Amphiphilic Magnesium Hydroxide Nanosheets for Enhanced Oil Recovery

Two-dimensional nanosheets have attracted considerable attention as oil displacement agents due to their unique interfacial properties. However, the high cost limits the extensive application of conventional nanosheets in oilfields. In this study, an amphiphilic magnesium hydroxide (AMH) nanosheet was prepared through the surface modification of low-cost magnesium hydroxide nanosheets under mild conditions. The AMH demonstrates a two-dimensional structure with 50-200 nm of plane size and 3.23-4.12 nm of thickness size. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectrometry (FTIR), and thermogravimetric analysis (TGA) were used to characterize the AMH. Due to the amphiphilic groups on the surface, AMH exhibited favorable interfacial activity and the oil-water interfacial tension (IFT) could be reduced by approximately two-thirds at a very low AMH concentration (100 mg/L). Meanwhile, an elastic film could be formed by the AMH at the oil-water interface. Furthermore, emulsions could be formed by AMH at an ultralow concentration (10 mg/L) and the oil-wet solid surface was transformed into intermediate-wet under the wettability alteration effect of AMH. Due to its amphiphilicity, 17.11% of additional oil could be recovered by AMH in a heterogeneous core with the permeability of 50/250/1000 mD. Considering the favorable ability in enhancing oil recovery and relatively low cost compared to conventional nanosheets, AMH has great potential in large-scale applications in oilfields as an oil displacement agent.