Parametric excitation response experiment method for ocean platform-marine riser-underwater wellhead coupling system

Abstract

The invention provides an ocean platform-marine riser-underwater wellhead coupling system parametric excitation response experiment method, and belongs to the technical field of marine riser systems. The ocean platform-marine riser-underwater wellhead coupling system parametric excitation response experiment method is based on actual ocean drilling marine riser system configuration parameters; based on a similarity theory and a truncation design theory, determining parameters of a reduced scale experiment similarity ratio, a model material and a structure size; all the devices are fastened and connected through flange plates and bolts; the heaving amplitude and the heaving frequency of the six-degree-of-freedom excitation platform are adjusted, and the drilling fluid circulating device is adjusted to control the flow speed and the pressure of the drilling fluid in the marine riser column; a plurality of groups of metal strain gauges are adhered to different positions of a pipe column of a marine riser, and meanwhile, a three-component dynamometer device is mounted at each of the top and the bottom of a marine riser system; the collected data are analyzed and processed; the problem that the influence mechanism on the parameter excitation vibration of the pressure-controlled drilling riser coupling system under the complex load is not clear can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of riser systems, and in particular, relates to a parametric excitation response experimental method for an ocean platform-riser-underwater wellhead coupling system. Background Art

[0002] As the exploitation of oil and gas resources on land becomes increasingly severe, in order to meet the growing energy demand, the development of oil and gas resources has gradually turned to deep-sea and ultra-deep-sea areas. Different from land drilling, the gap between the formation pressure and the fracture pressure in deep-water drilling is smaller, the safe density window of drilling operation is narrow, the wellbore pressure control is more difficult, and the frequent occurrence of complex downhole situations such as overflow and leakage leads to extended non-production time and increased drilling costs. It is more likely to cause major safety accidents such as blowouts, polluting the marine environment and the personal safety of workers. In order to solve the problem of well control in deep-water narrow density window formations, managed pressure drilling (Managed Pressure Drilling) technology is an important technology for achieving safe and efficient drilling in deep and ultra-deep waters. Its core is to achieve real-time monitoring and precise control of bottom hole pressure through MPD high-pressure riser single root device, deck pressure control equipment, back pressure control pipeline, etc., and to keep the bottom hole pressure within the safe density window by adjusting the back pressure inside the pipe string and adjusting the drilling fluid flow rate, so as to ensure efficient and safe deep-water drilling operations.

[0003] According to the survey and research, the basic theoretical research and practical application of managed pressure drilling (MPD) technology at home and abroad have achieved certain results. However, there are few reports on the parametric vibration response analysis of the pipe system under the combined effects of the uplift and sinking movement of the drilling platform, the high pressure in the pipe and the flow rate of the drilling fluid in the offshore platform-rise pipe-underwater wellhead coupling system. The loads on the managed pressure drilling riser coupling system are more complex than those on the conventional drilling riser system. Summary of the invention

[0004] In view of this, the present invention provides a parametric excitation response experimental method for an offshore platform-rise pipe-underwater wellhead coupling system, which can solve the problem of unclear influence mechanism of parameter excitation vibration of the pressure-controlled drilling riser coupling system under complex loads.

[0005] The present invention is achieved in that:

[0006] The present invention provides a parametric excitation response experimental method for an offshore platform-riser-underwater wellhead coupling system, which comprises the following specific steps:

[0007] S10: This experimental method is truly in line with actual operations, and the actual marine drilling riser system configuration is selected as the basis. However, due to the huge size of the actual marine drilling riser system, it is necessary to conduct similarity ratio scaled experimental research and select appropriate similarity criteria according to the specific experimental requirements and experimental objects required. For this experiment, the parametric lateral vibration response of the marine platform-riser-underwater wellhead coupling system is mainly considered, so the geometric similarity, Cauchy similarity, and Froude similarity criteria are mainly met. Since the scale of the model is still far greater than the scale of the experimental pool after scaling, in order to meet the experimental requirements, the equivalent water depth truncation design theory is adopted, that is, after scaling according to the similarity theory, the boundary motion condition of the truncation point is applied to the top of the experimental model according to the maximum experimental water depth requirement.

[0008] Among them, the geometric similarity criterion is:

[0009] Cauchy similarity criterion:

[0010] Froude's similarity criterion:

[0011] Where: λ represents the scale ratio, subscripts s and m represent the physical model and the scaled model respectively; L represents the model length, B represents the model width; ρ represents the model fluid density, V represents the model characteristic velocity, E represents the model elastic modulus; g is the gravitational acceleration.

[0012] According to the scale relationship between various physical quantities, the model material of the scaled experimental model is determined (in this experimental method, the actual riser material is X80 steel with an elastic modulus of E=210GPa. According to the determined scale ratio, the final material is copper with an elastic modulus of 108GPa, which is mainly used to complete the design of the bending stiffness of the scaled model. The corresponding catheter scaled model is selected as aluminum alloy material), structural dimensions (including length, mass, inner and outer diameters of the pipe column, bending stiffness, etc.), and other important parameters to complete the design of each component of the experimental device; the correction coefficient γ in the table represents the ratio of seawater density to freshwater density, generally γ=1.025.

[0013] Table 1: Scale conversion table corresponding to physical quantities

[0014]

[0015] S20: The devices are fastened together by flanges and bolts;

[0016] S30: After the installation of the whole device is completed, the pressure value in the column required for the experiment is designed according to the pressure scale conversion relationship determined in the table, specifically: The corresponding drilling fluid flow rate value is the actual drilling operation condition. The designed parametric excitation experimental operation condition is completed. The drilling fluid flow rate and pressure in the watertight pipe are controlled by adjusting the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjusting the drilling fluid circulation device to simulate the parametric excitation vibration during the actual marine watertight pipe pressure drilling operation.

[0017] The heave amplitude of the six-degree-of-freedom excitation platform is calculated according to the requirements:

[0018]

[0019] Where S is the heave amplitude displacement, m; s1 is the initial displacement, m; ω is the heave amplitude frequency, rad / s.

[0020] S40: By pasting multiple sets of metal strain gauges at different positions of the riser string and installing a three-force meter device at the top and bottom of the riser system, the real-time collection of experimental analysis data of the parametric response of the riser system under different platform heave amplitudes and frequencies and different drilling fluid flow rates and pressures is completed;

[0021] S50: By analyzing and processing the collected data, the modal vibration analysis, parametric vibration displacement analysis and pipe string axial force analysis of the offshore platform-riser-underwater wellhead coupling system under parameter excitation are completed.

[0022] The overall experimental device is designed and processed based on similarity theory and truncation design theory to determine important parameters such as similarity ratio, material of scaled experimental model, and structural dimensions. The overall experimental device includes a six-degree-of-freedom excitation platform, a tensioner model, an expansion joint device, an upper flexible joint, a watertight pipe system, a lower flexible joint, a blowout preventer group, a guide column model, an underwater wellhead system, a drilling fluid circulation device, a three-dimensional force instrument test device, a stress-strain collector, an acquisition card, and a data transmission pipeline. The various devices are fastened together through flanges and bolts.

[0023] On the basis of the above technical solution, the parametric excitation response experimental method of the marine platform-riser-underwater wellhead coupling system of the present invention can also be improved as follows:

[0024] Before conducting the parametric excitation response experiment, the natural frequency of the riser coupling system is first measured through multiple sets of tapping experiments to determine the platform excitation frequency range required when parameter excitation vibration occurs. The specific steps are as follows:

[0025] A fixed force is used to strike the riser column, and the riser system performs free decay motion, while strain data is collected in real time on the computer.

[0026] Furthermore, when conducting the percussion test, a drilling fluid circulation device is used to select different pressures and drilling fluid flow rate values ​​to simulate the changes in internal pressure and flow rate of the watertight riser during actual pressure controlled drilling operations, so as to measure the natural frequency of the watertight riser corresponding to when the interior of the pipe is filled with high pressure and high drilling fluid flow rate.

[0027] Furthermore, the strain signal collected in the knocking experiment is a time-domain sinusoidal response signal. It is converted into a frequency-domain signal through Fourier transform using MATLAB software, and the frequency value corresponding to the sudden change in the vibration amplitude after Fourier transform is extracted, that is, the frequency of the modal vibration occurring during the free attenuation of the riser string after the knocking is completed. The data is recorded to complete the natural frequency analysis of the offshore platform-riser-underwater wellhead coupling system.

[0028] The main formula for Fourier transform is:

[0029] Assuming the stress-strain signal period is T, find the corresponding angular frequency According to the Fourier transform formula, the stress-strain periodic signal can be expressed as:

[0030]

[0031] Where A n , a n , b n are Fourier transform coefficients respectively;

[0032]

[0033] The display forms of signal data acquisition are generally divided into two types: time domain signal and frequency domain signal. These two types of signal storage are essentially the same, but they interpret the actual meaning of the signal from different perspectives.

[0034] The time-domain sinusoidal response signal is a signal that changes over time. For natural frequency analysis, it is necessary to complete the transformation of the time-domain response signal to the frequency-domain response signal to understand the amplitude signal changes caused by the corresponding frequency.

[0035] Furthermore, the specific steps of adjusting the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjusting the drilling fluid circulation device to control the drilling fluid flow rate and pressure in the watertight pipe string to simulate the parametric excitation vibration during the actual marine watertight pipe pressure drilling operation are as follows:

[0036] The first step is to use the drilling fluid circulation device to change the pressure in the watertight pipe string and the drilling fluid flow rate to simulate the actual pressure-controlled drilling operation;

[0037] The second step is to adjust the heave amplitude and heave frequency of the six-degree-of-freedom excitation platform according to the multiple relationship between the excitation frequency of the parameter excitation vibration and the natural frequency of the pipe string coupling system;

[0038] The third step is to change the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjust the internal pressure of the tubing and the drilling fluid flow rate through the drilling fluid circulation device, complete the parameter excitation vibration response analysis of the deepwater controlled pressure drilling riser coupling system under different riser string pressures and drilling fluid flow rates, and use the stress-strain device to collect the parameter excitation vibration response data of the riser coupling system in real time.

[0039] Different platform heave amplitudes and frequencies will change the effective axial tension of the pipe string. The change in the effective axial tension parameters causes the lateral vibration of the riser, which is the parameter excitation vibration of the deepwater drilling riser system.

[0040] Furthermore, the lateral vibration caused by the change of the effective axial tension parameter of the riser string is the parameter excitation vibration of the deepwater drilling riser system.

[0041] Furthermore, the three-division force instrument device is a resistive strain sensor, and its axial direction needs to be calibrated before the experiment to ensure the accuracy of the collected data.

[0042] The three-force instrument test device used can simultaneously measure the full force information in space (Cartesian coordinate system), namely three force components and three moment components. In this experiment, a three-force instrument device was installed at the top of the tensioner test model and the riser test model, and at the contact position between the bottom of the riser test model and the BOP test model, and the change law of the effective axial tension under the parameter excitation vibration of the offshore platform-riser-underwater wellhead coupling system was measured.

[0043] The three-force instrument device can be a three-force sensor, with a measuring range of ±3000kg in the axial direction, ±1000kg in the transverse and longitudinal directions, and a measuring error of 0.6-1.2kg.

[0044] The calibration formula for the three-division force instrument used in this experimental method is:

[0045] F1=-5843.15·ε+12.46;

[0046] F2=-5328.65·ε-5.24;

[0047] Wherein, F represents the calculated axial force, N; ε is the resistance strain signal measured by the three-division force instrument device.

[0048] Furthermore, for the lateral force on the riser string, the spring installed in the middle of the riser is used in the experiment to provide an approximate lateral static load to simulate the actual lateral external loads such as the actual ocean current that the riser system is subjected to in actual marine conditions. The spring stiffness and length are designed according to the size of the lateral force required by the experiment to meet the required lateral static load requirements;

[0049] Among them, for the design of the lateral static load spring, the calculation formula is:

[0050] F = K x;

[0051]

[0052] Where F is the required lateral static load, N; x is the elongation of the spring, m; K is the elastic stiffness of the spring, N / m; G is the shear modulus of the spring material; d is the spring wire diameter, m; d1 is the spring center diameter, m; and n is the effective number of coils of the spring.

[0053] Furthermore, the specific steps of analyzing and processing the collected data are as follows:

[0054] Firstly, low-pass Chebyshev type I filtering is performed, and appropriate cutoff frequency, sampling frequency and filter order are selected according to different data signals to eliminate data errors caused by noise or other experimental errors, improve analysis accuracy, separate useful signals and noise, improve analysis accuracy, and obtain a sinusoidal periodic function with good linearity and waveform.

[0055] Furthermore, the specific steps of completing the modal vibration analysis, parametric vibration displacement analysis and pipe string axial force analysis under parameter excitation of the offshore platform-riser-underwater wellhead coupling system include:

[0056] The data collected from each measuring point under different working conditions are filtered and then Fourier transformed. The multiple relationship between the parameter excitation frequency and the system natural frequency when the offshore platform-watertight pipe-underwater wellhead coupling system undergoes parametric vibration is used to determine the signal change when parametric vibration occurs. The node bending moment M can be calculated from the strain value measured in the experiment. The bending moment value of the measuring point is fitted with a sixth-order polynomial using MATLAB software to obtain the function M(z) of the bending moment changing with the position of the coupling system. The MATLAB program is used to perform a quadratic integral calculation on M(z) to obtain the distribution function y(z) of the displacement of the coupling system.

[0057]

[0058] Where M is the bending moment at the measuring point, N·m; ε is the bending stress at the cross section, dimensionless; R is the radius of the pipe string of the scaled test model, m; EI is the bending stiffness, N·m 2 ; y(z) is the system displacement distribution function, m.

[0059] In this experiment, the DH3817F strain acquisition system was used to complete the acquisition of parametric vibration stress and strain data of the experimental model of the offshore platform-rise pipe-underwater wellhead coupling system, including the acquisition drive software system and the acquisition system chassis. The acquisition instrument chassis has 16 signal channels, so 16 groups of metal strain gauges are pasted on the catheter and the riser column. The strain gauges are densely pasted on the catheter and near the wellhead and the top of the riser. From a theoretical analysis point of view, stress concentration is more likely to occur here, and before each experiment, each channel is balanced and cleared to ensure the accuracy of the collected data.

[0060] The metal strain gauge is affixed to different positions of the catheter and the riser model using the half-bridge method. Since the entire device is carried out in a water tank to simulate the marine environment, the metal strain gauge is treated with waterproof glue for waterproof protection to prevent failure. The metal strain gauge is connected to the stress and strain acquisition system using a signal input line to complete the collection of stress and strain data of the parametric vibration response of the marine platform-riser-underwater wellhead coupling system.

[0061] Compared with the prior art, the beneficial effects of the parametric excitation response experimental method of the marine platform-waterproof pipe-underwater wellhead coupling system provided by the present invention are as follows: first, based on the actual marine drilling waterproof pipe system configuration parameters, based on similarity theory and truncation design theory, the similarity ratio of the scaled experiment, the material of the model, the structural dimensions and other important parameters are determined, the design of each component of the experimental device is completed, and the various devices are fastened by flanges and bolts. After the installation of the entire device is completed, by changing the heave amplitude and frequency of the six-degree-of-freedom excitation platform and using the drilling fluid circulation device to change the pressure in the pipe and the drilling fluid flow rate and other variable parameters, the parametric excitation vibration response law of the pressure-controlled drilling waterproof pipe coupling system in the actual marine drilling operation is studied. This experimental research method simultaneously considers the platform heave motion, high pressure in the pipe, drilling fluid flow rate and other loads as well as the coupling interaction between the various component systems of the marine platform-waterproof pipe-underwater wellhead, providing a reference for the safe operation of deep-water pressure-controlled drilling waterproof pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0063] Figure 1 Schematic diagram of the experimental model of parametric excitation response of the offshore platform-riser-underwater wellhead coupling system;

[0064] Figure 2 This is a flow chart of the experimental analysis method of the parametric excitation response of the marine platform-riser-underwater wellhead coupling system of the present invention;

[0065] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0066] 1. Six-degree-of-freedom excitation platform; 2. Tensioner system; 3. Upper flexible joint; 4. Expansion joint device; 5. First three-dimensional force instrument test device; 6. Metal strain gauge; 7. Riser system model; 8. Spring; 9. Lower flexible joint; 10. Second three-dimensional force instrument test device; 11. BOP group; 12. Catheter model; 13. Underwater wellhead device; 14. Drilling fluid circulation device; 15. High-pressure water pump; 16. Flow meter device; 17. Pressure metering device; 18. Stress-strain acquisition system; 19. Signal input line. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0068] like Figure 2 As shown, it is a first embodiment of a parametric excitation response experimental method of an offshore platform-riser-underwater wellhead coupling system provided by the present invention. In this embodiment, the following specific steps are included:

[0069] S10: Based on the actual configuration parameters of the offshore drilling riser system, similarity theory and truncation design theory are used to determine the parameters of the scaled experiment similarity ratio, model material, and structural dimensions, and complete the design of each component of the experimental device;

[0070] S20: The devices are fastened together by flanges and bolts;

[0071] S30: After the installation of the whole device is completed, the flow rate and pressure of the drilling fluid in the watertight pipe string are controlled by adjusting the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjusting the drilling fluid circulation device to simulate the parametric excitation vibration during the actual marine watertight pipe pressure drilling operation;

[0072] S40: By pasting multiple sets of metal strain gauges at different positions of the riser string and installing a three-force meter device at the top and bottom of the riser system, the real-time collection of experimental analysis data of the parametric response of the riser system under different platform heave amplitudes and frequencies and different drilling fluid flow rates and pressures is completed;

[0073] S50: By analyzing and processing the collected data, the modal vibration analysis, parametric vibration displacement analysis and pipe string axial force analysis of the offshore platform-riser-underwater wellhead coupling system under parameter excitation are completed.

[0074] Parametric vibration is a special form of vibration. The external excitation of parametric vibration is not applied to the system in the form of external force, but is indirectly achieved through the periodic change of the system's internal parameters. Since the axial force of the pipe string caused by the platform's heave movement varies with the platform's movement, the stiffness of the riser system also changes, causing the pipe string to vibrate in the horizontal direction. The condition for resonance is that the external excitation frequency is close to or in multiples of the system's natural frequency. The amplitude-frequency response curve of ordinary resonance is a scattered point, while parametric resonance is a series of regions. Even if the excitation frequency is far away from the natural frequency, as long as the parameter excitation falls into the unstable area, parametric resonance will occur, so it is more difficult to avoid parametric resonance. For deep-sea marine structural systems, as the water depth continues to increase, the service environment is complex, and parametric resonance is very likely to occur, causing pipe string failure and fluid leakage, resulting in significant economic losses and environmental pollution.

[0075] Among them, Figure 1 As shown, the model device shown includes various devices in marine pressure-controlled drilling riser operation, including a six-degree-of-freedom excitation platform 1, a tensioner system 2, an upper flexible joint 3, an expansion joint device 4, a riser system model 7, a lower flexible joint 9, a blowout preventer group 11, a catheter model 12, an underwater wellhead device 13, a drilling fluid circulation device 14, a first three-dimensional force instrument test device 5, a second three-dimensional force instrument test device 10 and a stress-strain acquisition device 18;

[0076] The six-degree-of-freedom excitation platform 1 simulates an actual offshore drilling platform, sets certain amplitude and frequency parameters for the platform to realize the platform's heave and sink operations under ocean currents and waves, and gives a real-time displacement response excitation to the top of the riser, causing the axial force of the riser system 7 to vary with the heave and sink movement of the platform, thereby having an important influence on the lateral vibration of the riser system 7 as a parameter excitation.

[0077] The top of the watertight pipe system model 7 is connected to the main body of the six-degree-of-freedom excitation platform 1 through the tensioner 2. The tensioner model 2 is connected to the flexible joint 3 and the expansion joint 4 device. In the experiment, the expansion joint device 4 is simplified to a spring device. In the process of platform heave movement, the heave compensation device is a very important device. If the heave displacement is large, the flexible joint will turn too much and the watertight pipe system will suffer from excessive bending failure or even breakage. The six-degree-of-freedom excitation platform 1 transmits the tensioning force to the expansion joint 4 through the tensioner 2 and then to the watertight pipe system 7. When the platform heaves and sinks, the expansion joint 4 can provide a real-time changing tensioning force for the top of the watertight pipe while compensating for a certain displacement, converting the platform's displacement excitation into force excitation, so as to realize the real-time change of the axial force of the watertight pipe system 7 with the platform heave movement.

[0078] After the design of all the components in the experiment is completed, the material, number of turns, wire diameter, center diameter, etc. of the telescopic joint device 4 are set according to the weight of the entire device and the heave displacement requirements to determine the stiffness and length requirements of the telescopic joint model 4.

[0079] Among them, the drilling fluid circulation device 14 injects the drilling fluid into the watertight pipe column 7 through the high-pressure water pump 15 to simulate the circulation process of the drilling fluid during the actual drilling operation, and completes the real-time monitoring of the high pressure in the pipe and the drilling fluid flow rate through the flow metering device 16 and the pressure metering device 17 to adapt to the actual marine pressure-controlled drilling operation. The high-pressure water pump 15, the flow meter device 16 and the pressure meter device 17 are designed according to the experimental needs to meet the experimental requirements.

[0080] Among them, the first three-force meter testing device 5 can complete the real-time measurement of the effective axial tension of the marine platform-watertight pipe-underwater wellhead coupling system under different platform heave amplitudes and frequencies, as well as high pressure in the pipe and drilling fluid flow rate, to observe the parameter-excited vibration response caused by the pipe string under different axial tensions, and at the same time derive the change law of the axial force of the pipe string under the action of high pressure in the pipe and drilling fluid flow rate.

[0081] Among them, the metal strain gauge 6 is affixed to different positions of the conduit and the riser model using a half-bridge method. Since the entire device is carried out in a water tank to simulate the marine environment, the metal strain gauge is treated with waterproof glue for waterproof protection to prevent failure. The metal strain gauge 6 is connected to the stress and strain acquisition system 18 using a signal input line 19 to complete the collection of stress and strain data of the parametric vibration response of the marine platform-riser-underwater wellhead coupling system.

[0082] like Figure 2 In this experiment, the DH3817F strain acquisition system was used to complete the acquisition of parametric vibration stress and strain data of the experimental model of the offshore platform-rise pipe-underwater wellhead coupling system, including the acquisition drive software system and the acquisition system chassis. The acquisition instrument chassis has 16 signal channels, so 16 groups of metal strain gauges are pasted on the catheter and the riser column. The strain gauges 6 are densely pasted on the catheter and near the wellhead and the top of the riser. From a theoretical analysis point of view, stress concentration is more likely to occur here, and before each experiment, each channel is balanced and cleared to ensure the accuracy of data acquisition.

[0083] The experiment mainly studies the vibration response analysis of high-pressure riser string parameters under the action of platform heave and sink. The six-degree-of-freedom excitation platform 1 is used to simulate the longitudinal heave excitation. For the lateral force of the string, a spring 8 is used at approximately the middle position of the riser to provide an approximate lateral static load to simulate the actual lateral external loads such as ocean currents that the riser system is subjected to in actual ocean conditions. According to the size of the lateral force required by the experiment, the stiffness and length of the spring are designed to meet the required lateral static load requirements.

[0084] Figure 2 In the data processing, due to the influence of experimental errors such as the vibration of the six-degree-of-freedom excitation platform 1, the irregular flow of water in the water cylinder, and the interference of the transmission line, the measured parameter excitation vibration strain response data fluctuates, but the waveform is a sinusoidal function law consistent with the platform motion period. Therefore, in order to ensure the accuracy of the experimental precision, low-pass Chebyshev type I filtering is first performed before the experimental data analysis. By reasonably adjusting the cutoff frequency, sampling frequency, and filter order, the data errors caused by noise or other experimental errors are eliminated, the analysis accuracy is improved, the useful signal and noise are separated, and the analysis accuracy is improved. A sinusoidal periodic function with good linearity and waveform is obtained.

[0085] Figure 2 In the present study, before conducting parameter excitation vibration response, the natural frequency of the system is first determined, and a knocking vibration experiment of the offshore platform-riser-underwater wellhead coupling system is conducted to determine the natural frequency of the entire system.

[0086] After the installation of the offshore platform-rise pipe-underwater wellhead coupling system experimental device is completed, the natural frequency of the riser coupling system is first measured through multiple sets of tapping tests to determine the platform excitation frequency range required when parameter excitation vibration occurs. A fixed force is used to tap the riser column, and the riser system performs free decay motion, while the strain data is recorded and collected in real time on the computer. When conducting the tapping test, the drilling fluid circulation device 14 is used to select different pressures and drilling fluid flow rate values ​​to simulate the changes in the internal pressure and flow rate of the riser column during the actual pressure-controlled drilling operation, so as to measure the natural frequency of the riser corresponding to the high pressure and high drilling fluid flow rate inside the column.

[0087] Figure 2In the figure, the strain data of the knocking experiment of the offshore platform-rise-underwater wellhead coupling system is measured. The display forms of signal data acquisition are generally divided into two types: time domain signal and frequency domain signal. These two signal storage types are essentially the same, but they interpret the actual meaning of the signal from different angles. The strain signal collected in the knocking experiment is a time domain sinusoidal response signal, which is a signal that changes with time. For the natural frequency analysis, it is necessary to complete the transformation of the time domain response signal to the frequency domain response signal, understand the amplitude signal change caused by the corresponding frequency, and transform the stress-strain time domain response signal measured by the knocking experiment into a frequency domain signal through Fourier transform. The frequency value corresponding to the sudden change of the vibration amplitude after Fourier transform is extracted, that is, the frequency of the modal vibration occurring during the free attenuation of the pipe string after the knocking is completed, and record the data to complete the natural frequency analysis of the offshore platform-rise-underwater wellhead coupling system.

[0088] Figure 2 In the present invention, according to the measured natural frequency of the marine platform-riser-underwater wellhead coupling system, an experimental study on the parametrically excited vibration response of the marine platform-riser-underwater wellhead coupling system is carried out. The drilling fluid circulation device 14 is used to change the pressure in the high-pressure tubing and the drilling fluid flow rate to simulate the actual pressure-controlled drilling operation. The heave amplitude and frequency of the six-degree-of-freedom excitation platform 1 are adjusted according to the multiple relationship between the excitation frequency when the parameter-excited vibration occurs and the natural frequency of the tubing coupling system. Different platform heave amplitudes and frequencies will change the effective axial tension of the tubing. Changes in the effective axial tension parameters cause lateral vibration of the riser, which is the parameter excitation vibration of the deepwater drilling riser system. In the experiment, the parameter excitation vibration response analysis of the deepwater controlled pressure drilling riser coupling system under different tubing pressures and drilling fluid flow rates is completed by changing the heave amplitude and frequency of the six-degree-of-freedom excitation platform 1 and adjusting the internal pressure of the tubing and the drilling fluid flow rate by changing the drilling fluid circulation device 14. The stress-strain acquisition system 18 is used to collect the parameter excitation vibration response data of the pressure-controlled drilling riser coupling system in real time.

[0089] The present invention comprehensively considers the parameter-excited vibration response analysis under the combined effects of the platform heave motion, the high pressure in the pipe and the drilling fluid flow rate, and uses a six-degree-of-freedom excitation platform device 1 to achieve heave excitation. At the same time, the drilling fluid circulation device 14 is used to change the high pressure in the pipe and the drilling fluid flow rate to simulate the actual marine controlled pressure drilling operation, and the parameter-excited vibration response analysis of the marine platform-waterproof pipe-underwater wellhead coupling system under the influence of multiple factors is considered. At the same time, the first three-dimensional force instrument test device 5 and the second three-dimensional force instrument test device 10 are used to measure in real time the influence of the axial force of the pipe string caused by any factors when the platform heave amplitude, heave frequency, high pressure in the pipe and the drilling fluid flow rate are changed. This invention is more in line with the actual operation situation, and at the same time, a high-precision test device is used to complete data collection, complete the modal vibration type analysis, parameter-excited vibration displacement analysis and pipe string axial tension analysis under the parameter-excited vibration of the coupling system, and provide a theoretical reference for deepwater controlled pressure drilling waterproof pipe operations.

[0090] Specifically, the principle of the present invention is: when in use, based on the actual marine drilling riser system configuration parameters, based on similarity theory and truncation design theory, the scaled experiment similarity ratio, model material, and structural size parameters are determined to complete the design of each component of the experimental device; each device is fastened by a flange and bolts; after the overall device is installed, the drilling fluid flow rate and pressure in the riser string are controlled by adjusting the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjusting the drilling fluid circulation device to simulate the parametrically excited vibration during the actual marine riser pressure drilling operation; by pasting multiple groups of metal strain gauges at different positions on the riser string, and installing a three-force meter device at the top and bottom of the riser system, the real-time collection of the parametrically excited response experimental analysis data of the riser system under different platform heave amplitudes and frequencies and different drilling fluid flow rates and pressures is completed; by analyzing and processing the collected data, the modal vibration type analysis, parametrically excited vibration displacement analysis, and pipe string axial force analysis under parameter excitation of the marine platform-riser-underwater wellhead coupling system are completed.

Claims

1. A parametric response experimental method for an offshore platform-riser-underwater wellhead coupling system, characterized in that: The specific steps include: S10: Based on the actual configuration parameters of the offshore drilling riser system, similarity theory and truncation design theory are used to determine the parameters of the scaled experiment similarity ratio, model material, and structural dimensions, and complete the design of each component of the experimental device; S20: The devices are fastened together by flanges and bolts; S30: After the installation of the whole device is completed, the flow rate and pressure of the drilling fluid in the watertight pipe string are controlled by adjusting the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjusting the drilling fluid circulation device to simulate the parametric excitation vibration during the actual marine watertight pipe pressure drilling operation; S40: By pasting multiple sets of metal strain gauges at different positions of the riser string and installing a three-force meter device at the top and bottom of the riser system, the real-time collection of experimental analysis data of the parametric response of the riser system under different platform heave amplitudes and frequencies and different drilling fluid flow rates and pressures is completed; S50: By analyzing and processing the collected data, the modal vibration analysis, parametric vibration displacement analysis and pipe string axial force analysis of the offshore platform-riser-underwater wellhead coupling system under parameter excitation are completed.

2. The parametric response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 1 is characterized in that: Before conducting the parametric response experiment, the natural frequency of the riser coupling system is measured through multiple sets of tapping experiments to determine the platform excitation frequency range required when parametric excitation vibration occurs. The specific steps are as follows: A fixed force is used to strike the riser column, and the riser system performs free decay motion, while strain data is collected in real time on the computer.

3. The parametric response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 2 is characterized in that: When conducting the percussion test, a drilling fluid circulation device is used to select different pressures and drilling fluid flow rates to simulate the changes in internal pressure and flow rate of the watertight riser during actual pressure-controlled drilling operations, so as to measure the natural frequency of the watertight riser corresponding to the high pressure and high drilling fluid flow rate inside the pipe.

4. The parametric response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 3 is characterized in that: The strain signal collected in the knocking experiment is a sinusoidal response signal in the time domain. It is converted into a frequency domain signal through Fourier transform using MATLAB software. The frequency value corresponding to the sudden change in the vibration amplitude after Fourier transform is extracted, that is, the frequency of the modal vibration occurring in the free attenuation process of the riser string after the knocking is completed. The data is recorded to complete the natural frequency analysis of the offshore platform-riser-underwater wellhead coupling system.

5. The parametric response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 4 is characterized in that: The specific steps of adjusting the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjusting the drilling fluid circulation device to control the drilling fluid flow rate and pressure in the watertight pipe string to simulate the parametric excitation vibration during the actual marine watertight pipe pressure drilling operation are as follows: The first step is to use the drilling fluid circulation device to change the pressure in the watertight pipe string and the drilling fluid flow rate to simulate the actual pressure-controlled drilling operation; The second step is to adjust the heave amplitude and heave frequency of the six-degree-of-freedom excitation platform according to the multiple relationship between the excitation frequency of the parameter excitation vibration and the natural frequency of the pipe string coupling system; The third step is to change the heave amplitude and frequency of the six-degree-of-freedom excitation platform and adjust the internal pressure of the tubing and the drilling fluid flow rate through the drilling fluid circulation device, complete the parameter excitation vibration response analysis of the deepwater controlled pressure drilling riser coupling system under different riser string pressures and drilling fluid flow rates, and use the stress-strain device to collect the parameter excitation vibration response data of the riser coupling system in real time.

6. The method for parametric excitation response of an offshore platform-riser-underwater wellhead coupling system according to claim 5, characterized in that: The lateral vibration caused by the change of the effective axial tension parameters of the riser string is the parameter-excited vibration of the deepwater drilling riser system.

7. The parametric excitation response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 6 is characterized in that: The three-dimensional force instrument device is a resistive strain sensor, and its axial direction needs to be calibrated before the experiment, that is, to determine the quantitative relationship between the measured value and the force to ensure the accuracy of the collected data.

8. The parametric response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 7 is characterized in that: For the lateral force on the riser string, the experiment uses a spring installed in the middle position of the riser to provide an approximate lateral static load to simulate the actual lateral external loads such as ocean currents that the riser system is subjected to in actual ocean conditions. According to the size of the lateral force required by the experiment, the spring stiffness and length are designed to meet the required lateral static load requirements.

9. The parametric response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 8, characterized in that: The specific steps of analyzing and processing the collected data are as follows: Firstly, low-pass Chebyshev type I filtering is performed, and appropriate cutoff frequency, sampling frequency and filter order are selected according to different data signals to eliminate data errors caused by noise or other experimental errors, improve analysis accuracy, separate useful signals and noise, improve analysis accuracy, and obtain a sinusoidal periodic function with good linearity and waveform.

10. The parametric response experimental method of the offshore platform-riser-underwater wellhead coupling system according to claim 9, characterized in that: The specific steps of completing the modal vibration analysis, parametric vibration displacement analysis and pipe string axial force analysis under parameter excitation of the offshore platform-riser-underwater wellhead coupling system include: The data collected from each measuring point under different working conditions are filtered and then Fourier transformed. The multiple relationship between the parameter excitation frequency and the system natural frequency when the offshore platform-riser-underwater wellhead coupling system undergoes parametric vibration is used to determine the signal change when parametric vibration occurs. The node bending moment is calculated from the strain value measured in the experiment, and the bending moment value of the measuring point is fitted with a sixth-order polynomial using MATLAB software to obtain the function of the bending moment changing with the position of the coupling system. The MATLAB program is used to perform a quadratic integral calculation to obtain the distribution function of the displacement of the coupling system.

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