No abstract

No abstract

CO2 dissolution is considered as one of the most promising mechanisms for trapping of free-phase CO2 into brine. It causes an increased density of the brine and initiation of gravitational instability that eventually leads to density-driven natural convection in saline aquifers. Correct estimation of the onset time for convection and the rate of dissolution of CO2 into brine is important because the timescale for dissolution corresponds to the timescale over which free-phase CO2 has a chance to leak out. The gravitational instability of a diffusive boundary layer in porous media has been studied in several papers in recent years, but there are few works about the behavior of density-driven natural convection mechanism in heterogeneous saline aquifers. Barriers such as shales and calcites layers are common types of heterogeneities in geological formations that are important in the fluid flow. Despite the recognized importance of convective dissolution in these heterogeneous geological formations, there is no experimental data available for studying the accelerated mass transfer rate of CO2 into these media.In this paper, we investigated the effect of the regular distribution of barriers on the rate of dissolution of CO2 into water and geometries of convection fingers. A series of experiments were performed using a precise experimental set-up with barrier heterogeneous Hele-Shaw cell geometries and by using CO2 and water. The approach and procedure for performing the experiments give us this opportunity to have both qualitative (images and movies) and quantitative (amount of the dissolved CO2 into water) data at the same time. The behavior of convection pattern after onset time and the effect of system properties on the behavior of convective mixing process will be presented and discussed. Moreover, some speeded-up movies from the experiments that are suitable for improving public awareness of the problem have been uploaded on the internet platform. Lastly, the relationships between dissolution flux after onset time for convection and barrier properties are discussed.

No abstract

No abstract

Two-dimensional glass model experiments are used to investigate the residual trapping mechanism of CO 2 stored in saline aquifers. For this purpose, two proxy fluids are chosen to simulate the CO 2 -brine behavior under reservoir conditions. The first set of experiments is carried out by flooding n-heptane in a mixture of glycerol and water inside a glass bead porous media. Fluids and porous materials are designed so that the dimensionless groups are in the range of real storage sites. Another set of proxy fluid consists of dodecane and a different mixture of glycerol and water, representing the second wettability condition for the system. The size of the glass beads chosen was fine (70-110 lm) in order to investigate residual trapping phenomena. For each set, after complete drainage process, an imbibition process is performed and in each time step, images are taken from the phenomena. The images are processed using a red, green, blue (RGB) color concept using a Matlab code that was developed for this study. By using this process, it is possible to measure the residual trapping of CO 2 proxy fluid for each test and to determine the saturation profile in the model. Tests are carried out at various imbibition and drainage rates to study the effect of the rate on the results. Fine-scale numerical simulation models are constructed for comparison with experimental results. Good agreement is obtained between the simulation results and the image processing estimations, as well as the readings from the material balances during the experiments. This study could provide a framework for modeling different reservoir conditions for residual trapping mechanism and the impact of different parameters in future studies.

No abstract

In order to investigate effects of injection rate and aquifer influx in imbibition processes and also wettability behaviour for CO 2 storage in aquifers, two representative fluids are chosen for relative permeability measurements. These two fluids represent CO 2 and brine at the reservoir conditions. The first set of experiments is done by n-heptane and a mixture of glycerol and water, flowing in a glass beads porous medium. The density difference and viscosity ratio are designed to be in the range of CO 2 -brine systems normally found at reservoir conditions. Another set of experiments is designed based on dodecane and a mixture of glycerol and water. The second mixture is chosen so that the same ratios of density differences and viscosity ratios are maintained. Interfacial tension and contact angles are measured for both cases. By this set up, two cases of strongly water-wet and water-wet systems are designed. The purpose of this study is to quantify the impact of wettability and flow rate through relative permeability experiments. Results show that the relative permeability is sensitive to both rate and wettability, and after interpreting the data from experiments in a history matching process, based on the effects of drainage and imbibition rates and also the effect of wettability, correlations are developed to predict the amount of CO 2 trapped in the pores. This newly developed method will be useful in obtaining good estimations of real case trapping volume in CO 2 storage processes. Scaling analysis of the experiment shows that the tests are well designed in the range of real reservoir conditions.