Study on the main factors and mechanism of functional silica nanofluid spontaneous imbibition for enhanced oil recovery

Nanofluids have shown great potential as chemical additives for enhanced oil recovery in low-permeability reservoirs owing to their unique properties. However, their application in harsh reservoir conditions poses challenges due to the demanding stability requirements. In this work, the functional silica nanofluid capable of withstanding high salinity and elevated temperature was prepared by blending 0.1 wt% hydrophilic silica sol with the 0.1 wt% modifier lauramidopropyl hydroxy sulfobetaine. Multiple experiments of the nanofluid were conducted, encompassing characterization, interfacial tension (IFT) and contact angle measurements. The nanoparticles had an average size of approximately 17 nm, and the nanofluid exhibited excellent stability, interfacial activity and wettability alteration ability. Spontaneous imbibition tests demonstrated that the nanofluid achieved a remarkable recovery of 35.30 %, compared with only 5.53 % for simulated formation water. Subsequently, the relationship between spontaneous imbibition recovery and factors, such as temperature, salinity and core permeability, was investigated. The influence weight for each factor on the recovery is as follows: temperature (64.61 %) > core permeability (19.07 %) > salinity (16.32 %). Furthermore, a comprehensive description of the spontaneous imbibition mechanism of nanofluids was provided, incorporating insights from 1HNMR results. We expect that this study can offer valuable insights into nanofluid formulation, supporting the efficient development of low-permeability reservoirs and provide a theoretical basis for field applications.