Vibration generator for an drilling installation, underwater drilling installation and underwater drilling system

Abstract

A vibration generator (9) for a drilling installation comprises a housing (16), at least one rotation body (17), a suspension (24) by means of which the rotation body is suspended rotatably within the housing, the mass centre of the rotation body (17) being eccentric with respect to the rotation axis of the suspension, and a drive (18) for rotating the rotation body. The housing (16) holds a fluid (15) which is in contact with the rotation body (17) whereby relative rotation between the rotation body and the fluid generates a flow resistance and in that the rotation body comprises flow resistance reduction means (25).

Claims

1. A vibration generator for a drilling installation, said generator comprising a housing, at least one rotation body, a suspension by means of which the rotation body is suspended rotatably within the housing, the mass centre of the rotation body being eccentric with respect to the rotation axis of the suspension, and a drive for rotating the rotation body, wherein the housing holds a fluid which is in contact with the rotation body whereby relative rotation between the rotation body and the fluid generates a flow resistance and in that the rotation body comprises flow resistance reduction means; and wherein the circumference of the rotation body is fully circular, wherein the rotation body comprises at least one edge oriented transversely with respect to the rotational direction, said at least one edge being provided with said flow resistance reduction means.

2. The generator according to claim 1, wherein the rotation body has a circumference the contour of which is completely positioned between two circles which are concentric with respect to the rotation axis.

3. The generator according to claim 1, wherein all radial sections of the rotation body have a generally equal shape.

4. The generator according to claim 1, wherein the rotation body comprises at least two materials having different specific masses.

5. The generator according to claim 1, wherein the rotation body comprises a rotation body part having an asymmetrically positioned chamber, and a second rotation body part accommodated within the chamber, the specific mass of said second rotation body part being different from the specific mass of the first rotation body part.

6. The generator according to claim 5, wherein the second rotation body part snugly fits within the chamber of the first rotation body part.

7. The generator according to claim 1, wherein the rotation body is disc-shaped.

8. The generator according to claim 1, wherein the rotation body is submerged in the fluid.

9. The generator according to claim 1, wherein the housing is completely filled with the fluid.

10. The generator according to claim 1, comprising two identical rotation bodies, wherein the drive synchronously rotates said rotation bodies in opposite directions.

11. An underwater drilling installation, comprising a platform provided with support means for placement on the bottom of a body of water, and a drilling device for performing drilling operations in the bottom, said drilling device being provided with a vibration generator according to claim 1.

12. The underwater drilling installation according to claim 11, comprising a storage for drill pipes and a robot for transferring the drill pipes from the storage to the drilling device and for assembling the drill pipes into a drill string and vice versa.

13. An underwater drilling system, comprising a floating vessel, hoisting means supported on a barge and an underwater drilling installation according to claim 11 suspended from the hoisting means for lowering the underwater drilling installation on the bottom of a body of water respectively for retrieving the underwater drilling installation from said bottom.

14. The underwater drilling system according to claim 11, wherein a rotation axis of the suspension is oriented transverse, with respect to the rotation axis of the drilling device.

15. The underwater drilling system of claim 14, wherein the rotation axis of the suspension is oriented perpendicular with respect to the rotation axis of the drilling device.

16. The generator according to claim 1, wherein the fluid is oil.

Description

(1) The invention will now be described further with respect to the embodiment shown in the drawings.

(2) FIG. 1 shows an underwater drilling system.

(3) FIG. 2 shows an underwater drilling installation.

(4) FIG. 3 shows a longitudinal section through the vibration generator.

(5) FIG. 4 shows an enlarged view of the rotation bodies.

(6) The underwater drilling system shown in FIG. 1 consists of the underwater drilling installation 1 and the vessel or barge 2 from which the underwater drilling installation is suspended through the hoisting means 3. The barge is floating in a body of water 27, and in the situation shown, the underwater drilling installation is supported on the bottom 28 thereof. In this position, the underwater drilling installation 1 is fit for performing drilling operations in the bottom.

(7) To that end, the underwater drilling installation (see FIG. 2) has a base frame 4, supporting the actual drilling rig 5, a carrousel storage 6 which carries a number of drill pipes 6 and a robot 29. In the situation shown in figures a 1 and 2, the underwater drilling installation 1 is idle. In operation, by means of a robot 29, the drill pipes 7 are successively removed from the carrousel storage 6 and connected to each other so as to form the drill string 10. This is carried out in an automated way which is known per se. At the bottom end of the drill string, a drill bit is connected.

(8) As is known, by rotating the drill string through the drill string drive means 8 of the drill rig 5, a bottom hole is formed. As is further known, this operation may be enhanced by generating a vibration in the drill string. Such vibrations may be obtained from the vibration generator 9 which is mounted to the drive means 8. A view of the interior of the drill string drive means 8 and the vibration generator 9 is shown in FIG. 3.

(9) As shown in FIG. 3, the drive means consists of the electric or hydraulic motor 11, which through a gear set 12 is drivingly connected to the clamp head 13. In the clamp head 13, the drill string 10 is held and rotatably supported by means of the thrust bearing 30. The drive means has a compartment 14 in which these components have been accommodated. Onto the compartment 14, the vibration generator 9 is rigidly mounted.

(10) The vibration generator 9 consists of a housing 16 mounted to the compartment 14, which houses two disc-shaped rotation bodies 17 and a rotation body drive means 18. These rotation body drive means 18 consist of a gear set 19 and the electric or hydraulic motor 20. The gear set 19 of the rotation body drive means 18 has a gear 21 mounted to each of the rotation bodies 17, and an intermediate gear 22 camming which each of the gears 21 and connected to the motor 20. Thus, by energizing the motor 20, the rotation bodies 17 are rotated in opposite directions and at the same speed. In the view of FIG. 4, the rotation bodies 17 are shown in isolation, and in the same view as shown in FIG. 3.

(11) As the drilling installation is operating under water, care should be taken to avoid the surrounding water penetrating the housing 16 of the vibration generator. To that end, the internal space 15 of the housing 16 is completely filled with a fluid such as oil. Thus, the rotation bodies 17 as well as the drive means 18 thereof are fully operated in an oil bath. As will be clear, the oil fill will exert a flow resistance onto the rotation elements, and in particular onto the rotation bodies which as a result of their function usually have an eccentric shape.

(12) With the aim of restricting this flow resistance as much as possible, the rotation bodies are preferably carried out according to the embodiment shown in FIG. 4. Each rotation body 17 is mounted on a shaft 24 which also carries the gear 21. The rotation bodies each consists of a first rotation body part 25 having a fully circular circumference as well as a chamber 27 which is about kidney-shaped. Within the kidney-shaped chamber 27, a correspondingly shaped second rotation body part 26 has been fitted. As shown in FIG. 3, the second rotation body part 26 snugly fits within the corresponding chamber 27 of the first rotation body part 25.

(13) By selecting a different specific masses for the first and second rotation body parts 25, 26, an imbalance is obtained. Thus, upon rotation of the rotation bodies, vibrations are generated in the longitudinal direction of the drill string 10. On the other hand, as a result of the completely circular circumference of the rotation bodies, and the snugly fit of the second rotation body part 26 in the first rotation body part 25, only a low flow resistance is experienced by the rotation bodies while they are rotated with respect to the oil fill within the housing 16.

LIST OF REFERENCE NUMERALS

(14) 1. Underwater drilling installation 2. Barge 3. Hoisting means 4. Base frame 5. Drilling rig 6. Storage carrousel 7. Drill pipe 8. Drill string drive means 9. Vibration generator 10. Drill string 11. Motor drive means 12. Gear set 13. Clamp head 14. Compartment drive means 15. Internal space 16. Housing vibration generator 17. Rotation body 18. Drive means vibration generator 19. Gear set vibration generator 20. Motor vibration generator 21. Gear 22. Gear 23. Fluid fill 24. Shaft rotation body 25. First rotation body part 26. Second rotation body part 27. Body of water 28. Bottom 29. Robot 30. Thrust bearing