A low viscosity amphoteric polyacrylamide (LHPAM) was synthesized with Acrylamide and a Cationic etherifying agent. FTIR, SEM, and EDS all suggest that it successfully synthesized a new material. It can be demonstrated from TG and DSC that the temperature resistance of LHPAM is higher than that of partially hydrolyzed polyacrylamide (HPAM) and it can be found from ultraviolet–visible spectrophotometer that the flocculability of LHPAM is stronger than that of HPAM. The viscosity testing shows that the viscosity of LHPAM is greater than that of HPAM at the beginning, but the viscosity of LHPAM has been ultimately lower than that of HPAM after 1d. In addition, LHPAM reacts with Cr3+ to form a gel with an interpenetrating network structure, while HPAM is a gel with a comb‐shaped system, and the gelation time of LHPAM is longer than that of HPAM. However, the final gelation strength is the same. The final flow experiment shows that the plugging rates of LHPAM and HPAM are greater than 95%, but the resistance coefficient of LHPAM is smaller than that of HPAM. This study expands the application of HPAM in profile control and water shutoff, which is of great significance for enhanced oil recovery.

W/O emulsification flooding is a new type of oil displacement method, which can effectively improve oil recovery, but there are few materials used for W/O emulsification at present. Therefore, we prepared a hydrophobic nano calcium carbonate (WS-Ca) and compounded it with Span80 to form a nano oil displacement system. The contact angle experiment demonstrates that WS-Ca is lipophilic material. After testing the emulsification performance, viscosity, interfacial tension and oil displacement performance of the oil displacement system, it is found that the nano oil displacement system with the best performance is WS-Ca (800ppm) +Span80 (1%), and the displacement system and oil are emulsified into W/O emulsion, and the viscosity of emulsion is 25 times that of crude oil. Furthermore, the oil displacement system can successfully lower the oil-water interfacial tension and increase the oil recovery of injection water to 62.63%.