Title:

Geothermal Cements for Super-Critical Wells

Authors:

Toshifumi SUGAMA, Tatiana PYATINA

Key Words:

super-critical geothermal, cement, alumina cement, phosphate cement, alkali-activated cement, GEOTHERMICA, TEST-CEM

Conference:

Stanford Geothermal Workshop

Year:

2022

Session:

Reservoir Engineering

Language:

English

Paper Number:

Sugama

File Size:

3812 KB

View File:

Abstract:

This work is a part of a joint international effort to develop “sustainable geothermal well cement for challenging thermo-mechanical conditions” (Test-Cem) under the umbrella of Cofund GEOTHERMICA. The paper describes an exploratory study of cementitious composites for applications in geothermal wells under super-critical conditions. Preliminary screening of a wide range of blends was done on formulations mixed at room temperature, cured under hydrothermal conditions at 85oC (overnight) followed by overnight hydrothermal curing at 300oC and the final curing under the super-critical conditions at 400oC and pressure of 25.5 MPa (3,700 psi). The tested formulations included high-temperature Portland cement modified with silica (CaO-SiO2 system), P2O5-Na2O-CaO-Al2O3-SiO2 – based systems with varied Al/Si ratios, and P2O5-Na2O-CaO-Al2O3-SiO2-Fe2O3 phosphate systems, Na2O-CaO-Al2O3-SiO2-MgO-Fe2O3 and Na2O-CaO-Al2O3-SiO2-MgO Mg-containing systems, and Na2O-Al2O3-SiO2 cement system. Mechanical properties of the blends and crystalline phase transitions were determined after the initial curing and exposure to the super-critical conditions to understand effect of phase transitions upon materials performance. Formulations with short-term compressive strength development of no less than 6.9 MPa (1,000 psi) and stable phase compositions were identified for further testing to fully evaluate their true potential.


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