Marine derrick structure modeling method and system

Abstract

The invention discloses a marine derrick structure modeling method and system, and relates to the technical field of structure modeling, and the method comprises the steps: obtaining the point cloud data of a derrick main leg and a back cross beam; performing feature selection and filtering on the point cloud data to obtain effective point cloud data; constructing a curved surface according to the effective point cloud data, and establishing a derrick numerical model in combination with the actual sizes of the derrick main leg and the back cross beam; the method comprises the following steps: acquiring measured derrick vibration data by using one-way vibration sensors arranged on a derrick main leg in two directions; revising an elastic model 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, in combination with the revised derrick numerical model, obtaining a revised modal parameter, and constructing the derrick numerical model; and an accurate model basis is provided for safety evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of structural modeling, and in particular to a method and system for modeling an offshore derrick structure. Background Art

[0002] As an important infrastructure for offshore oil production, the structural safety and stability of the offshore derrick is of vital importance. Due to the particularity of the marine environment, the derrick is exposed to a humid and corrosive environment for a long time, and is also subject to the influence of multi-dimensional variable loads such as wind, waves, and currents, which can easily lead to damage such as corrosion, cracks, and bending of the rods. When these damages accumulate to a certain extent, they will seriously affect the bearing capacity of the derrick, and even cause catastrophic consequences such as rod breakage and derrick collapse, resulting in huge casualties and property losses. Therefore, accurate assessment of the bearing capacity of the offshore derrick, as well as timely defense and maintenance, are of great significance to ensure the safety of offshore oil and gas production.

[0003] At present, the establishment of numerical models for in-service offshore derricks mainly relies on the three-dimensional coordinate information of key points of the derricks provided by the design drawings. With this coordinate information, the structural model of the derrick can be constructed and its bearing capacity can be analyzed. However, due to the influence of various damages, the actual structure of the offshore derricks in service often differs from the design drawings, which will lead to a decrease in the accuracy of the numerical model, thereby affecting the reliability of the bearing capacity assessment results.

[0004] Therefore, how to establish a numerical model that accurately reflects the actual status of in-service offshore derricks has become a key issue in scientifically measuring their bearing capacity. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the main purpose of the present invention is to provide a method and system for modeling an offshore derrick structure. Relying on three-dimensional scanning technology, the main structure of the offshore derrick is three-dimensionally scanned to obtain point cloud data. Through point cloud data processing, 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 a benchmark model of the offshore derrick structure to provide model support for its safety evaluation and life prediction.

[0006] To achieve the above object, the present invention adopts the following technical solution, a method for modeling an offshore derrick structure, comprising the following steps: Obtain point cloud data of the main legs and back beam of the derrick; Performing feature selection and filtering on the point cloud data to obtain valid point cloud data; According to the effective point cloud data, a surface is constructed, and a numerical model of the derrick is established in combination with the actual dimensions of the main legs and the back beam of the derrick; The derrick vibration data is obtained by using unidirectional vibration sensors arranged in two directions on the main legs of the derrick; Revising 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, in combination with the revised derrick numerical model, the modal parameters of the revised derrick numerical model are obtained after iteration, until the modal parameters of the revised derrick numerical model are compared with the measured derrick vibration data, and when the comparison result meets the preset threshold condition, the confirmed derrick numerical model is obtained as the benchmark model of the offshore derrick.

[0007] The comparison result is the difference between the modal parameters of the derrick numerical model and the measured derrick vibration data; 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%.

[0008] The cross-characteristic scaling factor is expressed as: , Among them, the cross-characteristic scaling factor is CSF , Nf is the number of frequency points, represents the frequency response function analysis amplitude matrix, The measured amplitude matrix of the frequency response function. This criterion represents the vibration mode correlation between the measured response and the predicted response. The value range is between 0 and 1, where 0 indicates no correlation and 1 indicates complete correlation.

[0009] The cross-signature guarantee criteria CSAC It is expressed as: , Among them, the cross-feature guarantee criterion is CSAC , Nf is the number of frequency points, represents the frequency response function analysis amplitude matrix, The measured amplitude matrix of the frequency response function. This criterion represents the vibration mode correlation between the measured response and the predicted response. The value range is between 0 and 1, where 0 indicates no correlation and 1 indicates complete correlation.

[0010] The construction of the derrick numerical model comprises the following steps: The regional range of the derrick is specified, the local neighborhood of the boundary point is given, a local surface is fitted in the local neighborhood using a polynomial function, and the boundary point is projected onto the corresponding local surface to obtain multiple projection points; Triangulate the plurality of projection points to form a triangular mesh, and obtain a triangle normal vector; Combining the normal vector information with the triangle vertex information, the internal points of the triangle are obtained through interpolation methods to obtain a local continuous surface until the surface construction is completed; The numerical model of the derrick is constructed by combining the actual dimensions of the main legs and back beam of the derrick with the specific dimensions of other given derrick components.

[0011] A method for modeling an offshore derrick structure, comprising: A data processing module is used to obtain point cloud data of the main legs and back beam of the derrick; perform feature selection and filtering on the point cloud data to obtain valid point cloud data; A derrick model building module is used to build a curved surface based on the effective point cloud data, and to establish a derrick numerical model in combination with the actual sizes of the derrick main legs and the back crossbeam; to obtain measured derrick vibration data using unidirectional vibration sensors arranged in two directions on the derrick main legs; to revise the elastic modulus of the derrick numerical model based on the derrick vibration data to obtain a revised derrick numerical model; The benchmark model construction module is used to obtain the modal parameters of the derrick numerical model according to the cross-feature scale factor and the cross-feature assurance criterion in combination with the revised derrick numerical model; perform a difference comparison 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, obtain the confirmed derrick numerical model as the benchmark model of the offshore derrick.

[0012] Compared with the prior art, the beneficial effects of the present invention are: The present invention performs feature selection and filtering on the point cloud data obtained by scanning, effectively removes background noise and irrelevant point clouds, and ensures the high quality and accuracy of the point cloud data used for modeling. The surface is constructed using effective point cloud data, and combined with the actual size, an accurate derrick numerical model is established to reflect the real structural characteristics of the derrick. Real-time data is obtained by the vibration sensor installed on the main leg of the derrick, which is used to revise the elastic modulus of the numerical model to make the model more in line with the actual working conditions. By using the cross-feature scale factor and the cross-feature guarantee criterion, accurate derrick modal parameters are obtained through iterative optimization, which improves the dynamic characteristics prediction ability 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. 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. The numerical model constructed by the present invention can accurately restore the actual deformation or corrosion of its main rods. Combined with vibration testing, a benchmark numerical model of the offshore drilling rig derrick can be constructed to provide an accurate model basis for its safety evaluation and provide scientific data support and decision-making basis for the design, construction, maintenance and upgrading of the derrick. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are used to provide 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 improper limitations on the present application.

[0014] Figure 1 It is a schematic diagram of the process framework of the present invention; Figure 2 1 is a diagram showing the arrangement positions of sensors on a derrick in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The offshore drilling rig derrick has been in service for many years. In the harsh marine environment, it has been affected by environmental corrosion and alternating operating loads, resulting in deformation, pitting and other damages to varying degrees. In the past, the modeling of the offshore drilling rig derrick was mainly based on drawings, which could not truly reflect the actual structure of the offshore drilling rig derrick in service. The numerical model constructed by the present invention can accurately restore the actual deformation or corrosion of its main rods. Combined with vibration testing, a benchmark numerical model of the offshore drilling rig derrick can be constructed to provide an accurate model basis for its safety evaluation.

[0016] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0017] Embodiment 1: ① Obtain point cloud data of the main leg structure and back beam of the derrick through 3D scanning; the number of 3D scanning points of the back beam bending of the offshore derrick is 40,995, and the number of 3D scanning points of the main leg of the derrick is 49,855 ②Perform feature selection and filtering on step ① to remove background point cloud and obtain valid point cloud data; ③Connect the effective point cloud data of step ②, obtain the surface, reconstruct the structure, measure the actual dimensions of the main legs and back beam of the derrick, establish the numerical model of the derrick, and perform modal parameter analysis; ④ Arrange two unidirectional vibration sensors on each section of the main leg of the derrick to measure the vibration data of the derrick; refer to Figure 2 , the arrows indicate the location and direction of the vibration sensor.

[0018] ⑤Change the elastic modulus of the numerical model built in step ③ through the data obtained in step ④, according to CSAC and CSF , iteratively calculate the modal parameters of the revised derrick numerical model. When the deviation between the calculated mode and the measured vibration data is less than 10%, it is converged, and the revision is stopped to obtain the benchmark model of the offshore derrick.

[0019] , in: for k Point frequency, is the sensitivity matrix, As parameters, CSAC The cross-feature guarantee criterion is expressed as: , in: is the k-point frequency; 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, represents the frequency response function analysis amplitude matrix, is the measured amplitude matrix of the frequency response function. This criterion represents the vibration mode correlation between the measured response and the predicted response. The value range is between 0 and 1, where 0 indicates no correlation and 1 indicates complete correlation.

[0020] CSF The cross-characteristic scaling factor is expressed as: , Its value range is the same as CSAC .

[0021] by CSAC , CSF Less than 10% is taken as the indicator. After iterative convergence, the benchmark finite element model of the offshore derrick is obtained.

[0022] Table 1 Modification results of derrick finite element model under measured modal parameters

[0023] Embodiment 2: In this embodiment, a typical offshore oil and gas derrick model is modeled. Figure 1 , when the main legs and back beam of the derrick have been scanned and point cloud data has been generated, the specific steps include: First, the point cloud data of the main legs and back beam of the derrick is obtained by laser scanning technology or other point cloud acquisition methods. Assume that the point cloud data of the main legs and back beam of the derrick contains the following information: The amount of point cloud data obtained is about 500,000 points; the spatial range of the point cloud is the main leg and back beam of the derrick, with a size of about 20 meters in width, 50 meters in length, and 80 meters in height. The accuracy of each sample point is about 0.01 meters.

[0024] To remove noise and invalid data, the following filtering methods are applied: First, the point cloud data is processed by gridding and reduced to 100,000 points to reduce the amount of calculation. Then, the Statistical Outlier Removal filter is used to further remove the noise points that deviate from the main distribution, and the remaining valid point cloud data is 80,000 points.

[0025] The processed valid point cloud data is used to construct the surface of the derrick, and the Poisson surface reconstruction method is used to construct the three-dimensional surface of the derrick. The main leg of the derrick is 80 meters high and 5 meters wide, and the back beam is 50 meters long and 10 meters wide.

[0026] After surface reconstruction of the effective point cloud data, the three-dimensional models of the main legs and back beam are obtained.

[0027] The unidirectional vibration sensors in the two directions of X-axis and Y-axis on the main legs of the derrick are used to collect the vibration data of the derrick at different frequencies. Assuming that at a certain frequency, the vibration data is: X-direction vibration data: amplitude is 2.5mm / s, frequency is 1Hz; Y-direction vibration data: amplitude is 3.1mm / s, frequency is 1Hz.

[0028] Based on the actual measured derrick vibration data, the elastic parameters of the derrick numerical model are revised. The elastic modulus of the derrick is optimized by the finite element analysis (FEA) method. In this implementation, the derrick material is steel, the elastic modulus E=210GPa 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 measured data.

[0029] The natural frequencies and vibration modes of the revised derrick numerical model are calculated using modal analysis. Through modal analysis, the modal parameters of the derrick numerical model are obtained, including: the first-order natural frequency is 1.2Hz, the second-order natural frequency is 3.5Hz; after the main deformation is the longitudinal bending of the main leg as the first-order vibration mode, the modal parameters of the revised derrick numerical model are compared with the actual measured vibration data. It is assumed that through comparison, the difference between the first-order natural frequency and the measured data is 0.1Hz, and the second-order difference is 0.2Hz.

[0030] According to the cross-feature scale factor and the cross-feature guarantee criterion, combined with the revised derrick numerical model, the modal parameters of the revised derrick numerical model are obtained after iteration until 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 measured data is less than the set threshold of 10%, which meets the set threshold. This means that the revised derrick numerical model is accurate.

[0031] Finally, based on the comparison results of modal parameters and vibration data, the revised derrick numerical model was confirmed as the benchmark model of offshore derricks. This model can be used for further structural analysis and optimization.

[0032] In this embodiment, it is assumed that Nf For example, 100 frequency points are used, and the measured amplitude matrix and predicted amplitude matrix of the frequency response function are calculated. Cross-characteristic scaling factor CSF and cross-feature assurance criteria CSAC represents the mode shape correlation between the measured response and the predicted response. CSF The value is 0.95 and the CSAC value is 0.92, indicating that the measured vibration response is highly correlated with the predicted response of the numerical model.

[0033] 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%, which meets the design requirements. In terms of modal analysis, the modal parameters obtained are consistent with the measured data, confirming that the numerical model can be used as a benchmark model. In terms of vibration data, the vibration data measured by the unidirectional vibration sensor is 2.5mm / s (X direction) and 3.1mm / s (Y direction).

[0034] 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 it was finally confirmed as the benchmark model of the derrick.

[0035] It should be noted that, in the present invention, relational terms such as first and second, etc. 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 "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0036] The above embodiments are merely examples of the present invention and do not limit the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A method for modeling an offshore derrick structure, characterized in that: The following steps are involved: Perform feature selection and filtering on the acquired point cloud data of the main legs and back beam of the derrick to obtain valid point cloud data; According to the effective point cloud data, a surface is constructed, and a numerical model of the derrick is established in combination with the actual dimensions of the main legs and the back beam of the derrick; Using unidirectional vibration sensors arranged in two directions on the main legs of the derrick, measured derrick vibration data are obtained; the elastic modulus of the derrick numerical model is revised 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, in combination with the revised derrick numerical model, the modal parameters of the revised derrick numerical model are obtained after iteration until the modal parameters of the revised derrick numerical model are compared with the measured derrick vibration data. When the comparison result meets the preset threshold condition, the confirmed derrick numerical model is obtained as the benchmark model of the offshore derrick.

2. The offshore derrick structure modeling method according to claim 1, characterized in that: 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 offshore derrick structure modeling method according to claim 1, characterized in that: The cross-characteristic scaling factor is expressed as: ， in, CSF is the cross-characteristic scaling factor, Nf is the number of frequency points, is the k-point frequency, n is the number of frequency points, i For a specific index; H is the frequency response function; represents the frequency response function analysis amplitude matrix, is the measured amplitude matrix of the frequency response function. This criterion represents the vibration mode correlation between the measured response and the predicted response. The value range is between 0 and 1, where 0 indicates no correlation and 1 indicates complete correlation.

4. The offshore derrick structure modeling method according to claim 1, characterized in that: The cross-feature guarantee criterion is expressed as: ， in, CSAC Guarantee criteria for cross-features; is the k-point frequency; n is the number of frequency points; i For a specific index; H is the frequency response function; Nf is the number of frequency points, represents the frequency response function analysis amplitude matrix, is the measured amplitude matrix of the frequency response function. This criterion represents the vibration mode correlation between the measured response and the predicted response. The value range is between 0 and 1, where 0 indicates no correlation and 1 indicates complete correlation.

5. The offshore derrick structure modeling method according to claim 1, characterized in that: The construction of the derrick numerical model comprises the following steps: The regional range of the derrick is specified, the local neighborhood of the boundary point is given, a local surface is fitted in the local neighborhood using a polynomial function, and the boundary point is projected onto the corresponding local surface to obtain multiple projection points; Triangulate the plurality of projection points to form a triangular mesh, and obtain a triangle normal vector; Combine the triangle normal vector information with the triangle vertex information, obtain the internal points of the triangle through interpolation method, and obtain the local continuous surface until the surface construction is completed; The numerical model of the derrick is constructed by combining the actual dimensions of the main legs and back beam of the derrick with the given dimensions of other derrick components.

6. A method for modeling an offshore derrick structure, characterized in that: include: Data processing module, used to obtain point cloud data of the main legs and back beam of the derrick; Performing feature selection and filtering on the point cloud data to obtain valid point cloud data; A derrick model building module is used to build a curved surface based on the effective point cloud data, and to establish a derrick numerical model in combination with the actual sizes of the derrick main legs and the back crossbeam; to obtain measured derrick vibration data using unidirectional vibration sensors arranged in two directions on the derrick main legs; to revise the elastic modulus of the derrick numerical model based on the derrick vibration data to obtain a revised derrick numerical model; The benchmark model building module is used to obtain the modal parameters of the revised derrick numerical model after iteration according to the cross-feature scale factor and the cross-feature assurance criterion in combination with 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 comparison result meets the preset threshold condition, the confirmed derrick numerical model is obtained as the benchmark model of the offshore derrick.

7. 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, the method according to any one of claims 1 to 5 is implemented.

8. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in any one of claims 1 to 5 is implemented.

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