| Abstract |
Thermal and structural modeling of multi-cased high-temperature geothermal wells have shown that permanent plastic strains are formed as wells warm-up to production temperatures subsequently can cause severe casing failures. Additionally, thermally expanding annular fluids and/or thermal cycling can contribute to collapse of the production casing, greatly impacting productivity. Casing design for deep geothermal wells has been improved and streamlined over the decades, e.g. by standardization, particularly by the New Zealand standard for deep geothermal wells. However, well design and available state-of-the-art materials have their limits. Mainly due to elevated temperatures and thermal expansion of constrained cemented casings along with harsh chemical conditions. Budget limit of geothermal projects largely prevent selection of desirable but expensive CRA materials and such materials do not solve all issues. Attempts to harness superhot geothermal resources, e.g. in the Iceland Deep Drilling Project (IDDP) and other deep drilling projects around the world, have shown that casing failures limit their success. Novel technology, e.g. improved casing selection options, novel casing connections combined with appropriate cementing procedures, have the potential to meet these goals. The paper discusses the main challenges and potential solutions for future well designs for conventional high-temperature to ambitious ultra-high-temperature geothermal wells. The patented Flexible Couplings have been developed within ÍSOR from the year 2015 within several research projects (EU Horizon 2020 supported GeoWell and DEEPEGS, and GEOTHERMICA project GeConnect) and a patent pending Annular Pressure Relief Casing Collapse Preventor is in development within the EU Horizon Europe supported project COMPASS. |