Internal blow out preventer

1. An internal blow out preventer comprising:

a housing having a central axis and a bore extending axially therethrough;

a spherical outer valve closure element rotatably disposed in the housing, wherein the outer valve closure element is configured to move between an open position and a closed position; and

a spherical inner valve closure element rotatably disposed within the outer valve closure element, wherein the inner valve closure element is configured to move between an open position and a closed position within the outer valve closure element;

wherein the outer valve closure element comprises a pair of radially extending shafts rotatably coupled to the housing.

2. The internal blow out preventer of claim 1 , further comprising a first ring coaxially disposed in the housing axially adjacent the outer valve closure element, wherein the first ring includes an annular sealing surface that slidingly engages the outer valve closure element and is configured to seal against the outer valve closure element.

3. The internal blow out preventer of claim 2 , further comprising a second ring coaxially disposed in the housing axially adjacent the outer valve closure element, wherein the second ring includes an annular sealing surface that slidingly engages the outer valve closure member and is configured to seal against the outer valve closure element.

4. The internal blow out preventer of claim 1 , wherein the outer valve closure element comprises a bore extending therethrough, and wherein the outer valve closure element is configured to rotate about an axis of rotation between the open position and the closed position;

wherein the inner valve member comprises a bore extending therethrough, and wherein the outer valve closure element is configured to rotate about the axis of rotation between the open position and the closed position.

5. The internal blow out preventer of claim 1 , wherein a flow area of a valve opening of the inner valve closure element is substantially the same size as a flow area of a valve opening of the outer valve closure element.

6. The internal blow out preventer of claim 1 , wherein the outer valve closure element comprises:

an annular recess extending into an inner surface of the outer valve closure element; and

an annular seal disposed within the annular recess, wherein the annular seal is configured to slidingly engage and seal against the inner valve closure element.

7. The internal blow out preventer of claim 1 , wherein the inner valve closure element comprises a pair of radially extending shafts rotatably coupled to the housing and disposed within the radially extending shafts of the outer valve closure element.

8. The internal blow out preventer of claim 1 , wherein the internal blow out preventer has an open configuration with the inner valve closure element in the open position and the outer valve closure element in the open position;

wherein in the open configuration the internal blow out preventer is configured to allow for the flowing of a fluid between a first end of the housing and a second end of the housing.

9. The internal blow out preventer of claim 8 , wherein the internal blow out preventer has a mud saver configuration with the inner valve closure element in the closed position and the outer valve closure element in the open position;

wherein in the mud saver configuration the internal blow out preventer is configured to prevent the flowing of a fluid between a first end of the housing and a second end of the housing.

10. The internal blow out preventer of claim 8 , wherein the internal blow out preventer has a blow out preventer configuration with the inner valve closure element in the open position and the outer valve closure element in the closed position;

wherein in the blow out preventer configuration the internal blow out preventer is configured to prevent the flowing of a fluid between a first end of the housing and a second end of the housing.

11. An internal blow out preventer comprising:

a housing having a first end, a second end and a central bore extending between the first end and the second end along a longitudinal axis of the housing;

an outer valve member rotatably disposed within the housing, wherein the outer valve element has a bore extending therethrough and an axis of rotation; and

an inner valve member rotatably disposed within the outer valve member, wherein the inner valve member has a bore extending therethrough and an axis of rotation coaxially aligned with the axis of rotation of the outer valve member;

wherein the inner valve member has a spherical outer surface that slidingly engages an inner surface of the outer valve member;

wherein the outer valve member comprises a pair of radially extending shafts rotatably coupled to the housing.

12. The internal blow out preventer of claim 11 , further comprising a first ring coaxially disposed in the housing axially adjacent the outer valve member, wherein the first ring includes a first annular sealing surface that slidingly engages the outer valve closure member and is configured to seal against the outer valve member.

13. The internal blow out preventer of claim 12 , further comprising a second ring coaxially disposed in the housing axially adjacent the outer valve member, wherein the second ring includes a second annular sealing surface that slidingly engages the outer valve closure member and is configured to seal against the outer valve member.

14. The internal blow out preventer of claim 11 , wherein the first annular sealing surface of the first ring slidingly engages a spherical outer surface of the outer valve member.

15. The internal blow out preventer of claim 11 , wherein the outer valve member comprises:

an annular recess extending into an inner surface of the outer valve member; and

an annular seal disposed within the annular recess, wherein the annular seal is configured to slidingly engage and seal against the spherical outer surface of the inner valve member.

16. The internal blow out preventer of claim 11 , wherein the inner valve member comprises a pair of radially extending shafts rotatably coupled to the housing and disposed within the radially extending shafts of the outer valve member.

17. The internal blow out preventer of claim 11 , wherein the internal blow out preventer has an open configuration with the inner valve member in the open position and the outer valve member in the open position;

wherein in the open configuration the internal blow out preventer is configured to allow for the flowing of a fluid through the central bore of the housing.

18. The internal blow out preventer of claim 17 , wherein the internal blow out preventer has a mud saver configuration with the inner valve member in the closed position and the outer valve member in the open position;

wherein the internal blow out preventer has a blow out preventer configuration with the inner valve member in the open position and the outer valve member in the closed position;

wherein in the mud save configuration and the blow out preventer configuration the internal blow out preventer is configured to prevent the flowing of a fluid through the central bore of the housing.