Probabilistic Analyses for Lateral Buckling of Pipe-in-Pipe Systems

摘要

In order to meet the growing demand for oil production in even deeper waters, new technologies havernbeen developed, making the exploration of such fields possible. A system used as an alternative for therncontrol of extreme operating conditions (high temperatures and pressures) of such exploration fields is thernpipe-in-pipe system. This kind of system is extensively used in offshore applications in which exceptionalrnthermal insulation capability is required, preventing hydrate/wax formation and maintaining the productionrntemperature up to the arrival facilities.rnHowever, extreme operating conditions can cause the system to experience thermomechanical buckling,rnwhich can lead to a structural failure of the system. In order to control these thermomechanical loadsrnand ensure that pipeline is within a safe operating margin, the potential buckling formation locations needrnto be assessed and may need to be mitigated. The key point in the thermomechanical design of offshorernpipelines is to define whether the buckling phenomena should be controlled or not. The optimal solutionrnmay often involve addressing natural imperfections whilst establishing the required engineered mitigationrnmeasures.rnDesign assumptions such as the pipeline as-laid lateral Out-Of-Straightness (OOS) and the pipe-soilrninteraction parameters are common input data uncertainties existent during design of HP/HT offshorernpipeline systems. A robust design should be impervious to variations in the values of these designrnparameters, considering values that lie within reasonable and feasible limits, such that the project canrnproceed with reasonable certainty and within sensible cost limits. In this scenario full of uncertainties,rnreliability analysis has been implemented in the thermomechanical design of offshore pipeline systems.rnThe purpose of reliability analysis is to reduce the design conservatism by quantifying the probability ofrnfailure associated with the pipeline system.rnThis paper presents a novel and viable proposal for conducting probabilistic analysis associated withrnlateral buckling of a full length pipe-in-pipe system, through the application of detailed finite elementrnanalysis. The information contained in the paper can be used as guidance for future reliability evaluationsrnof offshore pipeline systems.