Multi-lock adapters for independent screwed wellheads and methods of using same

1. A lockdown flange for use with an independent screwed wellhead, comprising:

an annular body having an axial passageway with an internal diameter at least as large as a passageway through the wellhead, a bottom surface adapted to be mounted to a top of a casing mandrel in the wellhead the bottom surface including an annular groove that retains a fluid seal between the lockdown flange and the casing mandrel, an annular shoulder for supporting a lockdown nut that engages a pin thread on an external periphery of the wellhead to secure the lockdown flange to the wellhead, and a top flange for secure connection of one of: a flanged adapter pin, a high pressure valve, a well stimulation tool, and a blowout preventer.

2. The lockdown flange as claimed in claim 1 wherein the top flange comprises an annular groove for receiving a flange gasket, and a plurality of bores for respectively receiving and retaining flange bolts for securing the well stimulation tool or the blowout preventer thereto.

3. The lockdown flange as claimed in claim 1 wherein the top flange comprises a peripheral pin thread for engaging a box thread of a lockdown nut of the flanged adapter pin.

4. The lockdown flange as claimed in claim 1 further comprising an adapter pin chamber at a bottom end of the lockdown flange, the adapter pin chamber receiving a threaded adapter pin.

5. The lockdown flange as claimed in claim 4 wherein the adapter pin chamber has a chamber wall that includes a box thread complementary with a pin threads on an exterior wall of the threaded adapter pin for interconnecting the adapter pin and the lockdown flange.

6. The lockdown flange as claimed in claim 4 wherein the adapter pin chamber further includes at least one annular groove for receiving at least one high-pressure seal that provides a fluid seal between a wall of the chamber and an exterior wall of the adapter pin.

7. The lockdown flange as claimed in claim 5 wherein an exterior wall of the adapter pin includes at least one annular groove for receiving at least one high-pressure seal that provides a fluid seal between the chamber wall and the exterior wall of the adapter pin.

8. The lockdown flange as claimed in claim 4 further comprising a gasket received in a gap between a top of the adapter pin and a top of the adapter pin chamber.

9. The lockdown flange as claimed in claim 4 wherein the threaded adapter pin further comprises a bottom end with a pin threaded nipple for engaging box threads in a top of the casing mandrel.

10. A multi-lock adapter for a flanged adapter pin for an independent screwed wellhead, comprising:

an adapter pin having a pin threaded nipple for engaging top box threads in a central passage of a casing mandrel of the wellhead;

a lockdown flange for locking the adapter pin to the independent screwed wellhead;

a lockdown nut for locking the lockdown flange to the independent screwed wellhead; and

means for interconnecting the adapter pin and the lockdown flange;

wherein the means for interconnecting the adapter pin and the lockdown flange comprises a top lockdown nut supported by an annular shoulder on a top flange of the adapter pin, and a pin thread on a top flange of the lockdown flange engaged by a box thread of the top lockdown nut.

11. A multi-lock adapter for a flanged adapter pin for an independent screwed wellhead, comprising:

an adapter pin having a pin threaded nipple for engaging top box threads in a central passage of a casing mandrel of the wellhead;

a lockdown flange for locking the adapter pin to the independent screwed wellhead;

a lockdown nut for locking the lockdown flange to the independent screwed wellhead; and

means for interconnecting the adapter pin and the lockdown flange;

wherein the means for interconnecting the adapter pin and the lockdown flange comprises an annular shoulder on an outer periphery of a mandrel of the adapter pin, the annular shoulder supporting a top lockdown nut, and a pin thread on a top of the lockdown flange engaged by a box thread of the top lockdown nut.

12. A method for stimulating a well equipped with an independent screwed wellhead, in order to complete or re-complete the well, comprising:

mounting a lockdown flange to the independent screwed wellhead;

locking the lockdown flange to the independent screwed wellhead using a lockdown nut that engages a pin thread on an outer periphery of the independent screwed wellhead;

inserting a mandrel of a flanged adapter pin through an axial passage in the lockdown flange; and

screwing a threaded nipple on a bottom of the adapter pin into top box threads in a casing mandrel of the independent screwed wellhead;

mounting one of a high pressure valve, a blowout preventer and a well stimulation tool to a top flange of the flanged adapter pin; and

pumping high pressure fluid through the one of the high pressure valve, the blowout preventer and the well stimulation tool.

13. A lockdown flange and a flanged adapter pin for use with an independent screwed wellhead, comprising in combination:

the lockdown flange comprising an annular body having an axial passageway including at least one annular groove for retaining a fluid seal that seals against an elongated mandrel of the flanged adapter pin when it is received in the axial passageway, a bottom surface adapted to be mounted to a top of a casing mandrel in the wellhead, the bottom surface including an annular groove that retains a fluid seal between the lockdown flange and the casing mandrel, an annular shoulder for supporting a lockdown nut that engages a pin thread on an external periphery of the wellhead to secure the lockdown flange to the wellhead, and a top flange comprising peripheral pin threads; and

the flanged adapter pin comprising the elongated mandrel that extends through the axial passageway of the annular body, a bottom end of the elongated mandrel having a pin threaded nipple for connection to the casing mandrel, a flanged adapter pin axial passageway with an internal diameter at least as large as a diameter of an internal passage through the casing mandrel, a lockdown nut supported by the elongated mandrel for engaging the peripheral pin threads on the top flange of the lockdown flange, and a flange at a top end of the elongated mandrel for supporting one of: a high pressure valve; a well stimulation tool; and a blowout preventer.

14. The combination as claimed in claim 13 wherein the lockdown nut of the flanged adapter pin is supported by an annular shoulder formed on an outer wall of the elongated mandrel.

15. The combination as claimed in claim 13 wherein the lockdown nut of the flanged adapter pin is supported by an annular shoulder formed on the flange at the top end of the elongated mandrel.

16. The combination as claimed in clam 13 wherein the flange at the top end of the elongated mandrel comprises a stud pad.

17. The combination as claimed in claim 13 wherein the flanged adapter pin further comprises a pin sleeve threadedly connected to a bottom end of an outer wall of the elongated mandrel, the pin sleeve being movable into seating contact with the top of the casing mandrel, to stabilize the flanged adapter pin.

18. The combination as claimed in claim 17 wherein the pin sleeve comprises a bottom end that provides an enlarged base for bearing against the top of the casing mandrel, the enlarged base including an annular groove for receiving a gasket that provides a fluid seal with the top of the casing mandrel.

19. The combination as claimed in claim 13 wherein the flanged adapter pin comprises two separable pieces, an adapter pin comprising the pin threaded nipple, and a flanged connector comprising the flange at the top end of the elongated mandrel, the two separable pieces being threadedly connected together.

20. The combination as claimed in clam 19 further comprising high pressure fluid seals disposed between the adapter pin and the flanged connector.