A Design Method for the Anchor Laying Scheme of a Jack-up Platform with a Base Circle

Abstract

The present invention provides a design method for the base circle type anchor dropping scheme of a jack-up platform. Determine the relative position between the jack-up platform and the docking platform according to the in-place technical requirements; take the intersection point of the center line of the hull of the jack-up platform and the stern as the center of a circle, and draw a circle with a radius of 700 meters; take the bow direction of the jack-up platform as the direction of the center line of the hull and draw a direction arrow, which is the bow direction line; if there are no underwater and overwater obstacles around the docking platform, determine the anchor dropping point; if there are pipelines and cables around the docking platform, determine the anchor dropping angle; if there are obstacles such as production platforms overwater, adjust the anchor line according to the position of the overwater obstacles, connect the anchor line to the leg of the obstacle, and the included angle between the anchor line and the center line of the hull ranges from 30° to 60°. This method helps to provide a reasonable anchor dropping position and angle, provide reasonable pulling force during the in-place operation of the jack-up platform in the early stage of oilfield development, control the jack-up platform from colliding with the docking object, and ensure the safety of the in-place operation of large-scale offshore facilities.

Description

Technical Field

[0001] The present invention relates to the technical field of the positioning technology of jack-up platforms in offshore oilfields, and more specifically to a design method for the base-circle type anchor-laying scheme of a jack-up platform. Background Art

[0002] With the implementation of the national energy seven-year action plan, CNOOC has increased its exploration and development efforts. 80% of offshore oilfield development is completed through jack-up platforms. After the jack-up platform is towed and put into operation and reaches the initial positioning position, pile driving is carried out at the initial positioning position, and then anchor-laying operations are carried out. Generally, 4 anchors are laid, and the jack-up platform is gradually brought closer to the docking object by retracting and releasing the anchors. Due to the existence of above-water and underwater facilities and obstacles in the offshore oilfield area, anchor-laying is restricted, and some complex anchor-laying situations have occurred. For example, if the anchor-laying angle and length are inappropriate, the anchor holding force is insufficient; if the anchor-laying scratches the submarine pipelines and cables, it will cause production suspension or even ecological pollution; and if the tensile resistance of the docking object is insufficient when tying the anchor, the stability of the jacket and the production platform will be affected. Therefore, how to do a good job in the anchor-laying design and on-site operations during the positioning operation is the premise for ensuring the success rate and efficiency of positioning.

[0003] The existing technology is that engineers use AUTOCAD software to draw the anchor-laying scheme, and the selection of the anchor-laying length and angle depends on work experience. Often, the designed anchor-laying scheme for positioning does not meet the actual requirements, and the safety distance between the anchor-laying point and above-water and underwater obstacles does not meet the requirements, etc. This has caused the designed anchor-laying scheme not to meet the requirements of on-site operations and cannot ensure the safety of large offshore facilities. Summary of the Invention

[0004] The present invention overcomes the deficiencies in the prior art. Engineers use AUTOCAD software to draw the anchor-laying scheme, and the selection of the anchor-laying length and angle completely depends on work experience. Often, the designed anchor-laying scheme for positioning does not meet the actual requirements, and the safety distance between the anchor-laying point and above-water and underwater obstacles does not meet the requirements, etc. The present invention provides a design method for the base-circle type anchor-laying scheme of a jack-up platform. This method helps to provide a reasonable anchor-laying position and angle, provide reasonable tensile force, control the jack-up platform from colliding with the docking object, ensure the safety of the positioning operation of large offshore facilities, and further provide guarantee for the safe and efficient operation of subsequent drilling devices, and provide technical support for the efficient development of oilfields and the safety of large offshore facilities.

[0005] The object of the present invention is achieved by the following technical solutions.

[0006] A design method for the base-circle type anchor-laying scheme of a jack-up platform is carried out according to the following steps:

[0007] Step 1: Determine the relative positions of the jack-up platform and the docking platform according to the requirements of the positioning technology;

[0008] Among them, the relative positions of the jack-up platform and the docking platform are determined by the positioning plan, and the technical requirements are determined in the positioning design plan;

[0009] Step 2: Take the intersection point of the center line of the jack-up platform hull and the stern as the center, and draw a circle with a radius of 700 meters;

[0010] Among them, the center line of the jack-up hull is the axisymmetric line of the hull sketch drawn according to the hull drawings;

[0011] Step 3: Take the heading of the jack-up platform as the direction of the hull center line, draw a direction arrow, and define it as the heading line;

[0012] Step 4: If there are no underwater and above-water obstacles around the docking platform, starting from the heading line obtained in Step 3, that is, 0°, and taking the center point obtained in Step 2 as the starting point, draw out 4 line segments. The included angles between the above 4 line segments and the hull center line are 45°, 135°, 225°, and 315° respectively. The intersection points of the above 4 line segments and the circle with a radius of 700 meters are the anchor points;

[0013] Among them, the heading line coincides with the hull center line, the included angles between the 4 line segments and the heading line are all 45°, and the lengths of the 4 line segments are the anchor lengths;

[0014] Step 5: If there are pipeline cables on the seabed around the docking platform, proceed according to the following steps:

[0015] 1) Repeat Step 2, that is, take the intersection point of the center line of the jack-up platform hull and the stern as the center, and draw a circle with a radius of 700 meters. The above circle with a radius of 700 meters intersects with several pipelines and cables;

[0016] 2) Starting from the heading line obtained in Step 3, that is, 0°, and taking the center point obtained in Step 2 as the starting point, draw out 4 groups of line segments. Each group of line segments contains two lines. The included angles between the first group of line segments and the hull center line are 30° and 60° respectively, the included angles between the second group of line segments and the hull center line are 120° and 150° respectively; the included angles between the third group of line segments and the hull center line are 210° and 240° respectively, and the included angles between the fourth group of line segments and the hull center line are 300° and 330° respectively. If there are no pipelines and cables within the range framed by each group of the above line segments and the hull center line, then the two line segments in this group can be removed;

[0017] 3) Taking the pipeline and cable in the angular range of the first group of line segments as an example, draw a perpendicular line from any point on the 30° - 60° arc to the pipeline and cable. The connection line between the arc point corresponding to the longest perpendicular line segment and the center is the anchor line and the anchor angle;

[0018] Among them, pipelines and cables not only include those connected to the docking platform, but also include pipelines and cables passing within a range of 1 to 2 kilometers with the docking object as the center of the circle. The angular difference between each group of line segments is 30 - 35°, and the angular difference is the included angle;

[0019] Step 6, if there are obstacles such as production platforms on the water, repeat Steps 2, 3, and 4. According to the position of the underwater obstacle, that is, if the anchor line on the jack-up platform is closest to the obstacle, adjust the above-mentioned anchor line and connect the above-mentioned anchor line to the pile leg of the obstacle. The included angle range between the above-mentioned anchor line and the hull center line is 30 - 60°;

[0020] Among them, when the anchor line is connected to the pile leg of the obstacle, it is necessary to meet the tensile strength check, that is, the tied pile leg can provide sufficient tensile force for the anchor line.

[0021] In Steps 5 and 6, the selection method for the safety distance from the anchor point to the pipelines and cables is as follows:

[0022] 1) The anchor point needs to be more than 100 meters away from the pipelines and cables;

[0023] 2) If there are clear requirements in the operation area, it is necessary to execute according to the regulations of the operation area;

[0024] 3) If it is stipulated in the towing and positioning standard, it is necessary to execute according to the towing and positioning standard.

[0025] In Steps 4, 5, and 6, the anchor length needs to be designed according to the specified value in the ship handling manual of each ship.

[0026] The beneficial effects of the present invention are as follows: With the base circle as the basis and boundary conditions, the anchoring limit is defined. The anchoring design is carried out within the circle according to the standard requirements and actual conditions, making the anchoring angle and length more reasonable and accurate;

[0027] The anchoring angle designed under the base circle effectively avoids obstacles such as water platforms and underwater pipelines and cables, protects the safety of the oil mining area, and avoids the shutdown of oil fields and ecological pollution caused by the anchor head scraping the pipelines and cables;

[0028] The anchoring angle and length designed under the base circle are both beneficial for the anchor head to better combine with the formation, provide better anchor holding force, improve the success rate of anchoring, and ensure the safety of positioning and large facilities. Description of the Drawings

[0029] Figure 1 is a conventional anchoring diagram in the prior art;

[0030] Figure 2 is an anchoring diagram for underwater obstacles with a base circle using the method of the present invention;

[0031] Figure 3It is the drawing of dropping anchor for the base circle water obstacles using the method of the present invention;

[0032] Figure 4 It is the corresponding schematic diagram of Step 1 in the embodiment;

[0033] Figure 5 It is the corresponding schematic diagram of Step 2 in the embodiment;

[0034] Figure 6 It is the corresponding schematic diagram of Step 4 in the embodiment;

[0035] Figure 7 It is the corresponding schematic diagram of Step 5 in the embodiment;

[0036] Figure 8 It is the corresponding schematic diagram of Step 6 in the embodiment.

[0037] For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on the above drawings. Detailed implementation manners

[0038] The technical solutions of the present invention will be further described below through specific embodiments.

[0039] Embodiment

[0040] A design method for the base circle type anchor dropping scheme of a jack-up platform is carried out according to the following steps:

[0041] Step 1, determine the relative position of the jack-up platform and the docking platform according to the in-place technical requirements, with the bow direction being 314°, as Figure 4 shown;

[0042] Among them, the relative position of the jack-up platform and the docking platform is determined by the in-place scheme, and the technical requirements are determined in the in-place design scheme;

[0043] Step 2, take the intersection point of the center line of the jack-up platform hull and the stern as the center, and draw a circle with a radius of 700 meters, as Figure 5 shown;

[0044] Among them, the center line of the jack-up hull is the axis of symmetry of the hull sketch drawn according to the hull drawing;

[0045] Step 3, take the bow direction of the jack-up platform as the direction of the center line of the hull, draw a direction arrow, and define it as the bow line;

[0046] Step 4, design 4 anchors. Based on the bow line, the two front anchors, that is, the two anchors at the bow of the ship, have no water or underwater obstacles. Starting from the bow line, that is, 0°, the included angles between the two anchor lines and the bow line are 45°, as Figure 6 shown;

[0047] Step 5: Taking the bow line as the reference, there are pipeline cables on the seabed around the anchoring direction of the right rear anchor. Starting from 0° of the bow direction line, an arc segment corresponding to the right rear anchor is delimited within the range of 74° - 104°. Perpendicular lines to the pipelines and cables are drawn from the points on this arc segment. Finally, it is determined that the direction of 99° is the most suitable, that is, the safety distance from the pipeline cables is satisfied and the tension is maximized, as Figure 7 shown;

[0048] Step 6: There is an offshore platform in the direction of the left rear anchor, so it is impossible to anchor and only cable mooring can be carried out. Because the cable mooring angle and the tension for retracting and releasing the anchor at the proximal leg of the obstacle do not meet the requirements, finally the cable mooring is carried out at the distal leg of the obstacle, and the cable mooring angle is 35°, as Figure 8 shown.

[0049] For ease of explanation, spatial relative terms such as "upper", "lower", "left", "right", etc. are used in the embodiments to describe the relationship of one element or feature shown in the figure relative to another element or feature. It should be understood that, in addition to the orientations shown in the figure, the spatial terms are intended to include different orientations during the use or operation of the device. For example, if the device in the figure is inverted, the element described as being "below" other elements or features will be positioned "above" the other elements or features. Thus, the exemplary term "lower" can encompass both the upper and lower orientations. The device can be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein can be interpreted accordingly.

[0050] Moreover, relative relationship terms such as "first" and "second" are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components.

[0051] The present invention has been described in detail above, but the above content is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A design method for the base circle type anchor dropping scheme of a jack-up platform, characterized in that: Proceed as follows: Step 1: Determine the relative position between the jack-up platform and the docking platform according to the in-place technical requirements; Among them, the relative position between the jack-up platform and the docking platform is determined by the in-place plan, and the technical requirements are determined in the in-place design plan; Step 2: With the intersection point of the center line of the jack-up platform hull and the stern as the center, draw a circle with a radius of 700 meters; Among them, the center line of the jack-up hull is the axisymmetric line of the hull sketch drawn according to the hull drawing; Step 3: With the heading of the jack-up platform as the direction of the hull center line, draw a direction arrow and define it as the heading line; Step 4: If there are no underwater and above-water obstacles around the docking platform, starting from the heading line obtained in Step 3, that is, 0°, and with the center point obtained in Step 2 as the starting point, draw out 4 line segments. The included angles between the above 4 line segments and the hull center line are 45°, 135°, 225°, and 315° respectively. The intersection points of the above 4 line segments and the circle with a radius of 700 meters are the anchor points; Among them, the heading line coincides with the hull center line, the included angles between the 4 line segments and the heading line are all 45°, and the lengths of the 4 line segments are the anchor lengths; Step 5: If there are pipeline cables on the seabed around the docking platform, proceed as follows: 1) Repeat Step 2, that is, with the intersection point of the center line of the jack-up platform hull and the stern as the center, draw a circle with a radius of 700 meters. The above circle with a radius of 700 meters intersects with several pipelines and cables; 2) Starting from the heading line obtained in Step 3, that is, 0°, and with the center point obtained in Step 2 as the starting point, draw out 4 groups of line segments. Each group of line segments contains two line segments. The included angles between the first group of line segments and the hull center line are 30° and 60° respectively, the included angles between the second group of line segments and the hull center line are 120° and 150° respectively; the included angles between the third group of line segments and the hull center line are 210° and 240° respectively, and the included angles between the fourth group of line segments and the hull center line are 300° and 330° respectively. If there are no pipelines and cables within the range framed by each group of line segments and the hull center line, then remove the two line segments in this group of line segments; 3) When the pipeline and cable are within the angular range of the first group of line segments, draw a perpendicular line from any point on the 30° - 60° arc to the pipeline and cable. The connection line between the arc point corresponding to the longest perpendicular line segment and the center is the anchor line and the anchor angle; Among them, the pipeline and cable not only include the pipelines and cables connected to the docking platform, but also include the pipelines and cables passing through within a range of 1 - 2 kilometers with the docking object as the center. The angular difference between each group of line segments is 30 - 35°, and the angular difference is the included angle; Step 6: If there are production platform obstacles above water, repeat Step 2, Step 3, and Step 4. According to the position of the above-water obstacle, that is, if the anchor line on the jack-up platform is the closest to the obstacle, then adjust the anchor line and connect the anchor line to the leg of the obstacle. The included angle range between the anchor line and the hull center line is 30 - 60°; Among them, when the anchor line is connected to the leg of the obstacle, the tension check shall be satisfied, that is, the tied leg can provide sufficient tension for the anchor line.

2. The design method of the self-elevating platform base circle type anchor throwing scheme according to claim 1, characterized in that: In Step 5 and Step 6, the selection method for the safe distance from the anchor point to the pipeline and cable is as follows: 1) The anchor point needs to be more than 100 meters away from the pipeline and cable; 2) If there are clear requirements in the operation area, it is necessary to follow the regulations of the operation area; 3) It is stipulated in the towing and positioning standard, and it is necessary to execute in accordance with the towing and positioning standard.

3. A design method for the base circle type anchor dropping scheme of a jack-up platform according to claim 1, characterized in that: In steps 4, 5, and 6, the anchor length needs to be designed according to the specified value in the ship handling manual of each ship.

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