Abstract:

The paper presents a new model which has been developed in order to perform an innovative approach to any of the marine drilling system analyses which can be required. A powerful FEM model has been assembled and validated in order to carefully analyze complete marine drilling systems in detail, also dealing with the application of environmental loads, with the hydrodynamic response, with the wellhead behavior, with the usually nonlinear behavior of the already cemented conductor pipes. This original new system includes a complete user interface containing both data generation and result presentation facilities and also an analysis program section able to perform computations and to give results for subsequent review and validation processes. The database approach has thus been developed in order to allow all the possible system components (e.g.: soil, conductor pipe, wellhead, riser, connector, vessel, structure(s), environment) to be defined, stored in memory, edited and recalled directly upon any of the possible operator's selections. These data can be brought together in order to simulate either the entire complex, or any part of it. One of the most significant conclusions shows that qualification of a conductor pipe only on the basis of the cement height is usually inadequate, and that the interdependence of the riser outcoming response with respect to the conductor foundation stiffness really has strategical importance in most cases.

Introduction

During the last few years many Authors have published good scientific papers dealing with problems concerning behaviors and responses of huge deals of individual offshore drilling system components, such as BOPs, subsea wellheads, risers, conductors, etc. The most evident and important limitation of this approach is the difficulty in identifying the onset of coupled behavior between different components, which inhibits any possible validation or further separation of the parameters which govern the global system behavior.

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