Floating caisson for mining and drilling in the open sea (options)

 

(57) Abstract:

Floating caisson is designed for drilling and production in the open sea. The caisson is able to float by the buoyancy tanks and maintained in a predetermined position by mooring. The caisson has a Central well through which pass the vertical pipe, designed for drilling and/or production. One or more plates are of the caisson in the radial direction below the water surface. These plates provide additional mass and resistance movements that occur under the influence of waves due to the increase of the period of oscillations of the caisson. The design allows you to build the caissons shallower, i.e., to reduce their cost. 2 S. and 1 C.p. f-crystals, 3 ill.

The invention relates to the field devices located in the open sea and designed for drilling and production in the open sea, in particular to the caissons.

Previously used floating structures for drilling and production, had vertically mounted floating body, the upper part of which rose above the water, and the lower part was submerged to a predetermined depth. Such design-rayed at the m direction, and to the keel and side strokes. Have been proposed various means for reducing vibrations and pitching, which was a horizontally positioned elements spaced along the longitudinal axis design (US patent 4516882). The distance between these elements was large enough. The elements act as balancers when balancing, rolling, and, in addition, regulate the buoyancy of the caisson. Known design additionally contained anchor system, and mooring. Furthermore, the design could contain ballast. The disadvantages of the known designs should include low efficiency of damping.

The technical problem to be solved by the present invention is directed, is to develop a design that is more efficient damping of vibrations.

To solve this problem it is proposed to use the caisson performed with the opportunity to stay on the surface during drilling and production in the open sea, and the caisson contains at least one plate passing radially outwards from the casing below the water level in the working position of the caisson. When the caisson preferably contains numerous mooring, kadh in said plates, passing in a horizontal direction. According to the second variant of the invention it is proposed to use the caisson performed with the opportunity to stay on the surface during drilling and production in the open sea, and the caisson contains many plates, passing in a radial direction outward from the caisson lower the water level when the caisson is in the working position, and each of these plates has a diameter that is approximately 1.75 times the diameter of the caisson, when said plates are separated from each other at a distance that is approximately 60 % of the diameter of the caisson.

Hereinafter the invention will be illustrated with the use of graphic materials, where Fig. 1 shows an isometric image structures corresponding to the present invention. In Fig. 2 shows a side view (in section) of a design corresponding to the present invention. In Fig. 3 shows a graph which illustrates the influence of the distance between the plates and the diameter and number plates.

In Fig. 1 shows a construction corresponding to the present invention, indicated overall by the reference number 10. As follows from Fig. 2, the buoyancy of the caisson 10 the obligation of the cross-section of the casing 10 can be changed in its length, preferably uniform along the entire length of the cross-section. The caisson 10 can contain a variable volume ballast 14, compartments 16 oil storage, differentia tank 18 and the stationary ballast tank 20. As follows from Fig. 1, the casing 10 may be retained in a predetermined position by mooring 22. Vertical pipe 24 can be used for drilling or mining and pass through the Central well 26 in the casing 10 to the blowout preventer on its surface. Drilling rig 28 may be located on the upper surface of the caisson 10.

Unlike typical caisson with the draught order 152,4 - 213,4 m floating caisson, corresponding to this invention, has a draught of about 91,4 - 121,9 m In this case, the small oscillations in the vertical direction extinguished by the use of a variety of plates 30. Plate (plate) 30 is installed in the lower end of the casing 10 and spaced along the entire length of the caisson 10. Plate 30 is rigidly fixed in such a way as to pass through in the radial direction of the caisson 10, positioned horizontally relative to the surface of the water 32 in the case when the caisson is located in the sea in the working position. Plate 30 when the oscillations are capturing a lot of water, materialov maximum energy waves. This allows us to use less draft caisson. It should be noted that the smaller the length of the caisson and requires less effort when towing and when the transfer of the casing in a vertical position. In addition, this allows to reduce the consumption of steel in the construction of the caisson and, consequently, reduce its cost. This caisson can be used on smaller bodies of water. In this case, the upper part of the casing rises above the surface of the water approximately 15.2 m, supporting a drilling rig 28 and the deck 34. Although the graphic material shown that the plates 30 evenly spaced, but the spacing between the plates can vary depending on the desired effect on the period of oscillations of the caisson 10.

In Fig. 3 is a graph that is built in the model tests carried out on various designs of tiles and slabs. Weight plates together with the captured water influences the increase of the apparent precipitation of the spar. For example, in Fig. 3 shows that the effect of having two plates, separated from each other at a distance of 0.06 D ( i.e., distant from each other at a distance greater than the diameter of the caisson 0.06 times), and when the diameter of the plate, equal to 1.5 D (i.e., 1.5 times the diameter of the caisson) have led the, is provided that the presence of four plates of diameter D and spaced from each other at a distance of 0.5 D will increase the apparent subsidence of almost six times the diameter.

The distance between the plates and their size depends on the characteristics of waves, winds and currents, which are different in different parts of the world. For example, in the Gulf of Mexico, where the design of the caisson is mainly affected by the hurricanes, the required sediment upright caisson is 152,4 - 213,4 m to provide a smaller movement in the vertical direction. For caisson with limited draught of approximately 91.4 m and a diameter of about 30.5 m, the required effective length of the taking of water is approximately 91.4 m or three in diameter. It is evident from Fig. 3 shows that this can be achieved using four plates with a diameter of 1.5 D, separated from each other at a distance of 0.3 D - 0.5 D. If the spar has a diameter of 21.3 m, the corresponding increase in effective precipitation will require effective length of the captured mass, equal to four diameters. This will require an increase in the distance between the plates up to a size of approximately 0.7 D or to reduce the distance between the plates, the diameter of the plates will have to increase.

For the North sea, where the wave period is greater need for effective asamer.

In areas where the wave period is less than the distance between the plates and the diameter can be reduced.

Lines 22 with one end attached to the anchor 30, fixed to the seabed 40 and the other end on the caisson 10. As shown in Fig. 1, a method of fixing the moorings 22 to the caisson 10 provides for the transmission of them through guides 36 in the plates 30. The guides 36 prevent wear and chafing mooring 22 and provide an opportunity to strengthen the mooring to the caisson 10 at any desired point along its length. Preferably, they are fixed to the upper part of the caisson 10.

The caisson 10 can be made on the stocks in a horizontal position and then lowered into the water. Plate 30 can be installed after the caisson will be afloat. If the construction and descent took place in the shallow zone, the plates may be installed on the ship or afloat. Then the caisson can be towed on a deeper place and transferred in the vertical position with the dismantling of the remaining plates.

Because there are many possible variants of realization of the invention, it is obvious that the examples provided in the application materials, should be taken as illustrative and not restrictive.

1. Floating Cassie who obici in the open sea, characterized in that it additionally contains at least one plate, which pass radially outwards from the casing below the water level when the caisson in position.

2. The caisson under item 1, characterized in that it additionally contains many lines, each of which is attached at one end to the casing, and these mooring installed in the guide passing through the plate, oriented in a horizontal direction.

3. Floating caisson performed with the opportunity to stay on the water surface and is designed for drilling and production in the open sea, characterized in that it further comprises a set of plates that pass radially outwards from the casing below the water level when the caisson in position, and each of these plates has a diameter that is approximately 1.75 times the diameter of the caisson, when said plates are separated from each other at a distance of approximately 60% of the diameter of the caisson.

 

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