In view of the problem of poor flowability in the production and transportation of high-wax crude oil and high-viscosity crude oil, crude oil flow improvers are commonly used to reduce their viscosity and pour point. Although polymer-based crude oil flow improvers are highly effective in improving crude oil flowability, there are still problems such as high cost and the need for a large amount of solvent dilution when used. In this work, highly dispersed organic modified nano-montmorillonite was prepared by using Na-based montmorillonite and quaternary ammonium salts, and the influencing factors on the viscosity of the crude oil were investigated. The most effective modified nano-montmorillonite (B@MMT) can reduce the viscosity by 96.7% (21 °C) and depress the pour point by 15 °C. Furthermore, it has shown a high improvement in flowability in the other four different sources of crude oil, with viscosity reduction rates of 52.2, 93.4, 79.1 and 67.4%, respectively. B@MMT was characterized by FTIR, SEM, zeta potential and contact angle. Based on DSC and wax crystal structure analysis, the mechanism of the influence of B@MMT on crude oil viscosity and pour point was explored. Finally, the cost of B@MMT was estimated, and the result shows that, compared with the crude oil flow improver in use, B@MMT has considerable commercial competitive advantages.

The network formed by wax precipitation at low temperature and colloid asphaltene at high temperature leads to poor fluidity of heavy oil, and the gelling characteristics of crude oil lead to pipeline blockage, which affects the exploitation, transportation and refining of crude oil. This work prepares a series of cationic surfactant-modified nano hydrotalcite (CSNH) to weaken the network structure and enhance the fluidity of the crude oil by the interaction of organic and inorganic functional groups on the CSNH surface and the components of the crude oil. The results show that CSNHs can all reduce the viscosity of crude oil from different oilfields, among which BTNH can reduce the viscosity of Yanglou (YL) crude oil by 98.8% (31 °C) and depress the pour point by 16.0 °C at most. In the investigation of the universality of crude oil, the modified hydrotalcite was applied to the mixed crude oil (CQH) of Changqing Oilfield, the crude oil (J76) of Jidong Oilfield, the high pour point oil (GN) of Huabei Oilfield, and the crude oil (HQ) of Tuha Oilfield. The viscosity reduction rates were 53.2%, 86.2%, 42.7%, and 63.8%, respectively. The characterization of this nano material confirms the modification of quaternary ammonium cationic surfactant on the surface, resulting in a smaller particle size, and the nano particles are stable under conventional conditions. The mechanism of viscosity and pour point reduction in crude oil by BTNH was discussed by DSC and optical microscopy analysis. The OH- and long-chain alkyl groups on the BTNH surface may interact with the resins, asphaltene and wax through hydrogen bonding and co-crystal, weakening or dispersing their aggregates, thereby improving the fluidity of crude oil. Finally, a cost evaluation was conducted on BTNH, providing useful support for subsequent promotion and application.