Dynamic alteration behavior of granite under SC-CO2: proposal for a long-term accelerated test method

• Published in: Bulletin of engineering geology and the environment Vol. 81; no. 8
• Main Authors: Zhang, Qingsong, An, Qiyi, Yu, Hao, Li, Xianghui, Yin, Zhanchao, Zhang, Xiao
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2022
• Subjects: Earth and Environmental Science; Earth Sciences; Foundations; Geoecology/Natural Processes; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Nature Conservation; Original Paper; Dynamic alteration damage; Supercritical carbon dioxide; Rock mechanics; Granite; Accelerated test
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-022-02842-5

The efficient development of hot dry rock (HDR) using supercritical carbon dioxide (SC-CO 2 ) is severely restricted by the deficient mastery of the long-term damage laws of HDR reservoir. In this study, an accelerated test method for the long-term dynamic alteration damage of SC-CO 2 to granite was proposed. First, the feasibility of dynamic alteration accelerated test was verified by literature review. The rationality of increasing temperature as an acceleration method was analyzed and verified from three aspects of the acceleration mechanism on alteration damage, the effect on granite mechanical properties, and the effect on solution acidity. On this basis, the accelerated test method was proposed as follows: (1) perform high-temperature test as preparation, so as to obtain the linear equations of granite deformation characteristics with temperature. (2) Set the accelerating temperature, calculate the acceleration factor and reaction period, control temperature as the single variable, and perform the accelerated test to further obtain the mechanical properties. (3) Directly take the measured strength in accelerated test as the target strength, and convert the measured deformation characteristics to the target results without acceleration by the linear equations of deformation characteristics with temperature. The accuracy of accelerated test method was verified by comparing the mechanical properties of altered granite measured in accelerated and unaccelerated tests. As an application, this method was adopted to obtain the long-term dynamic alteration damage within 2 months.