Marine derrick structure modeling method and system
Through three-dimensional scanning and derrick vibration data revision and cross-feature optimization, a benchmark model of marine derricks was established, which solved the problem that the actual derrick state was difficult to accurately reflect, and improved the accuracy and safety of load-bearing capacity evaluation.
Patent Information
- Application Number
- CN202510320313.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2025-01-22
- Filing Date
- 2025-03-18
- Publication Date
- 2025-07-18
AI Technical Summary
The prior art is difficult to accurately reflect the actual status of the in-service marine derrick, resulting in a decrease in the reliability of the load-bearing capacity assessment results.
Derrick point cloud data is obtained through three-dimensional scanning, feature selection and filtering is performed, numerical models are revised in combination with derrick vibration data, cross feature scale factors and cross feature to ensure iterative optimization of criterion, and a derrick benchmark model is established.
A numerical model is constructed that accurately reflects the real structure of the derrick, which improves the reliability and safety of load-bearing capacity evaluation and ensures the dynamic characteristics prediction capability of the structure.
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Figure CN120337623A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of structural modeling, and particularly to a method and system for modeling the structure of an offshore derrick. Background Art
[0002] The offshore derrick, as an important infrastructure for offshore oil exploitation, its structural safety and stability are crucial. Due to the particularity of the marine environment, the derrick is long-term exposed to a humid and corrosive environment, and at the same time, it is affected by multi-dimensional variable loads such as wind, waves, and currents, which easily lead to damages such as corrosion, cracks, and bending of the members. When these damages accumulate to a certain extent, it will seriously affect the bearing capacity of the derrick, and even cause catastrophic consequences such as member fracture and derrick collapse, resulting in huge casualties and property losses. Therefore, accurately evaluating the bearing capacity of the offshore derrick and timely carrying out defense and maintenance are of great significance for ensuring the safety of offshore oil and gas exploitation.
[0003] Currently, establishing a numerical model for an in-service offshore derrick mainly relies on the three-dimensional coordinate information of the key points of the derrick provided by the design drawings. Through these coordinate information, the structural model of the derrick can be constructed and its bearing capacity can be analyzed. However, for an in-service offshore derrick, due to the influence of various damages, there are often differences between its actual structure and the design drawings, which will lead to a decrease in the accuracy of the numerical model, thus affecting the reliability of the bearing capacity evaluation results.
[0004] Therefore, how to establish a numerical model that accurately reflects the actual state of an in-service offshore derrick has become a key issue for scientifically determining its bearing capacity. Summary of the Invention
[0005] In order to overcome the above-mentioned shortcomings of the prior art, the main object of the present invention is to provide a method and system for modeling the structure of an offshore derrick. Depending on the three-dimensional scanning technology, the three-dimensional scanning of the main structure of the offshore derrick is carried out to obtain point cloud data. Through the processing of the point cloud data, the three-dimensional numerical model of the offshore derrick is reconstructed, and the material parameters of the offshore derrick are revised based on the measured vibration data to obtain the structural reference model of the measured offshore derrick, providing model support for its safety evaluation and life prediction.
[0006] To achieve the above object, the present invention adopts the following technical solutions. A method for modeling the structure of an offshore derrick includes the following steps:
[0007] Obtain the point cloud data of the main legs and the back crossbeams of the derrick;
[0008] Carry out feature selection and filtering on the point cloud data to obtain effective point cloud data;
[0009] According to the effective point cloud data, construct a surface, and combine with the actual dimensions of the main legs and the back crossbeams of the derrick to establish a numerical model of the derrick;
[0010] Utilize unidirectional vibration sensors in two directions installed on the main legs of the derrick to obtain the measured derrick vibration data;
[0011] Revise the elastic modulus of the derrick numerical model according to the derrick vibration data to obtain a revised derrick numerical model;
[0012] According to the cross-characteristic scale factor and the cross-characteristic assurance criterion, combined with the revised derrick numerical model, iteratively obtain the modal parameters of the revised derrick numerical model until when comparing the modal parameters of the revised derrick numerical model with the measured derrick vibration data, the result of the comparison meets the preset threshold condition, and obtain the confirmed derrick numerical model as the benchmark model of the offshore derrick;
[0013] Among them, the cross-characteristic scale factor is expressed as:
[0014]
[0015] Among them, CSF is the cross-characteristic scale factor, Nf is the number of frequency points, ω k is the frequency at the k-th point, n is the number of frequency points, i is a specific index; H is the frequency response function; α α represents the amplitude matrix of the frequency response function analysis; α e is the measured amplitude matrix of the frequency response function; CSF is the cross-characteristic scale factor, which represents the amplitude correlation between the measured response and the predicted response, and its value range is between 0 and 1, 0 means uncorrelated, and 1 means completely correlated;
[0016] The cross-characteristic assurance criterion is expressed as:
[0017]
[0018] Among them,; ω k is the frequency at the k-th point; n is the number of frequency points; i is a specific index; H is the frequency response function; Nf is the number of frequency points, α α represents the amplitude matrix of the frequency response function analysis, α e is the measured amplitude matrix of the frequency response function; CSAC is the cross-characteristic assurance criterion, which represents the mode shape correlation between the measured response and the predicted response, and its value range is between 0 and 1, 0 means uncorrelated, and 1 means completely correlated.
[0019] The result of the comparison is the difference between the modal parameters of the derrick numerical model and the measured derrick vibration data;
[0020] The preset threshold condition is that the difference between the modal parameters of the derrick numerical model and the measured derrick vibration data is less than 10%.
[0021] The construction of the derrick numerical model includes the following steps;
[0022] Specify the regional scope of the derrick, give the local neighborhood of the boundary points, fit the local surface within the local neighborhood using polynomial functions, and project the boundary points onto the corresponding local surfaces to obtain multiple projection points;
[0023] Triangulate the multiple projection points to form a triangular mesh and obtain the triangular normal vectors;
[0024] Combine the normal vector information and the triangular vertex information, and obtain the internal points of the triangle through interpolation to obtain a local continuous surface until the surface construction is completed;
[0025] Construct the derrick numerical model based on the actual dimensions of the derrick main legs and back crossbeams, combined with the specific dimensions of other derrick components given.
[0026] An offshore derrick structure modeling system includes:
[0027] A data processing module for obtaining the point cloud data of the derrick main legs and back crossbeams; performing feature selection and filtering on the point cloud data to obtain effective point cloud data;
[0028] A derrick model construction module for constructing a surface based on the effective point cloud data, combining the actual dimensions of the derrick main legs and back crossbeams to establish a derrick numerical model; using unidirectional vibration sensors in two directions arranged on the derrick main legs to obtain the measured derrick vibration data; revising the elastic modulus of the derrick numerical model according to the derrick vibration data to obtain a revised derrick numerical model;
[0029] A benchmark model construction module for obtaining the modal parameters of the derrick numerical model according to the cross-feature scale factor and the cross-feature assurance criterion, combined with the revised derrick numerical model; comparing the difference between the modal parameters of the derrick numerical model and the measured derrick vibration data, and when the comparison result meets the set threshold condition, obtaining the confirmed derrick numerical model as the benchmark model of the offshore derrick.
[0030] Compared with the prior art, the beneficial effects of the present invention are:
[0031] The present invention performs feature selection and filtering on the point cloud data obtained by scanning, effectively removing background noise and irrelevant point clouds, ensuring the high quality and accuracy of the point cloud data for modeling. Using the effective point cloud data to construct a surface and combining with the actual dimensions, an accurate numerical model of the derrick is established, reflecting the true structural characteristics of the derrick. Real-time data is obtained through vibration sensors installed on the main legs of the derrick and used to revise the elastic modulus of the numerical model, making the model more in line with the actual working conditions. By using the cross-feature scale factor and the cross-feature guarantee criterion, through iterative optimization, accurate derrick modal parameters are obtained, improving the prediction ability of the dynamic characteristics of the model. By comparing the modal parameters predicted by the model with the measured vibration data and confirming the benchmark model under the condition of meeting the preset threshold, the credibility and applicability of the model are ensured. The accurate numerical model and modal parameter analysis help to identify potential structural problems, carry out maintenance and reinforcement in advance, and improve the structural safety and service life of the derrick. Through the numerical model constructed by the present invention, the actual deformation or corrosion conditions of its main members can be accurately restored. Combining with vibration testing, a benchmark numerical model of the offshore drilling rig derrick can be constructed, providing an accurate model basis for its safety evaluation and scientific data support and decision-making basis for the design, construction, maintenance and upgrade of the derrick. Description of the Drawings
[0032] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application.
[0033] Figure 1 It is a schematic diagram of the process framework of the present invention;
[0034] Figure 2 It is a diagram showing the layout positions of the sensors on the derrick in the embodiment of the present invention. Detailed Embodiments
[0035] The offshore drilling rig derrick has been in service for many years. In the harsh marine environment, affected by environmental corrosion and alternating operating loads, it has suffered varying degrees of deformation, pitting and other damages. In the past, the modeling of the offshore drilling rig derrick mainly relied on drawings and could not truly reflect the real structure of the in-service offshore drilling rig derrick. Through the numerical model constructed by the present invention, the actual deformation or corrosion conditions of its main members can be accurately restored. Combining with vibration testing, a benchmark numerical model of the offshore drilling rig derrick can be constructed, providing an accurate model basis for its safety evaluation.
[0036] The present invention will be further described below in conjunction with the drawings and embodiments.
[0037] Embodiment 1:
[0038] ①Obtain the point cloud data of the main legs and the back crossbeam of the derrick through 3D scanning; there are 40,995 3D scanning points for the back crossbeam of the offshore derrick with bending, and 49,855 3D scanning points for the main legs of the derrick.
[0039] ②Perform feature selection and filtering on the data in step ①, remove the background point cloud, and obtain the effective point cloud data;
[0040] ③Connect the effective point cloud data in step ② to obtain a surface, perform structural reconstruction, measure the actual dimensions of the main legs and the back crossbeam of the derrick, establish a numerical model of the derrick, and conduct modal parameter analysis;
[0041] ④Arrange unidirectional vibration sensors in two directions on each section of the main legs of the derrick to measure the vibration data of the derrick; refer to Figure 2 , where the arrows indicate the arrangement positions and directions of the vibration sensors.
[0042] ⑤Change the elastic modulus of the numerical model established in step ③ according to the data obtained in step ④, and iteratively calculate the modal parameters of the revised numerical model of the derrick according to CSAC and CSF. When the deviation between the calculated mode and the measured vibration data is less than 10%, it is considered convergent, stop the revision, and obtain the benchmark model of the offshore derrick.
[0043]
[0044] Where: ω k is the frequency at point k, [S] is the sensitivity matrix, {Δp} is the parameter,
[0045] CSAC cross - feature assurance criterion, which is expressed by the formula:
[0046]
[0047] Where, ω k is the frequency at point k; n is the number of frequency points; i is a specific index; H is the frequency response function; Nf is the number of frequency points, α α represents the amplitude matrix of the frequency response function analysis, α e is the measured amplitude matrix of the frequency response function. CSAC is the cross - feature assurance criterion, which represents the modal correlation between the measured response and the predicted response, and its value range is between 0 - 1. 0 indicates no correlation, and 1 indicates complete correlation.
[0048] CSF cross - feature scale factor, which is expressed by the formula:
[0049]
[0050] Its value range is the same as that of CSAC. Specifically, Nf is the number of frequency points, ω k is the frequency at point k, n is the number of frequency points, i is a specific index; H is the frequency response function; α αdenote the amplitude matrix of the frequency response function analysis; α e is the measured amplitude matrix of the frequency response function; CSF is the cross-characteristic scale factor, which represents the amplitude correlation between the measured response and the predicted response, and its value range is between 0 and 1. 0 means uncorrelated, and 1 means completely correlated.
[0051] Taking CSAC and CSF less than 10% as the index, after iterative convergence, the benchmark finite element model of the offshore derrick is obtained.
[0052] Table 1 Modification results of the derrick finite element model under the measured modal parameters
[0053]
[0054] Example 2:
[0055] In this example, a typical offshore oil and gas derrick model is modeled. Refer to Figure 1 , when the main legs and back crossbeams of the derrick have been scanned and point cloud data have been generated, the specific steps are as follows:
[0056] First, through laser scanning technology or other point cloud acquisition methods, the point cloud data of the main legs and back crossbeams of the derrick are obtained. Assume that the point cloud data of the main legs and back crossbeams of the derrick contain the following information:
[0057] The amount of point cloud data obtained is about 500,000 points; the spatial range of the obtained point cloud is the main legs and back crossbeams of the derrick, with dimensions of about 20 meters in width, 50 meters in length, and 80 meters in height. And the accuracy of each sample point is about 0.01 meters.
[0058] In order to remove noise and invalid data, the following filtering methods are applied:
[0059] First, the point cloud data is processed by system meshing, and the point cloud data is reduced to 100,000 points to reduce the amount of calculation. Then, using Statistical Outlier Removal filtering, the noise points deviating from the main distribution are further removed, and the remaining effective point cloud data is 80,000 points.
[0060] Using the processed effective point cloud data, the surface of the derrick is constructed, and the Poisson surface reconstruction method is used to construct the three-dimensional surface of the derrick. The height of the main leg of the derrick is 80 meters, the width is 5 meters, the length of the back crossbeam is 50 meters, and the width is 10 meters.
[0061] After the surface reconstruction of the effective point cloud data, the three-dimensional models of the main legs and back crossbeams are obtained.
[0062] Two unidirectional vibration sensors for the X-axis and Y-axis directions are installed on the main legs of the derrick to collect vibration data of the derrick at different frequencies. Suppose at a certain specific frequency, the vibration data is as follows: Vibration data in the X direction: amplitude is 2.5 mm / s, frequency is 1 Hz; Vibration data in the Y direction: amplitude is 3.1 mm / s, frequency is 1 Hz.
[0063] Based on the actually measured vibration data of the derrick, revise the elastic parameters of the derrick numerical model. Through the finite element analysis (FEA) method, optimize the elastic modulus of the derrick. In this implementation, the derrick material is steel, the elastic modulus E = 210 GPa, and the Poisson's ratio is assumed to be ν = 0.3, so that the response of the numerical model is more consistent with the actual measurement data.
[0064] Use modal analysis to calculate the natural frequencies and vibration modes of the revised derrick numerical model. Through modal analysis, obtain the modal parameters of the derrick numerical model, specifically including: the first natural frequency is 1.2 Hz, and the second natural frequency is 3.5 Hz; the main deformation is the longitudinal bending of the main leg as the first vibration mode. Then, compare the modal parameters of the revised derrick numerical model with the actually measured vibration data. Suppose through comparison, the difference between the first natural frequency and the measurement data is 0.1 Hz, and the second difference is 0.2 Hz.
[0065] According to the cross characteristic scale factor and the cross characteristic assurance criterion, combined with the revised derrick numerical model, iterate to obtain the modal parameters of the revised derrick numerical model until when the modal parameters of the revised derrick numerical model are compared with the measured derrick vibration data, during the comparison process, the difference between the modal parameters and the measurement data is less than the set threshold of 10%, meeting the set threshold. This means that the revised derrick numerical model is accurate.
[0066] Finally, according to the comparison result between the modal parameters and the vibration data, confirm the revised derrick numerical model as the benchmark model for the offshore derrick. This model can be used for further structural analysis and optimization.
[0067] In this embodiment, suppose there are Nf frequency points, for example, 100 frequency points, and calculate the measured amplitude matrix and predicted amplitude matrix of the frequency response function. The cross characteristic scale factor (CSF) and the cross characteristic assurance criterion (CSAC) represent the mode correlation between the measured response and the predicted response. Suppose the CSF value is 0.95 and the CSAC value is 0.92, indicating that the measured vibration response and the predicted response of the numerical model are highly correlated.
[0068] In terms of model accuracy, the difference between the modal parameters of the revised derrick numerical model and the actual vibration data is less than 10%, meeting the design requirements. In terms of modal analysis, the obtained modal parameters are in agreement with the measured data, confirming that this numerical model can be used as a reference model. In terms of vibration data, the vibration data measured by the unidirectional vibration sensor is 2.5 mm / s (X direction) and 3.1 mm / s (Y direction).
[0069] Through the above steps, a numerical model of an offshore derrick was successfully established, and the accuracy of the model was verified through vibration testing and modal analysis, and finally it was confirmed as the reference model of the derrick.
[0070] It should be noted that in the present invention, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.
[0071] The above embodiments are only illustrative examples of the present invention and do not constitute a limitation on the protection scope of the present invention. Any design identical or similar to the present invention falls within the protection scope of the present invention.
Claims
1. A method for modeling an offshore derrick structure, characterized in that It includes the following steps: Perform feature selection and filtering on the obtained point cloud data of the derrick main legs and back crossbeams to obtain effective point cloud data; According to the effective point cloud data, construct a surface, and combine with the actual dimensions of the derrick main legs and back crossbeams to establish a derrick numerical model; Use unidirectional vibration sensors in two directions arranged on the derrick main legs to obtain the measured derrick vibration data; revise the elastic modulus of the derrick numerical model according to the derrick vibration data to obtain a revised derrick numerical model; According to the cross-feature scale factor and the cross-feature guarantee criterion, combine with the revised derrick numerical model, and iteratively obtain the modal parameters of the revised derrick numerical model until the modal parameters of the revised derrick numerical model are compared with the measured derrick vibration data, and when the result of the comparison meets the preset threshold condition, obtain the confirmed derrick numerical model as the reference model of the offshore derrick; Among them, the cross-feature scale factor is expressed as: where Nf is the number of frequency points, ω k is the frequency at the k-th point, n is the number of frequency points, i is a specific index; H is the frequency response function; α α represents the amplitude matrix of the frequency response function analysis; α e is the measured amplitude matrix of the frequency response function; CSF is the cross characteristic scale factor, which represents the amplitude correlation between the measured response and the predicted response, and its value range is between 0 and 1. 0 means uncorrelated, and 1 means completely correlated; The cross-feature guarantee criterion is expressed as: Among them, ω k is the frequency at point k; n is the number of frequency points; i is a specific index; H is the frequency response function; Nf is the number of frequency points, and α α represents the amplitude matrix of the frequency response function analysis, and α e is the measured amplitude matrix of the frequency response function; CSAC is the cross-characteristic assurance criterion, which represents the mode shape correlation between the measured response and the predicted response, and its value range is between 0 and 1, where 0 means uncorrelated and 1 means completely correlated.
2. The method for modeling the offshore derrick structure according to claim 1, wherein The preset threshold condition is that the difference between the modal parameters of the derrick numerical model and the measured derrick vibration data is less than 10%.
3. The method for modeling the offshore derrick structure according to claim 1, wherein The construction of the derrick numerical model includes the following steps; Specify the area range of the derrick, give the local neighborhood of the boundary points, fit the local surface within the local neighborhood using a polynomial function, and project the boundary points onto the corresponding local surfaces to obtain multiple projection points; Perform triangulation on the multiple projection points to form a triangular mesh, and obtain the triangular normal vectors; Combine the triangular normal vector information and the triangular vertex information, and obtain the internal points of the triangle through an interpolation method to obtain a local continuous surface until the surface construction is completed; Construct a derrick numerical model by combining the actual dimensions of the derrick main legs and back crossbeams with the given dimensions of other derrick components.
4. An offshore derrick structure modeling system, characterized in that, It includes: A data processing module for obtaining point cloud data of the derrick main legs and back crossbeams; Perform feature selection and filtering on the point cloud data to obtain effective point cloud data; A derrick model construction module for constructing a surface according to the effective point cloud data, combining with the actual dimensions of the derrick main legs and back crossbeams to establish a derrick numerical model; using unidirectional vibration sensors in two directions arranged on the derrick main legs to obtain the measured derrick vibration data; revising the elastic modulus of the derrick numerical model according to the derrick vibration data to obtain a revised derrick numerical model; A reference model construction module for obtaining the modal parameters of the revised derrick numerical model by iteration according to the cross-feature scale factor and the cross-feature guarantee criterion, combining with the revised derrick numerical model, until when the modal parameters of the revised derrick numerical model are compared with the measured derrick vibration data, and when the result of the comparison meets the preset threshold condition, obtain the confirmed derrick numerical model as the reference model of the offshore derrick.
5. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, and when the computer program is executed by a processor, it implements the method according to any one of claims 1 to 3 above.
6. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the method according to any one of claims 1 to 3 above.