CO2 Pipeline Integrity: Comparison of a Coupled Fluid-structure Model and Uncoupled Two-curve Methods

Abstract

One challenge in CCS is related to the prevention of running-ductile fracture in CO 2 -carrying pipelines. Commonly used tools for ensuring crack arrest in pipelines hinge mainly on semi-empirical models, which may not be appropriate for CO 2 transport since they have been developed and fitted for natural gas and older pipeline materials, and due to an assumed decoupling of the fluid decompression and fracture propagation phenomena. In this paper, we apply a coupled fluid-structure model to a case with pure dense liquid CO 2 in a modern high-toughness steel pipeline, and compare the results one would obtain from directly applying the uncoupled models to the same case without any re-fitting to test data. For this case, the coupled model indicates that a significantly thicker pipeline wall may be required to prevent running-ductile fracture than what is predicted by the uncoupled models. Therefore, using the uncoupled models for such cases might not be conservative.

Depressurization of CO2-rich mixtures in pipes: Two-phase flow modelling and comparison with experiments

“…It has been found that a pipeline transporting CO 2 will be more susceptible to running-ductile fracture than one carrying natural gas (Mahgerefteh et al, 2012;Aursand et al, 2014). One part of the design to avoid running-ductile fracture necessitates accurate models predicting the depressurization behaviour of the relevant CO 2 -rich mixtures, noting that existing semi-empirical models have been deemed not to be directly applicable to CO 2 pipelines (Jones et al, 2013).…”

Hybrid fluid–structure interaction modelling of dynamic brittle fracture in steel pipelines transporting CO 2 streams

“…Recently several authors have developed methodologies to couple pipeline outflow and crack propagation models (Greenshields et al, 2000;Aursand et al, 2014;Mahgerefteh et al, 2012;Nordhagen et al, 2012). These methodologies are largely based on the Homogenous Equilibrium Mixture (HEM) model of pipe flow and utilise various models describing the pipe wall rupture, ranging from HLP-type models (Makino et al, 2001;Mahgerefteh et al, 2012) to FEM models accounting for ductile fracture of elasto-plastic material (Aursand et al, 2014). While the above studies have been focused on simulation of ductile fractures, modelling of the brittle mode of pipeline failure has not received as much attention yet.…”