Preparation of Self-Healing Polyurethane Based on the Phase-Locking Effect and Application for Lost Circulation Control

Summary Lost circulation is a critical technical challenge in the process of drilling. Lost circulation materials (LCMs) with self-healing properties offer an effective method for lost circulation control by forming an integrated plugging layer within fractures. The phase-locking effect enables the confinement of dynamic bonds within the hard segment phase of self-healing polyurethane (PU), thereby restricting their kinetic exchange and controlling the self-healing properties of the material. In this work, a PU elastomer (HS-PU) with heat resistance and self-healing properties was prepared by using hydroxyl-terminated polybutadiene (HTPB) as the soft segment and 4,4'-diphenylmethane diisocyanate (MDI) as the hard segment and introducing dynamic disulfide bonds. HS-PU was systematically characterized by Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and thermogravimetric analysis. HS-PU exhibited excellent water resistance, and the retention rate of the tensile strength was as high as 91.3% after soaking in water for 36 hours. Besides, HS-PU has good heat resistance and can achieve self-healing in the range of 110–150°C, and the self-healing rate increases with increasing temperature. The pressure-bearing capacity of HS-PU at 130 and 150°C is 4 and 3.5 MPa, respectively, and the capacity can reach 13 MPa after the addition of bridge-plugging materials. Moreover, HS-PU still has excellent pressure-bearing performance in water-based muds (WBMs). This work provides a new approach for controlling lost circulation in complex formations at the field and developing heat-resistant self-healing LCM, holding significant practical importance for ensuring safe and efficient drilling operations.