High-strength and self-degradable sodium alginate/polyacrylamide preformed particle gels for conformance control to enhance oil recovery

Excess water production has become an important issue in the oil and gas extraction process. Preformed particle gels (PPGs), show the capability to control the conformance and reduce excess water cut. However, conventional PPGs have poor mechanical properties and their swollen particles are easily damaged by shearing force when passing through the fractures in formations, meanwhile PPGs can be also degraded into various byproducts, leading to permanent damage to the reservoir permeability after temporary plugging. Herein, a novel type of dual cross-linked PPGs (d_PPGs) was designed and synthesized using sodium alginate (SA) and acrylamide (AAm), cross-linked with N, N′-methylenebisacrylamide (MBA) and Fe3+. Results show that d_PPGs have excellent mechanical properties with a storage modulus up to 86,445 Pa, which is almost 20 times higher than other reported PPGs. Meanwhile, d_PPGs can be completely degraded into liquid without any solid residues or byproducts and the viscosity of d_PPGs degraded liquid was found to be lower than 5 mPa·s. A laboratory coreflooding test showed that the plugging efficiency of d_PPGs was up to 99.83% on open fractures. The obtained results demonstrated that d_PPGs could be used as economical and environment-friendly temporary plugging agent with high-strength, self-degradation, thermal stability, and salt stability, thus making it applicable to a wide range of conformance control to enhance oil recovery.