to the bushing 40 to ensure that the bushing will not be turned out of engagement with the housing 30.

The bushing 40 is a cylinder with an axial bore 41 therethrough and an upper external recess 42. The bushing 40 likewise has an axial recess 43 which extends downwards from its upper end 44 to produce an annular ledge 45. The axial recess 4 3 is provided with a first groove 46 which contains the first seal 47 to prevent fluid passage between the collar 50 and the bushing 40. The annular ledge 45 can be cone-shaped if this is desired. An external recess 42 is provided with another groove 46a

which contains another seal 47a to prevent fluid passage between the housing 30 and the bushing 40. The external recess 42 is also provided with a cavity to receive a set screw 39, and the external recess is provided with external threads corresponding to the lower internal threads 38 in the housing 30. The upper end 44 of the bushing 40 forms an annular abutment when the bushing 40 is screwed into the housing

30. The swivel 90 comprises a track bearing 91 and a thrust bearing 92. The thrust bearing 92 is an annular band with substantially the same annular area as the annular abutment ledge formed by the upper end 44 of the bushing 40 inside the housing 30, and the thrust bearing 92 is placed on top of the upper end 44 of the bushing 40. The bearing 91 has an annular cross-section with essentially the same area as both the thrust bearing 92 and the upper end 44, and the bearing 91 rests rotatably on top of the thrust bearing 92. The bearing 91 can be cone-shaped if desired.

The collar 50 comprises an upper retractable ledge part

51, an upper finger-like part 52, a middle main part 53,

a lower finger-like portion 54 bg a lower expandable ledge portion 55. The upper finger-like portion 52 has sufficient length to reach from the upper inner edge of the bearing 91 down past the thrust bearing 92 to just above the groove 46 in the bushing 40. The portion 52 is slotted and has less thickness to allow inward bending thereof. The lower finger-like portion 54 is of sufficient length to reach from just below the groove

46 downwards to the recess 77 on the intermediate piece 70 for the upper cementing plug as described below. The part 54 is slotted and has less thickness to allow this outward bending. The main part 53 has an external diameter that is larger than the diameter of the axial bore 41, but smaller than the diameter of the recess 43, so that downward movement of the main part 53 is limited by an annular shoulder 45. The contractible ledge part 51 has an outer ledge 56 intended for to

fit the upper edge of the bearing 91 when retained by the trumpet-shaped end 61 of the sleeve 60 as described below. The expandable ledge part 55 has an inner ledge 57 designed to fit inside an outer recess 77 in the upper intermediate piece 70 for the cementing plug as described below. The expandable ledge part 55 is internally held back by means of the axial bore 41 in the bushing 40.

The spacer 70 for the upper cementing plug is

an annular cylinder with an upper section 71, a middle section 72 and a bottom section 73. An axial bore 74 extends through the bottom section 73, while a countersunk bore 75 of larger diameter than the axial bore 74 extends through the upper section 71 and the middle section 72 to form a lower inner annular shoulder 76. The middle section 72 is provided with an outer recess 77 adapted to mate with the circumference of the inner recess 57 in the expandable shoulder portion 55 of the collar 50. The upper section 71 of the intermediate piece 7C

is provided with an external groove 71a which holds a seal 71b. The seal 71b rests against the main part 53 of the collar 50 for

to prevent fluid passage between the collar 50 and the intermediate piece 70. The upper part 71 also has a cutting hole 81 which can contain the transition end 82 of the cutting element 80. The cutting hole 81 lies next to a corresponding cutting recess 65 in the sleeve 60 as described below. The middle section 72 of the intermediate piece 70

is provided with an internal recess 78 for reasons to be described later. The recess 78 produces an upper internal annular shoulder 76a and a further recess with a lower internal annular shoulder 76. The bottom section 73

is provided with external threads 79 adapted for receiving corresponding threads in the upper cementing plug 23 in fig. 1.

The sleeve 60 is a cylinder with an axial bore 61 which comprises an upper external trumpet-shaped section 62. The trumpet-shaped end 62 is provided with a contact plate 65 intended for sealingly receiving the upper release plug 9 in fig. 1 in a conventional manner to thereby seal the axial bore 31 in the housing 30 against fluid passage in cooperation with the seals 46, 46a, 71a described above and the seal 66 described below. The trumpet-shaped end 62 has an external diameter which is somewhat smaller than the internal diameter of the upper contractible landing part 51 of the collar 50, so that the trumpet-shaped end 62 holds back the landing 56 on the bearing 91 as long as the end 62 rests against the landing part 51. The lower section 64 is provided with a cutting recess 65 arranged to receive the sleeve end 83 of the cutting element 80, in this way to hold the sleeve 60 in position with the end 62 in contact with the ledge part 51 of the collar 50. The lower section 64 is also provided with an external seal groove 67 which holds a seal 66 which abuts against the acrylic recess 75 in the transition part 70 to prevent fluid passage through the spacer

70 and the sleeve 60. The lower section 64 is further provided with an external locking recess 68 which holds an expandable locking ring 69 intended for expansion into the recess 78 as described below. The middle section 63 and lower section 64 have an outside diameter which is somewhat smaller than the diameter of the axial countersunk bore 75, but larger than the axial bore 74, so that downward movement of the sleeve 60 inside the intermediate piece 70 is limited by the shoulder 76.

The lower section 64 can be equipped with an axial for-

countersunk bore 61a to provide an annular detent boss 69a which can engage with the upper release plug 9 to

hold the plug 9 in a sealing position with the contact surface 65

and the axial bore 61 when the upper release plug has been fitted there as described below.

The cutting element 80 comprises a sleeve end 83 and an intermediate piece end 82 and portions between them. The cutting element is held by the cutting hole 81 in the intermediate piece 70 and the cutting recess 65

in the sleeve 60 as previously described, so that sufficient downward force on the sleeve 60 will cut across the element 80 and thereby initiate release of the upper cementing

plug 23 in fig. 1 in the manner described below.

The function of the device according to the present invention shall be described in connection with the preferred embodiment described above and shown in the drawings. This function will be described with particular reference to fig. 2a to 2d showing the release mechanism 20 for the upper plug in four successive stages of operation, these stages being the fully restrained stage of fig. 2a, the sleeve released in the step of fig. 2b, the collar triggered in the step of fig. 2c and the intermediate part £ triggered position in fig. 2d.

The mechanism 20 in fig. 1 is set in a completely fixed position as has already been described in connection with fig. 2. When the top plug release mechanism 20 is constructed as described,

and included in a cementation system as described above and shown in fig. 1, the plug release operation is initiated in the conventional manner by dropping the release ball 13 for the lower plug through the drill pipe 16 to a sealing position inside the lower cementing plug 24 and pumping cement into the drill pipe 16 through the cement inlet 15. Continued pumping causes shearing of studs (not shown) which holds the lower plug 24 to the upper plug 23 and the lower plug 24 is released and passes downward in the conventional manner. When sufficient cement has been pumped into the drill pipe 16, the upper release plug 9 is released by withdrawing the plunger piston 11 and ceasing

with pumping of cement and initiation of pumping of a typical displacement fluid, such as drilling mud.

With reference to fig. 1 and 2a, when the upper release plug 9 reaches the contact surface 65 and on conventional

nell manner locks to the annular shoulder 69a to thereby seal the axial bore 61 in the sleeve 60 against fluid passage, the release operation of the upper plug release mechanism 20 begins. The mechanism will remain in the fully restrained position of Fig. 2a until the predetermined release pressure is reached in the axial bore 31.

When this release pressure is reached, a sufficient downwardly directed force is exerted on the sleeve 60 to cut off the element 80, whereby the sleeve 60 is freed for downward movement in the intermediate piece 70 as shown in fig. 2b. This downward movement is limited by the annular shoulder or shoulder 76. Downward movement of the sleeve 60 results in downward directed movement of the trumpet-shaped end 62 relative to the retractable ledge portion 51 of the collar 50. As the trumpet-shaped end 62 moves below the retractable ledge portion 51, this part 51 is no longer held back outwards, and can retract and away from the bearing 91 as in fig. 2b.

With reference to fig. 2c it will be seen that when the sleeve

60 reaches the abutment 76, pressure will continue in the axial bore

31 causes the sleeve 60 to push the collar 50 downwards inside the axial bore 43 (see Fig. 2c) and thereby moves the expandable ledge part 55 downwards and out of the axial bore 41 in the bushing 40. This downward movement of the collar 50 causes downward movement of the intermediate piece 70 because the inner ledge 57 is retained inside the recess 77 in the intermediate

the piece 70 as already described, until the expandable ledge part 55 moves completely out of the axial bore 41

and expands outwards as shown in fig. 2d.

In this fig. 2d it is seen that when the main part 53 of the collar

50 when the annular ledge 45 in the bushing 40 further movement downwards is prevented by the collar 50. However, further movement is nee.. - . ri of the sleeve 60 and the intermediate piece 70 is not prevented by the main part 53 reaching the annular ledge 45, because the lower finger-like part 54 of the collar 50 has moved downwards out of the axial bore 41 and the finger-like part 54 can therefore bend outwards for movement of the inner ledge 57 out of the recess 77 in the middle piece 70

thereby releasing the intermediate piece 70, the sleeve 60 and the upper release plug 9 for movement down through the hole and opening of the axial bore 41 for fluid passage.

While the axial bore 41 can thus be opened for fluid passage, the axial bore 61 in the sleeve 60 is still sealed by means of the upper release plug 9

to prevent fluid passage through it

axial bore 61. Fluid passage around the intermediate piece 70 is prevented by means of wipers for the upper cementing plug 23 attached to the threads 79 on the intermediate piece 70.

By considering fig. 2a it will also be seen that the bearings

91 and 92 allow free rotation of the collar 50 inside the bushing

40 and thus allows rotation of the intermediate piece 70 which is initially held inside the collar 50 for free rotation. Thus, the plugs 23 and 24 can rotate freely in relation to the cementing head's intermediate piece 19. This freedom of rotation acts to prevent premature release of the plug 23 caused by turning forces that seek to turn the plug 2 3 in relation to the cementing

middle part of the head 19.

Returning to FIG. 1 and 2 again should be noted

that during the initial introduction of the subsurface portion 7 of the cementing plug system 1 into the inner casing 21,

<y>il the wipers for the plugs 2 3 and 2 4 seek to counteract such insertion and thereby produce an upwardly directed force on the intermediate piece 70 for the mechanism 20. This upwardly directed force on the intermediate piece 70 pushes the expandable ledge part 55 on

the collar 50 upwards inside the axial bore 41 in the bushing 40

and thus moves the retractable ledge part 51 upwards into contact with the annular ledge 37. Further upward movement of the collar 50 is prevented by the contact between the part 51

and the ledge 37. The part 51 is retained outwardly by the trumpet-shaped part 62 of the sleeve 60 also during this upward movement, because the cut-off part 80 attaches the sleeve 60 to the intermediate piece 70 so that the trumpet-shaped part 62 moves upwards together with the contractible ledge part 51. A alternative in-

direction for limiting the upward movement of the collar 50

would be to limit the upward movement of the intermediate piece 70 by designing the upper cementing plug 23 so that it rests against the lower edge of the bushing 40 when it is attached to the intermediate piece 70, thereby preventing the intermediate piece 70 from moving upwards. Preventing upward movement of the spacer 70 would prevent upward movement of the collar 50

which is attached to the same.

Although the device according to the invention is described in connection with a release mechanism for an upper plug for an oil well cementing plug system, it will be clear to those skilled in the art that the invention is in no way limited

set to such a mechanism, but has very wide application possibilities for releasable wire connections operated by means of a closing element.

Claims (6)

1. Device for releasably attaching an object, e.g. a borehole cementing plug (23), to a tubular casing (30), comprising a collar (50) which is connected to the casing over a radially movable holding device, a sleeve (60) which forces the holding device outwards to maintain said connection and which has an axial bore in which a closing element, e.g. a release plug (9) can be placed to release the connection, the sleeve, after applying the closing element and achieving a pre-given application pressure, is pushed down somewhat and releases the holding device for inward movement, and seals (46, 46a, 66, 71a) between the closing element and the housing, by means of which this is sealed when the closing element is attached to the sleeve, characterized in that the between the sleeve (60) and the housing (30) arranged collar (50) has an upper part (52) attached to a contractible, outwardly extended upper ledge part (51) which can be placed against an internal ledge (44) in the enclosure (30) and constitutes said holding device and that the object is carried by an intermediate piece (70) which is releasably attached to the collar (50). 2. Device according to claim 1, characterized in that between the collar's ledge part (51) and the internal ledge (44) in the enclosure (30) a pivoting direction (90) is arranged, by means of which the intermediate piece (70) can be rotated in relation to the enclosure when it is connected to the collar. 3. Device according to claim 2, characterized in that the sleeve (60) and the intermediate piece (70) are connected to each other by means of a cutting element (80) or the like which determines the position of the sleeve in relation to the intermediate piece. 4. Device according to claim 3, characterized in that a stop (45) is placed on the housing (30) which limits the downward movement of the collar (50) inside the housing (30), and that the collar (50) has a lower part (54) attached to an expandable, inwardly extended lower ledge part (55) which fits into an external depression (77) in the intermediate piece (70) and forms a detachable fastening device, the intermediate piece being released after a full downward movement of the collar in the enclosure. 5. Device according to claim 4, characterized in that the collar (50) has a central main part (53) which cooperates with the stop (45) in the housing (30) to limit the downward movement of the collar and that the upper (52) and lower part (54 ) of the collar has less thickness than the central main part (53) and is slotted finger-like, so that the upper and lower parts are designed to be springy. 6. Device according to claim 5, characterized in that the housing (30) has an inner ledge (37) which limits the upward movement of the collar (50) and that the housing (30) is provided below with an inner bushing (40), in which the ledge ( 44) for the collar's upper shoulder part (51) and the stop (45) which limits the collar's movement downwards, are formed.