Wetting properties of various reservoir rocks strongly influence the efficiency and security of geological storage of carbon dioxide in deep saline aquifers. Numerical simulation of Carbon Capture and Storage (CCS) has become a considerable research option now-a-days due to less time and cost-effective outcomes compare to traditional laboratory based experiments. This study provides a Computational Fluid Dynamics (CFD) methodology for the pore-scale displacement mechanism of supercritical CO2 under different wetting conditions and quantify the effect of wettability and direction of flow on supercritical CO2 trapping. A 3-Dimensional visualization software is used to build surface mesh from the micro-pores of the Bentheimer sandstone. A module of a commercial CFD software is used to generate volume mesh from the surface mesh and another module from the same CFD software is used to perform imbibition processes (supercritical CO2/brine) through the Bentheimer sandstone. Full Navier-Stokes equations are solved by using Eulerian-Eulerian multiphase transient flow approach. Free surface flow model is used to integrate the effect of capillary forces. This model determines the pressure gradient at the two-phase interface. The flow is assumed to be laminar, isothermal and there is no mass transfer between phases. The initial condition of the imbibition processes was obtained from a drainage process for a strongly water-wet system. For this, a Bentheimer sandstone was completely filled with brine and supercritical CO2 was injected. The simulation was stopped when brine was drained by supercritical CO2 and the system reached the steady state conditions. This phase distribution was used as an initial boundary condition for the imbibition processes. The imbibition processes were performed in two opposite direction for different contact angles (100° and 110°). The effect of wettability and direction of brine on supercritical CO2 trapping were observed. The residual saturation of supercritical CO2 was significantly different in two opposite direction of brine flow. In the reverse imbibition process, normalized residual supercritical CO2 saturation values are increased but, the amount of normalized trapped supercritical CO2 values are decreased. It was mainly due to the amount of normalized free supercritical CO2 saturation values (which were equal to the difference between normalized residual supercritical CO2 saturation and normalized free supercritical CO2 saturation values).

In this paper, pore-scale numerical modelling predictions are performed to investigate variations in relative permeability behaviour and oil fractional flow under a range of different parameters (contact angle, capillary number and flow direction) through Brine/Oil system in Ottowa F42 Sand Pack. AVIZO (high-performance 3D image processing software) is used to separate the Micro-computed tomography (micro-CT) images of the pore spaces of rocks from grains of Ottowa F42 Sand Pack. ANSYS-CFX (high- performance CFD based simulator) is used to generate volume mesh and carry-out numerical simulation. The simulation results were analysed and compared with other experimental and numerical works. At low capillary number, the relative permeability curves were not smooth. Almost similar trends for relative permeability were observed for the imbibition process by alternate injection of oil and brine. Increase in contact angle showed less effect on fluid relative permeability and oil fractional flow. Also, alternate injection of fluids in imbibition showed a little response on fluid relative permeability and oil fractional flow. The outcomes of this investigation will be extended to intermediate-wet and oil-wet media and also for carbonate formations.

Residual trapping of CO2 has been identified as a reliable and rapid way to dispose large CO2 quantities. Several experimental investigations have been completed where residual trapping in sandstone was measured; these programmes identified that initial CO2 saturation and rock porosity are significant parameters which influence the residual saturation and thereby residual trapping capacity and effectiveness. In order to further improve fundamental understanding a computational tool need to be developed with which residual CO2 saturations can be predicted. Pore-scale two-phase fluid flow simulation is performed based on the integration of x-ray micro-tomography images (which provide a detailed description of the rock's pore space) and Navier-Stokes equations. X-ray micro-tomography (approximately (6µm)3 voxel size) images of F42 sand pack were used. The extracted pore morphology of each medium was obtained by segmenting the images based on their greyscale contrast using image processing software AVIZO Fire. These binary images were converted initially into surface and volume meshes which were then fed into a commercially available computational fluid dynamics code (ANSYS-CFX). Three dimensional transient, laminar flow fields were obtained by solving the continuity and Navier-Stokes equations using an Eulerian-Eulerian multi-phase flow approach. To incorporate the effect of capillary forces, free surface model was used which solved the pressure gradient at the interface correctly. The model assumes isothermal condition with no mass transfer between the brine and CO2. The inlet and outlet boundary conditions include CO2 flow rate and the pressure respectively. We simulated the drainage condition in this paper. Approximately 1.5 million tetrahedral elements were used to generate volume mesh, and the convergence criterion for all variables was set to 10-3. Initially all pore space was filled with brine, and then CO2 was injected from one inlet side at constant flow rate, obtained from the experiments. When the system was at connate water saturation, we stopped our simulation. The residual saturation depends on the flow rate of super critical CO2. The computations described here are a rapid, cost-effective and can reveal vital information for the planning of carbon geo-sequestration projects and associated risk and capacity assessments.