Multiscale investigation into EOR mechanisms and influencing factors for CO2-WAG injection in heterogeneous sandy conglomerate reservoirs using NMR technology

作者：Junrong Liu, Dengfeng Zhang, Shuyang Liu, Rundong Gong, Li Wang · 发表于：Petroleum Science · 年份：2025 · DOI：10.1016/j.petsci.2025.04.004 · 被引用次数：18 · 研究领域：Hydrocarbon exploration and reservoir analysis、NMR spectroscopy and applications、Hydraulic Fracturing and Reservoir Analysis

The sandy conglomerate reservoir is tight and exhibits strong heterogeneity, rendering conventional water flooding and gas drive methods inefficient and challenging for the effective development. CO 2 water alternating gas (CO 2 -WAG) injection as an effective enhanced oil recovery (EOR) method has been applied in heterogeneous reservoirs. Simultaneously, it facilitates carbon sequestration, contributing to the green and low-carbon transformation of energy. However, the EOR mechanisms and influencing factors are still unclear for the development of heterogeneous sandy conglomerate reservoirs. In this paper, we conducted core flooding experiments combined nuclear magnetic resonance (NMR) technology to investigate EOR mechanisms of the CO 2 -WAG injection on the multiscale (reservoir, layer, and pore). The study compared multiscale oil recovery in sandy conglomerate reservoirs under both miscible and immiscible conditions, while also analyzing the effects of water–gas ratio and injection rate. In the immiscible state, the CO 2 -WAG displacement achieves an oil recovery of approximately 22.95%, representing a 7.82% increase compared to CO 2 flooding. This method effectively inhibits CO 2 breakthrough in high-permeability layers while enhancing the oil recovery in medium- and low-permeability layers. Furthermore, CO 2 -WAG displacement improves the microscopic oil displacement efficiency within mesopores and micropores. As the water–gas ratio increases, the total oil recovery ris...