Study On Monitoring Technique For Deepwater Drilling Riser

Deepwater drilling riser monitoring has become a routine work of the international offshore oil drilling operation,and the smooth implementation of the work is significant to enhance the operational security of the riser system in deepwater / Ultra deepwater.Supported by the National Major Science and Technology Project “Research on Deepwater Drilling Riser Operation Management and Safety Evaluation Technology”(2011ZX05026-001-05),this dissertation studies the application of the existing riser monitoring instruments based on the environment of South China Sea and the risers equipped on the Platform.The main works are as follows:(1)Based on the investigation of the studies domestic and foreign of vortex induced vibration,this paper presents a method to make monitoring scheme for the riser VIV by theoretical analysis method.Taking into account the VIV caused by the fluctuation of current during the the riser system operation cycle,a method that can optimize sensor locations for riser VIV monitoring,is proposed from the point of the probability of each VIV mode's occurence based on the Weibull distribution theory.Those two methods are demonstrated by their application on three typical riser deployments working where the water depth is 1000 m,1500m,2000 m respectively.(2)An inverse analysis method of riser system vortex induced vibration mode is put forward,in which the feedback data is processed to extract the riser VIV frequency,and then the actual mode of excited vibration of riser system is obtained.On the basis of the inverse analysis method of riser system VIV mode,an inverse analysis method of riser system VIV mode shape is studied,that is analyzing the actual riser VIV mode shape by using the actual mode of excited vibration of riser system,combined with the relevant normalized mode shapes analysed by the finite element method,And then the fessibility and accuracy of those two methods is validated by comparing the inverse analysis result to the finite element analysis of riser system.(3)Based on the existing riser monitoring instrument shell structure,and taking the riser of the platform “offshore oil” as the object,a connecting bracket is designed to connect monitoring instrument and riser,which employs the reliable mechanical joints,convenient and rapid installation process,and doesn't fray the surface of the riser.The designed connecting bracket is applied by manufacturing the prototype and the field test of installation.Further more,a software of the riser system VIV monitoring operation management is written to bring the investigation and field application much closer.