CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to EP Patent Application No. 17205082.5 filed 4 Dec. 2017, the entire contents of which is hereby incorporated by reference.

BACKGROUND

The present invention relates to a downhole inflow production restriction device for mounting in an opening in a well tubular metal structure arranged in a wellbore. The present invention also relates to a downhole completion system and to a completion method.

BRIEF SUMMARY

When completing a well, there is presently a need for a wash pipe for well clean-up, alternatively the known inflow control valves need to be operated subsequently by intervention via a tool or pipe. Such use of either a wash pipe and/or an intervention tool delays the completion process since time is spent assembling and running in the wash pipe and the tool.

In order to prevent intervention so as to make the well ready for production, attempts have been made to plug the openings in the casing with an acid-dissolvable plug. However, the acid is very corrosive to the casing and the components, and only a few very expensive completion components can withstand such acid treatment. Furthermore, some formations cannot withstand such acid either, and acid-dissolvable plugs can therefore not be used in such formations.

Furthermore, the mud circulated during run-in-hole (RIH) operations tends to get stuck in the annular space underneath the screen and the base pipe, around which pipe the space extends. The mud stuck under the screens is very difficult to remove subsequently, and the mud thus tends to fill out part of the screen, resulting in a significant decrease in screen efficiency.

It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved downhole completion system which is easier to deploy without the need of subsequent intervention and without damaging the formation and/or the completion components significantly.

It is another object of the present invention to provide a downhole completion system which makes it possible to remove mud from the screen and thus increase the efficiency of the screen during production.

The above objects, together with numerous other objects, advantages and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole inflow production restriction device for mounting in an opening in a well tubular metal structure arranged in a wellbore, the downhole inflow production restriction device comprising:a device opening, anda brine dissolvable element configured to prevent flow from within the well tubular metal structure through the device opening to an outside of the well tubular metal structure before being at least partly dissolved in brine,

wherein the brine dissolvable element is at least partly made of a magnesium alloy.

The brine dissolvable element may be part of a valve having a first position and a second position, and the valve may comprise a valve housing and a movable part.

Moreover, the brine dissolvable element may be the movable part of the valve, the brine dissolvable element being movable between the first position and the second position.

Also, the first position the valve may allow fluid to flow into the well tubular metal structure, and in the second position the valve may prevent fluid from flowing out of the well tubular metal structure.

Furthermore, the brine dissolvable element may comprise both at least part of the valve housing and the movable part.

In addition, the movable part may be at least partly arranged in the device opening.

The valve housing may comprise a first housing part and a second housing part, the first housing part being fixedly arranged in the opening of the well tubular metal structure and the second housing part being part of the brine dissolvable element.

Moreover, the main part of the brine dissolvable element and/or the main part of the valve may be extending into the well tubular metal structure from the opening in the well tubular metal structure.

Further, the brine dissolvable element may comprise a rod part, a first projecting flange arranged at a first end of the rod part and a second projecting flange arranged at a second end of the rod part, the rod part extending through the device opening, so that the first projecting flange is arranged outside the device opening at one side of the restriction device and has an outer diameter which is larger than an inner diameter of the device opening, and so that the second projecting flange is arranged outside the device opening at the other side of the restriction device and has an outer diameter which is larger than the inner diameter of the device opening.

Also, the second projecting flange may be facing the inside of the well tubular metal structure, the first projecting flange may have a flange opening allowing fluid to flow from outside of the well tubular metal structure to inside of the well tubular metal structure when the valve is in the first position.

Additionally, the rod part may have a part having a decreased outer diameter.

Furthermore, brine dissolvable element may be a plug.

Said brine dissolvable element may be fixedly arranged in the device opening.

Moreover, the brine dissolvable element may comprise a spring element, such as a spiral spring or a Belleville spring/washer.

The downhole inflow production restriction device according to the present invention may further comprise an insert defining the device opening.

Further, the insert may be made of ceramic material.

In addition, the brine dissolvable element may comprise an indentation forming a weak point, so that a pressure increase in the well tubular metal structure can cause the brine dissolvable element to break at this weak point.

The downhole inflow production restriction device according to the present invention may further comprise a snap ring for fastening the downhole inflow production restriction device in the opening of the well tubular metal structure.

The present invention also relates to a downhole completion system comprising the well tubular metal structure and the downhole inflow production restriction device according to the present invention.

Said well tubular metal structure may comprise at least one screen mounted on the outer face of the well tubular metal structure and opposite the downhole inflow production restriction device.

Moreover, the well tubular metal structure may comprise at least one annular barrier for providing zonal isolation.

Furthermore, the annular barrier may have an expandable metal sleeve surrounding the well tubular metal structure forming an annular space there between, the well tubular metal structure having an expansion opening through which fluid enters to expand the expandable metal sleeve.

The annular barrier may also have a valve system which may have a first position in which fluid from the well tubular metal structure is allowed to flow into the annular space and a second position in which fluid communication between the wellbore and the annular space is provided in order to pressure equalise the pressure there between.

Also, the annular barrier may be a swellable packer, a mechanical packer or an elastomeric packer.

In another embodiment, the downhole completion system may further comprise a sliding sleeve having a sleeve edge for breaking part of the valve.

The present invention also relates to a completion method for preparing a well for an optimal production, said completion method comprising:running a well tubular metal structure in the borehole while circulating mud, the well tubular metal structure having an opening in which a downhole inflow production restriction device mentioned above is mounted,circulating brine from inside the well tubular metal structure out through a bottom of the well tubular metal structure and up along the well tubular metal structure,decreasing the pressure in the well tubular metal structure, andinitiating production of fluid flowing into the well tubular metal structure through the device opening by dissolving the brine dissolvable element in the device opening so that mud is transported with the fluid uphole.

The completion method according to the present invention may further comprise:dropping a ball to be seated near the bottom of the well tubular metal structure to pressurise the well tubular metal structure from within, andexpanding an expandable metal sleeve of an annular barrier by allowing fluid of the increased pressure in the well tubular metal structure to enter an annular space between the expandable metal sleeve and the well tubular metal structure through an expansion opening in the well tubular metal structure.

Said completion method may further comprise breaking the weak points by the increased pressure in the well tubular metal structure.

