Structural and Thermal Optimization of Cased Insulated Flowlines

Abstract

Flow assurance and associated thermal insulation of pipelines is an important part of exploitation of deepwater reservoirs. Insulated pipelines and bundles offer a reliable and cost effective solution for deepwater flow assurance. Flexibility of pipe-in-pipe configuration in selection of geometrical parameters, pipe materials, and insulation materials allows optimizing thermal and structural properties of pipelines for specific water depth and operation requirements.The model proposed herein addressed the synergy between the design issues related to the structural performance and the thermal performance of the pipelines. The structural design of pipe-in-pipe is governed by buckling and collapse resistance of both inner and outer pipes, as well as the weight and overall stiffness of the pipeline. The stress state in each layer needs to be calculated during installation, operation, and maintenance conditions to address the structural design issues. The thermal insulation characteristics of the bundles are primarily governed by the geometric parameters and thermal conductivity of pipe materials, especially that of the insulation layer.