Conjoined-network induced highly tough hydrogels by using copolymer and nano-cellulose for oilfield water plugging

Hydrogels have been widely adopted for in-depth water control in mature oilfields, however, the poor mechanical properties limit their application. Herein, a conjoined-network induced hydrogel was prepared through the in-situ free radical copolymerization of acrylamide (AM), Acrylic acid (AA) and N,N′-methylenebis(acrylamide) (MBA) in the presence of nano-cellulose (CNF/ACNF), and the coordination effect between aluminium ion and carboxyl. The results showed that a small amount of nano-cellulose (0.2 %) increased the compressive strength of the hydrogel by 7 times. The presence of nano-cellulose endowed the hydrogel with excellent thermal stability and high shearing elasticity, at the same time, could effectively reduced the swelling rate that hindered its disintegration in practical application. The evaluation of sand-pack plugging suggested that the double cross-linked nano-cellulose hydrogel presented a significant capacity for efficient water plugging, where the breakthrough pressure gradient was as high as 23.73 MPa, the plugging rate reached 99.9%, and the maximum residual resistance factor was 3902.06. This work provided a novel design of hydrogel with high compressive strength and satisfactory stability for water shutoff and conformance control in heterogeneous oil reservoirs.