With the increasing exploration of oil and gas into deep waters,the necessity for material development increases for lighter conduits such as composite marine risers,in the oil and gas industry.To understand the resea...With the increasing exploration of oil and gas into deep waters,the necessity for material development increases for lighter conduits such as composite marine risers,in the oil and gas industry.To understand the research knowledge on this novel area,there is a need to have a bibliometric analysis on composite marine risers.A research methodology was developed whereby the data retrieval was from SCOPUS database from 1977–2023.Then,VOSviewer was used to visualize the knowledge maps.This study focuses on the progress made by conducting knowledge mapping and scientometric review on composite marine risers.This scientometric analysis on the subject shows current advances,geographical activities by countries,authorship records,collaborations,funders,affiiliations,co‑occurrences,and future research areas.It was observed that the research trends recorded the highest publication volume in the U.S.A.,but less cluster affiiliated,as it was followed by countries like the U.K.,China,Nigeria,Australia and Singapore.Also,thisfiield has more conference papers than journal papers due to the challenge of adaptability,acceptance,qualifiication,and application of composite marine risers in the marine industry.Hence,there is a need for more collaborations on composite marine risers and more funding to enhance the research trend.展开更多
This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a lo...This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a loading system,and a soil stirring system,are introduced in detail.A steel pipe with the same diameter as the in situ SCR has been used in the laboratory tests to investigate the vertical motion of the pipe and the effect of the trench on the lateral motion.As the amplitude of the vertical motion increases,the depth of the trench deepens,the bending moment range increases,and the excess pore water pressure at the bottom of the pipeline first accumulates and then dissipates during loading.The development trend of the trench depth and the influence of the soil strength on the SCR bending moment are also studied.During the test,a seabed trench develops,and its shape is similar to that of the in situ trench.展开更多
By large-scale cold mold experiments,pressure pulsation signals within the jet influence zone of riser reactor are processed by using Hilbert-Huang analysis(HHT)in this study.Effects of different jet forms and operati...By large-scale cold mold experiments,pressure pulsation signals within the jet influence zone of riser reactor are processed by using Hilbert-Huang analysis(HHT)in this study.Effects of different jet forms and operating conditions on the intrinsic mode function(IMF)energy and Hilbert-Huang spectrum are compared.Results show that the IMF energy and Hilbert-Huang spectrum of pressure pulsation signals show significant differences under the influence of upward and downward jets.Moreover,the change of jet velocity will also lead to significant changes in IMF energy and Hilbert-Huang spectrum.Among them,energy values and energy proportions corresponding to high-frequency pressure pulsations show a good correlation with the jet velocity.On this basis,energy value and energy proportion data in the high frequency range of the original pressure signal are clustered and analyzed by using the K-means clustering algorithm.Based on clustering results,the jet influence zone of riser can be defined into three regions.From partitioning results,it is found that the introduction of downward inclined jets could effectively improve the gas-solid mixing in the feed injection zone of riser.展开更多
The deep seabed is known for its abundant reserves of various mineral resources.Notably,the Clarion Clipperton(C-C)mining area in the northeast Pacific Ocean,where China holds exploration rights,is particularly rich i...The deep seabed is known for its abundant reserves of various mineral resources.Notably,the Clarion Clipperton(C-C)mining area in the northeast Pacific Ocean,where China holds exploration rights,is particularly rich in deep-sea polymetallic nodules.These nodules,which are nodular and unevenly distributed in seafloor sediments,have significant industrial exploitation value.Over the decades,the deep-sea mining industry has increasingly adopted systems that combine rigid and flexible risers supported by large surface mining vessels.However,current systems face economic and structural stability challenges,hindering the development of deep-sea mining technology.This paper proposes a new structural design for a deep-sea mining system based on flexible risers,validated through numerical simulations and experimental research.The system composition,function and operational characteristics are comprehensively introduced.Detailed calculations determine the production capacity of the deep-sea mining system and the dimensions of the seabed mining subsystem.Finite element numerical simulations analyze the morphological changes of flexible risers and the stress conditions at key connection points under different ocean current incident angles.Experimental research verifies the feasibility of collaborative movement between two tethered underwater devices.The proposed deep-sea mining system,utilizing flexible risers,significantly advances the establishment of a commercial deep-sea mining system.The production calculations and parameter determinations provide essential references for the system’s future detailed design.Furthermore,the finite element simulation model established in this paper provides a research basis,and the method established in this paper offers a foundation for subsequent research under more complex ocean conditions.The control strategy for the collaborative movement between two tethered underwater devices provides an effective solution for deep-sea mining control systems.展开更多
Deepwater drilling riser is the key equipment connecting the subsea wellhead and floating drilling platform.Due to complex marine environment,vortex-induced vibration(ViV)will be generated on riser,which will induce f...Deepwater drilling riser is the key equipment connecting the subsea wellhead and floating drilling platform.Due to complex marine environment,vortex-induced vibration(ViV)will be generated on riser,which will induce fatigue failure and even cause unpredictable drilling accidents.Therefore,it is important to study the ViV characteristics of deepwater drilling riser and reveal the main controlling factors for ensuring the safe and efficient operation of deepwater drilling engineering.In this paper,the ViV of deepwater drilling riser is numerically simulated in time domain based on the discrete vortex method(DvM).A hydrodynamic analysis model and governing equation of VIV is proposed with considering the effect of riser motion using DVM and slice method,where the governing equation is solved by Runge-Kutta method.Model validation is performed,which verified the correctness and accuracy of the mechanical model and the solution method.On this basis,the influence of the number of control points,current velocity,riser outer diameter,shear flow and top tension on the ViV characteristics of deepwater drilling risers are discussed in detail.The results show that with the increase of current velocity,the vibration amplitude of deepwater drilling riser decreases obviously,while the vibration frequency increases gradually.However,if the outer diameter of riser increases,the vibration amplitude increases,while the vibration frequency decreases gradually.The top tension also has great influence on the VIV of riser.When the top tension is 1.25 G,the VIV is suppressed to a certain extent.This study has guiding significance for optimal design and engineering control of deepwater drilling riser.展开更多
A new hang-off system has been proposed to improve the security of risers in hang-off modes during typhoons.However,efficient anti-typhoon evacuation strategies have not been investigated.Optimiza-tion model and metho...A new hang-off system has been proposed to improve the security of risers in hang-off modes during typhoons.However,efficient anti-typhoon evacuation strategies have not been investigated.Optimiza-tion model and method for the anti-typhoon evacuation strategies should be researched.Therefore,multi-objective functions are proposed based on operation time,evacuation speed stability,and steering stability.An evacuation path model and a dynamic model of risers with the new hang-off system are developed for design variables and constraints.A multi-objective optimization model with high-dimensional variables and complex constraints is established.Finally,a three-stage optimization method based on genetic algorithm,least square method,and the penalty function method is proposed to solve the multi-objective optimization model.Optimization results show that the operation time can be reduced through operation parameter optimization,especially evacuation heading optimization.The optimal anti-typhoon strategy is evacuation with all risers suspended along a variable path when the direction angle is large,while evacuation with all risers suspended along a straight path at another di-rection angle.Besides,the influencing factors on anti-typhoon evacuation strategies indicate that the proposed optimization model and method have strong applicability to working conditions and remarkable optimization effects.展开更多
Steel lazy-wave riser(SLWR)is one of the key technical components of offshore oil-gas production systems and is widely utilized in deepwater areas.On the basis of the vector form intrinsic finite element(VFIFE)method,...Steel lazy-wave riser(SLWR)is one of the key technical components of offshore oil-gas production systems and is widely utilized in deepwater areas.On the basis of the vector form intrinsic finite element(VFIFE)method,this study develops a reasonable numerical model for the SLWR to investigate the effects of the buoyancy section on its mechanical characteristics.In the SLWR model,the buoyancy section is simulated using an equivalent riser segment with the same outer diameter and unit weight.The riser is considered to be composed of a series of space vector particles connected by elements,and virtual reverse motions are applied to establish the fundamental equations of forces and displacements.The explicit central difference technique is used to solve the governing equations for particle motion within the riser through programming implementation.To provide a detailed explanation of the process by which the SLWR achieves a stable lazy-wave configuration,a numerical model of a 2800-m-long riser is established at a water depth of 1600 m,and the feasibility of this model for riser behavior analysis is validated.The remarkable influences of the position,length,number and spacing of the buoyancy section on the mechanical behavior of the SLWR are observed,which provides a theoretical foundation for the optimal design of the SLWR in deepwaters.展开更多
When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fa...When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.展开更多
An observer-based adaptive backstepping boundary control is proposed for vibration control of flexible offshore riser systems with unknown nonlinear input dead zone and uncertain environmental disturbances.The control...An observer-based adaptive backstepping boundary control is proposed for vibration control of flexible offshore riser systems with unknown nonlinear input dead zone and uncertain environmental disturbances.The control algorithm can update the control law online through real-time data to make the controller adapt to the environment and improve the control precision.Specifically,based on the adaptive backstepping framework,virtual control laws and Lyapunov functions are designed for each subsystem.Three direction interference observers are designed to track the timevarying boundary disturbance.On this basis,the inverse of the dead zone and linear state transformation are used to compensate for the original system and eliminate the adverse effects of the dead zone.In addition,the stability of the closed-loop system is proven by Lyapunov stability theory.All the system states are bounded,and the vibration offset of the riser converges to a small area of the initial position.Finally,four examples of flexible marine risers are simulated in MATLAB to verify the effectiveness of the proposed controller.展开更多
In order to study the response law of vortex-induced vibration(VIV)of marine risers under the combined action of roughness and interference effects,and to reveal the coupling mechanism of roughness and interference ef...In order to study the response law of vortex-induced vibration(VIV)of marine risers under the combined action of roughness and interference effects,and to reveal the coupling mechanism of roughness and interference effects on the riser,a VIV experiment of rough risers in tandem arrangement was conducted in a wave−current combined flume.The experiment characterized the risers’roughness by arranging different specifications of attachments on the surface of the risers.Three rough risers with different roughness and smooth risers were arranged in tandem arrangement,with the rough risers arranged downstream.The experimental results indicate that the suppression of the attachments on the downstream risers’vibration are more significant both in the CF and IL directions as the reduced velocity increases.For the downstream riser,the amplitude response of rough riser is more significantly weakened compared with the smooth one at high reduced velocity.For the upstream risers,changes in the roughness and spacing ratio have an impact on their‘lock-in’region.When the roughness of downstream risers is relatively large(0.1300)and the spacing between risers is small(S/D=4.0),the reduced velocity range of‘lock-in’region in the CF direction of upstream risers is obviously expanded,and the displacement in the‘lock-in’region is severer.展开更多
A vortex-induced vibration(VIV)experiment of rough risers with coupling interference effect under a side-by-side arrangement was carried out in a wave-current combined flume.The roughness of the riser was characterize...A vortex-induced vibration(VIV)experiment of rough risers with coupling interference effect under a side-by-side arrangement was carried out in a wave-current combined flume.The roughness of the riser was characterized by arranging different specifications of surface attachments on the surface of the riser.Rough risers with three different roughnesses were arranged side by side with smooth risers to explore the VIV response of the riser under the combined action of roughness and interference effect,and to reveal the coupling mechanism between roughness and interference effect.The experimental results show that,compared with that of a smooth riser,the VIV of a rough riser under the coupling interference effect has a wider"lock-in"region,and the displacement decreases more significantly at a high reduced velocity,which is more likely to excite higher-order modes and frequency responses.In addition,the displacement response and frequency response of the smooth riser are not significantly affected by wake interference from the rough riser,which is caused by the decrease of the wake region due to the delay of the boundary layer separation point of the rough riser.展开更多
When the free standing riser(FSR)is in service in the ocean,its mechanical properties are affected by various factors,including complex ocean current forces,buoyancy of the buoyancy can,and torque caused by the deflec...When the free standing riser(FSR)is in service in the ocean,its mechanical properties are affected by various factors,including complex ocean current forces,buoyancy of the buoyancy can,and torque caused by the deflection of the upper floating body.These loads have a great influence on the deformation and internal force of the FSR.The static performance of FSR is investigated in this research under various working conditions.The finite element model of FSR is established based on the co-rotational method.The arc length approach is used to solve the model.The load is exerted in increments.The current load on the riser changes with the configuration of the riser.The accuracy of the numerical method is verified by Abaqus software.The calculation time is also compared.Then,the effects of uniform current,actual current and floating body yaw motion on FSR are studied by parameter analysis.Additionally,the influence of the FSR on the ocean current after the failure of part of the buoyancy can chamber is analyzed.The results show that the numerical model based on the co-rotational method can effectively simulate the large rotation and torsion behavior of FSR.This method has high computational efficiency and precision,and this method can quickly improve the efficiency of numerical calculation of static analysis of deep-water riser.The proposed technology may serve as an alternative to the existing proprietary commercial software,which uses a complex graphical user interface.展开更多
A three-dimensional numerical scheme was developed to investigate the vortex-induced vibration(VIV)of a catenary-type riser(CTR)in the in-line(IL)and cross-flow(CF)directions.By using the vector form intrinsic finite ...A three-dimensional numerical scheme was developed to investigate the vortex-induced vibration(VIV)of a catenary-type riser(CTR)in the in-line(IL)and cross-flow(CF)directions.By using the vector form intrinsic finite element method,the CTR was discretized into a finite number of spatial particles whose motions satisfy Newton’s second law.The Van der Pol oscillator was used to simulate the effect of vortex shedding.The coupling equations of structural vibration and wake oscillator were solved using an explicit central differential algorithm.The numerical model was verified with the published results.The VIV characteristics of the CTR subjected to uniform flows,including displacement,frequency,standing wave,traveling wave,motion trajectory,and energy transfer,were studied comprehensively.The numerical results revealed that the multimode property occurs in the CF-and IL-direction VIV responses of the CTR.An increase in the flow velocity has slight effects on the maximum VIV displacement.Due to structural nonlin-earity,the double-frequency relationship in the CF and IL directions is rarely captured.Therefore,the vibration trajectories display the shape of an inclined elliptical orbit.Moreover,the negative energy region is inconspicuous under the excitation of the uniform flow.展开更多
The safety of risers in hang-off states is a vital challenge in offshore oil and gas engineering.A new hang-off system installed on top of risers is proposed for improving the security of risers.This approach leads to...The safety of risers in hang-off states is a vital challenge in offshore oil and gas engineering.A new hang-off system installed on top of risers is proposed for improving the security of risers.This approach leads to a challenging problem:coupling the dynamics of risers with a new hang-off system combined with multiple structures and complex constraints.To accurately analyze the dynamic responses of the coupled system,a coupled dynamic model is established based on the Euler-Bernoulli beam-column theory and penalty function method.A comprehensive analysis method is proposed for coupled dynamic analysis by combining the finite element method and the Newmarkβmethod.An analysis program is also developed in MATLAB for dynamic simulation.The simulation results show that the dynamic performances of the risers at the top part are significantly improved by the new hang-off system,especially the novel design,which includes the centralizer and articulation joint.The bending moment and lateral deformation of the risers at the top part decrease,while the hang-off joint experiences a great bending moment at the bottom of the lateral restraint area which requires particular attention in design and application.The platform navigation speed range under the safety limits of risers expands with the new hang-off system in use.展开更多
Flexible risers are crucial pieces of equipment for moving output fluids from wells to platforms during the extraction of oil and gas from deepsea resources.One of the causes of collapse in these pipes is the high hyd...Flexible risers are crucial pieces of equipment for moving output fluids from wells to platforms during the extraction of oil and gas from deepsea resources.One of the causes of collapse in these pipes is the high hydrostatic pressure applied to risers in deep water.The innermost layer of a riser,known as the carcass layer,plays a critical role in resistance to external pressure.In this study,we investigated the collapse(nonlinear buckling)of a riser under external pressure,and a novel design based on the structure of a beetle’s exoskeleton was used to increase the load capacity of the carcass layer.This type of beetle skeleton is constructed in such a way that it creates strong connections among the various parts of the external skeleton to considerably enhance strength against external pressure while allowing necessary movements.To assess the performance of the design in comparison with the original design,we examined the nonlinear buckling of the new structure under external pressure.Through genetic algorithm optimization,design parameters were obtained,and the maximum strength before collapse was determined.Results show that the critical pressure in the new design substantially increases relative to that in the original design.展开更多
In recent years, numerous exploration activities of oil and gas industry have been conducted in ultra deep water. The global offshore industry is building systems today for drilling in even deeper water, progressively...In recent years, numerous exploration activities of oil and gas industry have been conducted in ultra deep water. The global offshore industry is building systems today for drilling in even deeper water, progressively using new technologies, and significantly extending existing technologies. This is the general trend in the offshore oil and gas industry. So the technology of ultra-deepwater risers, which is the main tool in drilling oil, is more and more standard. This paper manly focuses on the global analysis of the drilling risers. And it is divided into two parts, operability analysis and hang-off analysis that are used to check the design of the riser. In this paper, the rotation angle and stress of the riser in the drilling mode are calculated to determine the operability envelop. The number of the buoyancy modules has been determined and according to the API standard, all the worked out values have been checked out. From all the above, it is concluded that the operability envelop is relatively small under harsh condition and the number of the buoyancy modules is a little large. And above all, the design of this riser is successful.展开更多
In re-entry, the drilling riser hanging to the holding vessel takes on a free hanging state, waiting to be moved from the initial random position to the wellhead. For the re-entry, dynamics calculation is often done t...In re-entry, the drilling riser hanging to the holding vessel takes on a free hanging state, waiting to be moved from the initial random position to the wellhead. For the re-entry, dynamics calculation is often done to predict the riser motion or evaluate the structural safety. A dynamics calculation method based on Flexible Segment Model （FSM） is proposed for free hanging marine risers. In FSM, a riser is discretized into a series of flexible segments. For each flexible segment, its deflection feature and external forces are analyzed independently. For the whole riser, the nonlinear governing equations are listed according to the moment equilibrium at nodes. For the solution of the nonlinear equations, a linearization iteration scheme is provided in the paper. Owing to its flexibility, each segment can match a long part of the riser body, which enables that good results can be obtained even with a small number of segments. Moreover, the linearization iteration scheme can avoid widely used Newton-Rapson iteration scheme in which the calculation stability is influenced by the initial points. The FSM-based dynamics calculation is timesaving and stable, so suitable for the shape prediction or real-time control of free hanging marine risers.展开更多
Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the ri...Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the risers must be installed to act as the conduits connecting surface platforms to subsea facilities. In this paper, the typical risers sorted by different classes are introduced, and the correspondent installation methods are presented. By investigating the recent projects performed in the deepwater hot spots, and combining the challenges of HYSY20 l for riser installation, a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of 1500 m in the South China Sea. Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of 3000 m in the South China Sea.展开更多
A prediction model of the deepwater steel catenary riser VIV is proposed based on the forced oscillation test data, taking into account the riser-seafloor interaction for the cross-flow VIV-induced fatigue damage at t...A prediction model of the deepwater steel catenary riser VIV is proposed based on the forced oscillation test data, taking into account the riser-seafloor interaction for the cross-flow VIV-induced fatigue damage at touch-down point （TDP）. The model will give more reasonable simulation of SCR response near TDP than the previous pinned truncation model. In the present model, the hysteretic riser-soil interaction model is simplified as the linear spring and damper to simulate the seafloor, and the damping is obtained according to the dissipative power during one periodic riser-soil interaction. In order to validate the model, the comparison with the field measurement and the results predicted by Shear 7 program of a full-scale steel catenary riser is carried out. The main induced modes, mode frequencies and response amplitude are in a good agreement. Furthermore, the parametric studies are carried out to broaden the understanding of the fatigue damage sensitivity to the upper end in-plane offset and seabed characteristics. In addition, the fatigue stress comparison at TDP between the truncation riser model and the present full riser model shows that the existence of touch-down zones is very important for the fatigue damage assessment of steel catenary riser at TDP.展开更多
Flexible risers and steel catenary risers often provide unique riser solutions for today’s deepwater field development. Accurate analysis of these slender structures, in which there are high-speed HP/HT internal flow...Flexible risers and steel catenary risers often provide unique riser solutions for today’s deepwater field development. Accurate analysis of these slender structures, in which there are high-speed HP/HT internal flows, is critical to ensure personnel and asset safety. In this study, a special global coordinate-based FEM rod model was adopted to identify and quantify the effects of internal flow and hydrostatic pressure on both flexible and deepwater steel catenary risers, with emphasis on the latter. By incorporating internal flow induced forces into the model, it was found that the internal flow contributes a new term to the effective tension expression. For flexible risers in shallow water, internal flow and hydrostatic pressure made virtually no change to effective tension by merely altering the riser wall tension. In deep water the internal pressure wielded a dominant role in governing the riser effective tension and furthering the static configuration, while the effect of inflow velocity was negligible. With respect to the riser seabed interaction, both the seabed support and friction effect were considered, with the former modeled by a nonlinear quadratic spring, allowing for a consistent derivation of the tangent stiffness matrix. The presented application examples show that the nonlinear quadratic spring is, when using the catenary solution as an initial static profile, an efficient way to model the quasi-Winkler-type elastic seabed foundation in this finite element scheme.展开更多
基金support of the School of Engineering,Lancaster University,UK,for the Engineering Department Studentship as well as the Engineering and Physical Sciences Research Council(EPSRC)’s Doctoral Training Centre(DTC)。
文摘With the increasing exploration of oil and gas into deep waters,the necessity for material development increases for lighter conduits such as composite marine risers,in the oil and gas industry.To understand the research knowledge on this novel area,there is a need to have a bibliometric analysis on composite marine risers.A research methodology was developed whereby the data retrieval was from SCOPUS database from 1977–2023.Then,VOSviewer was used to visualize the knowledge maps.This study focuses on the progress made by conducting knowledge mapping and scientometric review on composite marine risers.This scientometric analysis on the subject shows current advances,geographical activities by countries,authorship records,collaborations,funders,affiiliations,co‑occurrences,and future research areas.It was observed that the research trends recorded the highest publication volume in the U.S.A.,but less cluster affiiliated,as it was followed by countries like the U.K.,China,Nigeria,Australia and Singapore.Also,thisfiield has more conference papers than journal papers due to the challenge of adaptability,acceptance,qualifiication,and application of composite marine risers in the marine industry.Hence,there is a need for more collaborations on composite marine risers and more funding to enhance the research trend.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51879189 and 52071234).
文摘This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a loading system,and a soil stirring system,are introduced in detail.A steel pipe with the same diameter as the in situ SCR has been used in the laboratory tests to investigate the vertical motion of the pipe and the effect of the trench on the lateral motion.As the amplitude of the vertical motion increases,the depth of the trench deepens,the bending moment range increases,and the excess pore water pressure at the bottom of the pipeline first accumulates and then dissipates during loading.The development trend of the trench depth and the influence of the soil strength on the SCR bending moment are also studied.During the test,a seabed trench develops,and its shape is similar to that of the in situ trench.
基金sponsored by the National Key Research and Development Program of China(No.2022YFA1506200)the CNPC Innovation Found(No.2024DQ02-0203)the open foundation of State Key Laboratory of Chemical Engineering(No.SKL-ChE-23B02).
文摘By large-scale cold mold experiments,pressure pulsation signals within the jet influence zone of riser reactor are processed by using Hilbert-Huang analysis(HHT)in this study.Effects of different jet forms and operating conditions on the intrinsic mode function(IMF)energy and Hilbert-Huang spectrum are compared.Results show that the IMF energy and Hilbert-Huang spectrum of pressure pulsation signals show significant differences under the influence of upward and downward jets.Moreover,the change of jet velocity will also lead to significant changes in IMF energy and Hilbert-Huang spectrum.Among them,energy values and energy proportions corresponding to high-frequency pressure pulsations show a good correlation with the jet velocity.On this basis,energy value and energy proportion data in the high frequency range of the original pressure signal are clustered and analyzed by using the K-means clustering algorithm.Based on clustering results,the jet influence zone of riser can be defined into three regions.From partitioning results,it is found that the introduction of downward inclined jets could effectively improve the gas-solid mixing in the feed injection zone of riser.
基金Supported by Finance Science and Technology Project of Hainan Province under Grant No.ZDKJ2021027the National Natural Science Foundation of China under Grant No.52231012.
文摘The deep seabed is known for its abundant reserves of various mineral resources.Notably,the Clarion Clipperton(C-C)mining area in the northeast Pacific Ocean,where China holds exploration rights,is particularly rich in deep-sea polymetallic nodules.These nodules,which are nodular and unevenly distributed in seafloor sediments,have significant industrial exploitation value.Over the decades,the deep-sea mining industry has increasingly adopted systems that combine rigid and flexible risers supported by large surface mining vessels.However,current systems face economic and structural stability challenges,hindering the development of deep-sea mining technology.This paper proposes a new structural design for a deep-sea mining system based on flexible risers,validated through numerical simulations and experimental research.The system composition,function and operational characteristics are comprehensively introduced.Detailed calculations determine the production capacity of the deep-sea mining system and the dimensions of the seabed mining subsystem.Finite element numerical simulations analyze the morphological changes of flexible risers and the stress conditions at key connection points under different ocean current incident angles.Experimental research verifies the feasibility of collaborative movement between two tethered underwater devices.The proposed deep-sea mining system,utilizing flexible risers,significantly advances the establishment of a commercial deep-sea mining system.The production calculations and parameter determinations provide essential references for the system’s future detailed design.Furthermore,the finite element simulation model established in this paper provides a research basis,and the method established in this paper offers a foundation for subsequent research under more complex ocean conditions.The control strategy for the collaborative movement between two tethered underwater devices provides an effective solution for deep-sea mining control systems.
基金the financial support from National Key R&D Program of China(Grant number:2024YFC2815100)Natural Science Foundation of China(Grant number:52322110)Beijing Nova Program(Grant number:20230484341).
文摘Deepwater drilling riser is the key equipment connecting the subsea wellhead and floating drilling platform.Due to complex marine environment,vortex-induced vibration(ViV)will be generated on riser,which will induce fatigue failure and even cause unpredictable drilling accidents.Therefore,it is important to study the ViV characteristics of deepwater drilling riser and reveal the main controlling factors for ensuring the safe and efficient operation of deepwater drilling engineering.In this paper,the ViV of deepwater drilling riser is numerically simulated in time domain based on the discrete vortex method(DvM).A hydrodynamic analysis model and governing equation of VIV is proposed with considering the effect of riser motion using DVM and slice method,where the governing equation is solved by Runge-Kutta method.Model validation is performed,which verified the correctness and accuracy of the mechanical model and the solution method.On this basis,the influence of the number of control points,current velocity,riser outer diameter,shear flow and top tension on the ViV characteristics of deepwater drilling risers are discussed in detail.The results show that with the increase of current velocity,the vibration amplitude of deepwater drilling riser decreases obviously,while the vibration frequency increases gradually.However,if the outer diameter of riser increases,the vibration amplitude increases,while the vibration frequency decreases gradually.The top tension also has great influence on the VIV of riser.When the top tension is 1.25 G,the VIV is suppressed to a certain extent.This study has guiding significance for optimal design and engineering control of deepwater drilling riser.
基金supported by the National Natural Science Foundation of China(Grant No:52271300,52071337)National Key Research and Development Program of China(2022YFC2806501)+1 种基金High-tech Ship Research Projects Sponsored by MIIT(CBG2N21-4-25)Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT14R58).
文摘A new hang-off system has been proposed to improve the security of risers in hang-off modes during typhoons.However,efficient anti-typhoon evacuation strategies have not been investigated.Optimiza-tion model and method for the anti-typhoon evacuation strategies should be researched.Therefore,multi-objective functions are proposed based on operation time,evacuation speed stability,and steering stability.An evacuation path model and a dynamic model of risers with the new hang-off system are developed for design variables and constraints.A multi-objective optimization model with high-dimensional variables and complex constraints is established.Finally,a three-stage optimization method based on genetic algorithm,least square method,and the penalty function method is proposed to solve the multi-objective optimization model.Optimization results show that the operation time can be reduced through operation parameter optimization,especially evacuation heading optimization.The optimal anti-typhoon strategy is evacuation with all risers suspended along a variable path when the direction angle is large,while evacuation with all risers suspended along a straight path at another di-rection angle.Besides,the influencing factors on anti-typhoon evacuation strategies indicate that the proposed optimization model and method have strong applicability to working conditions and remarkable optimization effects.
基金supported by the National Natural Science Foundation of China(Grant Nos.52471275,U23A20663,51809048,51909236)the Natural Science Foundation of Fujian Province(Grant No.2022J01092)+1 种基金the Natural Science Foundation of Zhejiang Province(Grant No.LY23E090004)the Ningbo Natural Science Foundation(Grant No.2021J039).
文摘Steel lazy-wave riser(SLWR)is one of the key technical components of offshore oil-gas production systems and is widely utilized in deepwater areas.On the basis of the vector form intrinsic finite element(VFIFE)method,this study develops a reasonable numerical model for the SLWR to investigate the effects of the buoyancy section on its mechanical characteristics.In the SLWR model,the buoyancy section is simulated using an equivalent riser segment with the same outer diameter and unit weight.The riser is considered to be composed of a series of space vector particles connected by elements,and virtual reverse motions are applied to establish the fundamental equations of forces and displacements.The explicit central difference technique is used to solve the governing equations for particle motion within the riser through programming implementation.To provide a detailed explanation of the process by which the SLWR achieves a stable lazy-wave configuration,a numerical model of a 2800-m-long riser is established at a water depth of 1600 m,and the feasibility of this model for riser behavior analysis is validated.The remarkable influences of the position,length,number and spacing of the buoyancy section on the mechanical behavior of the SLWR are observed,which provides a theoretical foundation for the optimal design of the SLWR in deepwaters.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51109158,U2106223)the Science and Technology Development Plan Program of Tianjin Municipal Transportation Commission(Grant No.2022-48)。
文摘When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.
基金financially supported by the Sichuan Science and Technology Program(Grant No.2023NSFSC1980)。
文摘An observer-based adaptive backstepping boundary control is proposed for vibration control of flexible offshore riser systems with unknown nonlinear input dead zone and uncertain environmental disturbances.The control algorithm can update the control law online through real-time data to make the controller adapt to the environment and improve the control precision.Specifically,based on the adaptive backstepping framework,virtual control laws and Lyapunov functions are designed for each subsystem.Three direction interference observers are designed to track the timevarying boundary disturbance.On this basis,the inverse of the dead zone and linear state transformation are used to compensate for the original system and eliminate the adverse effects of the dead zone.In addition,the stability of the closed-loop system is proven by Lyapunov stability theory.All the system states are bounded,and the vibration offset of the riser converges to a small area of the initial position.Finally,four examples of flexible marine risers are simulated in MATLAB to verify the effectiveness of the proposed controller.
基金supported by the Natural Science Foundation of Shandong Province(Grant Nos.ZR2023ME040 and ZR2022QE118)the Key Technology Research and Development Program of Shandong Province(Grant No.2023CXGC010316)the Natural Science Foundation of Qingdao(Grant No.23-2-1-207-zyyd-jch),and the National Natural Science Foundation of China(Grant No.51709161).
文摘In order to study the response law of vortex-induced vibration(VIV)of marine risers under the combined action of roughness and interference effects,and to reveal the coupling mechanism of roughness and interference effects on the riser,a VIV experiment of rough risers in tandem arrangement was conducted in a wave−current combined flume.The experiment characterized the risers’roughness by arranging different specifications of attachments on the surface of the risers.Three rough risers with different roughness and smooth risers were arranged in tandem arrangement,with the rough risers arranged downstream.The experimental results indicate that the suppression of the attachments on the downstream risers’vibration are more significant both in the CF and IL directions as the reduced velocity increases.For the downstream riser,the amplitude response of rough riser is more significantly weakened compared with the smooth one at high reduced velocity.For the upstream risers,changes in the roughness and spacing ratio have an impact on their‘lock-in’region.When the roughness of downstream risers is relatively large(0.1300)and the spacing between risers is small(S/D=4.0),the reduced velocity range of‘lock-in’region in the CF direction of upstream risers is obviously expanded,and the displacement in the‘lock-in’region is severer.
基金financially supported by the Natural Science Foundation of Shandong Province(Grant Nos.ZR2023ME040 and ZR2022QE118)the Key Technology Research and Development Program of Shandong Province(Grant No.2023CXGC010316)+1 种基金the Natural Science Foundation of Qingdao(Grant No.23-2-1-207-zyyd-jch)the Introduction and Education Plan for Young Innovative talents in Colleges and Universities of Shandong Province(Marine Civil Engineering Materials and Structure Innovation Research Team).
文摘A vortex-induced vibration(VIV)experiment of rough risers with coupling interference effect under a side-by-side arrangement was carried out in a wave-current combined flume.The roughness of the riser was characterized by arranging different specifications of surface attachments on the surface of the riser.Rough risers with three different roughnesses were arranged side by side with smooth risers to explore the VIV response of the riser under the combined action of roughness and interference effect,and to reveal the coupling mechanism between roughness and interference effect.The experimental results show that,compared with that of a smooth riser,the VIV of a rough riser under the coupling interference effect has a wider"lock-in"region,and the displacement decreases more significantly at a high reduced velocity,which is more likely to excite higher-order modes and frequency responses.In addition,the displacement response and frequency response of the smooth riser are not significantly affected by wake interference from the rough riser,which is caused by the decrease of the wake region due to the delay of the boundary layer separation point of the rough riser.
基金supported by the National Natural Science Foundation of China(Grant No.52271299).
文摘When the free standing riser(FSR)is in service in the ocean,its mechanical properties are affected by various factors,including complex ocean current forces,buoyancy of the buoyancy can,and torque caused by the deflection of the upper floating body.These loads have a great influence on the deformation and internal force of the FSR.The static performance of FSR is investigated in this research under various working conditions.The finite element model of FSR is established based on the co-rotational method.The arc length approach is used to solve the model.The load is exerted in increments.The current load on the riser changes with the configuration of the riser.The accuracy of the numerical method is verified by Abaqus software.The calculation time is also compared.Then,the effects of uniform current,actual current and floating body yaw motion on FSR are studied by parameter analysis.Additionally,the influence of the FSR on the ocean current after the failure of part of the buoyancy can chamber is analyzed.The results show that the numerical model based on the co-rotational method can effectively simulate the large rotation and torsion behavior of FSR.This method has high computational efficiency and precision,and this method can quickly improve the efficiency of numerical calculation of static analysis of deep-water riser.The proposed technology may serve as an alternative to the existing proprietary commercial software,which uses a complex graphical user interface.
基金supported by the National Key R&D Program of China(No.2022YFB2602800)the National Science Foundation of China(No.51979257)+3 种基金the Basic Funding of the Central Public Research Institutes(Nos.TKS20210101,TKS20220103,TKS20230102)the Fundamental Research Funds for the Central Universities(No.202413018)the postdoctoral project of Shandong(No.SDCX-ZG-202400218)the postdoctoral project of Qingdao(No.QDBSH20240101013).
文摘A three-dimensional numerical scheme was developed to investigate the vortex-induced vibration(VIV)of a catenary-type riser(CTR)in the in-line(IL)and cross-flow(CF)directions.By using the vector form intrinsic finite element method,the CTR was discretized into a finite number of spatial particles whose motions satisfy Newton’s second law.The Van der Pol oscillator was used to simulate the effect of vortex shedding.The coupling equations of structural vibration and wake oscillator were solved using an explicit central differential algorithm.The numerical model was verified with the published results.The VIV characteristics of the CTR subjected to uniform flows,including displacement,frequency,standing wave,traveling wave,motion trajectory,and energy transfer,were studied comprehensively.The numerical results revealed that the multimode property occurs in the CF-and IL-direction VIV responses of the CTR.An increase in the flow velocity has slight effects on the maximum VIV displacement.Due to structural nonlin-earity,the double-frequency relationship in the CF and IL directions is rarely captured.Therefore,the vibration trajectories display the shape of an inclined elliptical orbit.Moreover,the negative energy region is inconspicuous under the excitation of the uniform flow.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52271300,52071337,and 51809279)the National Key Research and Development Program of China(Grant No.2022YFC2806501)the High-tech Ship Research Projects Sponsored by MIIT(Grant No.CBG2N21-4-2-5).
文摘The safety of risers in hang-off states is a vital challenge in offshore oil and gas engineering.A new hang-off system installed on top of risers is proposed for improving the security of risers.This approach leads to a challenging problem:coupling the dynamics of risers with a new hang-off system combined with multiple structures and complex constraints.To accurately analyze the dynamic responses of the coupled system,a coupled dynamic model is established based on the Euler-Bernoulli beam-column theory and penalty function method.A comprehensive analysis method is proposed for coupled dynamic analysis by combining the finite element method and the Newmarkβmethod.An analysis program is also developed in MATLAB for dynamic simulation.The simulation results show that the dynamic performances of the risers at the top part are significantly improved by the new hang-off system,especially the novel design,which includes the centralizer and articulation joint.The bending moment and lateral deformation of the risers at the top part decrease,while the hang-off joint experiences a great bending moment at the bottom of the lateral restraint area which requires particular attention in design and application.The platform navigation speed range under the safety limits of risers expands with the new hang-off system in use.
文摘Flexible risers are crucial pieces of equipment for moving output fluids from wells to platforms during the extraction of oil and gas from deepsea resources.One of the causes of collapse in these pipes is the high hydrostatic pressure applied to risers in deep water.The innermost layer of a riser,known as the carcass layer,plays a critical role in resistance to external pressure.In this study,we investigated the collapse(nonlinear buckling)of a riser under external pressure,and a novel design based on the structure of a beetle’s exoskeleton was used to increase the load capacity of the carcass layer.This type of beetle skeleton is constructed in such a way that it creates strong connections among the various parts of the external skeleton to considerably enhance strength against external pressure while allowing necessary movements.To assess the performance of the design in comparison with the original design,we examined the nonlinear buckling of the new structure under external pressure.Through genetic algorithm optimization,design parameters were obtained,and the maximum strength before collapse was determined.Results show that the critical pressure in the new design substantially increases relative to that in the original design.
基金Supported by the 111 Projects Foundation from State Administration of Foreign Experts Affairs of China and Ministry of Education of China under Grant No.B07019
文摘In recent years, numerous exploration activities of oil and gas industry have been conducted in ultra deep water. The global offshore industry is building systems today for drilling in even deeper water, progressively using new technologies, and significantly extending existing technologies. This is the general trend in the offshore oil and gas industry. So the technology of ultra-deepwater risers, which is the main tool in drilling oil, is more and more standard. This paper manly focuses on the global analysis of the drilling risers. And it is divided into two parts, operability analysis and hang-off analysis that are used to check the design of the riser. In this paper, the rotation angle and stress of the riser in the drilling mode are calculated to determine the operability envelop. The number of the buoyancy modules has been determined and according to the API standard, all the worked out values have been checked out. From all the above, it is concluded that the operability envelop is relatively small under harsh condition and the number of the buoyancy modules is a little large. And above all, the design of this riser is successful.
基金supported by the National Natural Science Foundation of China (Grant No. 51009092)the Doctoral Foundation of Education Ministry of China (Grant No. 20090073120013)the Scientific Research Foundation of State Education Ministry for the Returned Overseas Chinese Scholars
文摘In re-entry, the drilling riser hanging to the holding vessel takes on a free hanging state, waiting to be moved from the initial random position to the wellhead. For the re-entry, dynamics calculation is often done to predict the riser motion or evaluate the structural safety. A dynamics calculation method based on Flexible Segment Model （FSM） is proposed for free hanging marine risers. In FSM, a riser is discretized into a series of flexible segments. For each flexible segment, its deflection feature and external forces are analyzed independently. For the whole riser, the nonlinear governing equations are listed according to the moment equilibrium at nodes. For the solution of the nonlinear equations, a linearization iteration scheme is provided in the paper. Owing to its flexibility, each segment can match a long part of the riser body, which enables that good results can be obtained even with a small number of segments. Moreover, the linearization iteration scheme can avoid widely used Newton-Rapson iteration scheme in which the calculation stability is influenced by the initial points. The FSM-based dynamics calculation is timesaving and stable, so suitable for the shape prediction or real-time control of free hanging marine risers.
基金supported by the National Natural Science Foundation of China(Grant No. 50979113)the High Technology Research and Development Program of China(863 Program,Grant No. 2006AA09A105)
文摘Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the risers must be installed to act as the conduits connecting surface platforms to subsea facilities. In this paper, the typical risers sorted by different classes are introduced, and the correspondent installation methods are presented. By investigating the recent projects performed in the deepwater hot spots, and combining the challenges of HYSY20 l for riser installation, a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of 1500 m in the South China Sea. Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of 3000 m in the South China Sea.
基金supported by the National Natural Science Foundation of China(Grant No.51009089)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20100073120017)
文摘A prediction model of the deepwater steel catenary riser VIV is proposed based on the forced oscillation test data, taking into account the riser-seafloor interaction for the cross-flow VIV-induced fatigue damage at touch-down point （TDP）. The model will give more reasonable simulation of SCR response near TDP than the previous pinned truncation model. In the present model, the hysteretic riser-soil interaction model is simplified as the linear spring and damper to simulate the seafloor, and the damping is obtained according to the dissipative power during one periodic riser-soil interaction. In order to validate the model, the comparison with the field measurement and the results predicted by Shear 7 program of a full-scale steel catenary riser is carried out. The main induced modes, mode frequencies and response amplitude are in a good agreement. Furthermore, the parametric studies are carried out to broaden the understanding of the fatigue damage sensitivity to the upper end in-plane offset and seabed characteristics. In addition, the fatigue stress comparison at TDP between the truncation riser model and the present full riser model shows that the existence of touch-down zones is very important for the fatigue damage assessment of steel catenary riser at TDP.
基金Supported by the National High-tech Research and Development Program of China (863 Program) under Grant No. 2010AA09Z303the Key Project of National Natural Science Foundation of China (Grant No. 50739004)the National Natural Science Foundation of China (Grant No. 11002135)
文摘Flexible risers and steel catenary risers often provide unique riser solutions for today’s deepwater field development. Accurate analysis of these slender structures, in which there are high-speed HP/HT internal flows, is critical to ensure personnel and asset safety. In this study, a special global coordinate-based FEM rod model was adopted to identify and quantify the effects of internal flow and hydrostatic pressure on both flexible and deepwater steel catenary risers, with emphasis on the latter. By incorporating internal flow induced forces into the model, it was found that the internal flow contributes a new term to the effective tension expression. For flexible risers in shallow water, internal flow and hydrostatic pressure made virtually no change to effective tension by merely altering the riser wall tension. In deep water the internal pressure wielded a dominant role in governing the riser effective tension and furthering the static configuration, while the effect of inflow velocity was negligible. With respect to the riser seabed interaction, both the seabed support and friction effect were considered, with the former modeled by a nonlinear quadratic spring, allowing for a consistent derivation of the tangent stiffness matrix. The presented application examples show that the nonlinear quadratic spring is, when using the catenary solution as an initial static profile, an efficient way to model the quasi-Winkler-type elastic seabed foundation in this finite element scheme.
