An improved valve for sealing a wellbore and method of use, in particular for prevention of well blow outs. In one embodiment, the apparatus is designed to seal a well through rotation of rams. The rams may be actuated to seal the well without having to work against full well pressure as fluid volum
An improved valve for sealing a wellbore and method of use, in particular for prevention of well blow outs. In one embodiment, the apparatus is designed to seal a well through rotation of rams. The rams may be actuated to seal the well without having to work against full well pressure as fluid volumes in the apparatus housing, which also contains the rams, are preserved. This functionality allows the apparatus to be constructed with smaller dimensions than existing prior art blow out prevention valves aiding handling and manoeuvrability. The improved valve according to one embodiment also has a mechanism that guides a wireline or a pipeline being run in the wellbore to the centre of the bore and allows a seal to be formed around the wireline or pipeline.
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We claim: 1. Apparatus for sealing a wellbore, the apparatus comprising a ram assembly having a pair of rams mounted in a housing, the rams rotatable about a common axis of rotation, wherein the apparatus has a first open position in which fluid may pass through the wellbore and a second closed pos
We claim: 1. Apparatus for sealing a wellbore, the apparatus comprising a ram assembly having a pair of rams mounted in a housing, the rams rotatable about a common axis of rotation, wherein the apparatus has a first open position in which fluid may pass through the wellbore and a second closed position in which the rams abut to seal the wellbore, and wherein the apparatus is adapted to be moved between the open and closed positions by rotating the rams about their common axis of rotation, wherein the apparatus further comprises alignment means for guiding a wireline or pipe towards the centre of the wellbore during rotation of the rams, and wherein the alignment means is a drum adapted to rotate about an axis of rotation of the rams. 2. Apparatus as claimed in claim 1, wherein each ram is adapted to rotate about an axis perpendicular to a longitudinal axis of the wellbore. 3. Apparatus as claimed in claim 1, wherein the rams are adapted to be moved between the open and closed positions by rotating the rams in opposite senses. 4. Apparatus as claimed in claim 1, wherein the apparatus has a maximum lateral dimension of 80 cm. 5. Apparatus as claimed in claim 1, wherein a maximum lateral dimension is less than 50 cm. 6. Apparatus as claimed in claim 1, wherein a maximum lateral dimension is less than 40 cm. 7. Apparatus as claimed in claim 1, wherein the rams comprise locating formations for locating a wireline or pipe when in the closed position. 8. Apparatus as claimed in claim 1, wherein the drum is keyed with one of the rams and rotates with said ram. 9. Apparatus as claimed in claim 1, wherein the drum comprises a throughbore through which the wireline or pipe extends. 10. Apparatus as claimed in claim 9, wherein the throughbore defines an aperture extending in a longitudinal axis of the wellbore, arranged such that the aperture decreases in cross sectional area during rotation of the drum. 11. Apparatus as claimed in claim 9, wherein the throughbore is perpendicular to the axis of rotation of the drum. 12. Apparatus as claimed in claim 9, wherein a first opening of the throughbore is provided with a channel formed outwardly from an edge of the throughbore. 13. Apparatus as claimed in claim 12, wherein a second opening of the throughbore is provided with an edge formation diametrically opposed from the channel. 14. Apparatus as claimed in claim 13, wherein the edge formation is a second channel formed outwardly from an edge of the throughbore, such that the first and second channels together form an aperture extending through the drum perpendicular to the axis of rotation. 15. Apparatus as claimed in claim 14, wherein the aperture extends longitudinally in the wellbore and is central in the wellbore when the apparatus is in its closed position. 16. Apparatus as claimed in claim 13, wherein the edge formation is a cutting edge adapted to shear a wireline or pipe as the apparatus moves to its closed position. 17. Apparatus as claimed in claim 1, wherein each ram comprises a sealing assembly having one or more elastomeric seals. 18. Apparatus as claimed in claim 17, wherein each sealing assembly comprises an inner seal adapted to cooperate with an inner seal on the opposing ram to seal against the wireline or pipe. 19. Apparatus as claimed in claim 18, wherein the sealing assembly comprises an outer seal adapted to seal edges of the wellbore against well pressure. 20. Apparatus as claimed in claim 19, wherein the inner seal is retained on the ram by the outer seal. 21. Apparatus for sealing a wellbore around a wireline or pipe being run in the wellbore, the apparatus comprising: a ram assembly having a pair of rams mounted for rotation about a common axis of rotation; wherein the apparatus has a first osition in which the wellbore is open and a second position in which the wellbore is closed; and wherein the actuating means is adapted to cause the rams of the ram assembly to rotate about their common axis of rotation from a position in which the apparatus is in its first open position, to a position in which the apparatus is in its second closed position in which the wellbore is sealed around the wireline or pipe, wherein the pair of rams are rotatably mounted in a housing of the apparatus, wherein the apparatus further comprises alignment means for guiding a wireline or pipe towards the centre of the wellbore during rotation of the rams, and wherein the alignment means is a drum adapted to rotate about the axis of rotation of a ram. 22. Apparatus as claimed in claim 21, wherein the ram comprise formations for locating a wireline or pipe in the closed position. 23. Apparatus for sealing a wellbore, the apparatus comprising a pair of rams which are rotatable about a common axis of rotation between a first position in which the wellbore is open and a second position in which the rams seal the wellbore around a wireline or pipe, characterized in that when the apparatus is in its operating orientation, the apparatus has a maximum lateral dimension which allows it to pass through an aperture in a rig platform through which the wellhead control equipment passes, wherein the rams are rotatably mounted in a housing of the apparatus, and wherein the alignment means is a drum adapted to rotate about the axis of the rams. 24. Apparatus as claimed in claim 23, wherein the maximum lateral dimension is less than 80 cm. 25. Apparatus as claimed in claim 23, wherein the maximum lateral dimension is less than 50 cm. 26. Apparatus as claimed in claim 23, wherein the maximum lateral dimension is less than 40 cm. 27. Apparatus as claimed in claim 23, wherein the rams comprise formations for locating a wireline or pipe in the closed position. 28. Apparatus as claimed in claim 23, wherein the apparatus further comprises alignment means for guiding a wireline or pipe towards the centre of the wellbore during rotation of the rams. 29. Apparatus for sealing a wellbore, the apparatus comprising a pair of rams which are rotatable about a common axis of rotation between a first position in which the wellbore is open and a second position in which the rams seal the wellbore around a wireline or pipe, characterised in that when the apparatus is in its operating orientation, the apparatus has a maximum lateral dimension of less than 80 cm, wherein the rams comprise formations for locating a wireline or pipe in the closed position, wherein the apparatus further comprises alignment means for guiding a wireline or pipe towards the center of the wellbore during rotation of the rams, and wherein the alignment means is a drum adapted to rotate about the axis of rotation of the rams. 30. Apparatus for sealing a wellbore, the apparatus comprising: a ram assembly having a pair of rams, mounted for about a common axis of rotation; and actuating means; the apparatus having a first open position in which fluid may pass through the wellbore and a second closed position in which the rams abut to seal the wellbore; and wherein the rams are adapted to be moved from the first and second positions without substantially changing the volume of the actuating means exposed to well pressure, wherein the rams are rotatably mounted in the housing of the apparatus, wherein the apparatus further comprises alignment means for guiding a wireline or pipe towards the center of the wellbore during rotation of the rams, and wherein the alignment means is a drum adapted to rotate about the axis of rotation of the rams. 31. Apparatus as claimed in claim 30, wherein the rams comprise formations for locating a wireline or pipe in the closed position. 32. Apparatus for sealing a wellbore, the apparatus comprising: a ram assembly having a pair of rams rotatably mounted in a housing, apparatus having a first open position in which fluid may pass through the wellbore and a second closed position in which the ram abut to seal the wellbore, wherein the apparatus is adapted to be moved between the open and closed position by rotating the rams; and a drum adapted to rotate about an axis of rotation of the rams, for the guiding a wireline or pipe towards the center of the wellbore during rotation of the rams. 33. Apparatus for sealing a wellbore, the apparatus comprising: a ram assembly having a pair of rams rotatably mounted in the housing; actuating means; and a drum adapted to rotate about an axis of rotation of the rams; wherein the apparatus has a first open position in which fluid may pass through the wellbore and a second closed position in which the rams abut to seal the wellbore; and wherein the rams are adapted to be moved between the first and second positions by rotating the rams without substantially changing the volume of the drum exposed to well pressure; and further wherein the drum is for guiding a wireline or pipe towards the centre of the wellbore during rotation of the rams.
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