Land-to-sea large displacement geometric nonlinear drill pipe landing force analysis method

Abstract

The application discloses a kind of land-to-sea large displacement geometric nonlinear drill rod landing force analysis methods, comprising the following steps: S1, determine the sea area drill rod load and environmental parameter;S2, construct large displacement geometric nonlinear drill rod constitutive unit;S3, establish drill rod three-dimensional numerical analysis model;S4, drill rod landing force safety evaluation and bracket support length determination.The method establishes drill rod large displacement geometric nonlinear constitutive model, systematically considers the multi-field coupling load of drill rod under the condition of large height difference in deep water area, combined with adjustable bracket support boundary condition, realizes the accurate simulation and safety evaluation of the whole process force state of drill rod landing, and provides theoretical basis for drill rod safety receiving connection.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, specifically relating to a large displacement geometric nonlinear stress analysis method for accurate calculation of drill pipe coupled stress under deep-water, large elevation difference, and kilometer-level crossing conditions in deep-sea long-distance land-sea horizontal directional drilling projects. It is applicable to the quantitative calculation and safety verification of drill pipe stress, deformation, and ultimate pullback force in land-sea landing directional drilling projects for offshore wind power cables and submarine pipelines. Background Technology

[0002] With the continuous development of marine engineering, especially offshore wind power, offshore wind farms are expanding into deeper waters. This necessitates submarine cable landing sections traversing longer distances and facing complex coastal geology and sea conditions. Traditional construction techniques such as trenching and pipe laying, and floating and sinking methods are no longer sufficient to meet the demands of deep-sea development due to their significant ecological damage, long construction periods, susceptibility to window periods, and high costs. Long-distance onshore-offshore horizontal directional drilling, as a green and efficient construction technology, is gradually becoming the preferred solution for submarine cable landing.

[0003] However, in long-distance onshore-offshore directional drilling operations, the drill rod needs to be transferred from the sea exit point to the work vessel, a process that faces the following technical challenges:

[0004] (1) Problem of large elevation difference: The depth of deep sea water can reach 15~30m. At high tide, the vertical drop of the drill rod from the seabed to the deck of the ship can reach more than 26m, and the drill rod is suspended in a large span. (2) Complex stress: The drill pipe is simultaneously subjected to multiple coupled loads such as axial tension, torque, alternating bending moment, seawater buoyancy, and ocean current force, exhibiting significant large displacement geometric nonlinear characteristics; (3) Large deformation: The slenderness ratio of the kilometer-level drill pipe (the slenderness ratio can reach more than 2000) is prone to "S"-shaped large deformation during the large span lowering process. The stress and displacement are large, and the stability control of the drill pipe under large displacement is very critical.

[0005] Existing research largely focuses on short-distance directional drilling in shallow waters, employing conventional small-deformation truss elements for numerical simulation. However, research on the coupled stress analysis mechanism of drill pipes under large deformation in deep-water, kilometer-scale, long-distance onshore and offshore directional drilling remains insufficient. This makes it difficult to accurately grasp the complex stress state of the drill pipe and lacks targeted supporting technologies. Currently, the main shortcomings in the stress analysis of directional drilling drill pipes both domestically and internationally are as follows: (1) Limitations of linear analysis models: Existing numerical simulations mostly use small deformation linear elastic elements, which are only suitable for land or shallow shoal landing conditions, and cannot characterize the large displacement geometric nonlinear deformation characteristics of drill pipes under deep water with large elevation differences.

[0006] (2) Limitations of empirical methods: Some studies analyze the stress on the drill pipe through indoor tests, but only consider a single torque load, without superimposing the multi-field coupling effects such as axial tension, alternating bending, and seawater buoyancy, which are quite different from the actual working conditions.

[0007] (3) Lack of systematic analysis method for drill pipe landing force: Existing technology focuses more on the calculation of pipeline back pull force, and does not study the stress and deformation characteristics of drill pipe itself during the landing stage. In particular, it lacks a systematic analysis process for the specific working condition of drill pipe from the seabed to the ship deck.

[0008] Existing related patent technologies, such as the one disclosed in patent document (CN116663348A), describe a stress analysis method and system for coiled tubing drilling. This patent uses a finite element analysis model to analyze the buckling behavior of coiled tubing; however, the technical solution remains at the level of pure theoretical mechanics derivation, lacking key parameter settings for practical engineering applications: Buckling criteria are not disclosed: it does not explain how to determine the existence of buckling behavior (e.g., the calculation formula for critical load, the standard for eigenvalue buckling analysis, or the displacement mutation criterion for nonlinear post-buckling). Boundary conditions and load settings are not clearly defined: the coiled tubing running-in process involves complex wellbore contact. The document does not mention how to set multi-field coupled boundary conditions such as the frictional contact model between the tubing string and the wellbore, seawater buoyancy, axial tension, and alternating bending, making it difficult for this method to directly guide practical engineering.

[0009] To address the shortcomings of existing technologies, there is an urgent need for a method for analyzing the stress on drill pipes during large-displacement geometrical nonlinear landings from land to sea, particularly considering the large-displacement geometrical nonlinear stress characteristics of drill pipes under conditions of significant elevation differences in deep water. This method establishes a large-displacement geometrical nonlinear constitutive model for the drill pipe, systematically considering multi-field coupled loads under conditions of significant elevation differences in deep water. Combined with adjustable bracket support boundary conditions, it achieves accurate simulation and safety assessment of the stress state of the drill pipe throughout the landing process, providing a theoretical basis and safety guarantee for drill pipe receiving and connection. Summary of the Invention

[0010] This invention addresses the problem of insufficient accuracy in stress analysis of long-distance land-sea horizontal directional drilling steel pipes under complex working conditions in existing technologies. It proposes a land-to-sea large-displacement geometrical nonlinear drill pipe landing stress analysis method. This method establishes a large-displacement geometrical nonlinear constitutive model of the drill pipe, systematically considering multi-field coupled loads under large elevation differences in deep water conditions. Combined with adjustable bracket support boundary conditions, it achieves accurate simulation and safety assessment of the stress state of the drill pipe throughout the landing process, providing a theoretical basis for the safe reception and connection of the drill pipe.

[0011] To achieve the above objectives, the present invention provides the following technical solution: A method for analyzing the stress of a land-to-sea large displacement geometric nonlinear drill pipe during landing includes the following steps: S1, determining the drill pipe load and environmental parameters in the sea area; S2, constructing a large displacement geometric nonlinear drill pipe constitutive element; S3, establishing a three-dimensional numerical analysis model of the drill pipe; S4, conducting a safety assessment of the drill pipe's landing stress and determining the support length of the bracket.

[0012] Furthermore, in step S1, the determination of the marine drill pipe load and environmental parameters, combined with the specific project background, involves collecting and determining the following analysis parameters: (1) Structural parameters: Drill pipe specifications, including outer diameter d, wall thickness δ1, material yield strength; steel pipe specifications, including outer diameter D and wall thickness δ2. (2) Environmental parameters: seawater depth H, seawater bulk density γ w Ocean current speed v c , the magnitude of tidal changes; (3) Geometric parameters: excavation angle θ, horizontal distance Ls between the working vessel and the excavation point, and freeboard height h of the vessel deck. d 1. Pre-tension force F0 of the drill pipe clamp at the bow; (4) Load parameters: drill pipe self-weight, seawater buoyancy, ocean current horizontal load, mud viscosity resistance, and pipe-soil friction resistance.

[0013] Furthermore, step S2 involves constructing a large-displacement geometrically nonlinear drill pipe constitutive element. Addressing the geometrically nonlinear characteristics of the drill pipe under deep-water, high-elevation conditions—characterized by "large displacement, large rotation, and small strain"—this step overcomes the limitations of traditional small-deformation linear elastic elements. It constructs a tangent stiffness matrix that simultaneously incorporates material stiffness and geometric stiffness, coupled with an element stiffness matrix that couples multiple internal forces such as axial tension, torque, and bending moment. This accurately simulates the large deflection deformation of the drill pipe. (1) Recursive formula for incremental internal force of a unit: Axial force increment:

[0014] Torque increment:

[0015] Internal force vector:

[0016] (2) Element material stiffness matrix Geometric stiffness matrix

[0017] Material stiffness matrix:

[0018] Geometric stiffness matrix:

[0019] (3) Total tangent stiffness matrix

[0020] In the formula, each parameter represents the following meaning: : Axial force at time t+Δt; : Axial force at time t; E : Elastic modulus; A Cross-sectional area; : Axial strain increment; Torque at time t+Δt; Torque at time t; G Shear modulus; J : Torsional constant of cross section; : Increment of torsion angle; : Element length; : 3x3 identity matrix; : Axial force at time t; L : Element length; Original cell length; R Rotation matrix.

[0021] Furthermore, step S3 involves establishing a three-dimensional numerical analysis model of the drill pipe, specifically a large-span three-dimensional model of the drill pipe from the seabed protrusion point to the ship's deck. The steps are as follows: (1) Discretize the drill pipe using the large displacement geometric nonlinear beam element established in step two; (2) Boundary conditions: hinged constraint at the seabed where the soil is unearthed, hinged constraint at the buckle at the bow, and elastic support of the bracket with preload F0 applied. (3) Load application: drill pipe self-weight, buoyancy, ocean current force, pullback force; (4) Time history analysis: The superposition method is used to consider the initial stress generated by the initial bending of the drill pipe. The different pullback stages are combined with the time history of the drill pipe pullback, including the stress and deformation superposition analysis of the start-up, stable pullback and connection.

[0022] Furthermore, the specific steps for the drill pipe landing stress safety assessment and bracket support length determination in step S4 are as follows: (2) Calculate the maximum stress σ of the drill pipe max and maximum displacement δ max ; (2) If σ max >[σ] =σ y / K , where σ y The yield strength of the drill pipe material. K For a safety margin, a value of 1.5 to 2.0 is used. δmax > [δ], where [δ] is the allowable deformation of the drill pipe; Therefore, it is determined that an auxiliary bracket needs to be added; (3) Bracket support parameters: bracket cantilever length L b , Location and number of support points, and curvature of the bracket base; (4) The bracket support is simplified to a compression-only elastic support unit, and the support stiffness is determined according to the bracket structure design; (5) Under the condition of bracket support, the loading and calculation were repeated to obtain the maximum stress σ' of the drill pipe. max and displacement δ' max Until: σ' max ≤ [σ] =σ y / K , where σ y The yield strength of the drill pipe material. K For a safety margin, a value of 1.5 to 2.0 is used. δ' max ≤ [δ], where [δ] is the allowable deformation of the drill pipe; (6) Determine and optimize the bracket design parameters based on the calculation results: cantilever length, support point position, support stiffness, until the safety requirements are met.

[0023] Furthermore, this method, through a systematic stress analysis process of "comparative analysis without support → support optimization → safety assessment", can identify the risk of overstress in drill pipe under supportless conditions in advance, provide a quantitative basis for support design, and avoid drill pipe breakage accidents.

[0024] Furthermore, this method is applicable to various onshore and offshore directional drilling projects with water depths of 15-30m and crossing lengths of 1000-2000m, as well as various scenarios for the landing of submarine pipelines and cables.

[0025] Compared with the prior art, the present invention has the following significant advantages: (1) Improved accuracy: For the first time, the large displacement geometric nonlinear analysis method is used to replace the traditional small deformation linear elastic method. The coupling effect of axial tension and bending is accurately included in the geometric stiffness matrix, which overcomes the shortcomings of existing elements that cannot handle large displacement and large rotation at the same time. It can accurately characterize the actual stress and deformation state of the drill rod under deep water with large elevation difference, and the calculation accuracy is significantly improved.

[0026] (2) Safety assurance: Through the systematic stress analysis process of “comparative analysis without bracket → bracket support optimization → safety assessment”, the risk of overstress of drill pipe under bracket-less conditions can be identified in advance, providing a quantitative basis for bracket design and avoiding drill pipe breakage accidents.

[0027] (3) Wide applicability: This invention is applicable to various land and sea directional drilling projects with water depth of 15~30m and crossing length of 1000~2000m, and can be extended to various scenarios such as submarine pipelines and submarine cable landing.

[0028] (4) Economic optimization: By accurately analyzing and determining the optimal bracket parameters, we can avoid material waste caused by over-design, ensure construction safety, and reduce the overall project cost.

[0029] In summary, this invention addresses the shortcomings of existing technologies by proposing a method for analyzing the stress characteristics of drill pipes during large-displacement geometrical nonlinear landings from land to sea, particularly considering the large-displacement geometrical nonlinear stress characteristics of drill pipes under conditions of significant elevation differences in deep water. This method establishes a large-displacement geometrical nonlinear constitutive model for the drill pipe, systematically considering multi-field coupled loads under conditions of significant elevation differences in deep water. Combined with adjustable bracket support boundary conditions, it achieves accurate simulation and safety assessment of the stress state of the drill pipe throughout the landing process, providing a theoretical basis and safety guarantee for drill pipe receiving and connection. Attached Figure Description

[0030] Figure 1 A schematic diagram of the longitudinal section of a long-distance onshore-offshore directional drilling operation; Figure 2 Internal force diagram of nodal elements for constitutive elements of large-displacement geometrically nonlinear drill pipe; Figure 3 A schematic diagram of geometric nonlinear element modeling for large displacement of drill pipe; Figure 4 A simplified schematic diagram of a drill pipe pullback model without a support frame; Figure 5 This is a simplified schematic diagram of a drill pipe pullback model with a support bracket. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] like Figures 1 to 5 As shown in the figure, the method for analyzing the stress of a land-to-sea large displacement geometric nonlinear drill pipe landing provided by an embodiment of the present invention specifically includes the following steps: S1. Determine the drill pipe load and environmental parameters in the marine area; S2. Construct large-displacement geometrically nonlinear drill pipe constitutive elements; S3. Establish a three-dimensional numerical analysis model of the drill pipe; S4. Safety assessment of drill pipe landing stress and determination of bracket support length.

[0033] in: Step S1: Determine the drill pipe load and environmental parameters in the marine area. Based on the specific project background, the following analysis parameters were collected and determined: (1) Structural parameters: Drill rod specifications (outer diameter d, wall thickness δ1, material yield strength), steel pipe specifications (outer diameter D, wall thickness δ2). (2) Environmental parameters: seawater depth H, seawater bulk density γw Ocean current speed v c , the magnitude of tidal changes; (3) Geometric parameters: excavation angle θ, horizontal distance Ls between the working vessel and the excavation point, and freeboard height h of the vessel deck. d 1. Pre-tension force F0 of the drill pipe clamp at the bow; (4) Load parameters: drill pipe self-weight, seawater buoyancy, ocean current horizontal load, mud viscosity resistance, and pipe-soil friction resistance.

[0034] Step S2: Construct large-displacement geometrically nonlinear drill pipe constitutive elements To address the geometric nonlinear characteristics of drill pipes under deep water conditions with large elevation differences, characterized by "large displacement, large rotation, and small strain," this paper breaks through the limitations of traditional small-deformation linear elastic units and constructs a tangential stiffness matrix that simultaneously includes material stiffness and geometric stiffness. This matrix couples multiple internal forces such as axial tension, torque, and bending moment, enabling precise simulation of large deflection deformation of the drill pipe.

[0035] (1) Recursive formula for incremental internal force of unit Axial force increment:

[0036] Torque increment:

[0037] Internal force vector:

[0038] (2) Element material stiffness matrix Geometric stiffness matrix

[0039] Material stiffness matrix:

[0040] Geometric stiffness matrix:

[0041] (3) Total tangent stiffness matrix

[0042] The meanings of each parameter are as follows: : Axial force at time t+Δt; : Axial force at time t; E : Elastic modulus; A Cross-sectional area; : Axial strain increment; Torque at time t+Δt; Torque at time t; G Shear modulus;J : Torsional constant of cross section; : Increment of torsion angle; : Element length; : 3x3 identity matrix; : Axial force at time t; L : Element length; Original cell length; R Rotation matrix.

[0043] Step S3: Establish a three-dimensional numerical analysis model of the drill pipe The specific steps for creating a large-span 3D model of the drill pipe from the seabed protrusion point to the ship's deck are as follows: (1) Discretize the drill pipe using the large displacement geometric nonlinear beam element established in step two; (2) Boundary conditions: hinged constraint at the seabed where the soil is excavated, hinged constraint at the buckle at the bow, and elastic support of the bracket (if set) and apply preload F0. (3) Load application: drill pipe self-weight, buoyancy, ocean current force, pullback force; (4) Time history analysis: The superposition method is used to consider the initial stress generated by the initial bending of the drill pipe, and the stress and deformation superposition analysis of different pullback stages (start-up, stable pullback, connection, etc.) is carried out in combination with the time history of the drill pipe pullback.

[0044] Step S4: Safety assessment of drill pipe landing stress and determination of bracket support length (1) Calculate the maximum stress σ of the drill pipe max and maximum displacement δ max .

[0045] (2) If σ max >[σ] =σ y / K (where σ) y The yield strength of the drill pipe material. K For a safety margin, a value of 1.5 to 2.0 is used. δmax > [δ] ([δ] is the allowable deformation of the drill pipe); Then it is determined that an auxiliary bracket needs to be added.

[0046] (3) Set bracket support parameters: bracket cantilever length L b , Location and number of support points, and curvature of the bracket base; (4) The bracket support is simplified to a compression-only elastic support unit, and the support stiffness is determined according to the bracket structure design. (5) Under the condition of bracket support, the loading and calculation were repeated to obtain the maximum stress σ' of the drill pipe. max and displacement δ' max ; Until: σ' max ≤ [σ] =σ y / K (where σ) y The yield strength of the drill pipe material. K For a safety margin, a value of 1.5 to 2.0 is used. δ' max ≤ [δ] ([δ] is the allowable deformation of the drill pipe); (6) Determine and optimize the bracket design parameters (cantilever length, support point position, support stiffness) based on the calculation results until the safety requirements are met.

[0047] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the concept and scope of the present invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for analyzing the forces acting on a land-to-sea large displacement geometric nonlinear drill pipe during landing, characterized in that, Includes the following steps: S1. Determine the load and environmental parameters of the drill pipe in the sea area; S2. Construct a large displacement geometric nonlinear drill pipe constitutive element; S3. Establish a three-dimensional numerical analysis model of the drill pipe; S4. Conduct a safety assessment of the drill pipe's landing stress and determine the support length of the bracket.

2. The method according to claim 1, characterized in that, Step S1 involves determining the marine drill pipe load and environmental parameters. Based on the specific project background, the following analysis parameters are collected and determined: (1) Structural parameters: Drill pipe specifications, including outer diameter d, wall thickness δ1, material yield strength; steel pipe specifications, including outer diameter D and wall thickness δ2. (2) Environmental parameters: seawater depth H, seawater bulk density γ w Ocean current speed v c , the magnitude of tidal changes; (3) Geometric parameters: excavation angle θ, horizontal distance Ls between the working vessel and the excavation point, and freeboard height h of the vessel deck. d 1. Pre-tension force F0 of the drill pipe clamp at the bow; (4) Load parameters: drill pipe self-weight, seawater buoyancy, ocean current horizontal load, mud viscosity resistance, and pipe-soil friction resistance.

3. The method according to claim 1, characterized in that, Step S2 involves constructing a large-displacement geometrically nonlinear drill pipe constitutive element. Addressing the geometrically nonlinear characteristics of drill pipes under deep-water, high-elevation conditions—characterized by "large displacement, large rotation, and small strain"—this step overcomes the limitations of traditional small-deformation linear elastic elements. It constructs a tangent stiffness matrix that simultaneously incorporates material stiffness and geometric stiffness, coupled with an element stiffness matrix that couples multiple internal forces such as axial tension, torque, and bending moment. This accurately simulates the large deflection deformation of the drill pipe. (1) Recursive formula for incremental internal force of a unit: Axial force increment: Torque increment: Internal force vector: (2) Element material stiffness matrix Geometric stiffness matrix Material stiffness matrix: Geometric stiffness matrix: (3) Total tangent stiffness matrix In the formula, each parameter represents the following meaning: : Axial force at time t+Δt; : Axial force at time t; E : Elastic modulus; A Cross-sectional area; : Axial strain increment; Torque at time t+Δt; Torque at time t; G Shear modulus; J : Torsional constant of cross section; : Increment of torsion angle; : Element length; : 3x3 identity matrix; : Axial force at time t; L : Element length; Original cell length; R Rotation matrix.

4. The method according to claim 1, characterized in that, Step S3 involves establishing a three-dimensional numerical analysis model of the drill pipe, specifically a large-span three-dimensional model of the drill pipe from the seabed protrusion point to the ship's deck. The steps are as follows: (1) Discretize the drill pipe using the large displacement geometric nonlinear beam element established in step two; (2) Boundary conditions: hinged constraint at the seabed where the soil is unearthed, hinged constraint at the buckle at the bow, and elastic support of the bracket with preload F0 applied. (3) Load application: drill pipe self-weight, buoyancy, ocean current force, pullback force; (4) Time history analysis: The superposition method is used to consider the initial stress generated by the initial bending of the drill pipe. The different pullback stages are combined with the time history of the drill pipe pullback, including the stress and deformation superposition analysis of the start-up, stable pullback and connection.

5. The method according to claim 1, characterized in that, Step S4 involves a stress safety assessment of the drill pipe landing and determination of the bracket support length. The specific steps are as follows: (1) Calculate the maximum stress σ of the drill pipe max and maximum displacement δ max ; (2) If σ max >[σ] =σ y / K , where σ y The yield strength of the drill pipe material. K For a safety margin, a value of 1.5 to 2.0 is used. δmax > [δ], where [δ] is the allowable deformation of the drill pipe; Therefore, it is determined that an auxiliary bracket needs to be added; (3) Bracket support parameters: bracket cantilever length L b , Location and number of support points, and curvature of the bracket base; (4) The bracket support is simplified to a compression-only elastic support unit, and the support stiffness is determined according to the bracket structure design; (5) Under the condition of bracket support, the loading and calculation were repeated to obtain the maximum stress σ' of the drill pipe. max and displacement δ' max ; Until: σ' max ≤ [σ] =σ y / K , where σ y The yield strength of the drill pipe material. K For a safety margin, a value of 1.5 to 2.0 is used. δ' max ≤ [δ], where [δ] is the allowable deformation of the drill pipe; (6) Determine and optimize the bracket design parameters based on the calculation results: cantilever length, support point position, support stiffness, until the safety requirements are met.

6. The method according to any one of claims 1-5, characterized in that, This method, through a systematic stress analysis process of "comparative analysis without support → support optimization → safety assessment", can identify the risk of overstress in drill pipe under supportless conditions in advance, provide a quantitative basis for support design, and avoid drill pipe breakage accidents.

7. The method according to claim 6, characterized in that, This method is applicable to various onshore and offshore directional drilling projects with water depths of 15-30m and crossing lengths of 1000-2000m, as well as various scenarios for the landing of submarine pipelines and cables.

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