Abstract
In the transition from fossil fuels to sustainable, renewable energy sources, development of geothermal energies sources provides an important contribution to ensure the green shift. Per today, most geothermal wells operate at a temperature range of 150–300 °C, but in order to increase power production, a transition to more supercritical conditions (∼500 °C) is needed. It is generally accepted that Ordinary Portland Cement (OPC) is not suitable for supercritical wells.
In this paper we report mechanical properties and pressure cycling-test (function tests) results of two alternative Calcium-Aluminate-Cement (CAC)-based systems at 300°C and 400°C hydrothermal conditions.
Down-scaled simplified functional tests to mimic well-start up have been performed to evaluate cement sheath integrity under cycling pressure and constant temperature. The setup consists of a downscaled section of a wellbore with casing-cement-rock, and with the use of a pressure shaft inside the casing pressure cycling experiments are performed to investigate the cement sheath integrity and degradation under the increasing pressure loadings. Lower strength and Young’s modulus CAC/silica flour blend failure pressure was higher than that for CAC/silica/phosphate blend. Both CAC formulations outperformed OPC/Silica HT blend.
