The present invention relates to a well tool device and a method for breaking a breakable plug.

Background of the invention.

Packer setting devices / downhole isolation valves are used as a temporary barrier in a production tubing to be able to pressure up the production tubing for the purpose of setting a packer to seal of the annulus between the production tubing and a casing. Such devices can also be installed to pressure test production tubing, or as a temporary well barrier while performing other commission activities in the well.

There is a need for simpler and more reliable solutions that are easy and cost effective to manufacture.

Disclosure of the state of art.

Prior art includes various solutions for pressure cycling and activation systems, holding a glass-seat or a glass-plug in a housing to enable well operations like pressure test, packer setting and other. After well operations are completed, a mechanism for releasing the glass and breaking it is required.

Other solutions incorporate the following mechanisms:

- Break glass by intervention - mill or spear glass to break

- Shear out glass by predetermined pressure threshold

- Shear out glass activated by a pressure cycle counter system, typical a counter system that releases a holding and breaking mechanism at the predetermined number of pressure cycles

Prior art includes:

N0343585B1 describes a tool activation device. NO338780B1 describes a device for controlling and/or operating a tool, a device or underwater equipment employed in connection with exploration and recovery of hydrocarbons offshore or onshore.

N0336554 describes a disintegratable plug apparatus for use in connection with petroleum wells, especially during pressure testing of such petroleum wells.

NO20150701 A1 describes a plug comprising a crusher mechanism for a dissolvable sealing device, where the sealing device comprises one or more glass layers positioned in a wellbore.

Related prior art also includes the following publications: WO 2016/195508 A1 , WO 2014/154464 A2 and WO 2009/1 16871 A1

Objects of the present invention

Objects of the present invention can be one or more of the following:

- provide a new design for a packer setting device

- provide a new design for a downhole isolation valve

- provide a simple and reliable mechanism for removing a plug or a

obturator seat in a through bore

- provide a plug breaking mechanism with as few moving parts as possible

- provide a plug breaking mechanism that is not easily blocked by solids and particles in the well fluid

- provide a barrier device for a wellbore where the barrier can be opened or removed without the use of well interventions

- provide a packer setting device that is simple and cost effective to produce

- provide a downhole isolation valve that is simple and cost effective to

produce

- provide a new method for breaking a breakable plug or obturator seat without the use of well intervention

Summary of the invention

Said objects are achieved with a well tool device comprising

- a housing with a through bore, - a breakable plug slidable disposed in the through bore sealing off said through bore, and

- a plug breaking mechanism for breaking said breakable plug, the plug breaking mechanism comprises:

- a one-way relief valve, for relieving a pressure in a closed chamber,

- a breaking member, for breaking the breakable plug

- at least one support member for providing axial support for the breakable plug, the support member being radially yieldable when loosing radial support,

- a seal sleeve slidable disposed inside said housing, radially supporting said at least one support member, having an uphole piston area and a downhole piston area, where said uphole piston area is exposed to a pressure in the through bore and said downhole piston area is exposed to the pressure in a closed chamber, the seal sleeve further comprises a radial groove for receiving the at least one radially yieldable support member, and

- a ratchet mechanism or other retaining means preventing uphole movement of the seal sleeve.

The at least one support members can be a ring comprising a number of segments.

The one or more support members can be axially supported in the downhole direction by a slanted surface.

The support member can comprises a downhole facing slanted surface, the support member can yield radially outwards if loosing radial support and force is applied on the support member from above.

The seal sleeve can be movable down by increased pressure in the through bore above the plug, and the seal sleeve is prevented from moving back up by the ratcheting mechanism when said increased pressure is decreased.

The down movement of the seal sleeve can increases the pressure in the closed chamber and said increase in pressure can be relieved through the one-way relieve valve when pressure difference across the one way relieve valve is increased due to a pressure decrease in the through bore above the plug. The ratchet mechanism can be connected to the sliding sleeve and can comprises a spring loaded peg gripping grooves on the inside of the closed chamber.

The breakable plug can be an breakable obturator seat for receiving a well tool obturator.

The well tool obturator can be a dissolvable obturator.

The seal sleeve can be equipped with a number of seals for sealing between the breakable plug and the housing.

The breakable plug and the one or more support members can be separated by a slidable support seat.

The one way relief valve on an outlet side can be in pressure communication with the through bore.

The one-way relief valve can be accommodated in the seal sleeve.

The one-way relief valve can be separated from the fluid in the through bore by a floating piston.

An debris extension can be mounted above the plug to move a number of fluid ports further away from the plug.

The breakable plug can be made of glass.

The breakable plug can comprises more than one layer of breakable material.

Above mentioned objects can also be achieved with a method for breaking a breakable plug slidable disposed inside a through bore sealing of said through bore, comprising the steps of:

a) increase a pressure in the through bore above the plug to above a predefined level to push a seal sleeve in the downhole direction,

c) increase a pressure in fluid in a closed chamber below the seal sleeve said fluid being compressed by the movement of the seal sleeve, d) relief the pressure in the trough bore above the plug,

e) relief the pressure in the closed chamber through a one-way relief valve, based on a decrease in pressure in the through bore,

f) repeat steps a-e moving the seal sleeve in increments downhole until a groove in the seal sleeve is aligned with a radially yieldable support member,

g) increase the pressure in the through bore above the plug to push the plug in the downhole direction,

i) direct the downhole directed force to push the support member along a slanted surface and radially outwards into the groove,

j) exposing a breaking member between the plug and the yielded support member, and

k) push the plug further downhole against the exposed breaking member.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

Figure 1 - 5 shows the well tool device in cross section from the starting position (Figure 1 ) to the plug hits a breaking member (Figure 5).

Figure 6 shows an alternative embodiment of the well tool device in cross section. Figure 7-10 shows possible embodiments of the plug.

Description of preferred embodiments of the invention

In the following text word such as above/below, up/down and uphole/downhole is used to indicate directions and relative position of parts. These words should be understood in relation to the direction in the well that leads to the surface. In figure 1 - 5, the uphole direction or the direction to the surface is to the left. In figure 6 - 10, the direction to the surface is up on the figure.

The invention relates to a well tool device 1 . In a preferred embodiment the well tool device 1 comprises a housing 2 with a through bore 4 and a breakable plug 6 sealing of said through bore 4. The well tool device 1 further comprises a plug breaking mechanism 8 for breaking said breakable plug 6. The breakable plug 6 can also be a breakable obturator seat 6’ for accommodating an well tool obturator 7. For the convenience of the reader the term plug 6 is used both for a breakable plug 6 and a obturator seat 6’ in the rest of the description.

The plug breaking mechanism 8 comprises a seal sleeve 10, at least one one-way relief valve 16, at least one breaking member 28, at least one support member 30, and retaining means such as a ratcheting mechanism 12.

The seal sleeve 10 is placed between the housing 2 and the plug 6 where it can slide axially. The seal sleeve 10 seal of the annular space between the plug 6 and the housing 2 and can be equipped with seals 32 both on the inside and on the outside for this purpose. The seal sleeve 10 comprises a downhole piston area 22 bordering a closed chamber 18. This closed chamber 18 can be filled with compressible fluid, such as silicon oil. The seal sleeve 10 further comprises an uphole piston area 20 that is in pressure communication with the through bore 4 above the plug 6. The seal sleeve also comprises a radial groove 26 on the inside.

The one-way relief valve 16 can let out fluid from the closed chamber 18 when the differential pressure across the one-way relief valve 16 exceeds a predefined value.

The at least one support member 30 is placed below the plug 6. The purpose of the support member 30 is to give the plug 6 axial support in the downhole direction. In the embodiment showed in figure 1 -5 the support member comprises segments 30a placed in a ring around the through bore 4. The segments 30a can yield radially out when they lose radial support from the seal sleeve 10. The segments 30a can have a slanted downhole facing surface that is resting on a correspondingly slanted surface 34. In the embodiment in figure 1 -5 the support member 30 and the plug 6 is separated by a support seat 24 that supports the plug 6. The support seat 24 is resting on the support member 30.

In another possible embodiment the support member 30 can be a C-ring. The c-ring can be pre-tensioned, so it will snap radially out when loosing radial support. Or the C-ring can have slanted downhole facing surface towards the slanted surface that it is resting on, so it will be forced radially outwards if forced is applied from above.

The retaining means that can be a ratchet mechanism 12 prevents uphole

movement of the seal sleeve 10. The ratchet mechanism can be (as seen in figure 1 - 5) a spring loaded peg 13 connected to the seal sleeve 10 and a rack of teeth 14 on the inside of the closed chamber 18.

The breaking member 28 can be one or more breaking pins 28' placed below the plug 6 as seen in figure 1 -5. In the embodiment seen in figure 1 -5 the breaking pin 28’ is fixed on the side of the through bore 4 at a distance below the plug 6 when the plug 6 is in the starting position. The breaking pin 28’ can be accommodated in an aperture in the support seat 24, so that the support seat 24 can slide down on the breaking pin 28’ exposing a part of the breaking pin 28’ above the support seat 24.

In the following, the sequence of breaking the plug 6 will be explained with reference to figure 1 -5.

In figure 1 , the well tool device 1 is in the starting position. The seal sleeve 10 is in its upper position preventing the segments 30a of the support member 30 from yielding outwards. The plug 6 is resting on the support seat 24 and the support seat 24 is prevented from moving in the downhole direction by the support member 30.

In figure 2, the seal sleeve 10 have moved a distance in the downhole direction. This is done by increasing the pressure in the through bore 4 above the plug 6. The increased pressure will act with a force on the uphole piston area 20 on the seal sleeve 10, which is in pressure contact with the through bore 4 above the plug 6. When the force acting on the uphole piston area 20 is greater than the force acting on the downhole piston area 22, the seal sleeve 10 will move in the downhole direction compressing the fluid in the closed chamber 18 until the force is equal on both sides of the seal sleeve 10. The pressure above the plug 6 can then be bleed down. The ratcheting mechanism 12 will prevent the seal sleeve 10 from moving back up, as the pressure above the plug 6 is bleed down. As the pressure is bleed down above the plug 6 the differential pressure across the one-way relief valve 16 will increase, and the one-way relief valve 16 will open letting compressible fluid out from the closed chamber 18 until the pressure difference is below the predefined break open pressure.

The distance which the seal sleeve 10 moves each pressure cycle depends among other things on the compressibility of the fluid in the closed chamber 18, the size and geometry of the closed chamber 18 and the differential pressure across the seal sleeve 10. In figure 3, a number of pressure cycles has been applied and the seal sleeve 10 have moved in the downhole direction until the groove 26 on the seal sleeve 10 is aligned with the segments 30a. The support member 30 will then loose radial support and the segments 30a are free to yield radial out.

As seen in figure 4 when pressure again is increased above the plug the downward force from the plug 6 will push on the support seat 24 which again will push down on the support member 30. As a result of the slanted surface on the segments 30a and the corresponding slanted surface 34 on which the segments 30a is resting, the segments 30a will yield radially outwards into the groove 26 in the seal sleeve 10.

In figure 5 one can see that the segments 30a have moved radially out so the support seat 24 losses support and moves down followed by the plug 6. The at least one breaking member 28 in this case a breaking pin 28’ will as a result of the movement of the support seat protrude axially up out of the support seat 24 and will be exposed to the plug 6. As the plug 6 is forced against the breaking member 28, the plug 6 will shatter.

If the plug 6 is an obturator seat 6’ the obturator can be made of dissolvable material.

The breakable plug 6 can be made of glass or some other breakable material. The plug 6 can also comprise more than one layer of glass or some other breakable material as seen in figure 8. If the breakable plug 6 is an breakable obturator seat 6’ the breakable obturator seat 6’ can be made of glass or some other breakable material and the breakable obturator seat 6’ can comprise several layers of glass or some other breakable material as seen in figure 10. Combinations of different layers with different breakable material is also possible for use in the breakable plug 6.

In one possible embodiment, the well tool device 1 is equipped with a debris extension 42 as seen in figure 6. With the debris extension the fluid ports 36 for communication with the uphole side of the seal sleeve 10 is moved further up away from the plug 6. This is done to avoid blocking of the ports 36 by debris and other solids settling on top of the plug 6. The debris extension 42 also comprise a floating piston 38. The floating piston 38 is placed in a fluid channel 40 that leads from the fluid ports 36 to the uphole piston area 20 on the seal sleeve and to the outlet side of the on-way relief valve 16. The floating piston 38 separates the fluid in the through channel 4 from the clean compressible fluid in the plug breaking mechanism 8. At the same time the floating piston 38 allows pressure to be transferred from the through channel 4 to plug breaking mechanism 8 and vice versa. The reason for this is to avoid dirty fluid from the through channel 4 to block and or jam the plug breaking mechanism 8 especially the one-way relief valve 16.