Geothermal drilling using reprocessable shape memory polymer nanocomposite

Abstract

The use of efficient lost circulation materials (LCMs) is essential to reducing fluid loss in geothermal wells. The purpose of this work is to assess novel reprocessable smart shape memory polyurethane (SMPU) LCMs based on SMPU silica nanocomposite for geothermal drilling. Improving the recyclability of SMPU LCMs enhances resource utilization and minimizes drilling fluid waste. The novel isocyanate/amino-terminated surface of the modified silica nanoparticles (MSNPs) was chemically incorporated into the polyurethane during the synthesis of SMPU nanocomposite using an in-situ two-step polymerization method. The results show that the chemically integrated MSNPs effectively reinforce the SMPU matrix by improving the dispersion of the silica nanoparticles relative to unmodified silica-SMPU nanocomposites. After three cycles of the shape memory test, MSNPs-SMPU showed remarkable shape memory stability with a shape recovery ratio of over 80%. Fracture sealing at conditions encountered in geothermal drilling demonstrated 4% higher sealing pressure for MSNPs-SMPU LCMs coupled with 11% lower fluid loss, which increased drilling procedure safety and environmental protection. MSNPs-SMPU LCMs offer excellent reprocessability without affecting the fracture sealing capability. On the other hand, commercial Mica LCMs showed an 83% drop in fracture sealing pressure in their third cycle owing to particle crushing.