Safety Evaluation Of Offshore Platform Structure Based On On-Site Measured Data

With the advance in offshore oil & gas exploitation, there have been almost 200 fixed platforms constructed in China offshore areas. Many platforms are in the later part of their design lives, and their reliability is decreasing. On the other hand, new resource reservoirs are discovered, and these platforms are expected to continue their service. Therefore a workable techniques for safety evaluation of platform is in need.The dynamic characteristics predicted by finite element model constructed from design data usually deviate from behavior of real structure, so it is necessary to update the model to produce one that is consistent with its real behavior, which is the base for safety evaluation.As a part of the structural health monitoring system established in CB32A platform in Shengli Oil field, the finite element model of the platform is updated using the measured data, and deterministic safety evaluation and probabilistic reliability assessment of this structure are conducted. An initial finite element model is established in consideration of mass, rigidness and boundary conditions of platform structure. Updated model is obtained using the identified modes from on-site measured data. The difference between modal parameters by analytical model and identification are greatly reduced.Taking into account of the ocean environment condition at the location of CB32A, the environmental loads and their combination are determined. Then safety evaluations of this platform from both deterministic and probabilistic approaches are performed, and results show the model updating have significant influence on the outputs of structural safety evaluation.This research provides a basis for taking the advantage of monitoring data for safety evaluation of offshore platform structures.