DK143259B - Drilling rig - Google Patents

Description

(19) DENMARK (¾)

| P (12) PUBLICATION MANUAL od 143259 B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 6272/75 (51) | nt.ci.3 B 63 B 35/44 (22) Filing date 21 Nov. 1973 ^ 62 B 17/02 (24) Race day 21 Nov. 1973 ^ ® 21/00 (41) Aim. available Nov. 10; 1974 (44) Submitted 3 sucks. 1 981 (86) International application no. - (86) International filing day - (85) Continuation day - (62) Master application no. -

(30) Priority May 9, 1973 * 358670, US

(71) Applicant MARATHON MANUFACTURING COMPANY, Houston, US.

(72) Inventor Francis D. Koop Jr., US: John F. Woods, US: Kenneth J. Far »mer, US: Wayne D. Harbin, US.

(74) Associate Engineer Hofman-Bang & Boutard.

(54) Drilling platform.

The present invention relates to a drilling platform of the kind specified in the preamble of claim 1.

"ISLAND

[- ^ Searching for oil deposits beneath the seabed has resulted in the development of floating drilling platforms, either with their own propulsion machinery or for towing, so that the heavy costly equipment can be moved from one place to another in a short time. Such drilling platforms or vessels usually have legs that can be submerged to the seabed so that they can lift and carry the drilling platform during drilling, and which can be raised from the seabed when the platform is to sail to another location. As the studies take place at greater and greater depths, the legs have naturally become longer and now often have a length of 90 meters or more.

When such long legs are pulled up, they will raise the vessel's center of gravity so much that there is a danger that the entire platform will jerk, especially in troubled seas. Therefore, it has been found necessary to remove one or more of the upper sections of each leg so that the length of the legs raised above the deck of the platform is shortened so as to give the platform the required seaworthiness.

Of course, such separation of sections of the legs can occur in various ways, e.g. by a releasable connector coupling on each leg, of the kind known from the specification to U.S.A. Patent No. 3,628,336.

The object of the invention is to provide a new and improved, easily separable coupling to the legs of a floating drill platform with removable sections, in which the coupling will distribute the existing vertical and horizontal loads in such a way that damage to the coupling's connecting parts is prevented and so that separation and assembly of the couplings is facilitated.

This object is achieved by designing the drilling platform as set forth in the characterizing part of claim 1.

In this construction, all the vertical and horizontal loads on the coupling will be distributed to and absorbed by the coupling pin and bushing, and not by the weaker coupling elements of the coupling, except for the relatively small vertical forces exerted on the connecting members as the legs are moved upwards relative to platform. Furthermore, the coupling is easier to disassemble and assemble than the known couplings, which is important given the dimensions of the legs and couplings and the associated handling difficulties.

3 1Λ 3 2 5 9

The invention will be explained in more detail by the following description of some embodiments of a drilling platform according to the invention, with reference to the drawing, in which:

Fig. 1 schematically shows the drilling platform with the legs submerged to the working position,

FIG. 2 schematically shows one corner of the platform with a leg lifted and a removable section in dashed lines,

FIG. 3 is a vertical section through the coupling of the drilling platform according to the invention, while

FIG. 4 shows a horizontal section along line 4-4 of FIG. Third

The floating drilling platform 10 shown has a plurality of legs 12 arranged to be raised and lowered through the platform 10 by suitable, not shown, jacks. Each leg 12 has a base 13 'which rests on the bottom B, and the legs serve to carry the platform 10 above the water surface when the platform is in its working position.

Except for a crane 14, the usual drilling apparatus on the platform is not shown as not part of the present invention. Each of the legs 12 is generally an open grid structure with three or four vertical tubes 16, each having a conventional rack 18 for moving the leg up and down through openings in the platform 10. The platform preferably has three legs 12, but will within the scope of the invention could have four or more legs. According to the invention, each tube 16 is formed with at least one upper removable section 16a, which is connected to a section 16b below, by a readily soluble coupling J shown in detail in FIG. 3 and 4.

When each of the legs 12 has more than one tube 16, these are connected to form a grid column with horizontal grid bars 28, inclined diagonal bars 30 and, in the case of a square leg, horizontal diagonal bars 32 between the tubes 16 in the opposite corners of the leg.

The couplings J are similar in the different pins 12 and only one coupling J will be described in detail. Each coupling J consists of a pin, a bushing 22 and a bushing 22 so adapted that, in an interconnected position, an annular shoulder 24 of the pin 20 rests on a circular end surface 26 of the bushing 22 to absorb the compressive forces that occur when the leg 12 rests on the seabed B and carries the drilling platform 10 as shown in FIG. First

The portion 22 has on its inside two longitudinally spaced apart annular faces 22a and 22b smaller than the bore 22c of the portion, and such that the diameter at the surface 22b is smaller than at the surface 22a for the purpose described below. These annular or cylindrical faces 22a and 22b are short in relation to the total length of the coupling J. For example. at a coupling J with a total length of approx. 1.5 m, the height of each of the surfaces 22a and 22b is preferably only 50-75 mm. These surfaces are positioned to fit correspondingly elevated surfaces 20a and 20b on the outside 20c of the coupling pin 20. The top of the faces 22a is preferably arranged near the open end of the portion 22, preferably just below the lower face 22b. annular groove 22d carrying three identical locking segments 34, 36 and 38 and wedge-shaped guide 40 serving to prevent any lateral movement of the locking segments 34, 36 and 38 as described below.

The pin 20 of the coupling has an annular groove 20d which, in the coupled state, fits the groove 22d. The groove 20d occupies the locking segments 34, 36 and 38 when the coupling is made, as further described below.

It is an advantageous feature of the coupling according to the invention that the surfaces 20a and 20b on the outside of the part 20, when coupled together, rest against the surfaces 22a and 22b, respectively, so that the lateral forces acting on each leg 12 due to the influence of water or wind against the platform 10 or the legs 12 are distributed on these surfaces and thus span substantially the entire length of the coupling J, thereby preventing such forces from being concentrated on any single part of the coupling. When the coupling J is in the coupled state, it is sealed against the penetration of water by an 0-ring 24 or other suitable gasket in an annular groove 26a on the upper side 26 of the coupling sleeve 22.

In FIG. 4, the locking segment 34 is shown in the locking position and the locking segment 36 is shown fully retracted to the free position. Finally, the locking segment 38 is shown in an intermediate position while being retracted by means of a rod 56 which is moved by a power element not shown. The locking segment 34 is shown held in the locking position by a locking pin 58 inserted through a hole 60 off the groove 22d. At least part of the hole 60 has threads for retaining pin 58 by its thread 58a.

When the coupling J is coupled for normal use, each of the locking segments 34, 36 and 38 is retained by such a pin 58. The hole 60 is closed watertight by an O-ring 62 which may conveniently be placed on the pin 58.

Each of the locking segments 34, 36 and 38 has a threaded hole 52 adjacent the hole 60 for receiving the pin 58 in the locking position and for receiving the rod 56 for retracting the locking segment from the groove 20d. The thread in the hole 52 corresponds to an external thread on the rod 56, so that the female can be attached to the locking segment as shown by the locking segment 38 of FIG. 4, for retracting the segment from the groove 20d to the groove 22d or for inserting the segment into the locking position, where it resides in both grooves 20d and 22d as shown in the right side of FIG. 3 · In FIG. 4, the locking segment 36 is shown retained in the release position by a locking bolt 64 through the respective hole 60, the bolt 64 having on the inner part a thread corresponding to the thread in the hole 52 and on the outer part a thread corresponding to the thread in the hole 60 In this way, each of the segments can be held in the retracted position where they are completely free of the groove 20d when the coupling is to be separated or assembled.

The vertical height of the locking segments 34, 36 and 38 is as shown in FIG. 3 less than the height of the groove 20d, so that there will be a gap between the upper side 34a of the segment and the upper surface 20e of the groove 20d. As a result of this construction, downward vertical or compressive stresses on the legs cannot be transmitted to segments 34, 36 and 38 which are relatively weak compared to the pipe sections 16a and 16b, but such loads are taken up by the legs themselves at the contact surface between the annular surfaces. 24 and 26. The locking segments 34, 36 and 38 are thus only subjected to vertical upward forces or tensile stresses when the legs 12 are raised relative to the platform 10, and these loads are far less than the said compressive loads so that they can is absorbed by the segment without deformation or damage. In this way, when the locking segments are exempted from pressure loads, the risk of the segments being deformed or even over-cut is avoided, thereby avoiding the risk that they may cause difficulties when the coupling J is to be separated.

The locking segments 34, 36 and 38 are guided in the lateral direction by the wedge-shaped guides 40 secured in the groove 22d by means of pins 66 inserted in holes 72 next to the groove 22d. The pins 66 may be welded into the holes 72.

It will be seen that the guides 40 could be formed coherently with the portion 22, whereby the groove 22d would be segmented with a slot 22 * for each of the locking segments. Next to each of the locking segments, guides 40 have surfaces 40a and 40b, as shown in FIG. 4 in connection with the segment 38, which surfaces are parallel and parallel to the direction of movement of the locking segment and with its side surfaces 38a and 38b for controlling the movement of the segment.

Before the coupling is assembled, the locking segments 34, 36 and 38 are fastened in the retracted position by the bolts 64 as shown in FIG. 4 at segment 36. The portion 20 is inserted into the portion 22 until the shoulder 24 of the portion 20 rests on the circular end surface 26 of the portion 22 and is supported thereon. In this position, the annular surfaces 20a and 20b of the portion 20 will align with and rest against the annular surfaces 22a and 22b of the portion 22. Preferably, these surfaces have inclined edges to facilitate the coupling.

When the portion 20 has been brought into the seat of the portion 22, the bolts 64 and the rods 56 are removed and the segments are then slid into the groove 22d of the portion 22 by means of these rods.

Then the rods 56 are removed and the locking pins 58 are inserted through the holes 60 into the holes 52 without threaded connection with the last, but with the thread 58a engaging the thread in the holes 60, thereby locking the two coupling parts.

7 143259

A particular advantage is apparent when the sections of the leg 12 are to be removed after the drilling platform 10 has completed operations one place and must be moved to another. The legs 12 are led up through the drilling platform 10 by means of the jack until the coupling is raised to a position where the workers have access to it. The locking pins 58 are removed and instead the rods 56 are inserted into the holes 60 and screwed into the threads in the holes 62 in the segments as shown by the segment 38. Then the segments 34, 36 and 38 are pulled out of the locking position in the grooves 20d and 22d for the release in the groove 22d alone. . In this position, the segments are locked by means of the bolts 64 as shown by the segment 36. At this point another particular advantage is shown, the only surfaces where there is actual contact between the part 20 and the part 22 is the contact surface between the annular surfaces 22a and 20a and the annular faces 22b and 20b. The part 20 only needs to be lifted a short distance relative to the part 22 before the coupling is free and easily separable. This is especially true when the diameter of the surfaces 20b and 22b is smaller than the diameter of the surfaces 20a and 22a, the other surfaces of the part 20 having the diameter of the surfaces 20a and 22a having a smaller diameter and therefore providing no frictional resistance to the separation of the parts 20 and 22. This advantage does not exist in conventional tap joints where a significant portion of the surface of a tap rests against a bushing, as after a long time in a single location it often happens that a coupling is stuck due to corrosion or the unfortunate effect of the forces acting on the clutch. Such couplings often require a great deal of time and effort for separation. This disadvantage does not exist when using the coupling according to the invention.

A further advantage of the coupling on the drilling platform according to the invention in relation to known couplings, which contributes to easy separation, is that the coupling during the assembly can be lubricated, the part 22 being filled with a suitable lubricant such as a heavy oil or grease held by a closed membrane or plate 70 welded to the inside 22f of the portion 22 just below the coupling J. When the portion 20 is introduced into the portion 22, this lubricant will fill the open spaces, e.g. the space between the surfaces 20c and 22c and the grooves 22d and 20d. This serves to further protect the coupling against corrosion and facilitates the separation of the coupling.