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Although CO2injection significantly increases the amount of oil recovered, it can cause asphaltene deposition in oil reservoirs. Asphaltene deposition leads to formation damage, in which treatment is a costly and problematic operation. In this work, impact of asphaltene precipitation and deposition during CO2injection are investigated for recombined oil both in sandstone and carbonate core samples through dynamic flow experiments. Injection of oil and CO2was performed simultaneously. Then, pressure drops along the core were recorded continuously to estimate permeability reductions during the experiments. Online viscosity of injected fluid was measured by a designed capillary viscometer. Damaged permeabilities were calculated using Darcy equation from the pressure drops and measured viscosity data. The results show that permeability reduction behavior is completely different in sandstone and carbonate core samples. A core scale simulation study with tuned equation of state parameters was carried out to evaluate the experimental results. Then, sensitivity analysis is performed on injection rate and matching parameters, such as adsorption coefficient, plugging coefficient, and critical velocity. Simulation results only match experimental data at final injected pore volumes. The results of this work can be helpful for CO2injection applications and simulation of asphaltene deposition in oil reservoirs. [ABSTRACT FROM PUBLISHER]

The injection of hydrocarbon gases/CO2for enhanced oil recovery can promote asphaltene precipitation and consequently reservoir impairment, of which its impact is tremendous. In this work, the results of flow dynamic tests performed on sandstone as well as carbonate rocks were presented. The permeability reduction mechanisms were investigated during simultaneously injection of CO2and recombined oil into core samples through a static mixer at reservoir conditions. The permeability impairment data was monitored from analysis of recorded pressure and online viscosity measurements during the experiments. Analysis of obtained results revealed that for both sandstone and carbonate rocks, surface deposition and pore plugging mechanisms participate simultaneously in reduction of permeability in primary injected pore volumes. Therefore, a new permeability reduction model is proposed that considers a combination of surface deposition and pore plugging mechanisms. The results of the new model are in good agreement with the obtained experimental data. The results of this work can be helpful for modeling of asphaltene deposition due to CO2injection in petroleum reservoirs. [ABSTRACT FROM PUBLISHER]

This work is concerned with the experimental investigation of mass transfer, which occurs during diffusion of hydrocarbon solvents in heavy oil based on constant and concentration-dependent diffusion coefficient. Here, a series of free fall diffusion experiments have been conducted in sealed test tubes at fixed temperatures. Pentane, hexane, and octane were used as solvents and were placed on heavy oil in tubes. The diffusivity of heavy oil into solvents was monitored by a digital camera. The image analysis technique was applied to extract concentration profiles in diffusion zones of solvents by means of calibration curves. Fick's second law was used to obtain both constant and concentration-dependent diffusion coefficient. The measured diffusion coefficients are in agreement with the data reported in the literature for different heavy oils. The results show that the diffusion coefficient experiences an increasing trend with oil concentration till it reaches its maximum and then tails off to a constant value. The observed maximum happens around 0.12 for pentane and around 0.05 for both hexane and octane. Moreover, all transient concentration profiles as a function of lie on a unique line. For all solvents, it has been found that the average values of measured concentration-dependent diffusion coefficients were smaller than that of constant diffusion coefficients. The results of this work illustrate that constant diffusion coefficient assumption overestimated the total mass transfer; therefore, it may lead to unrealistic predictions of solvent penetration in solvent-based enhanced oil recovery processes. [ABSTRACT FROM PUBLISHER]

Abstract: Experimental permeability and diffusivity values for CO2 and CH4 through imidazolium-based ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf2N]) were determined in the temperature range of 300–320K using temperature correction factor defined in our previous study. According to literature, experimental values of permeability and diffusivity obtained in this study for CO2 in [hmim][Tf2N], showed good agreement with predictive models reported by other researchers. In addition, experimental values of permeability and diffusivity for CH4 in [hmim][Tf2N] as a function of pressure have been reported in this study. Considering the results of present study and those of our previous study on another imidazolium-based ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), predictive models for CH4 permeability and diffusivity through this group of ionic liquids were developed. [Copyright &y& Elsevier]

Abstract: In order to define a new temperature correction factor in this study, accurate experimental values were presented for permeability and diffusivity of carbon dioxide and methane in imidazolium-based room temperature ionic liquid: [bmim][PF6] (1-butyl-3-methylimidazolium hexafluorophosphate) immobilized on an inorganic membrane support. Results were presented as a function of temperature and pressure for temperatures within 300–320K and pressures below 50kPa. According to the literature, experimental values of permeability and diffusivity for CH4 in [bmim][PF6] vs. temperature are reported for the first time in this study. Results obtained for CO2 permeability revealed good agreement with data reported by other researchers. [ABSTRACT FROM AUTHOR]

In this research, organic solvent composed of hexane and methanol was used for lipid extraction from dry and wet biomass of Chlorella vulgaris. The results indicated that lipid and fatty acid extraction yield was decreased by increasing the moisture content of biomass. However, the maximum extraction efficiency was attained by applying equivolume mixture of hexane and methanol for both dry and wet biomass. Thermodynamic modeling was employed to estimate the effect of hexane/methanol ratio and moisture content on fatty acid extraction yield. Hansen solubility parameter was used in adjusting the interaction parameters of the model, which led to decrease the number of tuning parameters from 6 to 2. The results indicated that the model can accurately estimate the fatty acid recovery with average absolute deviation percentage (AAD%) of 13.90% and 15.00% for the two cases of using 6 and 2 adjustable parameters, respectively., (Copyright © 2015 Elsevier Ltd. All rights reserved.)