Subsea tubing hanger lockdown device

1. In combination with a subsea completion system which includes a subsea wellhead, a production member that is connected to the wellhead and a tubing hanger that is supported within a central bore in the production member, the improvement comprising a tubing hanger lockdown device which comprises:

a lockdown port which extends generally laterally through the production member to the central bore;

at least one lockdown member which includes a stem portion that is positioned in the lockdown port, a base portion that is attached to or formed integrally with a first end of the stem portion, and a lockdown profile that is attached to or formed integrally with a second end of the stem portion;

an actuator shaft which is rotatably supported relative to the production member and which includes a first end that comprises a tool profile and a second end that is threaded to the base portion;

wherein the stem portion is generally restricted from rotating axially within the lockdown port; and

wherein rotation of the actuator shaft moves the stem portion axially through the lockdown port and brings the lockdown profile into engagement with a corresponding locking profile on the tubing hanger to thereby secure the tubing hanger in the central bore.

2. The combination of claim 1 , further comprising a bonnet which is connected to an outer surface of the production member and which includes a receptacle within which the base portion is positioned.

3. The combination of claim 2 , wherein the the bonnet comprises an axial bore which is connected to the receptacle and through which the actuator shaft extends.

4. The combination of claim 3 , wherein the actuator shaft is rotatably supported in a bearing assembly which is supported on the bonnet.

5. The combination of claim 4 , wherein the bearing assembly is positioned in a housing which is connected to the bonnet.

6. A subsea completion system which comprises:

a subsea welihead which is installed at an upper end of a well bore;

a production member which is connected to the welihead and which comprises a body, a central bore that extends generally axially through the body, and a landing shoulder that is formed in the central bore;

a tubing hanger which is supported on the landing shoulder and which comprises an outer diameter surface and a locking profile that is formed on the outer diameter surface;

a lockdown port which extends generally laterally through the production member to the central bore;

at least one lockdown member which includes a stem portion that is positioned in the lockdown port, a base portion that is attached to or formed integrally with a first end of the stem portion, and a lockdown profile that is attached to or formed integrally with a second end of the stem portion;

an actuator shaft which is rotatably supported relative to the production member and which includes a first end that comprises a tool profile and a second end that is threaded to the base portion; p 1 wherein the stem portion is generally restricted from rotating axially within the lockdown port; and

wherein rotation of the actuator shaft moves the stem portion axially through the lockdown port and brings the lockdown profile into engagement with the locking profile on the tubing hanger to thereby secure the tubing hanger in the central bore.

7. The subsea completion system of claim 6 , further comprising a bonnet which is connected to an outer surface of the production member and which includes a receptacle within which the base portion is positioned.

8. The subsea completion system of claim 7 , wherein the bonnet comprises an axial bore which is connected to the receptacle and through which the actuator shaft extends.

9. The subsea completion system of claim 8 , wherein the actuator shaft is rotatably supported in a bearing assembly which is supported on the bonnet.

10. The subsea completion system of claim 9 , wherein the bearing assembly is positioned in a housing which is connected to the bonnet.

11. The subsea completion system of claim 6 , further comprising a THRT which is connected to the tubing hanger and a running string which is connected to the THRT.

12. The subsea completion system of clam 11 , wherein the THRT is threadedly connected to the tubing hanger.

13. The subsea completion system of claim 11 , further comprising:

a surface BOP which is supported on a surface vessel; and

a high pressure riser which includes a first end that is connected to the surface BOP and a second end that is connected to the production member;

wherein the tubing hanger is lowered from the surface vessel to the production member through the surface BOP and the riser.

14. The subsea completion system of claim 13 , further comprising an isolation member which is connected between the riser and the production member and which includes a set of shear rams that are capable of shearing the running string.

15. The combination of claim 5 , further comprising an ROV bucket which is connected to the housing and through which the tool profile is accessible.

16. The subsea completion system of claim 10 , further comprising an ROV bucket which is connected to the housing and through which the tool profile is accessible.