CO2 Transport

Chief Scientist
473 78 042

CO2 pipeline integrity

Overall objective:
To develop a coupled fluid-structure fracture propagation model to enable safe and cost-effective design and operation of CO2 pipelines.

CO2 Pipeline integrity and its importance for CCS

Most large-scale implementations of CCS will require CO2 to be transported as dense phase in a pipeline. Parts of this CO2 transportation will in some situations interfere and be visible from areas with public access. For public acceptance of CCS, it is therefore of great importance that such pipelines are considered not to pose a threat to public safety.

A particular challenge for pipeline transport of CO2 in dense phase (compared to e.g. natural gas), is the risk of long running fractures in the pipeline. Due to the two-phase behaviour of CO2 during decompression from dense phase — e.g. as a result of a rupture caused by third party impact — a high CO2 saturation pressure might cause a fracture to propagate for a long distance unless the pipeline material has sufficient fracture resistance.  Though there is a DNV recommended practice (RP-J202) on design and operation of CO2 pipelines, there are today no established methods, standards or tools to assess and predict the behaviour of running fractures in CO2pipelines. It is the aim of Task 2.1 to provide a numerical tool and method that can be used to provide safe and cost-effective design and operation of CO2 pipelines.

Contribution to the overall objectives of BIGCCS
The International Energy Agency’s two-degree scenario is one realistic way of limiting the global warming to 2 °C. In this scenario, CCS accounts for about 1/5 of the CO2-emission reduction in 2050, corresponding to seven billion metric tonnes per year.

Fracture propagation control (FCP), that is, the estimation of risk of long running fractures, is of great importance in design and operation of high pressure pipelines. For natural gas and hydrogen pipelines, FCP is well handled by existing (empirical) methods. However, there is limited worldwide experience in design and operation of CO2 pipelines. Mainly due to the two-phase behaviour of CO2 during decompression from dense phase, today’s FPC methods yields non-conservative estimates of the required pipeline properties. An important element in reducing cost, while maintaining the highest safety, is to understand how long running fractures in the CO2 pipelines can be avoided. This is what we aim for in BIGCCS Task 2.1.

Task 2.1 achievements thus far

  • A coupled fluid-structure  fracture propagation-control model has been developed, and it has been verified using  data from hydrogen and methane crack-arrest experiments.
  • The coupled fluid-structure model has been extended to account for CO2 properties, including the formation of solid CO2.
  • Five journal articles and three conference articles have been published
  • One PhD has been completed.
We aim to avoid running fractures in a cost-effective way by developing physics-based models.
We aim to avoid running fractures in a cost-effective way by developing physics-based models.

 

Related publications

CO2Mix: CO2 mixture properties

Overall objective:
To acquire accurate data for thermophysical properties of CO2-rich mixtures at conditions relevant for CCS.

Contribution to one or more of the overall goals/objectives of BIGCCS

CO2 captured in a CCS process will never be absolutely pure. Even small quantities of impurities can significantly affect the thermophysical properties of CO2. Therefore, to be able to design capture processes, transport systems and injection schemes, we need high-quality data for the various impurities in the relevant range of concentrations, pressure and temperature. Presently, there are several white areas on the map, and we aim to fill some of them.

Task 2.2 achievements thus far

  1. Accurate experimental setups have been constructed to measure the following properties of CO2-rich mixtures
    • Vapour-liquid equilibrium
    • Density of gas and super-critical phases
    • Speed-of-sound of gas and super-critical phases
  2. All setups are currently conducting measurement campaigns
  3. Two PhD candidates are being educated
  4. Three conference articles have been published, and several presentations at scientific conferences held

Phase Equilibrium Cell for CO2 Mixtures (SINTEF ER)


The phase equilibrium setup is using an analytical technique and allows for very precise control of pressure and temperature. The film clip above shows the magic moment of phase separation as the pressure of a CO2-N2 mixture is reduced from supercritical to subcritical.

Density and Speed of Sound Measurements (Ruhr-Universität Bochum)
The speed of sound meter measures the echo time of short acoustic pulses. The density is found by measuring the buoyancy of a single sinker using a magnetic coupling technique developed at RUB. The two apparatuses are connected by the same manifold such that the two properties easily can be measured for the same mixtures.

Pulse-echo cell for speed of sound measurements
Pulse-echo cell for speed of sound measurements
Single sinker densimeter and manifold
Single sinker densimeter and manifold
Professor Span and Markus Richter at work
Professor Span and Markus Richter at work

Related publications: