Study on the influencing factors of imbibition in tight reservoirs based on molecular dynamics simulation

Abstract

Nanopores are in dominant positions in tight reservoirs. Recently, global scholars have focused on the role of imbibition in tight reservoirs on the macroscale, which is insufficient for understanding the process and mechanism of imbibition in tight reservoirs on the microscale. Therefore, it is of great significance to adopt a new microscopic research method to study the imbibition of water in micropore and nanopore spaces in tight reservoirs. In this paper, models of the quartz nanopore imbibition effect and water drive oil reservoirs are established through molecular dynamics simulation. Then, the impacts of different factors on the imbibition effect and the roles of this effect in the water drive process are investigated. The results show that the percolation rate of water in the nanopore is related to the temperature, pore size, and wettability. The permeation strength increases with increasing wettability. Warming accelerates the movement of water molecules in the system, thereby increasing the rate of osmosis, enhancing the strength of osmosis, and shortening the time needed for equilibrium. However, the total amount of osmosis remains unchanged. The smaller the pore size is, the stronger the sorption strength. Imbibition plays a dominant role at lower injection rates, and expulsion plays a dominant role as the injection rate gradually increases.