Evaluation of Physical and Chemical Properties of High-Temperature Cement for Supercritical Geothermal Wells

Abstract This study evaluates cement materials for supercritical geothermal wells by examining the properties of candidate cement samples exposed to extreme temperature and pressure conditions (450 °C, 37.9 MPa). Two types of cement, a commercial geothermal well cement (GWC) and a newly developed high-durability calcium aluminate cement (CaC), were compared for compressive strength and water permeability. After two weeks of immersion in supercritical water at 450 °C and 37.9 MPa, CaC achieved 15.5 MPa strength and low permeability (<0.001 mD), meeting the required standards, while GWC showed strength degradation. These results demonstrate the potential of CaC for practical application, with further tests on pipe cement planned to enhance its suitability for real-world use. In addition to the above experiments, XRD and SEM analyses were also carried out.