The GRE-GEO workshop series, which took place on September 18 at Celle Drilling 2024, was a complete success. Under the direction of Javier Holzmann from Clausthal University of Technology, around 40 participants came together to discuss the results and progress of the GRE-GEO project. The workshops formed the conclusion of the Celle Drilling event program and were among the highlights of the conference.

In a total of four sessions, different topics related to the comparison of glass fiber reinforced epoxy (GRE) and steel in geothermal applications were discussed. In addition to the workshops, project partner Future Pipe Industries presented the project at its own GRE-GEO stand.

In the first workshop, Ferid Seyidov (Vulcan Energy) gave a comprehensive overview of the origins, objectives and partners of the GRE-GEO project. He presented the newly developed GRE borehole design and the custom-made GRE handling tool from Drilltec. In addition, Seyidov explained the HAZID (Hazard Identification) analysis, which was specially developed for fiber-reinforced thermoplastic pipes (FRTP), and showed its importance for various project aspects such as wear resistance. He concluded by discussing new tools developed specifically for the testing and design requirements of the project.

Stefan van der Sar (NRG) then compared steel and GRE-based geothermal systems in terms of conventional and radioactive deposits. He pointed out that the deposits on GRE adhere three to ten times less than on steel, which is mainly due to the lower hardness of the GRE material. This finding was integrated into a model developed in the project, which takes the entire geothermal pipe system into account. With this approach, the overall benefit of GRE in terms of deposition rates is slightly lower, but still significant. There is no difference in the radioactivity concentration (Becquerel per gram of deposit) between steel and GRE-based wells, but the total radioactivity (Becquerel) builds up more slowly with GRE.

Leo de Mul (Dynaflow) presented the mechanical properties of GRE pipes under surface and underground conditions and presented the differences between GRE and steel in terms of load-bearing capacity, time-dependent material behavior and methods for determining performance. A key result was the development of an empirical-analytical prediction curve for the collapse pressure as a function of the pipe wall thickness (D/t ratio), which will serve as a basis for future research and further developments in underground applications.

Javier Holzmann (TU Clausthal) showed how traditional steel standards can serve as a basis for new GRE standards, with a special focus on the API 5CT/5C3 and API 5C5 qualification tests for pipes and joints. He explained how experience from ISO 14692 for composite pipes can be combined with API standards to improve the design of laminates and joints for geothermal applications. Holzmann proposed a method to bridge the gap between these standards and increase the acceptance of GRE materials in geothermal applications. His presentation ended with an outlook on a key project goal that the GRE-GEO team is currently finalizing: a guideline for the design and qualification of composite pipes for low-enthalpy geothermal wells, specifically adapted to new operating conditions.

As the GRE-GEO project funded by the GEOTHERMICA program draws to a close, this series of workshops has successfully showcased the project’s significant progress and contributions to the advancement of geothermal technology. The presentation materials will soon be available for download on the project website.

We would like to thank all participants and visitors for their active participation and contribution to this successful event.