Synthesis and performance evaluation of novel polyacrylonitrile-based preformed particle gel (PPG) for water shut-off applications at high-salinity and high-temperature conditions of petroleum reservoirs

• Introduction of resilient PPG based on polyacrylonitrile and carboxymethylcellulose • PAN-based PPGs exhibit outstanding resistances to temperature and salinity shocks • Salinity has the highest and temperature the lowest impacts on the PPGs swelling • As packed in a partially open fracture (POF), the RRF increases with injection rate • RRF values of up to 40 are recorded during post-flushing of the POF The oil and gas industry face challenges associated with excessive water production. In this study, a co-polymer of polyacrylonitrile (PAN) and carboxymethyl cellulose (CMC) was synthesized and characterized well. The PAN-CMC co-polymer was then used to synthesize a PAN-based hydrogel by a metal cross-linker for water shut-off applications. The polymer concentration and cross-linker to polymer ratio were optimized to achieve a hydrogel structure with high swelling ratios, mechanical strength, and thermal stability. The hydrogel was dried and grinded to form preformed particle gels (PPGs) with definite particle size distributions. Swelling ratio of the PPGs was mapped as a response to salinity, pH, and temperature via a design of experiments. A glass microfluidics with a partially open fracture (POF) was employed to evaluate the plugging performance and residual resistance factor (RRF). It is found that the swelling ratio of the PPGs decreases with salinity and temperature. However, the PPGs are swollen up with pH. Salinity has the highest and pH has the lowest impacts. The ratio of viscous-to-elastic modulus of the PPGs increases with the salinity, leading to a lower effective injectivity but a higher plugging performance. When the swollen PPGs are placed in the POF model, the RRF and plugging efficiency are improved with the injection rate during post flush. This indicates that the compaction, dehydration, and deformation of the PPGs are enhanced by exposure to higher shear stresses. When the PPGs are swollen at higher salinity conditions and then placed in the POF, an almost complete blockage is observed.