Performance of Geopolymers in Geothermal Wells

ABSTRACT Geothermal wells play an important role in harnessing geothermal energy stored underground as the push for the strategic development of renewable energy increases. The use of conventional wellbore cement in geothermal wells is commonly associated with challenges due to the harsh and highly corrosive environment encountered in geothermal wells. In this study, we numerically evaluated the performance of a granite-based geopolymer based on its mechanical properties under different underground conditions, such as normal (30°C), moderate temperature (90°C), and elevated temperature (120°C). The elastic parameters of the geopolymer were evaluated under triaxial testing. The values were then input into the numerical model to perform a finite element analysis (FEA). Thermal loads were considered when evaluating the effect of temperature on cement performance. Hoop and radial stresses around the wellbore are presented. This study highlights the advantages of the granite-based geopolymer applied in geothermal well conditions. INTRODUCTION Global warming is a fact, and green transition is a must. Geothermal energy is a sub-set of geo-energy that has demonstrated its potential in locations such as Reykjavik in Iceland, San Diego in California, and Turin in Italy. The primary cost drivers associated with geothermal energy production are subsurface activities, including well construction and maintaining well integrity. Poor zonal isolation or loss of well integrity can significantly increase the capital and operational expenses associated with geothermal energy production. Zonal isolation is crucial, and cement is the prime material used for well cementing applications in geothermal wells. However, the performance of API class G cement in temperatures above 120 °C is negatively impacted by retrogression and thus excess source of silica is required (Wang et al., 2017). Furthermore, the shortcomings of cement and the environmental impacts of Ordinary Portland Cement (OPC) production have led to the search for alternatives to fully replace OPC (Arbad & Teodoriu, 2020; Carey et al., 2007). Of these materials, one may refer to geopolymers, blended cement, and pozzolanic cement (IEA, 2022).