RU2710573C1 - Method of protecting underwater pipelines - Google Patents

Abstract

FIELD: pipelines.

SUBSTANCE: invention relates to protection of underwater pipelines, in particular, by laying stone dumps at the bottom of water reservoir, and can be used for filling off sagging of offshore pipelines. Method of protecting underwater pipelines includes steps of: a) determining the location of the stone dump, b) filling the sacs with stones of specified dimensions and closing said bags, c) delivering the filled and closed mesh bags on the vessel to the zone located above the place of laying, d) hanging the mesh bags on the cranes, e) lowering the mesh bags filled with stones into the water, f) placing stones on bottom; g) lowering filled with stones mesh bags into water at height of 3.5–5 m above pipeline, h) opening mesh bags, providing free falling of stones from mesh bag.

EFFECT: technical result consists in improvement of pipeline protection reliability at maintaining simplicity of used equipment, reduction of material consumption and labor intensity.

7 cl, 6 dwg

Description

The invention relates to the protection of underwater pipelines, in particular by laying a stone dump at the bottom of a reservoir, and can be used for dumping sagging offshore pipelines.

Pipelines laid along the bottom of the sea are affected by storms and currents, under the influence of which the soil around and under the pipelines is gradually eroded, which leads to the formation of free sagging pipelines. They represent an operational risk for pipelines due to static and dynamic loads, which over time can lead to mechanical damage and possible loss of pipeline integrity.

To prevent damage to the pipeline due to its sagging, stone filling is used, which can be carried out in various ways.

For example, in RU 2601567, a method is described for laying stone dumping from a vessel at a predetermined site at the bottom of a reservoir, according to which the dumping stones are fed into a drain pipe connected to the vessel, which is inclined vertically to the place where the stones are laid.

However, a device that implements this method of filling is complicated and expensive, and the use of existing stone-laying vessels is also very expensive, since a significant part of the cost of the work is mobilizing the vessel to a place of work remote from the port of registration and returning this vessel to the port of registration.

There is also known a method of protecting an underwater pipeline, described in the application US 2011/158747 A1, according to which in a predetermined place, mesh bags filled with stones of predetermined sizes are lowered from the vessel and these bags are laid to the bottom.

This method, which is closest to the invention, eliminates the need to use specialized vessels, thereby reducing the cost of work to protect the pipeline, but it has lower reliability compared to the method described above, since bags filled with stones cannot fill the bags formed under a pipeline of voids with the same density as individual stones.

Thus, the problem to which the invention is directed is the development of a pipeline protection method that does not require large expenditures and complex equipment, as in the method according to the patent RU 2601567, but allows for high reliability of the pipeline protection, as in the method according to the application US 2011 / 158747.

This problem is solved in a method of protecting underwater pipelines, which includes the steps at which to determine the location of the laying of the stone dump; fill the mesh bags with stones of specified sizes and close these bags; deliver filled and closed mesh bags on board to the area above the place of laying; hanging mesh bags on cranes; lower the mesh bags filled with stones into the water; and lay the stones at the bottom.

According to the invention, the mesh-filled bags filled with stones are lowered into the water to a height of 3.5-5 above the pipeline, they are opened, allowing the stones to fall freely from the mesh bag.

The technical result achieved by the implementation of this method is to increase the reliability of the protection of the pipeline while maintaining the simplicity of the equipment used. This result is achieved due to the fact that the opening of mesh bags at a specified height above the pipeline instead of laying on the bottom of the filled bags allows you to fill the cavity formed under the pipeline with stones, without damaging the pipe falling stones.

Preferably, the location of the stone dump is determined by locating the sagging areas of the pipelines using a remotely controlled apparatus.

In addition, after lowering the mesh bags filled with stones into the water, it is desirable to monitor the position of the mesh bag to the place of laying the stone dump, and in case of inconsistency, adjust the position of the vessel or ship crane.

Preferably, said control is carried out using a remotely controlled apparatus.

The height of the mesh bags filled with stones dropped into the water above the pipeline can be controlled using a remotely controlled device, or using a cable meter, or a signal buoy.

Preferably, the mesh bags are opened remotely using an underwater acoustic breaker.

Preferably, after the stones fall to the bottom, their location relative to the pipeline is controlled using a remotely controlled device and, if necessary, the mesh bags filled with stones are re-lowered into the water to a height of 3.5-5 above the pipeline and the mesh bags are opened, allowing stones to fall freely from the mesh bag, to until the protected pipeline is covered with stones to at least half the diameter.

The invention is illustrated by drawings.

In FIG. 1 schematically shows a mesh bag filled with stones lowered from a ship;

in FIG. 2 - mesh bag without stones;

in FIG. 3 schematically shows a mesh bag filled with stones lowered from a vessel before being opened;

in FIG. 4 - mesh bag after opening it;

in FIG. 5 - a fully open mesh bag;

in FIG. 6 schematically shows a stone berm obtained at the end of the dumping, a cross-sectional view of the pipeline.

To protect the underwater pipeline from damage due to sagging, a preliminary hydrographic study is carried out to determine the place of sagging and its parameters (length, height).

The location of the stone dumping is determined by inspection with a multi-beam echo sounder, for example, SeaBet; or using an underwater controlled vehicle, for example, a Tiger type.

In FIG. 1 shows the place 1 of laying a stone dump, corresponding to the place of sagging of the pipeline 2.

After determining the place of laying the stone dump, mesh bags are prepared for filling with stones of a certain fraction. In FIG. 2 schematically shows the construction of the mesh bag 3. A central sling 4 is attached to the bottom of the mesh bag 3, which, using a cable hook 5 through the central sling 4, forms the central lifting sling 6 shown in FIG. 3-5. An annular sling 7 passes to the perimeter of the mesh bag 3 near its edge, to which disconnecting slings 8, shown in FIG. 3 and 4. Mesh bags 3 are filled with stones of a given size and close these bags so that the disconnecting slings 8 and the central lifting sling 6 are freely accessible. Filled and closed mesh bags 3 are delivered on the ship 9 (Fig. 1) to the area located above the place 1 laying. Then, as shown in FIG. 3, mesh bags 3 filled with stones 10 are suspended on cranes 11 (Fig. 1) so that the central lifting sling 6 through the connecting ring 12, carabiners 13, cable 14 and connecting ring 15 is attached to the crane hook 16, and the disconnecting slings 8 are attached to the underwater acoustic disconnect 17, connected, for example, through the connecting ring 12 to the hook 16 of the crane. After that, the closed mesh bags 3 filled with stones are lowered into the water above the place of laying 1. In this case, it is desirable to check the correspondence of the position of the mesh bag 3 to the place 1 of laying the stone dump, in particular, using a remotely controlled device 18, for example, of the Tiger type. If a discrepancy is found, the position of the vessel 9 or ship crane 11 is adjusted. The mesh bags 3 are lowered to a height of 3.5-5 m above the pipeline, while controlling the indicated height using a remotely controlled device 18. Remote-controlled device 18 should be located above the pipeline 2 in the direction of the sagging area, to keep the mesh bag 3 in sight, while at a safe distance of at least 5 m (to prevent damage to this apparatus 18 from falling stones). Alternatively, monitoring the height of the mesh bag over the pipeline can be controlled by a marine multi-beam echo sounder, such as SeaBet.

The choice of the lowering height of the mesh bag over the pipeline, at which this bag is opened, is due, on the one hand, to the fact that at a height of less than 5 m, stones falling in water when they hit the pipeline do not cause noticeable damage to it, but on the other hand, the fact that with a height greater than 3.5 m, the probability of contact of the filled mesh bag with the pipeline in the presence of vertical rolling is excluded.

Then an acoustic signal is supplied to open the underwater acoustic disconnect 17 and reset the stones. When the underwater acoustic breaker 17 is activated, the disconnecting slings 8 are released, and the mesh bag 3, held by the central lifting sling 6 at its bottom, begins to open, turning out, as shown in FIG. 4. In FIG. 5 shows the fully opened position of the mesh bag 3, allowing the stones 10 to freely sink to the bottom in place 1 laying. After the stones 10 fall to the bottom, their location relative to the pipeline 2 is controlled using a remotely controlled apparatus 18 and, if necessary, the process of stone discharge described above is repeated until the protected pipeline 2 is covered with stones 10 to at least half the diameter, as shown in FIG. 6.

Claims (16)

1. A method of protecting underwater pipelines, comprising the steps of: a) determine the location of the stone dump; b) fill the mesh bags with stones of specified sizes and close these bags; c) deliver on the vessel filled and closed mesh bags to the area located above the place of laying; d) hang mesh bags on cranes; e) lower the mesh bags filled with stones into the water; e) lay the stones on the bottom, characterized in that g) lower the mesh bags filled with stones into the water to a height of 3.5-5 m above the pipeline; h) open the mesh bags, ensuring the free fall of stones from the mesh bag. 2. The method according to p. 1, characterized in that the place of laying the stone dump is determined by finding areas of sagging pipelines using a remotely controlled device. 3. The method according to p. 1, characterized in that after lowering the mesh bags filled with stones into the water, the correspondence of the position of the mesh bag to the place of laying the stone dump is monitored and, if a mismatch is found, the position of the vessel or ship crane is adjusted. 4. The method according to p. 3, characterized in that the said control is carried out using a remotely controlled device. 5. The method according to p. 1, characterized in that the height of the mesh bags filled with stones dropped into the water above the pipeline is controlled using a remotely controlled device, or using a cable meter, or a signal buoy. 6. The method according to p. 1, characterized in that the mesh bags open remotely using an underwater acoustic disconnect. 7. The method according to p. 1, characterized in that after the stones fall to the bottom control their location relative to the pipeline using a remotely controlled device and, if necessary, repeat steps e) and g) until the protected pipeline is covered with stones at least at least half the diameter.

Images