Cost-Effective Sealing of Geothermal Wells by Modifying Existing Elastomers

Abstract Sealing a geothermal well has been a challenging problem due to high temperatures surrounding the well, which may induce thermal deformation and degradation to the constituent polymer of a seal, impairing the hydraulic integrity of the well and thus reducing the thermal energy production of the well. To address this issue, this study focuses on developing an advanced nano-reinforcement technique to create thermally resistant polymer nanocomposites for sealing geothermal wells. The surface property of graphite nanoplatelets (GNPs) is improved via acid functionalization introducing stable carboxyl (-COOH) groups. Subsequently, polymeric nanocomposites are synthesized by respectively compounding various concentrations, namely 1.5 wt.%, 3.0 wt.%, 6.0 wt.%, and 9.0 wt.%, of modified GNPs with ethylene propylene diene monomer (EPDM). The compounding method enables GNPs’ dispersion within the EPDM matrix and GNPs’ connection to the matrix. It is found that incorporating 6.0 wt.% of modified GNPs increases the high-temperature storage modulus of EPDM by up to 210.11% and enhances the loss modulus by 156.27%. Compared to pure EPDM, the developed nanocomposites demonstrate superior deformation resistance by effectively dissipating energy. Furthermore, the nanocomposite containing 6.0 wt.% of GNPs possesses noticeably higher thermal stability than pure EPDM. These findings suggest that this prepared nanocomposite holds significant potential as a sealing material for geothermal wells.