Digital Structural Integrity Management Technique For Submarine Pipeline

More and more submarine pipelines are put into use with the advance of offshore oil and gas resources development. In poor working environment, there are many possibilities to accidents with submarine pipeline, which can cause serious damage. Submarine pipeline is a key equipment for transporting offshore oil and gas. It's significant to study safety technology for submarine pipeline. This dissertation mainly focuses on the need of offshore oil and gas transportation, with submarine pipeline as research object, which is a part of Special Research Funds for the Doctoral Program of Higher Education"Virtual Safety System and Its Engineering Application for Submarine Pipeline"and Fundamental Research Funds for the Central Universities"Fundamental Research on Risk Control Techniques Application for Deepwater Oil and Gas exploitation in South China Sea". Digital structural integrity management technique for submarine pipeline was carried on.After learning from integrity management research of pipeline, combined with GIS, computer network, virtual reality and other digital technology, the framework of digital integrity management system for submarine pipeline was designed in terms of data layer, logic layer and application layer. Using by finite element analysis method, the dynamic response and parameter sensitivity with vortex-induced vibration of a free spanning pipeline were analyzed in use of ANSYS, based on environmental load digital model and the pipe-soil coupling nonlinear model. The fatigue damage was also calculated by applying Miner linear cumulative damage formula and S-N curve method. Calculation results show that submarine pipeline span with long span, small diameter and small wall thickness is more likely to occur vortex-induced vibration if the span is on soft soil under large current speed. According to the unascertained measure theory, the index of safety assessment on consideration of factors that influencing submarine pipeline safety and unascertained assessment model were constructed by determining index weight on the base of information entropy, the credible degree rule was used to deal with the value of unascertained measure to judge the grade of submarine pipeline and the radar char was provided to show the result. Hierarchy structure and detailed work processes of submarine pipeline digital integrity management system were set up. By using Visual Basic tools, digital integrity management program to submarine pipeline was developed by integrating with ANSYS, MATLAB software and ACCESS database, which were composed by nine modules including digital loads modeling module, the overall structure digital modeling module, stability analysis module, reign strength analysis module, pipeline span analysis module, limited span sloving module, reliability analysis module, VIV fatigue analysis module and data output module. Test results show that the simulation module has enough precision and practical value through testing software by which engineering examples are calculated. Combined with simulation results, safety warning model to submarine pipeline based on risk assessment was established, also the models of digital safety warning to corrosion and pipeline span were structured to analysis error of BP neural network prediction using by finite element and BP neural network technology through building sample database of safety warning on two main failure modes including pipeline corrosion and pipeline span. Finally, the modules of safety warning were carried out.