High pressure dual casing drilling risers have been installed on spars and tension leg platforms. These systems have the BOP at the surface, on the platform. During drilling operations differential temperatures between the inner riser and outer riser have been observed. The inner riser is typically held in pre-tension to avoid compressive stresses. Pre-tension loss may occur in the inner riser due to differential thermal expansion. In the past, an expansion joint has been utilized to accommodate the thermal expansion of the inner drilling riser (IDR). A new strategy proposed is to overpull the inner riser before transferring to the drilling riser tensioner (DRT) and connecting to the outer riser. Overpulling prevents compression at the bottom of the inner riser after expansion due to thermal loads. This paper presents a methodology of and procedure for tensioner schedule (tension adjustment) during the drilling riser installation stage. The dual casing drilling riser installation sequence is modeled using general purpose non-linear finite element software, ABAQUS. The finite element (FE) model consists of an inner and outer riser with the interaction simulated using pipe-in-pipe elements. Critical steps of the inner and outer casing installation sequence are simulated. Thermal loads, due to the temperature variation from the inner to outer riser, are taken into account in the warm up steps. The riser tension redistribution in each string is extracted from the analysis. The optimized drilling riser top tension is then determined. Finite element analysis (FEA) results are also verified using an analytical tool.
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