Ningjun Zhu

Magnetic resonance imaging study on near miscible supercritical CO2 flooding in porous media

CO2 flooding is one of the most popular secondary or tertiary recoveries for oil production. It is also significant for studying the mechanisms of the two-phase and multiphase flow in porous media. In this study, an experimental study was carried out by using magnetic resonance imaging technique to examine the detailed effects of pressure and rates on CO2/decane flow in a bead-pack porous media. The displacing processes were conducted under various pressures in a region near the minimum miscibility pressure (the system tuned from immiscible to miscible as pressure is increasing in this region) and the temperature of 37.8 °C at several CO2 injection volumetric rates of 0.05, 0.10, and 0.15 ml/min (or linear rates of 3.77, 7.54, and 11.3 ft/day). The evolution of the distribution of decane and the characteristics of the two phase flow were investigated and analyzed by considering the pressure and rate. The area and velocity of the transition zone between the two phases were calculated and analyzed to quanti...

Visualization of asphaltene deposition effects on porosity and permeability during CO2 flooding in porous media

In the present study, three types of experiments on immiscible CO2 flooding in porous media were conducted and high-resolution images of asphaltene precipitation obtained using X-ray micro-CT scanner. It was found that the effective oil mobility is reduced due to the adsorption of deposited asphaltene onto the rock which blocks the pore throats, whereby the formation wettability is changed and both the effective porosity and permeability are reduced. The deposited asphaltene cannot be redissolved or displaced by the reinjected crude oil, and the formation damage is irreversible. In addition, the porosity-based permeability model was applied to study the effective permeability reduction that results from porosity reduction. The porosity-based permeability was calculated based on the Kozeny–Carman equation and experimental data. The effective permeability variation rate obtained by the porosity-based permeability model agreed well with the results obtained by Darcy’s law, which demonstrates that the method is feasible in evaluating the effective permeability variation rate based on the porosity of the cores acquired from micro-CT images.Graphical abstract

Measurement of Two Phase Flow in Porous Medium Using High-resolution Magnetic Resonance Imaging

Abstract Measurement of two phase flow in porous medium for sequestration was carried out using high-resolution magnetic resonance imaging (MRI) technique. The porous medium was a packed bed of glass beads. Spin echo multi sequence was used to measure the distribution of CO 2 and water in the porous medium. The intensity images show that the fluid distribution is non-uniform due to its viscosity and pore structure of porous medium. The velocity distribution of fluids is calculated from the saturation of water and porosity of porous medium. The experimental results show that fluid velocities vary with time and position. The capillary dispersion rate donated the effects of capillary, which was largest at water saturations of 0.45. The displacement process is different between in BZ-02 and BZ-2. The final water residual saturation depends on permeability and porosity.

MRI investigation of water–oil two phase flow in straight capillary, bifurcate channel and monolayered glass bead pack

The study of immiscible fluid displacement between aqueous-phase liquids and non-aqueous-phase liquids in porous media is of great importance to oil recovery, groundwater contamination, and underground pollutant migration. Moreover, the attendant viscous, capillary, and gravitational forces are essential to describing the two-phase flows. In this study, magnetic resonance imaging was used to experimentally examine the detailed effects of the viscous, capillary, and gravitational forces on water-oil flows through a vertical straight capillary, bifurcate channel, and monolayered glass-bead pack. Water flooding experiments were performed at atmospheric pressure and 37.8°C, and the evolution of the distribution and saturation of the oil as well as the characteristics of the two-phase flow were investigated and analyzed. The results showed that the flow paths, i.e., the fingers of the displacing phase, during the immiscible displacement in the porous medium were determined by the viscous, capillary, and gravitational forces as well as the sizes of the pores and throats. The experimental results afford a fundamental understanding of immiscible fluid displacement in a porous medium.