阅读说明：本技术 一种海上单点系泊更换维修方法 (Offshore single-point mooring replacement and maintenance method ) 是由 吴凯强 薛建 高尚磊 潘闻 张于 王韬 林铁双 肖伟 胡雪 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种海上单点系泊更换维修方法,采用DP船舶进行施工,具体步骤如下：1)在水下锚链的中上部连接吊带,在吊带下端连接配重模块；2)将绞车钢丝绳下入水中,并使其绕经定滑轮转向后与水下锚链的中上部连接；3)收紧钢丝绳,解除连接水下锚链和锚桩的卡环；4)放松钢丝绳,水下锚链和浮筒上浮至水面；5)拆除配重模块,完成浮筒和/或水下锚链的更换；6)将配重模块连接在新系泊结构的水下锚链中上部；7)收紧钢丝绳,潜水员下水利用卡环将新系泊结构的水下锚链与锚桩连接在一起；8)解除配重模块和钢丝绳。本发明无需起出锚桩,无需动用大型浮吊、船舶设施,施工工期短,风险低,成本低。(The invention discloses a method for replacing and maintaining marine single-point mooring, which adopts DP ships for construction and comprises the following specific steps: 1) the middle upper part of the underwater anchor chain is connected with a hanging strip, and the lower end of the hanging strip is connected with a counterweight module; 2) the winch steel wire rope is put into water, and is connected with the middle upper part of the underwater anchor chain after being deflected by the fixed pulley; 3) tightening the steel wire rope, and removing a snap ring for connecting the underwater anchor chain and the anchor pile; 4) loosening the steel wire rope, and floating the underwater anchor chain and the buoy to the water surface; 5) dismantling the counterweight module to complete the replacement of the buoy and/or the underwater anchor chain; 6) connecting the counterweight module to the middle upper part of the underwater anchor chain of the new mooring structure; 7) the steel wire rope is tightened, and a diver uses the clamp ring to connect the underwater anchor chain of the new mooring structure with the anchor pile; 8) and releasing the counterweight module and the steel wire rope. The invention does not need to lift out anchor piles, does not need to use large-scale floating cranes and ship facilities, and has short construction period, low risk and low cost.)

1. A method for replacing and maintaining single point mooring on the sea is characterized in that a DP ship is adopted for construction, and the method comprises the following specific steps:

1) the middle upper part of the underwater anchor chain is connected with a hanging strip, a fixed pulley is arranged on the anchor pile, and the lower end of the hanging strip is connected with a counterweight module, so that the buoy can reach neutral buoyancy;

2) the winch steel wire rope is put into water, and is connected with the middle upper part of the underwater anchor chain after being deflected by the fixed pulley;

3) tightening the steel wire rope to enable the buoy to move downwards, and after the lower end of the underwater anchor chain is loosened, matching with a diver to release a snap ring for connecting the underwater anchor chain and the anchor pile, so that the underwater anchor chain is separated from the anchor pile;

4) loosening the steel wire rope to enable the underwater anchor chain and the buoy to float up to the water surface under the control of the steel wire rope;

5) dismantling the counterweight module, and completing the replacement of the buoy and/or the underwater anchor chain under the coordination of the ship crane on the DP ship to obtain a new mooring structure;

6) before the new mooring structure is lowered, the counterweight module is connected to the middle upper part of the underwater anchor chain of the new mooring structure on the water surface;

7) tightening the steel wire rope, moving the new mooring structure and the counterweight module to the anchor pile under the traction of the steel wire rope, and connecting the underwater anchor chain of the new mooring structure and the anchor pile together by using a clamping ring when a diver launches water;

8) and releasing the counterweight module and the steel wire rope, floating the buoy to the designed position, and finishing the replacement of the underwater mooring structure.

2. The offshore single point mooring replacement and repair method according to claim 1, wherein step 5) the buoy and the underwater anchor chain are replaced together and are on deck of the DP vessel.

3. The offshore single point mooring replacement and maintenance method according to claim 1, wherein in step 5), the buoy is not replaced, and only the underwater anchor chain is replaced and the replacement is carried out at the water surface.

Technical Field

The invention relates to a maintenance method of a single point mooring system, in particular to a replacement and maintenance method of offshore single point mooring.

Background

The single point mooring system is matched with the FPSO and the oil storage wheel to carry out outward transportation operation, the outward transportation mode is suitable for the exploitation and production of marginal oil fields with small reserves and scattered distribution, and the single point mooring system has the advantages of less investment, quick response, reusability and the like, does not need to greatly refit ships during outward transportation, and is quick to install. But also has the defects of less storage, frequent export, larger influence of weather and ocean current during export, high mooring risk coefficient, small tonnage of moored ships, oil tanker collision with a platform during export, continuous severe weather, oil field production pressure, production halt, larger anchor chain abrasion and the like.

According to the detection results of a mooring system of a certain platform in recent years, the positions of a pin shaft of a snap ring of an underwater anchor chain, an anchor chain, a connecting snap ring and the like are seriously abraded due to ocean currents, mooring stress and the like, so that the problem can cause the loss of a buoy or the failure of mooring due to the positioning failure of the anchor chain, the threat to the production and the export operation of an oil field can be caused in serious cases, and even serious environmental pollution, the collision of an oil tanker platform and other serious risks can be caused, and the method belongs to serious risk potential hazards.

The current hidden danger treatment method mainly comprises the steps of replacing an underwater connecting anchor chain and a snap ring or replacing an integral single-point mooring facility.

The conventional maintenance needs to use large-scale floating cranes and ship facilities, and has long construction period, high risk and high cost.

The following disadvantages mainly exist:

1) the method needs a whole set of large equipment such as a large floating crane, a tugboat, an anchor throwing boat, a pile driver and the like.

2) The working period is long, the normal production operation of the offshore facility is seriously influenced, and the platform is required to be stopped for production and matched when being maintained and replaced;

3) the operation risk is high, the change of the sea weather is constant, the anchor walking and emergency anchor taking-off and evacuation time in severe weather is long, part of the area is close to the platform, and the collision risk of the platform is large;

4) the construction resource requirement is high, large-scale equipment such as a floating crane ship is needed, and the overall construction cost is high.

Disclosure of Invention

The invention provides a method for replacing and maintaining offshore single-point mooring, which solves the technical problems in the prior art, does not need to lift out anchor piles, does not need to use large floating cranes and ship facilities, and has short construction period, low risk and low cost.

The technical scheme adopted by the invention for solving the technical problems in the prior art is as follows: a method for replacing and maintaining single point mooring on the sea adopts DP ships for construction, and comprises the following specific steps:

1) the middle upper part of the underwater anchor chain is connected with a hanging strip, a fixed pulley is arranged on the anchor pile, and the lower end of the hanging strip is connected with a counterweight module, so that the buoy can reach neutral buoyancy;

2) the winch steel wire rope is put into water, and is connected with the middle upper part of the underwater anchor chain after being deflected by the fixed pulley;

3) tightening the steel wire rope to enable the buoy to move downwards, and after the lower end of the underwater anchor chain is loosened, matching with a diver to release a snap ring for connecting the underwater anchor chain and the anchor pile, so that the underwater anchor chain is separated from the anchor pile;

4) loosening the steel wire rope to enable the underwater anchor chain and the buoy to float up to the water surface under the control of the steel wire rope;

5) dismantling the counterweight module, and completing the replacement of the buoy and/or the underwater anchor chain under the coordination of the ship crane on the DP ship to obtain a new mooring structure;

6) before the new mooring structure is lowered, the counterweight module is connected to the middle upper part of the underwater anchor chain of the new mooring structure on the water surface;

7) tightening the steel wire rope, moving the new mooring structure and the counterweight module to the anchor pile under the traction of the steel wire rope, and connecting the underwater anchor chain of the new mooring structure and the anchor pile together by using a clamping ring when a diver launches water;

8) and releasing the counterweight module and the steel wire rope, floating the buoy to the designed position, and finishing the replacement of the underwater mooring structure.

And 5), replacing the buoy and the underwater anchor chain together, and performing on a deck of the DP ship.

And 5), replacing the underwater anchor chain only without replacing the buoy on the water surface.

The invention has the advantages and positive effects that:

1) the method is simple and efficient: anchor piles do not need to be lifted out, and the construction process is greatly simplified.

2) Construction resources: the invention needs simpler construction resources and does not need supporting facilities such as large ships and the like.

3) Safety: the invention has the advantages of no need of anchoring, accurate positioning, strong emergency response capability and low underwater operation risk of divers.

4) Construction cost: the construction cost is low, and is reduced by 80 percent compared with the existing construction method.

5) The production influence is: compared with the prior art, the method has the advantages that production stop is not needed, and production operation is not affected.

In conclusion, the method has the advantages of low cost, low construction resource requirement and high construction efficiency; the construction safety is high; the method has no influence on the production condition of the existing oil field, can safely and efficiently eliminate the hidden danger of the single point mooring structure, and keeps the safe production of offshore facilities.

Drawings

FIG. 1 is a schematic structural diagram of step 3) of the present invention.

In the figure: 1. a DP vessel; 2. hoisting by a ship; 3. a wire rope; 4. a fixed pulley; 5. anchoring piles; 6. a float bowl; 7. an underwater anchor chain; 8. a sling; 9. a counterweight module.

Detailed Description

In order to further understand the contents, features and effects of the present invention, the following embodiments are illustrated and described in detail with reference to the accompanying drawings:

referring to fig. 1, a method for replacing and maintaining an offshore single-point mooring by using a DP ship 1 includes the following steps:

1) the middle upper part of the underwater anchor chain 7 is connected with a hanging strip 8, the anchor pile 5 is provided with a fixed pulley 4, and the lower end of the hanging strip 8 is connected with a counterweight module 9, so that the buoy 6 achieves neutral buoyancy.

2) And a steel wire rope 3 on the winch is put into water, is turned around the fixed pulley 4 and then is connected with the middle upper part of the underwater anchor chain 7. The winch is mounted on the DP vessel 1, and the wire rope 3 on the winch plays a role in towing a mooring structure containing an underwater anchor chain 7.

3) And (3) tightening the steel wire rope to enable the buoy 6 to move downwards, and after the lower end of the underwater anchor chain 7 is loosened, the diver is matched to release the snap ring for connecting the underwater anchor chain 7 and the anchor pile 5, so that the underwater anchor chain 7 is separated from the anchor pile 5.

4) And (3) loosening the steel wire rope 3 to enable the underwater anchor chain 7 and the buoy 6 to float up to the water surface under the control of the steel wire rope 3.

5) And (3) dismantling the counterweight module 9, and completing the replacement of the buoy 6 and/or the underwater anchor chain 7 under the cooperation of the ship crane 2 to obtain a new mooring structure. The buoy 6 is turned and fixed by using the ship crane and the steel wire rope for assistance, and the anchor chain is replaced or the mooring structure is integrally replaced.

When both the buoy 6 and the underwater anchor chain 7 need to be replaced, they can be lifted up to the deck of the DP vessel and replaced on the deck. When the buoy 6 is not replaced, only the underwater anchor chain 7 is replaced, and the operation can be carried out on the water surface without hoisting the deck.

6) Before the new mooring structure is lowered, the counterweight module 9 is connected to the middle upper part of the underwater anchor chain of the new mooring structure on the water surface.

7) And (3) tightening the steel wire rope 3, moving the new mooring structure and the counterweight module 9 to the anchor pile 5 under the traction of the steel wire rope 3, and connecting the underwater anchor chain of the new mooring structure with the anchor pile 5 by using a clamping ring when a diver launches water.

8) And (4) releasing the counterweight module 9 and the steel wire rope 3, floating the buoy of the new mooring structure to the designed position, and finishing the replacement of the underwater mooring structure.

The method for replacing the underwater anchor chain is compared with the conventional maintenance method in the aspects of equipment allocation, personnel allocation, construction period cost and risk by the following steps:

the method effectively improves the potential hazard treatment capability of the single-point mooring facility, and saves the cost by 80 percent compared with the original construction method with the cost of more than 1000 ten thousand yuan.

The counterweight scheme of the counterweight module and the path of the traction type steel wire rope need to be analyzed, calculated and determined according to the original file of the single-point mooring device and by combining the actual engineering situation and considering factors such as buoyancy, seabed, flow velocity, counterweight, anchor chain length and the like.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make many modifications without departing from the spirit and scope of the present invention as defined in the appended claims.