THERETHROUGH

The invention concerns a packer arrangement for sealingly guiding a drillstring therethrough that has geometrical differences between passing drill pipes and joint couplings, more specifically in that a packer holder forms a housing with an axially through- going centre passage that in a portion comprises a flexible packer sleeve, and an internal annulus is delimited by a centre portion of the packer sleeve and the packer holder and is in fluid communication with an external annulus that encloses the packer holder, and the packer arrangement comprises a device for length compensation and unloading of a packer sleeve that encloses the drillstring.

More specifically, it concerns a packer sleeve that typically forms part of a rotatable sealing device in a packer arrangement, the packer sleeve being arranged to absorb geometrical differences between passing drill pipes and pipe couplings in a drillstring during drilling in the petroleum industry, among others in Managed Pressure Drilling (MPD) and Dual Gradient Drilling (DGD). The packer sleeve can also be used where enclosure about a drillstring is desired, without requirements for the sealing device to be rotatable, typically when screwing together new drill pipe lengths during drilling. The packer arrangement may be mounted on or at a surface installation, form part of a riser between the surface installation and a blow-out preventer (BOP) on a wellhead, or be mounted on top of a BOP when drilling in open sea. The device should seal against the drillstring during drilling and cementing, and typically direct returned drilling fluid from a well to a side outlet below the packer arrangement to a pump and a valve arrangement that can be arranged in different ways depending on the drilling technique used in the relevant case.

A packer sleeve of this type is typically moulded in a polyurethane material, and can be reinforced with embedded fibre ropes that are disposed in the longitudinal direction of the

RECTIFIED SHEET (RULE 91 ) packer sleeve and are anchored in embedded steel rings in end terminations in the packer sleeve.

The packer sleeve should seal against a differential pressure from the bottom side or the top side depending on the pressure conditions during the operation, while it at the same time should withstand axial friction load from passing drill pipes while the sleeve clamps around the pipe. The friction load depends on the length of a sealing centre portion in the packer sleeve, the external actuation pressure of the packer sleeve, and the friction between the packer sleeve and the drill pipe. The end terminations of the packer sleeve, which should be able to withstand combinations of stretching and bowing of the packer sleeve during actuation of the packer arrangement, are the most important mechanical restriction in relation to the maximum differential pressure and the friction load with which the sleeve can be operated.

It is preferable to minimise the length of the packer sleeve and thereby also the contact area against the drillstring to reduce the friction load and concurrently restrict the build height of the packer arrangement as well as minimising an annulus volume that surrounds the packer sleeve. It is also preferable that the packer sleeve is able to seal around several drill pipe and coupling dimensions. However, regard must be given to conditions like the flexibility of the packer sleeve, buckling, and sealing area against the drillstring, and this sets restrictions for minimising the build length of the packer arrangement when it comes to achieving the best possible function.

A solution that is known from NO 341994 B1 consists of, among other things, a flexible packer sleeve that is arranged to abut in a sealing manner against a drillstring with an external pressure from a fluid in a volume-compensated annulus, in an external housing, which can be part of a drilling riser. When the packer sleeve is actuated, it rotates with the drillstring, while rotational sealing and support of the sealing elements are taken care of by packer gliding rings at each end of the device.

US 2005/0241833 A1 discloses a packer arrangement for use in a rotating sealing arrangement. A thick-walled packer sleeve is at a first end portion anchored in a fastening ring, typically in that a sleeve-shaped extension of the fastening ring extends axially into the end portion of the packer sleeve. A second end portion of the packer sleeve is connected to a piston ring. The packer sleeve is pressed in a sealing manner against a passing pipe body by a first hydraulic pressure pressing the piston ring towards the fastening

RECTIFIED SHEET (RULE 91 ) ring, or by a second hydraulic pressure being applied to the external side surface of the packer sleeve.

The purpose of the invention is to remedy or reduce at least one of the disadvantages of prior art, and increase the ability of a packer sleeve to withstand differential pressure as well as reduce and withstand friction load from a drillstring.

The invention provides a packer arrangement, wherein a relatively thin-walled, flexible packer sleeve and a packer holder delimit an internal annulus that can be pressurised. End portions in the packer sleeve form end terminations that each comprise a ring that is axially displaceable in the packer holder by means of one or more actuators, to thereby hold a non-actuated packer sleeve extended as well as allow the axial extension of the packer sleeve to be reduced when a centre portion of a pressure-activated packer sleeve is pressed radially against a passing drill pipe.

The actuators may be arranged as yielding, non-controlled arrangements, typically as springable devices, or as controlled arrangements, typically as hydraulic arrangements affected by a controlled, applied hydraulic pressure.

The invention concerns more specifically a packer arrangement for sealingly passage of a drillstring therethrough that has geometric differences between passing drill pipes and joint couplings, wherein a packer holder forms a housing with an axially through-going centre passage that in a portion comprises a flexible packer sleeve, and an internal annulus is delimited by a centre portion of the packer sleeve and the packer holder, and is in fluid communication with an external annulus that encloses the packer holder, characterised in that the packer sleeve comprises end terminations that are axially displaceable in the packer holder, wherein each end termination is coupled to an actuator arranged to be able to apply an axial tensile force to the packer sleeve.

Each actuator may be provided with springs arranged to push the end terminations away from each other. An effect of this is that the packer arrangement can be provided with simple and cost-effective actuators.

Alternatively, each actuator may be formed as a hydraulic piston ring arranged to push the

RECTIFIED SHEET (RULE 91 ) end terminations away from each other. An effect of this is that better control of the movements of the actuators is achieved.

The packer holder may be provided with stabiliser springs arranged to cushion the impact of the piston rings against end stops in the packer holder. An effect of this is that a more gentle movement of the actuators is achieved.

Each ring may be provided with a support collar that is arranged to restrict bowing of a transition zone between each end termination and the centre portion of the packer. An effect of this is that the service life of the packer sleeve is increased.

The supporting collars that are arranged to restrict bowing of a transition zone between each end termination and the centre portion of the packer sleeve, may be integrated in the packer holder. An effect of this is that the design of said rings is simplified.

In the following, examples are described of preferred embodiments which are illustrated in the attached drawings, wherein:

Fig. 1 shows in an axial section a principle drawing of a first embodiment of a packer arrangement according to the invention, wherein a passive, spring- activated actuator arrangement applies a tensile load to a packer sleeve;

Fig. 2 shows in an axial section a principle drawing of a second embodiment of the packer arrangement according to the invention, wherein an actuator arrangement that can be used in riser applications, by means of hydrostatic pressure from a liquid column in the riser ensures that the actuator arrangement holds the packer sleeve extended when pressure has not been applied to it from the outside; and

Fig. 3 shows in an axial section a principle drawing of a third embodiment of the packer arrangement according to the invention, intended for use where there is no requirement for rotation of the packer arrangement, wherein a controlled hydraulically activated actuator arrangement ensures length compensation of the packer sleeve.

All position indicators refer to the position shown on the figures.

The same or corresponding elements are indicated with the same reference number on

RECTIFIED SHEET (RULE 91 ) the figures. For the sake of clarity some elements may not have reference numbers on some of the figures.

A person skilled in the art will understand that the figures are only principle drawings. The relative ratios between individual elements may also be distorted.

On the figures, the reference number 1 indicates a packer holder that forms a housing that encloses a relatively thin-walled, flexible packer sleeve 2. The packer sleeve 2 is arranged to fit in a sealing manner against a portion of a drill pipe 3 that is inserted through a centre passage 1a in the packer holder 1. The sealing function of the packer sleeve 2 against the drill pipe 3 is activated through external pressurisation from an external annulus 4 that encloses the packer holder 1 and is delimited by a riser 14 (see figure 1). An internal annulus 2b that is delimited by the packer sleeve 2 and the packer holder 1 , communicates with the external annulus 4 that encloses the packer holder 1 through openings 5 in the packer holder 1. The packer sleeve 2 comprises end terminations 6 that are fastened to a respective ring 7 axially displaceably supported in the packer holder 1.

As a joint coupling 9 between two drill pipes 3 passes through the packer sleeve 2, the packer sleeve 2 expands radially out towards the packer holder 1 and displaces a liquid volume from the external annulus 4 to a pressure compensator (not shown). Deformation, for example buckling of the expanded packer sleeve 2, is prevented by the rings 7 being pushed in their respective axial direction and the packer sleeve 2 being extended.

When the packer sleeve 2 is not pressure-actuated to enclose in a sealing manner about a drill pipe 3, it is advantageous if the packer sleeve 2 contacts the drill pipe 3 as little as possible.

The packer sleeve 2 can be held extended by means of passive or active actuators, i.e. as yielding, non-controlled arrangements, typically as springable devices, or as controlled arrangements, typically as hydraulic arrangements affected by a controlled, applied hydraulic pressure, or a combination of these, as shown in figures 1 , 2 and 3 and explained below.

Figure 1 shows a passive, non-controlled, spring-actuated actuator arrangement 10 for length compensation of the packer sleeve 2. When the packer sleeve 2 is actuated by an external pressure from the annulus 4 between the packer holder 1 and the riser 14, and a centre portion 2a is pressed against a portion of a drill pipe 3, an axial stretch in the packer sleeve 2 contributes to pulling the rings 7 in an axial direction towards each other while

RECTIFIED SHEET (RULE 91 ) springs 10a that abut in a supporting manner between the rings 7 and an end surface in a recess 1 b in the packer holder 1 , are compressed. As the packer sleeve 2 is expanded radially by a passing joint coupling 9, the deformation of the packer sleeve 2 is absorbed by the rings 7, by means of the actuator arrangement 10, being pushed away from each other and stretching the packer sleeve 2. The force that acts on the rings 7 is a combination of spring force from the compressed springs 10a and rigidity of the packer sleeve 2. When the packer sleeve 2 does not have an external pressure applied to it to seal against the drill pipe 3, the packer sleeve 2 is stretched in the longitudinal direction of the springs 10a, and the packer sleeve 2 is held open in the packer holder 1 , i.e. there is clearance between the packer sleeve 2 and the drill pipe 3. A piston area 7b on the opposite side of the springs 10a will be exposed to the pressure in the external annulus 4 via channels 10b. Ventilation channels 10c ensure that the volume around the springs 10a is ventilated. The piston area 7b is adapted to the capacity of the springs 10a.

Figure 2 shows a balanced solution, where an annular recess 1 b that is delimited by end surfaces 7a on the rings 7, is in fluid communication with the annulus 4 via hydraulic channels 11a in the packer holder 1. Ventilation channels 11 b ensure that the volume around the springs 12 is ventilated to a low-pressure area over the packer sleeve 2.

Stabiliser springs 12 abut in a supporting manner between the opposite side of the rings 7 and an end stopper surface 1c in the packer holder 1. As the packer sleeve 2 is expanded radially by a passing joint coupling 9, the rigidity of the packer sleeve 2 and an applied hydraulic pressure from the external annulus 4 will push the rings 7 away from each other, while the packer sleeve 2 is stretched in the longitudinal direction.

The figures 1-3 show that the rings 7 are provided with support collars 8 that restrict the bowing of the pressurised packer sleeve 2 in a transition zone 2c between the end terminations 6 and the centre portion 2a of the packer sleeve 2 by pressure-actuation of the packer sleeve 2 from the external annulus 4. The solution is particularly appropriate for use where there is no requirement for the packer holder 1 to be able to rotate.

During Managed Pressure Drilling (MPD) from a surface installation, the packer arrangement according to the invention will typically be mounted internally in a marine riser 200- 500 meters below the drill deck of the surface installation, provided that the actual ocean depth is sufficient. Passive length compensation of the packer sleeve 2 is especially appropriate in a drilling riser 14 where hydrostatic pressure from the liquid column in the drilling riser 14 will expand the packer sleeve 2 in a radial direction when the packer sleeve 2

RECTIFIED SHEET (RULE 91 ) is not activated by pressure from the external annulus 4. Also, one avoids challenges related to hydraulic distribution channels and coupling of hydraulics from the outside for active control of length compensation of the packer sleeve 2.

Figure 3 shows a solution with controlled length compensation of the packer sleeve 2, where an end surface on each ring 7 is actively pressurised via channels 13 in the packer holder 1 by means of a control system (not shown). Stretching of the packer sleeve 2 is coordinated with bleeding of the annulus pressure 4 via said control system. The stabiliser springs 12 are compressed, and liquid is evacuated on the spring side via channels 13a.

Necessary seals are not described, but are known to a skilled person. It should be noted that all embodiments mentioned above illustrate the invention, but do not delimit it, and experts on the subject will be able to design many alternative embodiments without deviating from the scope of the attached claims. In the claims, the reference numbers in parenthesis shall not be considered delimiting.

The use of the verb “to comprise” and its different forms does not exclude the presence of elements or steps not mentioned in the claims. The indefinite articles “a” or “an” before an element do not exclude the presence of more such elements.

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