Experimental Determination of CO2 Diffusion Coefficient in a Brine-Saturated Core Simulating Reservoir Condition

Diffusion coefficients are necessary to describe the mass transfer and adsorption rate of CO2 in formation fluids. However, data is scarcely reported for actual reservoir conditions of high pressure and temperature, which are normal in most scenarios of the CO2-enhanced oil recovery process in China's fractured-vuggy reservoirs and carbon storage process. Accordingly, this work employed the pressure decay method (PD) and relevant mathematical models to determine the CO2 diffusion coefficient in both liquids and cavern filling porous media at 50 MPa and 393 K. The effects of the type of reservoir fluids, the properties of carven filling porous media, and water saturation on CO2 diffusion coefficients were investigated. Results in bulk reservoir liquids showed that the CO2 diffusion coefficient in the oil sample was 4.1243 × 10−8 m2 s−1, much higher than those in the pure alkane phase, pure water and brine sample from reservoirs. Results of CO2 diffusion in carven filling porous media saturated with oil demonstrated a significant dependence on properties such as porosity and permeability, and a correlation in the CO2 diffusion coefficients between the bulk oil phase and cavern filling porous media in the form of touristy was documented. CO2 diffusion in the fractured cavern porous media was much higher than that without fracture. An increase in water saturation reduced CO2 diffusion coefficients in the carven filling porous medium studied, herein. Thus, the CO2 diffusion coefficient is essentially related to the type of liquid and properties of the filling media.

Experimental determination of solubility and diffusion coefficients of CO2 and N2 in poly(dimethyl, methylphenyl siloxane) (PMPS) for the pressure range 0–150 kPa and the temperature range of −10°C to 45°C is discussed. The absorption isotherms were measured by pressure decay equilibrium. Diffusion coefficients were determined by modeling the transient absorption data by Fickian diffusion. The value of solubility coefficient for CO2 at 35°C was 1.21 ± 0.02 cm3 CO2 (STP)/(cm3 polymer.atm) and it increased to 2.07 ± 0.01 cm3 CO2 (STP)/(cm3 polymer.atm) at 1°C. The absorption isotherms of CO2 obtained were linear for the pressure range 0–200 kPa and the enthalpy of sorption value was −10.82 kJ/mole for CO2. However, the diffusion coefficients of CO2 changed with feed pressure. The diffusion coefficient of CO2 in PMPS at 22°C and 128.6 kPa equilibrium pressure was 7.22 × 10−6 cm2/s and thus the permeability value at these conditions was 1392 Barrers. The diffusion coefficients of CO2 at 0°C and equilibrium pressures of 125.8 kPa and 10.5 kPa were 5.72 × 10−6 cm2/s and 4.31 × 10−6 cm2/s, respectively. Consequently, the CO2 permeability in PMPS decreases by about 20% when the pressure is reduced from 125.8 to 10.5 kPa at 0°C. © 2007 American Institute of Chemical Engineers AIChE J, 2008

Diffusion coefficients of CO2 molecule and bicarbonate ion in hemoglobin solution measured by fluorescence technique.

The effect of permeability on supercritical CO2 diffusion coefficient and determination of diffusive tortuosity of porous media under reservoir conditions

PurposeThis study aims to get the essential data of the solubility and diffusion coefficient of gas in jet fuel for appropriately designing a kind of on-board inert gas generation system.Design/methodology/approachA test apparatus based on pressure–decay method was constructed to measure solubility and diffusion coefficient of gas in liquid. The test apparatus and method were verified via measurement of solubility and diffusion of CO2 in the pure water.FindingsThe solubility of CO2 and O2 in RP-3 jet fuel with the temperature from 253 to 313 K under three various pressures were measured and compared with theoretical value calculated by a relative density method provided in the standard of ASTM D2780-92, and the deviation is within 10 per cent. The diffusion coefficients of CO2 and O2 in RP-3 jet fuel are determined by monitoring the gas pressure in a hermetic cell versus time with the temperature from 253 to 333 K. The measured diffusivity-temperature relation can be well fitted through the Arrhenius equation for engineering applications. The obtained correlation can be used to predict the diffusion coefficient of CO2 and O2 in RP-3 jet fuel under a wide temperature range.Practical implicationsThe semi-empirical correlation of solubility and diffusion coefficient in RP-3 jet fuel obtained from the experimental data could be used to support the design of an inert gas generation system.Originality/valueThere are no essential data of solubility and diffusion of CO2 and O2 in RP-3 jet fuel; therefore, it is fatal if the quantity and rate of mass transfer of CO2 and O2 in RP-3 jet fuel must be assessed, e.g. during the design of green on-board inert gas generation system.

To explore the CO2 diffusion in heavy oil saturated porous media, a mathematical model was developed to simulate the diffusion process by coupling the gas state equation. Then the experiment of CO2 diffusion in heavy oil saturated porous media was carried out and CO2 diffusion coefficient was determined by fitting the experimental data with the established model. Using the measured diffusion coefficient as an input parameter, the CO2 diffusion process in porous media was simulated and the factors that affected the diffusion process were analysed in this paper. The simulation results show that diffusion direction on the rock surface is in the tangential direction of the rock and points to where the CO2 concentration potential decreases. Furthermore, the contact area of the heavy oil and CO2 has a vital impact on the CO2 diffusion amount and CO2 concentration distribution. [Received: November 24, 2019; Accepted: August 7, 2020]

The diffusion coefficient (DC) of CO2 in brine is a key parameter in geological carbon sequestration and CO2-Enhanced Oil Recovery (EOR), as it governs mass transfer efficiency and storage capacity. This study employs three machine learning (ML) models—Random Forest (RF), Gradient Boost Regressor (GBR), and Extreme Gradient Boosting (XGBoost)—to predict DC based on pressure, temperature, and salinity. The dataset, comprising 176 data points, spans pressures from 0.10 to 30.00 MPa, temperatures from 286.15 to 398.00 K, salinities from 0.00 to 6.76 mol/L, and DC values from 0.13 to 4.50 × 10−9 m2/s. The data was split into 80% for training and 20% for testing to ensure reliable model evaluation. Model performance was assessed using R2, RMSE, and MAE. The RF model demonstrated the best performance, with an R2 of 0.95, an RMSE of 0.03, and an MAE of 0.11 on the test set, indicating high predictive accuracy and generalization capability. In comparison, GBR achieved an R2 of 0.925, and XGBoost achieved an R2 of 0.91 on the test set. Feature importance analysis consistently identified temperature as the most influential factor, followed by salinity and pressure. This study highlights the potential of ML models for predicting CO2 diffusion in brine, providing a robust, data-driven framework for optimizing CO2-EOR processes and carbon storage strategies. The findings underscore the critical role of temperature in diffusion behavior, offering valuable insights for future modeling and operational applications.

An experimental approach for measuring carbon dioxide diffusion coefficient in water and oil under supercritical conditions

New insights into bulk and interface properties of [Bmim][Ac]/[Bmim][BF4] ionic liquid/CO2 systems — Molecular dynamics simulation approach

Effect of maceral composition and coal rank on gas diffusion in Australian coals

Flooding carbon dioxide into oil reservoirs is a promising technique for improving the pressure of a reservoir when it is depleted through primary and secondary production. In the context of global warming, it is a viable method for geological storage of CO2 emissions. Once CO2 is injected into a reservoir, it is forced to come into partial contact with formation water. To estimate the rate of CO2 transfer and the total amount of CO2 dissolved in the formation water, correct estimation of CO2 diffusivity is required. In this study, the rate of CO2 diffusion in water was experimentally determined in a PVT cell using the pressure depletion method at reservoir conditions (temperature: 50–75 °C and pressure: 17,450 kPa). As expected, the rate of CO2 diffusion in water increases with increasing temperatures. In addition, the impact of salinity of the water on the rate of CO2 diffusion was investigated. A significant decrease in the rate of CO2 diffusion was found with increasing salinity. Subsequently, a diffusion model describing the experiments was developed to predict the behavior of CO2 diffusivity under simulated conditions. Unique correlations between CO2 diffusion coefficients and water at different temperatures and salinities were obtained using the results of modeling.

Electrochemical sensors based on proton-conducting electrolytes for determination of concentration and diffusion coefficient of CO2 in inert gases

The effect of CO2-philic thickeners on gravity drainage mechanism in gas invaded zone

Solubility and diffusivity of CO2 in polypropylene/micro-calcium carbonate composites

Under air flotation conditions, the effect of an electric field (EF) to the interfacial properties of hydrophobic particles in salt solution was investigated by using molecular dynamics simulation. The varieties of thickness of the hydrophobic layer on the surface of the hydrophobic particles, radial distribution function of Na+, diffusivity of CO2 and H2O, residence time of H2O in the solvent shell of Na+, and the distribution of CO2 near the graphene caused by the applied EF in different NaCl systems were calculated, and all those results were compared with those where there is no EF applied. The results reveal that the thickness of the hydrophobic layer near the hydrophobic particles is decreased under an EF. The coordination number and residence time of H2O in the solvent shell of Na+ are also decreased, which indicates that the restraint of Na+ on surrounding H2O is weakened, and the H2O molecules are more mobile. Under an external EF, the diffusion coefficient of CO2 and H2O is increased, and the quantity of CO2 near the surface of graphene is decreased according to the numerical results of the radial distribution of graphene-CO2. All the results indicate that the EF will decrease the thickness of the hydrophobic layer near hydrophobic particles, which can therefore weaken the adsorption between the hydrophobic particles and the gas molecules. The simulation results in the present study can provide theoretical support for brine mineral flotation under an external EF.