Flexible Pipe Integrity Management by Experimental Assessment Under Industrial Lab-Scale Conditions – LAB-TWIN

Abstract

This paper describes innovative methodologies in industrial lab-scale, named LAB-TWIN, developed within a joint industry project (JIP) for flexible pipes integrity assessment under harsh environments, focused on CO2 induced failure phenomenon (SCC CO2). The LAB-TWIN comprises applying specific conditions according to the pipe application – e.g., production oil (PO), gas injection (GI) – to assess gas permeation through the pipes and explore the SCC CO2 degradation mechanism in a controlled environment, from initiation until failure. To reproduce, as closely as possible, the operational field conditions, the experiments were designed to allow the application of specific boundary conditions in flexible pipe sections, including chemical content in the pipe bore (such as gas mixtures and oil), internal and external pressure and temperature, and axial static loads. The flexible pipe samples were assembled with customized test end-fittings that provide privileged annulus access, allowing the monitoring and measuring of annulus conditions throughout the tests. The samples were submitted to a corrosion process called degradation. After this period (months or even years), each pipe sample is dissected and inspected. Then, the materials are assessed at the laboratory level to determine the environmental impact in their main mechanical properties. During the experiments, the gas permeation phenomenon through the polymeric layers occurs. It allows the generation of experimental data that can be used to calibrate theoretical permeation models based on annular pressure building up and annulus environment content, such as CO2. The LAB-TWIN delivers valuable data to support permeation methodologies, better understand the SCC CO2 phenomena, and the up-to-date assessment of the flexible pipes service life prediction.