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For the first time, the effect of calcination process on characteristics and catalytic performances of Pd supported on different MOFs (MIL-101(Cr), NH2-MIL-101(Cr), and HKUST-1) was evaluated. Besides, the various orders of calcination process and reduction one on Pd/MOF and Pd/calcinated-MOF were studied, and their performances in CO oxidation reaction were presented to find the effect of H2 and O2. Results showed that the effect of calcination and reduction processes on the catalytic activities and characteristics strongly depends on the nature of MOF. Among MIL-based catalysts, the catalyst with no calcination treatment showed the best activity. Among MNH2-based catalysts, high activity was obtained for Pd/MNH2, Pd/MNH2-C, and Pd/MNH2(RC) samples and Pd/calcinated-MNH2was the best. Catalytic activities of HKUST-1-based catalysts decreased with calcination due to high changes in their structures. The results are useful for predicting the performance of MOFs in oxidation processes, especially reactions in which high oxygen concentrations are involved.

Amine-functionalized MIL-101(Cr) has been synthesized by hydrothermal (MNH2) and post-synthetic modification (MNH2-p) approaches. Pd/MNH2 and Pd/MNH2-p have been tested in CO oxidation reaction as a gas phase reaction to clarify the difference between two synthesis approaches. Their performance has also been compared with that of Pd supported on MIL as a common MOF and CuBTC as a commercial one. The results show the significant difference between Pd/MNH2-p and Pd/MNH2, where CO conversion of 100% was not observed for Pd/MNH2-p, whereas Pd/MNH2 outperformed the others and exhibited the high reaction rate thanks to the active sites created by amorphization during the reduction process because of impressive effect of hydrogen on its structure. The effect of Space Velocity of Reduction Stream (SVr) has also been studied and the results show that the activity of Pd/CuBTC dramatically enhances at higher SVr and its activity further improves as a result of the formation of 8.9 nm CuO nanoparticles during the CO oxidation process.

Gas flooding is a practical secondary scenario for enhanced oil recovery. Channeling and fingering of the injected gas are the major problems facing this technique. These challenges can be mitigated by the injection of gas as foam. However, foam stability influences the overall efficiency of the process, which could be improved by nanoparticles (NPs). This work provides a theoretical and experimental analysis of the NPs wettability effects on foam behavior, in both static and dynamic states. The treated calcite (CaCO3) NPs along with a cationic surfactant (HTAB) were used for this purpose. By comparison of theoretical and experimental data, it was shown that the foam stability in the presence of NPs can be forecasted qualitatively using Reynold's formula and the extended Derjaguin–Landau–Verwey–Overbeek (xDLVO) theory. According to the theoretical results, the disjoining pressure decreases by increasing of NPs hydrophobicity, while the destructive effect of capillary pressure reduced. Based on the rheological measurements, the behavior of foam in the presence of NPs was less pseudo-plastic with the increasing of NPs hydrophobicity. For a fixed shear rate, the shear stress passed through a maximum by passing of the time, which could be justified by theoretical predictions. Finally, a series of flooding tests was carried out to evaluate the effect of NPs wettability on the Implicit Texture model parameters. It was concluded that while fmmob (foam mobility parameter) increased for more hydrophobic NPs, they suffered from large value of epdry (foam dry-out parameter), which indicated a sharp transition between high-quality and the low-quality regions.

Acidizing is one of the most effective techniques to remove the formation damage and restore (or even increase) the permeability of the near wellbore region. Although this technique is widely used to resolve the skin problem, it could initiate new damages itself that hinder the fluid flow and decrease the well production, consequently. Acid-oil emulsion and sludge formation are known as two major induced formation damage and the main reasons for the oil well acid treatment failures. Despite its critical effects, no comprehensive study has been addressed this specific type of formation damages in details. In this study, the acid-oil emulsion and asphaltic sludge formation were evaluated quantitatively. Multiple compatibility tests were conducted using HCl and six Iranian acid sensitive crude oil samples. The acid concentration, ferric ion presence, and acid-mixture ratio were selected as the main factors affecting the emulsion stability and the amount of sludge. To mimic the real condition the interference of the effects of these factors was noticed besides the crude oil type which has not been addressed before. The results revealed that controlling the iron ion presence, choosing the best acid concentration, and regulating the acid-mixture ratio would drastically reduce the risk of emulsion and sludge formation without any preventative additives presence. The quantitative values derived from this experimental work showed that the weight of dried asphaltic sludge formed was diminished to 7%, 5.6%, 2.4%, 22%, 7.5% and 10% of the most critical sludging condition for the crude oil samples A, B, C, D, E, and F respectively. Besides, for the first time, the volumetric measurement of the massive asphaltic sludge was performed to approach more realistic damage evaluation. The results confirmed it is possible that the solid sludge occupies 60 vol % of the primitive acid-oil mixture volume at high concentration of HCl and ferric besides high acid-oil ratio condition.

Despite numerous studies, fundamental understanding of how pore-level displacements in heavy crude oil–water/chemicals systems are controlled by ultrasonic radiation is not well understood, especially for heterogeneous porous media. In this study, a series of water/chemical flooding were performed on a heterogeneous rock-look-alike micromodel, which was initially saturated with the crude oil, and the pore-level displacements in the presence of ultrasounds are investigated. It has been observed that although the ultrasounds improve the recovery of oil adhered to the pores’ walls, the bypassed oil in the case of injection of surfactant and polymer solutions is relatively high. For the case of water injection, depending on frequency, the ultrasounds can profoundly improve the recovery efficiency up to 17% in comparison to the absence of ultrasounds by peristaltic movement of oil on the walls and forming the ganglia in invading phase, which first affect the minor fingers and then influence the major fingers by developing them through the untouched pores. In addition, some analyses on fingers development during water/chemical injections are presented. The results of this work help to better understand the role of ultrasound on displacement patterns in crude oil–water/chemical systems.

Amino acids partitioning including phenylalanine, glutamic acid, and tryptophan in aqueous and ionic liquid phases at temperature of 298.15 K and atmospheric pressure were measured. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide used in this work can produce two phases with water immediately. The effect of aqueous solution pH on amino acids partitioning was studied and revealed that amino acid partitioning coefficient was decreased with increasing pH. This phenomenon pertains to the electrostatic interaction between cations of amino acid and the anions of ionic liquid which is decreased when pH increases. Considering the effect of pH, liquid-liquid equilibrium data of amino acids were obtained in a pH owning maximum partitioning coefficient. It was observed that chemical structure of amino acid has an important effect on partitioning of amino acids between two phases. Experimental data indicated that glutamic acid is mostly transferred to aqueous phase while tryptophan moves to the ionic liquid phase. In the modeling section, equilibrium behavior of water, amino acid and ionic liquid system were predicted by SAFT equation of state. Necessary parameters of water and pure ionic liquid for equation of state were measured and amino acid parameters were obtained from literature. Binary interactions of components were optimized by equilibrium data. NRTL model was used in order to analyze cabapility of SAFT EoS to predict the behavior of system. The results indicate that SAFT model anticipates liquid-liquid equilibrium of the system better than NRTL model. The percentage of average absolute deviation for SAFT equiation is 1.9%.

Graphene oxide membranes were prepared by vacuum and pressurized ultrafiltration methods on the 12% modified Polyacrylonitrile (12mPAN) substrate to specify challenges, salient features, future directions, and potential of GO membrane for separation fields using characterization techniques and gas separation test (studied gases are CO2, He and N2), which is an efficient tool for better understanding of GO membrane behavior. GO membrane structure was examined over a wide range of parameters, such as pore size range of substrate and its surface properties, pH of GO dispersion, GO content, synthesis pressure, operating pressure and temperature. The results show that the GO content does not hold a linear relationship with the permeance and selectivity. Film thickness, aggregates, synthesis pressure defects and interlayer spacing have significant effects on the gas separation performance of GO membranes which originate from the synthesis method and its conditions.

Temperature dependency of infrared band intensity for methylene rocking vibration could be used as indication for creation of solid crystals while decreasing temperature. In this work, different experiments were conducted to measure wax appearance temperature, WAT, such as cross polarized microscopy, rheometry and FTIR spectroscopy. Three Iranian crude oils were characterized based on the SARA test and PC-SAFT model was developed to predict WAT. The obtained results by FTIR spectroscopy and PC-SAFT model were in quite agreement. FTIR spectroscopy determined higher WAT values which may be due to its higher sensitivity to smaller wax crystals. Also, the effect of a polymeric crystal modifier (EVA) and an aromatic solvent (toluene) on wax precipitation was investigated. EVA dramatically decreased the pour point of lower waxy crude oils. Toluene dissolved polar compounds such as asphaltene and consequently decreased WAT and pour point. This observation confirmed that asphaltene supports the wax crystallization and its growth.

Asphaltene deposition in porous media, wellbore and surface facilities has been a severe problem in petroleum industry which causes considerable remediation costs annually. Asphaltenes are heavy and polydisperse fractions of crude oil which are insoluble in n-alkanes such as n-heptane. In this work, three Iranian crude oils were prepared for titration experiments with n-pentane, n-heptane and n-dodecane at different solvent ratios and constant temperature. The experimental data were correlated by perturbed chain form of statistical associating fluid theory (PC-SAFT). The association of asphaltene molecules has been considered in this model with adjusting the uncertain parameters (such as association energy and association volume of asphaltene pseudo component) to match the experimental data. PC-SAFT parameters for other non-associating pseudo components have been calculated using the correlations proposed in literature. The present study also evaluated the performance of SVR method as a supervised learning approach in prediction of asphaltene precipitation. Deviation of proposed models has been validated using the statistical evaluation criteria and graphical analysis. The results show that the proposed models have AAD values less than 0.073 and a high potential in prediction of asphaltene precipitation.

Acidizing is widely used to remove near-wellbore damage and enhance the inflow performance of the reservoir to boost the well oil production rate. However, when the injected acid exposes to reservoir oil, either asphaltic sludge or emulsion forms as acid-induced damages. Therefore, laboratory compatibility tests are required before every acidizing job to determine both the acid sensitivity of oil samples and the optimal dosage of chemical inhibitors that should be used to prevent sludge and emulsion formation. The lack of knowledge to predict the risk of asphaltic sludge and emulsion damages for different oil and acid systems necessitates expensive and time-consuming compatibility tests prior to each acidizing process to select the best additives and optimize their dosages. A modified API RP-42 as the well-known standard procedure of the acid-sludge test is introduced here to overcome nuisance effects, estimate damage type and mimic the down-hole condition. Then, a robust database of 240 data (120 mass and 120 vol) is created for six different oil samples and three operational variables: 1) HCl mass fraction, 2) acid volume concentration, 3) iron contamination. Besides, statistical analysis is used to control the quality of the testing method and the prepared databank. Furthermore, an artificial intelligence (AI) model is trained by the database prepared to estimate sludge formation potential of all crude samples by utilizing their Saturate to Aromatic ratio (S/Ar) and Asphaltene to Resin ratio (A/R). According to the results, sludge formation potential strongly depends on the crude samples. Also, both A/R and S/Ar are good representations of crude samples. The statistical analysis shows that individual oil models are more than 90% accurate. Likewise, the error of the AI model developed is 10.5% that indicates good predictability. A logical criterion for damage type diagnosis (pore-clogging or tight emulsion block) is proposed. The models' performance is sound for HCl acid solution without additives, and further work is needed to generalize it by adding other effective parameters.

Deposition of asphaltenes upon precipitation is a main flow assurance concern, which propelled the development of various experimental and modeling techniques to accurately predict its occurrence. This work develops an integrated approach combining thermodynamic and deposition modules with a multiphase flow simulator to simultaneously model asphaltenes precipitation and deposition in wellbores. The Peng-Robinson equation of state and the modified Miller-Flory-Huggins theory are used to calculate the thermodynamic properties of the oil and asphaltenes precipitation, respectively. The deposition module is based on conservation laws for asphaltenes transport and is linked to the flow simulator to account for the impact of asphaltenes deposit layer on the fluid flow. Two case studies of wells producing through their tubing and casing are analyzed. The results show that failing to update the pressure, temperature and velocity profiles to capture the growth of the asphaltenes layer in the wellbore underestimates the asphaltenes layer thickness. In addition, the bubble point and the asphaltenes lower-onset pressures are predicted to occur closer to the surface. Approximately 20% difference in the asphaltenes deposition thickness after 60 days production is calculated between updating and fixed profile scenarios. Applying different flow models revealed the dependency of the deposition behavior onto model choice. For wellbore that produces through casing, asphaltenes deposition suddenly increases at the entrance then gradually decreases as the casing diameter changes. Despite the higher amount of deposited asphaltenes predicted for casing production, the flow cross-sectional area remained higher compared with tubing production. The integrated approach developed in this work successfully captured the field results, while significantly reduced the required computational time.

The results of the minimum miscibility pressure (MMP) determination for miscible injection of two gases (CO2 and an associated gas of one of Iranian gas reservoirs) into two different oil samples from two Iranian oil reservoirs using a slim tube apparatus are presented in this work. For efficient determination of MMP, prior to slim tube experimentation, cell-to-cell simulation of the slim tube experiment was performed using a tuned Peng Robinson equation of state as a pre-experiment and the results were used as initial estimates of MMP to select the pressure steps for the slim tube experiment. Finally, a comparison between the measured MMP values obtained by the slim tube experiments and those calculated by cell-to-cell simulation was made. It was shown that the cell-to-cell slim tube simulation predicts the results of slim tube experiments with a relative error of less than 6 %. This low error value shows that cell-to-cell simulation can replace the slim tube test in the cases where time is a major concern. Moreover, since the slim tube is an expensive and time-consuming experiment and selecting the pressures to run the test is very important, cell-to-cell simulation can help us select the pressures for performing a slim tube experiment.

Wax precipitation may occur in production or transportation of crude oil form field which is a serious problem in petroleum industry. Flow assurance issues concerning wax precipitation make it necessary to develop a precise thermodynamic model to predict the wax appearance temperature and amount of precipitation at different conditions. In this work a new procedure has been proposed to characterize crude oil based on the SARA test considering the wax and asphaltene as single pseudo components. Two scenarios have been investigated for the survey of the crude oil characterization, with and without asphaltene pseudo component. Also, in this work, the Perturbed Chain form of the Statistical Associating Fluid Theory, PC-SAFT, has been developed to evaluate its ability for modeling of wax precipitation prediction. It is demonstrated that the developed PC-SAFT model can correlate the wax precipitation amount better than basic models (multiple solid, solid solution) typically used in the industry. The results obtained with the proposed model show a remarkable matching with the experimental data for wax precipitation values. The obtained results are very promising in providing better approach to model wax precipitation. The effect of asphaltene molecules on wax precipitation has been investigated by sensitivity analysis using Monte Carlo algorithm and the Artificial Neural Network as the base model. In this work, a three layer FFBP neural network has been constructed using the Levenberg–Marquardt training method to predict the wax precipitation amount at different conditions which are the network input parameters. Positive effect of asphaltene on wax precipitation confirmed that asphaltene molecules act like the nucleation sites for wax crystals. The obtained results in this work show that the asphaltene content of crude oil should be considered in wax precipitation models.

Classical molecular dynamics simulations are used to compute the solvation free energy of two pharmaceutical solids, namely ibuprofen and acetaminophen in carbon dioxide (CO2), over the density range of interest in supercritical processes. In order to examine the influence of the solvent model on the resulting free energies, three popular CO2 models (Zhang, EPM2, and TraPPE) are studied. Relatively large discrepancies for the solvation free energy exist between these CO2 models, suggesting that the former is sensitive to the different balances between dispersive and electrostatic forces used in these models. In particular, for the solvation of the highly polar (dipole moment of ∼5.2 Debye) acetaminophen molecule, such discrepancies are more pronounced than for the moderately polar ibuprofen (dipole moment of ∼1.6 D) molecule. Since there is an exponential relationship between the solvation free energy and solubility, the choice of the solvent model substantially affects the predicted solubility. For the solubility of the studied solutes, the value obtained using the TraPPE model is the highest, that of the EPM2 model is intermediate, and that of the Zhang model is the lowest. Generally, the simulations results show that the model with the largest quadrupole moment leads to a more negative solvation free energy and a higher solubility over the entire density range. Further, the decomposition of the solvation free energy into contributions stemming from electrostatics and dispersion interactions shows that the electrostatic interactions are important for a quantitative prediction of solid solubility, while the Lennard–Jones parameters of the solute and solvent are more important for qualitative agreement. Additionally, the infinite-dilution partial molar volume of the two solutes is estimated from the pressure derivative of the solvation free energies. With density increasing beyond the value corresponding to the zero partial molar volume of the solute (minimum solvation free energy), the repulsive part of Lennard–Jones potential wins over the attractive interactions, and the solvent strength of supercritical CO2 decreases; however, due to the increase in the chemical potential of the pure solid (effect of the Poynting correction), the solubility further increases. Overall, these results demonstrate the importance of a proper choice of quadrupole moment of the solvent model, which is crucial for quantitative predictions of the solid solubility in supercritical CO2.

In this work, PC-SAFT, an equation of state based on perturbation theory, is applied to predict the reservoir fluids phase behavior. PC-SAFT parameters for pure components have previously been assessed, but they cannot be determined for petroleum fractions with unspecified components and composition. In order to remove this difficulty and making use of PC-SAFT model in the reservoir fluids simulations, a new approach is studied which leads to appearing generalized correlations for the estimation of PC-SAFT parameters for petroleum cuts and plus fractions using only their molecular weight and specific gravity, without the essential need for the characterization of petroleum fractions in different homologous hydrocarbon families. The proposed technique is then validated with the reliable experimental PVT data of reservoir fluids, including saturation pressure and differential liberation test (oil formation volume factor, soluble gas oil ratio, and liquid phase density) for 10 oil samples. Subsequently, available experimental data are compared to results calculated by PC-SAFT model for all existing samples. Afterwards, a comparison between PC-SAFT model and two widely used cubic equations of state (PR and SRK EOS) was also conducted. The results demonstrated PC-SAFT model estimation capabilities and ease of use as an effective tool for describing the phase behavior of reservoir fluids in a wide range of scales and applications. Moreover, the effect of parameter tuning process on reduction of error values was investigated and acceptable results were obtained.

The solubility of carbon dioxide and hydrogen sulfide gases in the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C2mim][OTf]) was measured at temperatures from (303.15–353.15) K and pressures up to about 3.0 MPa. The Henry's law constants were determined from the new experimental data, which in turn were used to derive the change of some thermodynamic functions of dissolution of the gases in that particular ionic liquid. The new experimental data were correlated by a combination of the extended Henry's law and Pitzer's model for the excess Gibbs energy. The average relative percent deviation (ARD%) of correlated molality values from experimental data are within experimental uncertainties, which indicate quite good correlative accuracy of the Pitzer's model for the systems under investigation. Results show that at the same temperature and pressure, the solubility of H2S in [C2mim][OTf], expressed on the molality scale, is more than four times that of CO2. Comparison of the obtained experimental data indicates that the solubility of H2S, expressed on the molality scale, in [C2mim][OTf] is much more than its magnitude in the high-capacity ionic liquids 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate ([C2mim][eFAP]) and 1-ethyl-3-methylimidazolium bis(trifluoromethyl) sulfonylimide ([C2mim][Tf2N]). For example the molality of H2S at 303.15 K and 2.0 MPa is 2.5 times and 1.3 times that of [C2mim][eFAP] and [C2mim][Tf2N], respectively. Solubility of CO2 in the ionic liquids follows the order [C2mim][OTf]

Parameters of the PC-SAFT Equation of State (EoS) for pure components are generally determined by matching the saturation pressure and liquid density experimental data. These experimental data are unavailable for petroleum cuts and plus fractions of the petroleum reservoir fluids. In this work, new correlations as functions of specific gravity and molecular weight were developed to estimate the PC-SAFT parameters of petroleum cuts with unknown composition. It was shown that the proposed correlations accurately estimate the PC-SAFT parameters of the pure components published in the literature. Then, the obtained correlations were used and the PVT experimental data for various real reservoir fluids was modeled using the PC-SAFT EoS and the results were compared to the modeled results using the Peng-Robinson EoS. The obtained results showed that the PC-SAFT EoS along with the proposed correlations presents acceptable results for phase behavior modeling of the reservoir petroleum fluids.

Photocatalytic reduction of CO2 is considered as a promising strategy for production of a wide range of renewable hydrocarbon fuels by solar energy. In this investigation, a series of Ni and Bi doped TiO2 catalysts with different Ni and Bi contents were synthesized by the conventional sol-gel method and tested for CO2 photo-reduction under visible light irradiation. Synthesized nano-photo-catalysts were characterized by XRD, FESEM, TEM, DRS, PL, FTIR and BET analyses. BET results indicated that the doping of Ni or/and Bi in the TiO2 framework resulted in BET specific surface area increment with respect to pure TiO2. DRS analysis showed that Ni doped TiO₂, Bi doped TiO2, and co-doped samples had narrower band gap energy and consequently considerably higher light absorption in the visible region compared with pure TiO₂. Doping Ni and Bi in TiO2 suppressed the rate of electron-hole recombination as indicated by PL spectra. CO2 adsorption capacity were increased in presence of Bi ions in comparison with pure TiO2 and Ni doped sample as a result of reactant adsorption increase on the surface of catalyst. The yield of methane considerably increased in the presence of Ni and Bi doped samples. The highest methane production (21.13 μmol/gcat) was obtained for 1 wt% Ni–3 wt% Bi co-doped TiO₂, which was almost 6.5 times greater than that for pure TiO2.

Foam flooding has been applied as a promising method in enhanced oil recovery to obviate the challenges of gas flooding such as fingering, channeling and overriding. However, long-term foam stability is crucial for mobility control. In this work, the effective mechanisms on foam stability in the presence of CaCO3 nanoparticles were assessed both theoretically and experimentally. The static and dynamic behaviors of cationic surfactant (HTAB) foam in the presence of CaCO3 nanoparticles with different hydrophobicity were evaluated. The CaCO3 nanoparticles were treated with a series of long-chain fatty acids to generate a range of wettability. Afterward, the underlying mechanisms were revealed by conducting the supplementary experiments, including measurements of effective diffusion coefficient (Deff), Henry's constant (KH), interfacial tension (IFT), and zeta potential of nanoparticles. Further, efforts were made to analyze the interfacial interactions using xDLVO theory. By increasing of nanoparticles hydrophobicity, the continuous reduction of effective diffusion coefficient, solubility, and IFT was observed, which means higher foam stability. However, the adsorption of modified nanoparticles on the air-solution interface could reduce the total disjoining pressure between two parallel plates, supported by xDLVO prediction. This phenomenon has an adverse effect on the thin film stability. Therefore, there would be an optimum extent of nanoparticles surface modification to obtain the most stable foam stability, which was in agreement with the both bulk and porous media observations. The optimum condition was shifted to the nanoparticles modified with the lower chain fatty acids by increasing the concentration of fatty acid solutions. In this case, the negative effect of reduced disjoining pressure was more pronounced.

In this study, application of ultrasound wave for permeability enhancement of reservoir rocks was experimentally examined. In this regards, a specific core holder apparatus was designed with the ability of in-situ exposure of ultrasound to the plug at high-pressure condition, which is a better representative of ultrasound application in real wellbores. The effect of ultrasound power and exposure time as well as probe-plug distance on permeability stimulation was evaluated. The results showed that ultrasound could stimulate the permeability of asphaltene-damaged rocks, in which its efficiency is significant in sandstone rock. Analysis of asphaltene content in the output fluid showed that, as the result of ultrasound exposure, 84% of deposited asphaltenes in the sandstone plug was removed, which is corresponding to 67% of permeability recovery. It was also found that the stimulated permeability increases with increasing exposure time and power while decreases with increasing probe-plug distance, however an optimum value for exposure time and power, after which the permeability recovery is not significantly enhanced, was observed. Analysis of experiments also showed that probe-plug distance has the most prominent effect on recovery of damaged permeability in comparison to ultrasound time and power.

Field evidence indicates that the thermal and chemical regimes in wellbore considerably affect the wellbore stability. This study presents a general coupled model for transport of solute, solvent and heat including their combined effects on the wellbore stability. Optimization of drilling fluid parameters is crucial for wellbore stability analysis particularly in high pressure-high temperature environments. The coupled effects of chemical potential and temperature gradients on fluid flow significantly change the pore pressure and stress around a borehole. The effects of various parameters such as mud weight, solute concentration gradient, shale properties, and temperature gradient on wellbore stability have been investigated.

In recent times, single layer graphene oxide (GO) has been of intense interest for a broad spectrum of applications. Size and surface charge of GO sheets are two key factors in the most of these fields. These structural properties can be tuned by adjusting pH manipulating the content of oxygen-containing groups. Furthermore, the pH value extremely affects on the surface chemistry and functional groups of GO sheets which are crucial in providing a high stable solution and chemical activity of particles. In this study, Graphene oxide is synthesized by improved hummer method and characterized by XRD, AFM, FTIR, DLS and zeta potential. pH value can be tuned trough titration with NaOH and HCl and effect of pH on GO dispersion stability and optical properties is investigated.

In this work, asphaltene adsorption in a sandstone core sample under dynamic conditions and during miscible CO 2 injection was studied using live oil sample which is close to real conditions in petroleum reservoirs. In order to investigate of damage in sandstone core sample by the deposited material such as asphaltene, the morphology analysis of sandstone core sample using scanning electron microscopic method was studied. Also analyses of the adsorbed material in sandstone core sample by Soxhlet extraction using an azeotrope mixture and with SARA method were performed. The experimental results show that by increasing the flow rate of injected CO 2 , the amount of asphaltene in retained material within sandstone core sample and consequently permeability and porosity reduction increased significantly. It can be observed that the accumulation of deposited asphaltene is more in inlet section than outlet section and decreases along the core sample. The elemental and SEM analyses of sandstone core sample indicate that the asphaltene is adsorbed as multilayer with formation of large clusters of asphaltene on surface of studied core sample during dynamic condition. Also, the SEM images indicate that the pore throats are blocked and no discernible holes are present on surface of core sample after CO 2 flooding. It can be found by increasing the flow rate of injected CO 2 ; the surfaces seem rougher due to the more adsorbed asphaltene on surface of sandstone core sample. Also, a modified model based on multilayer adsorption theory was compared with existing models based on monolayer adsorption theory to account asphaltene adsorption in sandstone core sample during gas injection. These results show that the asphaltene adsorption behavior in core sample is far from monolayer kinetic adsorption model and is closer to modified model which is based on multilayer behavior. It can be concluded that the modified model is capable of predicting the permeability reduction experimental data with AADs of 1.1–1.3%, whereas modeling based on monolayer kinetic adsorption is less accurate in the modeling of CO 2 flooding processes with AADs 5.7–7.4%. Therefore, the developed model based on multilayer adsorption theory is more accurate than models based on monolayer adsorption theory and is in good agreement with the experimental data reported in this work.

One of the most commonly used artificial lift methods in the petroleum industry is continuous gas lift. In continuous gas lift, gas at suitable pressure is injected in an appropriate depth into the tubing to gasify the oil column and, thus, facilitate the production. In gas lift, by increasing the gas injection rate into the well, the oil production rate enhances. At a point that is an optimal point of the well, by increasing gas injection rate, the oil production rate declines. At this point, the well produces the most oil. If there is no limitation in the total amount of available gas, a sufficient amount of gas could be injected into each well to get the maximum amount of production. However, often the total amount of available gas is insufficient to inject enough gas to an optimal point of each well and to reach the maximum oil production for each well. Therefore, allocating an optimum amount of gas to each well to obtain the field maximum oil production rate is necessary. In this work, a hybrid genet...

In this work, a new model based on multilayer kinetic adsorption mechanism has been proposed to account asphaltene adsorption in porous media under dynamic condition and the model was verified using experimental data obtained in this work and also with those reported in the literature. In the proposed model two steps are considered for asphaltene adsorption. The first step is taken as adsorption of asphaltenes on the surface of the porous media and the second step is taken as adsorption of asphaltenes on the asphaltenes already adsorbed on the porous media. The Crank-Nicholson method, central difference in space and trapezoidal rule in time, giving second order convergence in time was applied to develop a computer program using MATLAB software. Also, the Rung-Kutta fourth order scheme has been applied to calculate the volume fraction of asphaltene adsorption. The results show that the proposed model based on multilayer adsorption kinetic mechanism of aphaltene with the absolute average deviation 0.7% can predict more accurately the asphaltene adsorption experimental data in comparison to the previous models based on the monolayer adsorption kinetic and equilibrium mechanism. Sensitivity analysis shows that the proposed model is more sensitive to the first step of adsorption than the second step of adsorption. Also, a series of experiments was carried to investigate the asphaltene adsorption using UV–vis spectroscopy in order to study the effect of different parameters on asphaltene adsorption mechanisms during dynamic condition in porous media such as concentration, asphaltene composition, flow rate and type of porous media. The experimental results show that adsorption is controlled by the type of porous media rather than the asphaltene concentration of solution. Also, it was found that the adsorption process in porous media is controlled by kinetics mechanism during dynamic condition.

In this work, the thermodynamic behavior of aqueous solutions containing the solutes NaCl, glucose, and/or urea is investigated. These substances are vital components for living bodies and further they are main components of blood serum. Osmotic coefficients were determined by cryoscopic measurements in single-solute and multi-solute aqueous solutions containing salts (NaCl, KCl, CaCl2), glucose, and/or urea. The results show that NaCl determines the osmotic coefficients in the urea/glucose/NaCl/water system. Investigation of the effect of different salts on osmotic coefficients revealed ion-specific effects. At physiologically important solute concentrations in typical blood serum solutions, the osmotic coefficients were found to be in the range of 0.90–0.93. In a second step, the state of water in different glucose/salt/water and urea/salt/water systems was investigated. Depending on the kind of salt, the chemical potential of water in urea/salt/water is either higher or lower than in glucose/salt/water systems at equal nonelectrolyte concentrations. This result was found to be independent of the salt molality. Finally, the investigated systems were modeled with the Pitzer model and the ePC-SAFT equation of state, which allowed predicting of the properties of these multi-solute aqueous solutions.

Gas injection into reservoirs can be used to increase oil recovery. However, reservoir heterogeneity and high gas mobility reduce sweep efficiency and decrease recovery. Using foam can reduce gas mobility and therefore increase sweep efficiency. Foam is thermodynamically unstable, so it is important to predict the foam stability. In order to understand the influence of oil presence on foam stability, static experiments performed on foam by varying the type and amount of added oil and molecular weight of added alkane. Also static foam properties have been investigated by varying the surfactant concentration, ionic strength, composition of different salts in the sample, and addition of polymer.

When the reservoir energy is too low for the well to flow, or the production rate desired is greater than the reservoir energy can deliver, using some kind of artificial lift method to provide the energy to bring the fluid to the surface, seems to be necessary. Continuous flow gas lift is one of the most common artificial lift methods widely used in the oil industry during which, at appropriate pressure, gas is injected in a suitable depth into the tubing to gasify the oil column, and thus assist the production. Each well has an optimal point at which it will produce the most oil. In ideal conditions, at which there is no limitation in the total amount of available gas, a sufficient amount of gas could be injected into each well to get the maximum amount of production. However, often the total amount of available gas is insufficient to reach the maximum oil production for each well. Therefore, allocating an optimum amount of gas to each well to obtain field maximum oil production rate is necessary. In thi...

In this work, experimental studies were conducted to determine the effect of asphaltene deposition on the permeability reduction and porosity reduction of carbonate, sandstone and dolomite rock samples using an Iranian bottom hole live oil sample which is close to reservoir conditions, whereas in the majority of previous work, a mixture of recombined oil (a mixture of dead oil and associated gas) was injected into a core sample which is far from reservoir conditions. The effect of the oil injection rate on asphaltene deposition and permeability reduction was studied. The experimental results showed that an increase in the oil injection flow rate can result in an increase in asphaltene deposition and permeability reduction. Also, it can be observed that at lower injection flow rates, a monotonic decrease in permeability of the rock samples can be attained upon increasing the injection flow rate, while at higher injection rates, after a decrease in rock permeability, an increasing trend is observed before a steady-state condition can be reached. The experimental results also showed that the rock type can affect the amount of asphaltene deposition, and the asphaltene deposition has different mechanisms in sandstone and carbonate core samples. It can be seen that the adsorption and plugging mechanisms have a more important role in asphaltene deposition in carbonate core samples than sandstone core samples. From the results, it can be observed that the pore volumes of the injected crude oil are higher for sandstone cores compared with the carbonate cores. Also, it can be inferred that three depositional types may take place during the crude oil injection, i.e., continuous deposition for low-permeability cores, slow, steady plugging for high-permeability cores and steady deposition for medium-permeability cores. It can be seen from the experimental results that damage to the core samples was found to increase when the production pressures were increased. The experimental results show that the amount of remaining asphaltene in carbonate core samples is higher than those in sandstone core samples. Also, SEM (Scanning Electron Microscopy) micrographs of carbonate core samples showed the formation of large clusters of asphaltene in comparison with sandstone core samples during natural depletion. It can be seen from the modeling results that the proposed model based on the multilayer adsorption equilibrium mechanism and four material balance equations is more accurate than those obtained from the monolayer adsorption equilibrium adsorption mechanism and two material balance equations, and is in agreement with the experimental data of natural depletion reported in this work and with those reported in the literature.

New experimental results are presented for the solubility of carbon dioxide, hydrogen sulfide in the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]) at temperatures range from (303.15 to 353.15) K and pressures up to about 2 MPa. The solubility of the mixture of CO2/H2S in [C8mim][PF6] under various feed compositions were also measured at temperatures of (303.15, 323.15 and 343.15) K and the pressure up to 1 MPa. The solubility of carbon dioxide and hydrogen sulfide increased with increasing pressure and decreased with increasing temperature and the solubility of H2S is about three times that of CO2 in the particular ionic liquid studied. The measured data were correlated using extended Henry’s law included Pitzer’s virial expansion for the excess Gibbs energy, and the generic Redlich–Kwong cubic equation of state proposed for gas/ionic liquid systems. The correlations from the two models show quite good consistency with the experimental data for CO2/IL and H2S/IL binary mixtures within experimental uncertainties. For CO2/H2S/IL ternary mixtures, the RK model shows better correlation with the experimental values. We also studied the effect of cation alkyl chain length on the CO2 and H2S solubility by comparison of the experimental data of this study with those of previous reports. As the cation alkyl chain length became longer, the solubility of CO2 and H2S increased in the ionic liquid. Additionally, the influence of the anion on the solubility is studied by comparing the solubility of CO2 and H2S in [C8mim][PF6] with those in [C8mim][Tf2N]. As a result, CO2 and H2S have higher solubility in the IL with [Tf2N]− as the anion.

Wellbore stability is a main concern in drilling op- eration. Troublesome drilling issues are chemically active for- mations and/or high-pressure-high-temperature environments. These are mainly responsible for most of wellbore instabilities. Wellbore failure is mostly controlled by the interaction between active shales and drilling fluid in shale formations. The factors influencing this interaction consist of fluid pressure, tempera- ture, composition of drilling fluid, and exposure time. In this paper, a non-linear fully coupled chemo-thermo-poroelasticity model is developed. At first, a fully implicit finite difference model is presented to analyze the problem, and then, it is verified through comparison with analytical models. For this purpose, a computer code has been written in MATLAB envi- ronment. Results indicate that chemical osmosis and thermal osmosis significantly influence the wellbore stability in shale formations. Cooling and high salinity in mud decrease pore pressure and total tangential and radial stresses in the formation and vice versa. Moreover, CaCl2 solutions result in higher osmotic pressure than NaCl solutions. The type of constitutive model is investigated on wellbore failure. In addition, the proposed model is applied for wellbore instability in Ahwaz oil field, SW Iran. Results show that the proposed model considerably predicts the wellbore instability in this field.

In recent years, some numerical models have been proposed to investigate the effects of the elastic wave such as ultrasonic on fluid flow behavior in porous media. Nevertheless, none of these models are applicable to the fractured reservoirs, especially when the fluid is a Bingham plastic. In this work, the model proposed by P. P. Iassonov and I. A. Beresnev (2003) for flow under exposure of elastic wave in nonfractured porous media is considered and used for development of a new model of steady state flow of a Bingham plastic fluid in fractured reservoirs. The Kazemi's “block and fracture” model assuming negligible vertical permeability in blocks is considered for modeling. In addition, two-phase flow behavior under elastic wave in fractured system is investigated. The results showed that, at higher pressure gradients, vibration amplitude cannot highly influence the fluid percolation, in contrast at lower pressure gradients, the fluid flow through the fractured porous media can considerably be improved b...

Rheological behavior of two crude oils and their surfactant-stabilized emulsions with initial droplet sizes ranging from 0.5 to 75 µm were investigated at various temperatures under steady and dynamic shear testing conditions. In order to evaluate the morphology and Stability of emulsions, microscopic analysis was carried out over three months and average diameter and size distribution of dispersed droplets were determined. The water content and surfactant concentration ranged from 10 to 60% vol/vol and 0.1 to 10% wt/vol, respectively. The results indicated that the rheological properties and the physical structure and stability of emulsions were significantly influenced by the water content and surfactant concentration. The crude oils behaved as Newtonian fluids over a wide range of shear rates, whereas the emulsions behaved as non-Newtonian fluids, indicating shear-thinning effects over the entire range of shear rates. The viscosity, storage modulus and degree of elasticity were found to be significantl...

The strong bases statistical associated fluid theory (SAFT) equations of state allow modeling for a wide range of scales and applications. The equilibrium calculations are very time-consuming in SAFT-based family of equations of state; therefore the number of components used in describing a fluid mixture must be reduced by grouping. On the other hand, in some applications it is required to retrieve the detailed fluid description from equilibrium calculation performed on the lumped fluid description. The purpose of this paper is to develop a systematic approach for lumping and delumping with equilibrium calculations using the Perturbed Chain (PC)-SAFT equation of state. The methodology proposed by this paper is to calculate some delumping coefficients from flash calculations performed on the lumped system. Later on those delumping coefficients will be used to retrieve the detailed compositions of the fluid phases from the lumped mixture. To prepare the lumped system, the components are classified into groups through a clustering algorithm and the group properties are calculated according to mixing rules. To examine the accuracy and efficiency of the suggested methodology, it is applied to four synthetic gas samples and two real samples, one being a natural gas condensate and the other one is an oil reservoir fluid. It will be shown that based on the proposed method the delumped equilibrium ratios are close to detailed equilibrium ratios. The observed deviations are small and can be accepted.

In this work, a new model based on the multilayer adsorption kinetic mechanism and four material balance equations for oil, asphaltene, gas, and water phase has been developed to account for asphaltene deposition in porous media under dynamic conditions and the model was verified using experimental data obtained in this work and also with those reported in the literature. The results showed that the developed model based on multilayer adsorption kinetic mechanism can correlate more accurately the oil flooding experimental data in comparison to the previous models based on the mechanical plugging mechanism, in particular in carbonate core samples. Also, a series of experiments was carried to determine the permeability reduction of carbonate, sandstone, and dolomite core samples due to asphaltene deposition using an Iranian bottom hole live oil sample which is close to reservoir conditions in order to study the effect of different parameters on asphaltene deposition mechanisms during dynamic conditions in p...

In this paper, oil recovery and permeability reduction of a tight sandstone core sample in miscible CO2 flooding processes due to asphaltene deposition were studied using an Iranian bottom hole live oil sample in order to distinguish between the mechanical plugging and adsorption mechanisms of asphaltene involved in the interfacial interaction of the asphaltene/mineral rock system. A novel experimental method was designed and proposed to measure the amount of deposited asphaltene due to different mechanisms using the cyclohexane or toluene reverse flooding and spectrophotometer. In this work, the bottom hole live oil sample was injected first to a long core and then CO2 injection was performed which is close to reservoir conditions, whereas in the majority of previous works, the mixture of recombined oil (mixture dead oil and associated gas) and CO2 was injected in a short core sample which is far from reservoir conditions. Then, the cyclohexane and toluene reverse flooding was performed, and the amount o...