Volume 34: CCUS Technologies for the Carbon Neutrality: Part II

Pore-scale study on interfacial characteristic of CO2-oil-glass beads during CO2-EOR Xin Wang, Jilong Zheng, Shaohua Li, Pengfei Lv, Lanlan Jiang, Yongchen Song

Abstract

CO2-EOR (Enhanced Oil Recovery) is a vital method to increase oil recovery while significantly lower greenhouse gas emissions. The near-miscible conditions are useful to improve displacement efficiency and oil recovery by CO2 injection. In this study, at the near-miscible condition of 8MPa, 40°C, using X-ray micro-tomography (micro-CT), pore-scale interfacial characteristics can be obtained in the CO2-oil-glass beads system, such as wettability, which represents the tendency of fluids in the solid. A displacement of oil by CO2 was performed to examine the two-phase interfacial characteristics in the gas-oil-solid system. With the multi-phase identification approach and in-situ spatial distribution of contact angle (\theta), the \theta at 5.5PV was nearly 66.99° at near-miscible conditions, which indicates an intermediate-wet system. With increasing injection pore volumes (PV) from 5.5PV to 16.4PV, the contact angle increases from 66.99° to 70.42°, indicating a decrease in the water-wet property. Although oil resides in pores of all sizes (big, medium, and small), gas often fills the larger pores. The interfacial curvature examination revealed that in-situ capillary pressure provides a distribution with an average value near zero. The rock performed a wettability reversal from a water-wet to an intermediate-wet condition. The knowledge of near-miscible two-phase flow is helpful to enhance oil recovery and storage efficiency.

Keywords CCUS, pore-scale, wettability, interfacial property, micro-CT