Double network self-healing hydrogel based on hydrophobic association and ionic bond for formation plugging

Self-healing hydrogels have attracted tremendous attention in the field of oil and gas drilling and production engineering because of their excellent self-healing performance after physical damage. In this study, a series of double network self-healing (DNSA) hydrogels based on hydrophobic association and ionic bond were prepared for plugging pores and fractures in formations in oil and gas drilling and production engineering. The mechanical, rheological, and self-healing properties of the DNSA hydrogels were investigated. Results revealed that the DNSA hydrogels exhibited excellent mechanical properties with a tensile stress of 0.67 MPa and toughness of 7069 kJ/cm3 owing to the synergistic effect of the double network. In addition, the DNSA hydrogels exhibited excellent compression resistance, notch insensitivity, and self-healing properties. The DNSA-2 hydrogel was granulated and made into gel particles with different particle sizes and used as a plugging agent. The self-healing mechanism of DNSA-2 hydrogel particles in fractures was explored, and it's plugging effect on fractures of different widths and porous media of different permeabilities were investigated. Experimental results revealed that the plugging capacity of the DNSA-2 hydrogel particles for a fracture with width of 5 mm and a porous medium with a permeability of 30 μm2 was 3.45 and 4.21 MPa, respectively, which is significantly higher than those of commonly used plugging agents in the oilfield. The DNSA hydrogels with excellent mechanical and self-healing properties prepared in this study will provide a new approach for applying hydrogels in oil and gas drilling and production engineering.