Geothermica - Test-CEM

Publieke samenvatting / Public summary

Making geothermal wells sustainable reduces financial risks, attracting investments in geo-energy. An important risk in these wells is durability of cements providing well integrity under extreme temperatures (high-enthalpy wells), large temperature variations and chemically-aggressive environments common for all geo-wells. Current cement solutions either have problems under these conditions or have not been validated for durable well-applications. This project aims to reduce risks associated with compromised well integrity and use recently gained insights in the field of materials to evaluate advanced cement systems in a wide temperature range (up to super-critical) and under thermal cycling, raise their current TRL to 5-6 by optimizing and validating them in laboratory and large-scale experiments and enabling operators to select a preferred cement formulation for target conditions.

TEST-CEM aims to reduce risks associated with geothermal well cementing and use recently gained insights to develop advanced cement systems resistant to repeated thermo-mechanical cycling and chemically-aggressive environments relevant for a wide temperature range from low-mid enthalpy geothermal up to super-critical conditions. Lastly, the project aims at better informing operators and stakeholders on preferred cement formulations for dedicated applications.

Korte omschrijving
The focus of the Dutch partners will be on cementing solutions for 'standard' low-enthalpy and the potential future ultra-deep geothermal wells. The Masterplan Aardwarmte (2018), by a consortium of partners, aims at 160 new doublets in 2030. To reach these aims it suggests that safe and durable exploitation of geothermal projects is required, this is exactly what this project aims at. This project will contribute to increasing the safety of geothermal energy, longer lifetimes of geothermal wells combined with lower maintenance costs and increasing the scope of application of geothermal, e.g. towards UDG. TNO will be mainly involved in the development of an updated OPC formulation with improved flexibility that would be relevant for the Dutch standard low enthalpy geothermal wells (up to 80-100°C) and additionally would be relevant for the potential exploration of mid-enthalpy UDG projects (up to 250°C). These will be tested at lab scale to relevant conditions. EBN will be consulted to provide an industry perspective and relevant experimental conditions.

If successful, the project will offer a protocol of cementitious materials evaluation and sustainable cementing solution for challenging geothermal wells. The weak point of likely cement sheath failure will be identified by modelling and confirmed experimentally in a wide range of conditions. - The team will report experimental data of selected cement systems before and after exposure ranging from moderate up to extreme temperatures and simulation modelling of casing-cement-formation system under these environments. - These findings will generate the knowledge about short- and long-term stability of cements with different compositions under relevant underground conditions. - The integrated information from this work will allow predicting mechanisms of cement failure and durability under a range of conditions including super-critical and proposing a robust well-integrity solution for these challenging environments. - Indications will be established to help making decisions under what conditions the tested non-OPC systems and Portland cement-based systems should preferably be used.