The key to improving geothermal efficiency is preventing or controlling deleterious physical and chemical reactions such as degassing and mineral precipitation that result in corrosion and scaling.

Within the framework of the REFLECT project, experiments have been carried out to investigate how degassing can be prevented. One of these experiments is the recent milestone ‘Refit pre-existing PEEK core holder for CT monitoring’. This milestone has been achieved by the use of PEEK (polyether ether ketone) core holder in CT assisted coreflood experiments, i.e. gas-brine flow experiments in rock cores.

The experimental setup has been designed for visualising the emergence of free gas bubbles during CO2-brine coreflood experiments and to determine to which extent the flow is affected by these bubbles. A 40 cm long and 4 cm diameter rock core is housed inside a PEEK core holder, which is placed horizontally inside the CT scanner. PEEK is used due to its minimised effect on the CT scans compared to other materials. The pressure along the length of the core is monitored during the experiments to assess the effect that the free gas bubbles have on the flow inside the rock core using various pressure transducers. Pressure within the core itself is measured at five locations and additional transducers are installed up- and downstream of the core.

Figure: Photograph of the core flooding setup in the CT scanner

The setup is meant for use at ambient temperatures at pressures up to 100 bar. The core holder is capable of withstanding elevated temperatures up to 90 °C, but this would require heating elements that do not cause any CT scanning artefacts. Tubing and connections in direct proximity to the core holder are also made of PEEK such that these also do not cause scanning artefacts. Most of the setup is installed on the sliding table of the CT.

These experiments show that the setup is capable of capturing details of the evolution of the gas front inside rock cores as a function of the pressure.

With this work, the REFLECT project has achieved a new milestone that will contribute to the research for the better operation of geothermal systems for sustainable use.