Theoretical prediction model for indentation of pipe-in-pipe structures

Abstract

Pipe-in-pipe structures have been widely used in deepwater offshore oil and gas fields because of its excellent thermal insulation, good stability and outstanding resistance to thermal and external loads. Unfortunately, there is no theoretical prediction model for studying the indentation of pipe-in-pipe structures which is important in improving its design and optimization. In this paper, a theoretical model is proposed to predict the indentation of pipe-in-pipe structures by evaluating three stages of PIP indentation: the indentation of outer pipe only, the indentation of rigidly supported outer pipe and overhanging inner pipe, and the indentation of rigidly supported outer and inner pipes, which forms that describes the mechanical behavior of the inner and outer pipes of the PIP system. Finite element models of the lateral and normal sections of pipe-in-pipe are established and analyzed at each loading and indentation conditions of the inner and outer pipes. Parametric analysis of PIP properties is conducted to evaluate their effects on the nature of pipe-in-pipe indentation. The results of the comparative studies show that the proposed model has a better performance and provides a theoretical solution for design and analysis of pipe-in-pipe structures.