The main scope of the work related to the physical and dynamical processes associated with the injection of carbonated water in porous media. Carbonated water flooding is an alternative for traditional CO2 flooding. Both methods have the potential to recover any oil left behind after primary and secondary recovery while storing CO2 at the same time. The advantage of Carbonated Water flooding as compared to CO2 flooding is related to the high buoyancy of CO2 that results in gravity separation if the CO2 is not dissolved in water. This results in sub-optimal flooding of the reservoir and possible leakage of CO2.

Bentheimer sandstone is a quartz-rich permeable hard sedimentary rock used for core flooding experiments. When fired to stabilize clays (subjected to high temperatures), pyrometamorphical phase changes induce texture and pore framework alteration. As a consequence the new dielectric response may influence wettability. The literature regarding pyrometamorphical behavior during and after thermal treatment is ambiguous, so we evaluate desirable effects (fixation of clay minerals) and undesirable effects (dielectric surface changes) in the matrix. Porosity, permeability, surface charge, specific surface area and dielectric respond were measured before and after firing of samples up to View the MathML source∼1000°C under oxidizing and non-oxidizing conditions. The matrix properties were determined using X-ray diffraction and X-ray fluorescence, scanning electron microscope imaging, and thermomechanical-, and thermogravimetric analysis with differential scanning calorimetry.

Firing causes dehydration, dehydroxylation and irreversible transformation of original clays, organic matter, and carbonates to glass, oxides and feldspars. During heating quartz transfers from α- to β -quartz and back during cooling. This changes the grain volumes and consequently reduces the matrix integrity. The sandstone has a slight porosity and permeability increase (∼5%∼5%). Further, a shift in the point of zero charge toward a higher pH may result in wettability alteration from strongly water-wet to oil-wet. Additionally, a decrease in the permittivity value and marginal dispersion of the dielectric constant (∼5%∼5%) between the high and the low frequencies was observed. Due to firing and related dispersion of the iron oxides within the matrix framework, Bentheimer sandstone becomes a weaker insulator.

Release of CO2 as a by-product of industrial and domestic operations around the world is undesirable due to its negative impact on the environment climate. As an option for reduction many efforts are made to develop methods for the capture and storage of CO2. One potential option, the CO2 enhanced oil recovery (CO2-EOR) technique, is already in use for decades and widely accepted as a promising solution for mobilization and recovery of residual oil in water wet rock. It is also a mitigation prospect for CO2 reduction and an opportunity for permanent storage after the production stage. For better understanding of the mechanisms controlling the oil displacement and CO2 sequestration, the interaction between pore system, flow and phase equilibrium were conducted in a series of CO2 flooding experiments. As an improvement, we propose to inject CO2 as a 2nd stage EOR action after water flooding and accurately monitor and measure CO2 in the system. The experimental part involves brine injection into vertical positioned cylindrical Bentheimer sandstone (BS) cores at residual oil saturation, which mimic depleted oil reservoirs. Next, CO2 is injected at the bottom side of the column to recover oil and to trap CO2. The trapped and residual saturations are measured by mass balance and visualized by a CT - scanner during the experiment to discriminate different phases through time. The oil recovery and trapped saturations of oil and gas are determined as functions of initial oil and gas saturation. Different from previous experimental studies, a continuous CO2 injection technique was used for coupled CO2 sequestration and EOR. The experiments show for CO2 flooding experiments an increase in the back pressure between tests that result in higher CO2 storage and in higher oil recovery. The laboratory results are used for upgrading and building of a model for three phase flow in sandstone reservoir. This paper gives a better understanding of three phase trapping mechanisms and shows results on gas phase behavior with various injection flow rates. In addition, we assess whether the flow and pressure schemes are feasible and we show prospective recoveries and storage efficiency. The experimental results help to improve up-scaling conditions for recovery at field scale.