Downhole inflow production restriction device

1. 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, and

a 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 the brine dissolvable element is at least partly dissolved in brine,

wherein the brine dissolvable element is at least partly made of a magnesium alloy and comprises an indentation forming a weak point where an increase in pressure in the well tubular metal structure is configured to cause the brine dissolvable element to break at the weak point, and

wherein a part of the brine dissolvable element is configured to extend into the well tubular metal structure from the opening in the well tubular metal structure.

2. Downhole inflow production restriction device according to claim 1 , wherein the brine dissolvable element is part of a valve having a first position and a second position, and the valve comprises a valve housing and a movable part.

3. Downhole inflow production restriction device according to claim 2 , wherein the brine dissolvable element is the movable part of the valve, the brine dissolvable element being movable between the first position and the second position.

4. Downhole inflow production restriction device according to claim 2 , wherein in the first position the valve allows fluid to flow into the well tubular metal structure, and in the second position the valve prevents fluid from flowing out of the well tubular metal structure.

5. Downhole inflow production restriction device according to claim 2 , wherein the brine dissolvable element comprises both at least part of the valve housing and the movable part.

6. Downhole inflow production restriction device according to claim 3 , wherein the movable part is at least partly arranged in the device opening.

7. Downhole inflow production restriction device according to claim 2 , wherein the valve housing comprises 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.

8. Downhole inflow production restriction device according to claim 1 , wherein the brine dissolvable element comprises 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 (OD1) which is larger than an inner diameter (IDD) 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 (OD2) which is larger than the inner diameter of the device opening.

9. Downhole inflow production restriction device according to claim 8 , wherein the second projecting flange is facing the inside of the well tubular metal structure and the first projecting flange has 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.

10. Downhole inflow production restriction device according to claim 1 , further comprising a snap ring configured to fasten the downhole inflow production restriction device in the opening of the well tubular metal structure.

11. Downhole completion system comprising the well tubular metal structure and the downhole inflow production restriction device according to claim 1 .

12. Downhole completion system according to claim 11 , wherein the well tubular metal structure comprises at least one screen mounted on the outer face of the well tubular metal structure and opposite the downhole inflow production restriction device.

13. Downhole completion system according to claim 11 , wherein the well tubular metal structure comprises at least one annular barrier for providing zonal isolation.

14. Downhole inflow production restriction device according to claim 1 , wherein the weak point is configured to allow at least a part of the brine dissolvable element to break off due to the indentation if the brine dissolvable element is not dissolved or not dissolved to a sufficient extent for the brine dissolvable element to be released to open the opening.

15. Downhole inflow production restriction device according to claim 14 , wherein the part is a flange.

16. Downhole inflow production restriction device according to claim 1 , wherein the weak point is configured to break at or along the indentation in case the element is not released through dissolving alone.

17. Downhole inflow production restriction device according to claim 1 , wherein the brine dissolvable element is configured to be released to open the opening by both dissolving and by breaking at or along the indentation.

18. Completion method for preparing a well for 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 is mounted, the downhole inflow production restriction device comprising

a device opening, and

a 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 the brine dissolvable element is at least partly dissolved in brine,

wherein the brine dissolvable element is at least partly made of a magnesium alloy and comprises an indentation forming a weak point where an increase in pressure in the well tubular metal structure is configured to cause the brine dissolvable element to break at this weak point

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, and

initiating 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.

19. Completion method according to claim 18 , further comprising:

dropping a ball to be seated near the bottom of the well tubular metal structure to pressurise the well tubular metal structure from within, and

expanding 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.