Research On Integrity And Typhoon Accident Coping Strategy For Deepwater Drilling Riser

This dissertation is supported by the National Major Science and Technology Project “Research on Deepwater Drilling Riser Operation Management and Safety Evaluation Technology”. According to the site actual drilling demand of HYSY981 and NH8 platform, systematic research on integrity and typhoon accident coping strategy for deepwater drilling riser has been carried out based on natural environments of the South China Sea. The research covers fatigue analysis of deepwater drilling riser system, local fatigue and its reliability analysis of riser, multi-failure analysis of riser, integrity management of riser, accident analysis and typhoon accident coping strategy of riser, which acquires major progress. The theory of integrity assessment and management for deepwater drilling riser is enriched. Analysis method and coping strategy for deepwater drilling riser accident in typhoon condition is established. The research findings provide effective technical supports for the pre-drilling design, integrity assessment and management and typhoon coping strategy of deepwater drilling riser. 1 Research on fatigue analysis methods for deepwater drilling riser systemWave-induced fatigue analysis methods for deepwater drilling riser system are studied. Wave-induced fatigue analysis models based on time-domain method and frequency-domain method are established respectively. Strategy for riser wave-induced fatigue analysis is determined based on the comparison of computational efficiency and accuracy between two wave-induced fatigue analysis methods. And a method for selecting wave-induced fatigue analysis parameters under different operation modes is proposed. Then vortex-induced fatigue analysis method and process are established. Simulation method of long-term current condition is proposed in order to improve the computing accuracy. The combined fatigue analysis method is created based on Miner criterion. The fatigue hotspots and occupancy of different fatigue damages are identified. In a word, analysis methods and relevant parameter selecting methods for wave-induced fatigue, vortex-induced fatigue and combined fatigue are established, which contribute to normalization and routinization of riser fatigue analysis. 2 Research on local fatigue and fatigue reliability of deepwater drilling riserRiser fatigue fracture analysis method, local fatigue analysis method and dynamic fatigue reliability analysis method are firstly developed. Methods for fatigue crack growth calculation and fatigue engineering critical assessment of riser under random load are established. Fatigue crack propagation curve, dynamic failure figure, maximum inertial crack size and critical crack size of riser are determined, which can supply reference to engineering. Local fatigue analysis method and process of riser connector are proposed. The analysis process includes dynamic analysis of riser system, equivalent fatigue stress calculation, finite element analysis of riser connector and multi-scale fatigue analysis of riser connector. Fatigue reliability analysis models for riser joint, riser system and operation of riser system are built. Fatigue reliability analysis methods are studied and the analysis strategy is determined. 3 Research on multi-failure analysis methods of deepwater drilling riserMechanical analysis method for multi-string system is studied. Finite element analysis model for drilling riser-drillstring coupled system is established based on gap element. Coupled mechanism for drilling riser and drillstring is reveled and wear hotspots are identified. Cumulative wear volume of drilling riser during a well drilling and completion is proposed. Theory calculation methods for riser collapse are summarized systematacially and a non-linear finite element analysis model for riser collapse is also established based on Riks method. Analysis method for riser collapse in complicated load condition is established with consideration of riser axial force and bending moment. And the theory method and finite element method for riser collapse analysis are verified by analyzing the actual riser collapse accident happened in the Gulf of Mexico. The quantitative evaluation model for cumulative damage and resistance degradation of riser under the influence of different defect types and failure modes is established. The analysis methods for fatigue reliability and collapse reliability of riser under the influence of corrosion and wear are proposed. 4 Research on integrity management of deepwater drilling riserIntegrity management program of deepwater drilling riser is established. And the relevant key technologies of riser integrity management are solved, including risk assessment, risk based inspection, integrity management criteria and methods, and electronic tag and identification of riser. Reliability updating models for riser fatigue and collapse are built based on Bayes theory considering riser inspection and maintenance. And the relevant calculation method and process for reliability updating are proposed, including normalizing of random variables, standard normalizing of random variables, linearization of limit state equation and failure probability calculation. Optimization method for riser inspection and maintenance is established based on least cost criterion considering different defect types and failure modes. And the relevant analysis process is proposed based on genetic algorithm. In order to simplify the application of riser integrity management technology, drilling riser integrity manage system of HYSY981 is developed with Visual Basic 6.0. 5 Research on accident analysis and accident coping strategy of deepwater drilling riser in typhoon conditionIn terms of the riser grounding accident happened in the South China Sea, a mechanical analysis model of deepwater drilling riser grounding is established based on large angle deformation theory. The mechanical characteristics of riser grounding, equipment failure reasons and potential failure risk are identified. The analysis method and process for riser retrival operation window are proposed and the relevant retrival operation program is determined. In terms of the riser fracture accident happened in the South China Sea, analysis methods for riser hangoff dynamics and hangoff fracture accident are established. The risk of LMRP and BOP retrival operation is identified and the analysis process of retrival operation window is proposed. In addition, prevention measures of riser accident in typhoon condition are studied. An accident prevention program for drilling riser in typhoon condition is established considering typhoon prediction, typhoon emergency, hangoff mode and stormsafe drilling riser. Then the coping strategy for riser in typhoon condition is developed.