Molecular dynamics simulation of oil–water flow behavior in single and double nanochannels

Abstract

In tight oil exploitation, the heterogeneity of reservoirs has a crucial influence on the oil sweep volume and oil displacement efficiency. This study employs molecular dynamics simulations to investigate the oil displacement behavior in water flooding and the impact of the heterogeneity of oil reservoirs. By simulating single nanochannels with sizes ranging from 4 nm to 8 nm and double channels with combined sizes ranging from 4–5 nm to 4–8 nm, the effects of reservoir heterogeneity on oil displacement processes are analyzed. Results show that in single nanochannel systems, a larger nanochannel size significantly reduces threshold injection pressure, thereby lowering the resistance for water entry and enhancing oil displacement efficiency. In double-channel systems, water preferentially enters the larger-sized nanochannel, and the efficiency of oil displacement in the smaller-sized channel is constrained. The oil displacement processes of single and double nanochannel systems are discussed in detail, including the threshold injection pressure, atom number distribution, oil displacement efficiency, and nanochannel size effect. This work establishes a theoretical foundation for understanding microscale displacement mechanisms in heterogeneous tight oil reservoirs and offers practical guidance for optimizing development strategies in low-permeability reservoirs.