Tough, Notch-Insensitive, Heat-Resistant Hydrogels Constructed by Vinylated Polylysine for Temporary Oilfield Water Plugging

Polyacrylamide hydrogels make up a category of widely used oilfield water-plugging agents. However, their poor mechanical properties and insufficient heat resistance severely limit their applications. In this work, a novel strategy for the construction of tough and heat-resistant polyacrylamide hydrogels using vinylated modified polylysine (PLL) as a multifunctional cross-linker (named APLL) is proposed. The multifunctionality of APLL leads to a three-dimensional network of hydrogels containing a uniform network structure that distributes stress and a dynamic cross-linked structure that dissipates energy. Meanwhile, APLL retains the thermal stabilization properties of PLL, and its use as a cross-linking site in the polymer network can effectively improve the heat resistance of hydrogels. As a result, hydrogels exhibit ultrastretchability to 3295%, excellent notch-insensitivity (75% prefabricated notched samples still have a fracture energy of 15,728 J/m2), and good heat resistance (better aging performance than N, N-methylene bis-acrylamide cross-linked hydrogels at 130 °C). In addition, the saline suspension composed of preformed gel particles of APLL cross-linked hydrogels can age at 80 °C for more than 10 days and effectively seal the pores with a sealing rate of 95% in percolation experiments. Such mechanical properties, notch insensitivity, and heat resistance enable the APLL cross-linked hydrogels to serve as a potential temporary water-plugging agent for heterogeneous reservoirs of the oilfield.