Simulation of Flue Gas Flooding and Sensitivity Analysis in Low-Permeability Reservoirs Considering Miscible Effects: Core Experiments and Lattice Boltzmann Simulations

As an important enhanced oil recovery (EOR) method, flue gas flooding enhances reservoir energy, reduces the crude oil viscosity, and improves the flow capability of the crude oil. This technique significantly optimizes crude oil extraction performance, achieving a higher oil recovery factor while simultaneously facilitating flue gas sequestration and efficient utilization of resources. In this study, a series of high-temperature and high-pressure PVT experiments are conducted to measure the relationship between the dissolved gas–oil ratio and saturation pressure. Core flooding experiments are then used to examine the effects of the injection rate and core fractures on flue gas flooding under immiscible conditions. Additionally, the multiple relaxation time lattice Boltzmann method (MRT-LBM) is employed to simulate the flue gas-oil two-phase flow, taking into account the impact of miscible effects on the flue gas flooding process. Experimental results show that as the dissolved gas–oil ratio increases, the saturation pressure gradually increases but the rate of increase slows down. With the increasing flue gas injection rate, gas channeling occurs earlier, leading to a reduction in the oil recovery factor. Fractures intensify the occurrence of gas channeling, resulting in a further decrease in the final oil recovery factor, which is only 24.93%. Simulation results show that a lower injection rate and a higher miscible effect both contribute to improving the oil recovery factor. Miscibility facilitates the mixing of gas and crude oil, allowing the gas to carry and mobilize the oil more effectively, creating a wider gas distribution area. This promotes the flowing of flue gas into a broader range of pores around fractures, continuously expanding the gas-swept region and achieving a higher sweep efficiency and oil recovery. This study provides a theoretical basis for optimizing flue gas flooding technology and offers a scientific reference for simulating the oil–gas multiphase flow under complex reservoir conditions.