Development of downhole sealing tools undergoing deeply self-degradation following sealing operations in unconventional oil and gas extraction is becoming a big challenge. In practical engineering applications, materials must undergo complete disintegration into fine fragments or powder under hydrothermal conditions. The degradation products should be able to pass through a 4 × 4 mm mesh without external force. In this study, calcium oxide (CaO) composited water-degradation millable polyurethane (MPU) composites were prepared employing CaO as a degradation accelerator in the composite system. The degradation behavior of MPU composites in a hydrothermal environment at 100°C was systematically investigated. As demonstrated by scanning electron microscopy (SEM) and optical photographs, the presence of CaO exacerbated damage to the composite surface morphology. The degradation mechanism was elucidated at the molecular level using techniques such as Fourier-transform infrared spectroscopy (FTIR). At a loading of 20 phr CaO, the PU composites disintegrated into powder within 24 h, passing through a 4 × 4 mm mesh. The incorporation of CaO into MPU achieves deep degradability of polyurethane, providing modified insights and an experimental foundation for the development of high-performance, deeply degradable downhole tool sealants.

Keywords: deeply degradable, calcium oxide, degradation behavior, millable polyurethane, aqueous medium.