Volume 57

The miscible behaviors and mechanism of CO2 and crude oil within nanoslits in ultra-deep reservoir: molecular dynamic simulation Zechen Yan, Xiaofang Li, Boxin Ding, Lei Zhu, Haonan Li, Chao Yan, Sen Wang, Qingzhong Xue, Bo Liao

Abstract

It is crucial to expose the miscible mechanism of CO2 and crude oil for the development of ultra-deep reservoirs. The influence of oil composition and electrical properties of rock surface on the miscible process of CO2 and crude oil (C7H16, C7H16S, C7H17N, C7H16O, C7H14O2, C9H20, C11H24) at 453 K and 90 MPa is investigated by using the molecular dynamics simulation. The simulation results indicate that the adsorption of CO2 and C7H16 on the calcite surface limits the diffusion of CO2 and C7H16 along the Z direction. Meanwhile, high pressure could weaken the effect of temperature on the adsorption of CO2 and C7H16 on the calcite surface. In addition, the functional group and long chain of crude oil molecules adversely affect the miscibility between crude oil and CO2. Moreover, the positively charged surface could promote the miscibility of C7H16 and CO2. The miscibility of C7H14O2 and CO2 could be facilitated in nanoslits with the same surface charges while it could be hindered in nanoslits with the opposite charges. This work could shed new light on the further research on the application of CO2 flooding in ultra-deep reservoirs.

Keywords Ultra-deep reservoir, CO2 flooding, Molecular dynamics simulation, Miscible mechanism