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Objective(s): To detcnninc the short-term reacrogenicity of diphtheria-tetanus-whole cell pertussis (DTwP) vaccine administered to preschool children in a number of health centers of Tehran in 2006. Methods: In this prospective cohort study, 337 children aged 4-6 years were injected with DTwP vaccine manufactured by Razi Institute of Iran. Reactogenicity was assessed by the parents for 7 days post vaccination using diary cards. Local (pain, redness and swelling) and systemic (fever, loss of appetite, gasterointestinal symptoms, vomiting and eczema) side effects were recorded daily. Results: Out of 337 children, 312 (92.6%) reported local reactions and 220 (65.3%) reported systemic reactions. No serious adverse events related to vaccination were reported. Among local reacuons, pain was the most frequent (86.9%), but 11 was mostly mild or moderate. Redness (52.8%) and swelling (41.2%) were the most frequently observed signs in the second day. The systemic reactions observed in children included fever (48.4%), loss of appetite (24%), gastrointestinal symptoms (5 6%), vomiting (8%) and eczema (2.7%). Only 3.6% of children had auxiliary fever above 39 chr('39')c. All signs were observed to have reduced or completely disappeared during a week. Conclusion: Compared with previous reports in Iran, reactogenicity of DTwP of Razi Institute seems to be reduced, but it was still more frequent than the internationally approved cellular vaccine counterparts. Reactogcnicity of the cellular triple vaccine may be related to the vaccine formulation or the bacterial cell fragments used in vaccine production.

The ternary potassium sulfido and selenido ferrates K9[Fe2S(e)7] were synthesized as pure phases through a facile and straightforward solid‐state method. The compounds crystalize isotypic as has been reported previously. UV‐visible measurements indicate semiconductivity, showing direct optical band gaps with energies of 1.91 eV for the sulfido and 1.72 eV for the selenido ferrate. Investigations of dielectric and impedance properties provide their dielectric constants in the range of 60 to 74 at room temperature at a frequency of 1 kHz, as well as ionic conductivity values in the range of 2.08 ⋅ 10−5 and 2.61 ⋅ 10−5 mS cm−1. Both, the dielectric constants and the calculated ionic conductivity of the selenido ferrate are higher compared to the sulfido ferrate, corresponding to the larger unit cell volume and increased bond lengths in the selenido ferrates. The dielectric constants are comparably higher than the reference material of SiO2, which might introduce them for dielectric applications. [ABSTRACT FROM AUTHOR]

The novel potassium sulfido cobaltate, K2[Co3S4] is introduced, with 25% vacancies of the cobalt positions within a layered anionic sublattice. The impedance and dielectric investigations indicate a remarkable ionic conductivity of 21.4 mS cm−1 at room temperature, which is in the range of highest ever reported values for potassium‐ions, as well as a high electrical permittivity of 2650 at 1 kHz, respectively. Magnetometry results indicate an antiferromagnetic structure with giant intrinsic exchange bias fields of 0.432 and 0.161 T at 3 and 20 K respectively, potentially induced by a combination of the interfacial effect of combined magnetic anionic and nonmagnetic cationic sublattices, as well as partial spin canting. The stability of the exchange bias behavior is confirmed by a training effect of less than 18% upon 10 hysteresis cycles. The semiconductivity of the material is determined, both experimentally and theoretically, with a bandgap energy of 1.68 eV. The findings render this material as a promising candidate for both, active electrode material in potassium‐ion batteries, and for spintronic applications. [ABSTRACT FROM AUTHOR]

Availability of hydrocarbon gases at the field makes it attractive for gas-based enhanced oil recovery (EOR) methods such as water alternating gas (WAG) injection. Optimization of EOR methods requires too many simulation runs, which are time consuming and expensive. Therefore, developing a proxy model, which emulates simulator outputs, is considered as an appropriate alternative technique. In this work, effects of composition changes of injection gas, WAG ratio, and slug size on produced oil and water were investigated. In addition, the optimum value of the previous parameters, including some constraints, are presented using response surface methodology. Experimental design is also applied to construct different polynomial regression models as proxy models for a sector of an Iranian oil reservoir under the WAG injection scenario. A new workflow is introduced for optimization of the WAG parameters, for which all effecting parameters are changing simultaneously. [ABSTRACT FROM AUTHOR]

In this article a series of experiments were performed to demonstrate the effect of carbon dioxide injection pressure on a huff and puff process. The experimental data are used in a lab-scale model simulated with a commercial simulator to investigate the effect of soaking time, injection pore volume, and rate of injection on the heavy oil recovery. The result of experiments showed that a huff and puff process under miscible pressure conditions gives the most recovery. Simulation results illustrated that there is an optimum value for soaking time, which, for soaking times less than this value, recovery increases and for values greater than optimum the recovery decreases. The simulation study demonstrated that oil recovery increases with increasing volume of injected miscible fluid and recovery decreases with injection rate increase. [ABSTRACT FROM AUTHOR]

The authors simulated a reservoir by using two-layer perceptron. Indeed a model was developed to simulate the increase in oil recovery caused by bacteria injection into an oil reservoir. This model was affected by reservoir temperature and amount of water injected into the reservoir for enhancing oil recovery. Comparing experimental and simulation results and also the erratic trend of data show that the neural networks have modeled this system properly. Considering the effects of nonlinear factors and their erratic and unknown impacts on recovered oil, the perceptron neural network can develop a proper model for oil recovery factor in various conditions. The neural networks have not been applied in modeling of microbial enhanced oil recovery since now. Finally, we are going to design a controller for the neural network. This controller is designed for the case where output of the network is oil recovery factor. For this purpose, the network is designed as a one-layer network in which just one output matches each time. In this case, a one-layer network will have acceptable results. [ABSTRACT FROM PUBLISHER]

1-Introduction Protecting civilians is one of the most important objectives for Officials in order to mitigate vulnerabilities and Building safe spaces and shelters is an action to achieve this goal. According to expensive costs of building shelters, if a multifunctional space belongs to specific function in time of peace and use as shelter in time of crises; it will be logical, affordable and consequential. The purpose of this research is the site selecting of a public multifunctional space that require to zone 14 of Tehran city municipal with the ArcGIS software that will be a shelter in times of crisis. For this aim, with applying required Indexes that assessed by experts, the amount of investment required, Operational level, Sustainability in times of crisis and flexibility; the parking was selected in the range the study. Localization index Clarified base on operation in time of peace and also in time of crisis as a defilade. This important issue done by analysis at previous studies and expert opinions. In this research we have tried to create layers corresponding to each index in GIS software by the Analytic Hierarchy Process (AHP) and weighting to the Positioning index. The final location is detected and introduced by the overlaid layers. 2-Theoretical bases 2-1- Location The process of locating is a complex process in which a range of criteria to determine a suitable location for a particular application will be considered (Farrokhzad & Danesh, 1390, 67). Some of the most important of localization is given in Table 1 are trying to express general rules based on the factors and variables that explain influence the localization of the existing structure of localization of industrial activities, trade, services, etc. and introduce best places establishment. In general, the main ideas of the places are divided into three groups: • Theories relating to minimize cost: Determining of place with emphasis on minimizing the cost of production factors. • Theories of the Market Analysis: Emphasis on demand and maximize the revenue. • Theories relating to maximize profits: Logical combination of the above to approaches (shuokoie, 1382, 380). As is shown in Table 1, in conventional theories of localization has not been addressed to functional security issue. But since there is always threat and safety and preserve the lives of the people is high priority, it is essential given the probability of threats in relation to the location, considerations relating to the security of the user are taken into consideration. One of the functions that can guarantee the security of lives and properties of people, establishing a secure environment that is not possible due to restrictions in effect and economically is • Theories of the Market Analysis: Emphasis on demand and maximize the revenue. • Theories relating to maximize profits: Logical combination of the above to approaches (shuokoie, 1382, 380). not affordable. But for ability to integrate urban functions required, in times of threat, it could play an important role in ensuring public safety. So given that security is a vital component of human needs, it is necessary to make multi - purpose of urban spaces and correct to locate them, to note how they function in times of peace and crisis. So that in peace time to be given special work and in times of crisis to help protect the lives of people. In this regard, the work location that is considered in this research is parking that emphasized to be shelter, in addition to compliance with the theories of localization, based on maximizing the profitability of parking in crowded places (zone 14 of Tehran city municipal), special attention is to the issue of physical and psychological security of the residents , up in the shadow of that in mind, several advantages are achieved. 3-Discussion Establishing large parking in city centers which often lacks suitable space for keeping the vehicles is highly expensive due to ground costs and limitations. Table 2 shows some significant criteria for the location of storey parking and safe space of defilades. The presented criteria are extracted based on the current rules and standards. As well, they are scored and judged by the experts in the field of passive defense urbanization. Also, some efficiencies are given in the 4th and 5th columns for every single of the needed criteria to be applied by the software GIS. 4-Conclusion Achieving a desired location on a wide range of different options is always considered to be expert in this field. Parking versatile interchangeable safe shelter is one of the main requirements of threatened major cities, including Tehran. Therefore, in this study, the location of the urban public has been implemented on the zone 14 municipal. Parking location and construction of a versatile in range of this research is to meet the unique features that it will has several advantages. Protecting and the vehicles is highly expensive due to ground costs and limitations. Table 2 shows some significant criteria for the location of storey parking and safe space of defilades. The presented criteria are extracted based on the current rules and standards. As well, they are scored and judged by the experts in the field of passive defense urbanization. Also, some efficiencies are given in the 4th and 5th columns for every single of the needed criteria to be applied by the software GIS. (Reference: The authors) improving people’s lives and so increasing the threshold of psychological security and stability of the people, the main advantage of construction the parking is capable of shelter for a safe shelter in times of crisis to facilitate access to space. Reducing traffic, easing congestion on adjacent streets, reducing noise pollution , from the other benefits of this research is to construct the specified function so that would minimize the costs and maximize the profits. The table3 shows the percentage of the main criteria for locating a parking space is a safe shelter. 5-Suggestions The researcher's main think-worthy suggestion is emphasizing multi-functioning different utilities of a city. In this respect, the following research improvement areas can be obtained (which are classifiable into two fields of Urbanization and Construction): S Extracting different utility location indices potential for being transformed into safe defilades and putting them up in city zones S Using other methods of multi criteria decision making and Compare with the results of this research S Presenting potential utility design observations which can be transformed into safe spaces S Feasibility study of establishing the proposed utilities in the extracted points and designing them [ABSTRACT FROM AUTHOR]

Despite numerous experimental and modeling studies, the role of temperature changes on phase behavior modeling of asphaltene precipitation and, in consequence, developing of asphaltene phase envelope in heavy crudes, remains a topic of debate in the literature. In this work, a computer code based on the non-isothermal improved solid model has been developed and used for predicting asphaltene precipitation data for one of the Iranian heavy crudes at different levels of temperature and pressure. The parameters of the non-isothermal model were tuned using three onset pressures at three different temperatures, and the asphaltene phase envelope was developed. The results showed that at high temperatures, increasing the temperature results in a lower amount of asphaltene precipitation and also it causes the convergence of lower and upper boundaries of asphaltene phase envelope. This work illustrates successful application of non-isothermal improved solid model for developing the asphaltene phase envelope of heavy crude. [ABSTRACT FROM PUBLISHER]

Asphaltene precipitation problems manifest themselves in different stages of oil reservoirs production. Experimental and modeling investigations are, therefore, employed as promising tools to assist in predictions of asphaltene precipitation problems and selection of proper production facilities. This study concerns experimental and modeling investigations of asphaltene precipitation during natural production and gas injection operations for a heavy Iranian crude oil at reservoir conditions. First, with design and performance of high pressure–high temperature experiments, asphaltene precipitation behavior is comprehensively investigated; the effects of pressure and temperature are fully studied during pressure depletion tests and the role of injection gas composition on precipitation is described in gas injection experiments. In the next stage, the obtained experimental results are fed into a commercial simulator to develop the asphaltene precipitation model. The results for the pressure depletion experiments indicate that the maximum amount of asphaltene precipitation takes place at fluid bubble point pressure. Increase in the temperature, as seen, causes to reduce the amount of precipitation for the entire range of pressures. For gas injection experiments, the onset of precipitation for CO2, associated, and N2gases takes place at around 0.20, 0.28, and 0.50 gas to mixture mole ratios, respectively. Carbon dioxide shows the highest asphaltene precipitation values and nitrogen has the lowest amounts for the whole range of gas mole fractions. Finally, the results for modeling indicate successful asphaltene precipitation predictions for both pressure depletion and gas injection processes. [ABSTRACT FROM PUBLISHER]

Many reservoir and production engineers face asphaltene precipitation as a major problem during miscible carbon dioxide flooding projects. Experimental studies regarding asphaltene precipitation are therefore employed to assist in selecting appropriate facilities and proper operation schemes. During this study, a series of high pressure, high temperature experiments are designed and performed to analyze asphaltene precipitation behavior of an Iranian light reservoir crude at reservoir conditions due to natural production and miscible CO2gas injection. For both sets of experiments, two different temperature levels (including reservoir temperature) are selected to investigate the role of temperature on asphaltene precipitation as well. Results of natural production experiments indicate that the maximum amount of precipitation occurs at reservoir bubble point pressure, while for each specified pressure asphaltene precipitation increases as the temperature is raised for the whole range of pressures. Carbon dioxide injection experiments, however, have terminated in some remarkable findings: for small CO2concentrations, CO2behaves as a hindering agent and lowers the amount of precipitation; on the contrary, for higher fractions (values larger than critical CO2concentration), the injection of CO2results in more asphaltene precipitation. An increase in temperature during CO2injection results in (1) the increase of asphaltene precipitation, (2) the shift of the critical CO2concentration to lower values, and (3) the decrease of the rate of asphaltene precipitation with CO2concentration. [ABSTRACT FROM PUBLISHER]

In past decades, many attempts have been made to use water-soluble polymers as a mobility control agent to improve sweep efficiency of enhanced oil recovery processes. However, sensitivity of the thickening behavior of these polymers to some harsh conditions, such as high salinity, has cast serious doubt on their applicability in reservoir conditions. By expansion of nanotechnology, scientists discovered that nanoparticles can be utilized as thickening and rheology control agents in many polymer solutions. In this study, hydrophilic fumed silica is added to hydrolyzed polyacrylamide and sulfonated polyacrylamide solutions. The effect of the addition of nano silica on the thickening and stability of the polymer solutions is investigated at different silica and electrolyte concentrations. Augmentation of nano silica has been found to have small but different effects on the thickening behavior of the two polymer solutions. It causes a viscosity increase in sulfonated polyacrylamide solutions while its effect on hydrolyzed polyacrylamide is decreasing at lower silica concentrations and increasing at higher silica concentrations. By increases in electrolyte concentration, the effect of nano silica on viscosity diminishes, and a severe coagulation problem is observed. These results question the applicability of nano silica particles as a thickening additive for solutions of these high molecular weight polymers, unless some treatments are done on the silica surface. [ABSTRACT FROM PUBLISHER]

Although most heavy oil reservoirs contain discontinuous shaly structures, there is a lack of fundamental understanding how the shaly structures affect the oil recovery efficiency, especially during surfactant flooding to heavy oils. Here, an experimental study was conducted to examine the effect of discontinuous shales on performance of surfactant flooding by introducing heterogeneities to represent streaks of shale in five-spot glass micromodels. Results show that oil recovery in presence of shale streak is lower than in its absence. Based on the authors’ observations, the presence of flow barriers causes premature breakthrough of injected fluids and also an unstable displacement front. As well, displacement efficiency of surfactant flooding is dependent strongly on the shale distribution configuration. Increasing shale content causes reduction of ultimate oil recovery and also severe fingering during water flooding while it compensates during surfactant flooding considerably. In shaly patterns, in the case of surfactant flooding, the oil recovery after breakthrough increases significantly, while it changes much less for the case of water flooding as well as flooding in homogeneous model. Oil recovery efficiency and breakthrough time improved with increasing surfactant concentration. However, beyond a specific limit of sodium dodecyl sulfate concentration, around 2000 ppm, incremental oil recovery becomes insignificant. Presence of connate water in surfactant flooding scheme can improve the recovery efficiency in shaly patterns. Results of this work can be helpful to investigate the optimal location of injection/production wells during enhanced oil recovery schemes in shaly reservoirs using five-spot micromodels. [ABSTRACT FROM AUTHOR]

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]

In this work, the process of free gravity drainage under the influence of ultrasonic waves was investigated. A glass bead pack porous medium was used to perform free fall gravity drainage experiments. The tests were performed in the presence and absence of ultrasonic waves, and the data of recovery were recorded versus time under both conditions. The wetting phase relative permeability curves were obtained using the data of recovery versus time, based on the Hagoort backward methodology. Subsequently, using the wetting phase relative permeability curve, the relative permeability of non-wetting phases were calculated by performing history matching to the experimental production data. The results revealed that ultrasound considerably increases the recovery factor of the free gravity drainage process. It was also observed that the relative permeability of both wetting and non-wetting phases increases under exposure to ultrasonic waves. The results of this work can be helpful in better understanding/evaluating the behavior of the relative permeability curves of both wetting and non-wetting phases during a free gravity drainage process under exposure to ultrasonic waves. [ABSTRACT FROM AUTHOR]

Capillary pressure is one of the most important parameters for reservoir engineering studies. Although different experimental methods are devised to measure capillary pressure, these methods do not represent the physics of fluid flow, which happens at reservoir conditions. Thus, it is attempted to extract the capillary pressure from spontaneous imbibition data, the common mechanism of oil production in water wet porous media. In this work, a new approach is developed to obtain the imbibition capillary pressure curve by using spontaneous water imbibition data in oil-water-rock systems. Comparison of calculated imbibition capillary pressure curves by the new approach with experimental values shows a good accordance with each other. [ABSTRACT FROM AUTHOR]

Despite numerous studies, there is a lack of fundamental understanding about the displacement behavior of surfactant-crude oil systems under the influence of different fractures' geometrical properties in five-spot systems. In this work, a series of flow visualization experiments were carried out on one-quarter five spot glass micromodels at various fractures' geometrical properties, such as fracture density and fracture continuity, under oil-wet condition. The influences of injection of Linear Alkyl Benzene Sulfonate and Sodium Dodecyl Sulfate surfactants as well as the effect of fracture geometrical parameters, on macroscopic and microscopic displacement behavior have been investigated. The micromodels were initially saturated with crude oil. Precise analyses of the high quality pictures, which were taken during experiments, were used to explore the surfactant's displacement efficiency. It has been found that two mechanisms govern such a process at the pore scale. One is responsible for decreasing the residual oil saturation and the other mechanism is increasing the matrix-fracture interactions through the porous media. The experimental results show that the magnitude of interfacial tension between the existing fluids was the most important parameter that altered the flow behavior at pore level. The observations revealed that high penetration of surfactant solutions from fractures into the matrixes perfectly postponed the breakthrough time and increased the oil recovery. As a result of better dispersion of surfactant through the matrix, it has been found that the higher fracture density yields a higher oil recovery. The media containing continuous fractures showed that higher oil recovery compared to discontinuous fractures. The results also showed that the average oil recovery during water injection is a strong function of the fracture properties, whereas use of Sodium Dodecyl Sulfate solution extremely reduces the effect of fracture geometrical properties. The results of this work can be helpful to better understanding the surfactant-crude oil displacements in fractured 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]

During miscible displacements in fractured porous media, one of the most important factors that plays a significant role in oil production is the matrix-fracture interaction. In this work, a series of hydrocarbon injection experiments have been performed on a fractured glass micromodel that was designed specifically to study matrix-fracture interaction. A high quality image analysis method was used to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that in the case of unit viscosity ratio, the injection rate increased the slope of recovery curve and consequently improved the final oil recovery. However, when using a viscosity ratio of 65, the injection rate increased the oil recovery at earlier times due to the breakthrough and fracture drainage. At later times, diffusion and dispersion became dominant and oil recovery decreased. Studying the effect of molecular diffusion revealed that by using an optimum solvent the oil recovery at both early and late times increased. Fingering phenomena appeared in the matrix as fingers and in the matrix as channeling, which drained fracture in early times of the process. In higher viscosity ratios, dispersion dominantly takes place in an upward direction, however, in the lower viscosity ratio the effect of fracture in flooding decreased and dispersion takes place in a left-to-right direction. It can be concluded that during miscible displacement in fractured porous media dispersion in fracture is directly proportional to viscosity ratio while dispersion in matrix is inversely proportional to it. The results of this work are helpful in understanding the matrix-fracture interaction, the effect of injection rate, molecular diffusion, and viscous fingering behavior, which are crucial for accurate prediction of oil recovery in fractured reservoirs during miscible displacements. [ABSTRACT FROM PUBLISHER]

The use of water-alternating-gas injection can potentially lead to improved oil recovery from the fields; simultaneous water and gas injection is a form of water-alternating-gas injection. However, there is still an incomplete understanding of these processes and the need for comparative work is inevitable. Core flood experiments and compositional simulations of water-alternating-gas and simultaneous water and gas processes are presented. Immiscible, near miscible, and miscible modes of injection are covered. Matching process is done and optimization of design parameters (injection rate, slug size, water-alternating-gas ratio, and injection gas) is performed. Experimental data demonstrate that simultaneous water and gas injection accelerate oil production as compared to water-alternating-gas injection in all modes of injection, and miscible simultaneous water and gas injection with CO2produces more than 74% of original oil in place. The simulation results indicate that with different water-alternating-gas ratios (water/gas volumetric) the ultimate oil recovery during simultaneous water and gas injection in operational range (water-alternating-gas ratios between 0 and 2) is almost independent of water-alternating-gas ratio. [ABSTRACT FROM PUBLISHER]

Surfactant flooding is known to lower the interfacial tension and, hence, reduces capillary forces responsible for trapping oil. Despite numerous experimental studies, little is known about the role of fracture geometrical properties on oil recovery efficiency during surfactant floods, especially in five-spot systems. In addition, application of sodium dodecyl sulfate for oil recovery in fractured media is not discussed well. In this study, two types of surfactant solutions have been injected into micromodels, which were initially saturated with crude oil, having different length, orientation, and distribution of fractures under oil-wet conditions. Precise analyses of continuously recorded pictures during the experiments were used to determine the oil recovery efficiency. The observations reveals that high penetration of surfactant solutions from fractures into the matrixes perfectly postponed the breakthrough time and increased the oil recovery by sweeping the oil in the matrix. This matrix-fracture interaction for the case of sodium dodecyl sulfate solution is much higher than linear alkyl banzene sulfonate floods. As a result of better dispersion of injected surfactant through the matrix, it has been found that the longer fracture yields a higher oil recovery. Fractures perpendicularly oriented to the pressure drop direction exhibit higher recovery than those oriented directly along the pressure drop path. As expected, the oil recovery of water flooding is highly dependent to fracture geometrical properties. Use of linear alkyl banzene sulfonate solution reduces the role of fracture geometrical properties, and this role is at minimum for the case of sodium dodecyl sulfate solution. Therefore, it can be concluded that the use of this surfactant can be a good candidate for decreasing the uncertainties of fractures' geometrical properties as an enhanced oil recovery method in fractured reservoirs. [ABSTRACT FROM PUBLISHER]

In this study, the nonlinear partial differential equations governing two phase flow through porous media are solved using two different methods, namely, finite difference and finite element. The capillary pressure term is considered in the mathematical model. The numerical results on a 2-D test case are then compared with the experimental drainage process and water flooding performed on a glass type micromodel. Based on the obtained results, finite difference technique needs less computational time for solving governing equations of two phase flow, but findings of this method show less agreement with the experimental data. The finite element scheme was found to be more adequate and its results are matched well with the obtained experimental data. [ABSTRACT FROM PUBLISHER]

Finger initiation/development at fluid-fluid interface during miscible floods can cause poor displacement efficiency, which is undesirable in enhanced oil recovery processes. In this work, a series of hydrocarbon injection experiments performed on 5-spot glass micromodels that were initially saturated with the heavy crude oil. The fractured micromodels with different fracture geometrical characteristics were used in the tests. High quality image analysis was applied to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that higher solvent dispersion in the fractures rather than matrix in both longitudinal and transversal directions cause the finger behavior to be affected by the fracture geometrical characteristics. It also diminishes and merges the fingers to a unit solvent front by increasing spreading in regions near fractures. Due to the heterogeneity induced by fractures in media, finger tip splitting initiates before solvent breakthrough. In fact, longitudinal dispersion improves shielding, while transversal dispersion increases the fingers spreading and splitting. In addition, it has been revealed that splitting, before and after breakthrough, as well as spreading in regions near fractures is directly proportional to the fracture scattering, fracture discontinuity, and fracture density of the medium. Also, it has been found that shielding phenomena is mostly affected by fracture orientation in which its maximum occurrence is for the case of zero degree to average flow path. The results of this work can be helpful for a better understanding of viscous fingering behavior, which is crucial for accurate prediction of oil recovery in fractured reservoirs during miscible displacements. [ABSTRACT FROM AUTHOR]

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 by increasing vibration amplitude. Also, it has been found that in two-phase flow systems, wave can increase the produced oil-water ratio in the fractured media. The results of this study can be applied to the fractured reservoir simulations and can be a path breaking to the future studies on the prediction of flow enhancement under elastic wave in the fractured reservoirs. [ABSTRACT FROM AUTHOR]

CO2injection is a potentially viable method of enhanced oil recovery for medium oil reservoirs. The authors compare the effect of gas injection strategy (simultaneous water-alternating gas [SWAG], water-alternating gas [WAG], and continuous gas injection [CGI]) on recovery in immiscible, near-miscible, and miscible modes of injection. It has been proved that CGI is not the most efficient injection scenario in oil-wet reservoirs. Miscible and near-miscible core flood tests demonstrated high oil recoveries in all injection strategies due to high capillary numbers achieved as a result of miscibility. The fluid mechanics of floods were discussed using pressure drop data, different mechanics was observed for SWAG, WAG, and CGI and better mobility control of SWAG was proven. Results show that tapering postponed gas breakthrough and less amount of gas was injected using this technique, making tapering favorable economically and operationally. Experiments with different gas–water ratios were performed and the results show that the ultimate oil recovery during SWAG injection is almost independent of gas–water ratio. This makes SWAG injection a promising recovery process especially for reservoirs where continuous and high-rate gas injection is not possible. [ABSTRACT FROM PUBLISHER]

The use of polymer flooding as one of enhanced oil recovery methods has recently increased. The occurrence of high shear rates in reservoir and near well bore through perforation nozzles during polymer flooding cause shear degradation of polymers and therefore polymer viscosity has decreased. Rheological behavior of polymer solution in different conditions of oil reservoir is one of the key factors to develop use of polymer solutions. A few researches are available regarding improving rheological behavior of polymeric solution. In this study, to investigate the effect of nanoparticles on rheological behavior of polymer solutions two samples were prepared: polyacrylamide solution in water and suspension of silica nanoparticles in polyacrylamide solution. The sample viscosities in different shear rates were measured. The best rheology models were developed to state rheological behavior of prepared samples and the measured data were compared to power law model. An increase in the viscosity of the suspension solution with respect to polymer solution in different shear rates was observed. Rheological analysis showed that power law model is a good rheology model to demonstrate rheological behavior of suspension in low and medium shear rates and is an acceptable model for polymer solution in low shear rates. Two types of flooding test were performed in a glass micromodel: flooding by polyacrylamide solution and suspension of silica nanoparticles in polyacrylamide solution. The results of flooding test showed a 10% increase in oil recovery for nanosuspension solution in comparison with polymer solution after one pore volume fluid injection. [ABSTRACT FROM PUBLISHER]

The role of micro-models for studying fluid flow mechanisms at the pore scale is undeniable. Recently, application of laser technology has been much attended for developing micro-models with different flow patterns. However, there is no reported experience in the literature that has been correlated with the laser parameters for direct control of micro-model pore size characteristics. In this work, a CO2laser device was used to construct flow patterns on the glass surfaces, and the effect of fractional power, engraving speed, and resolution ratio on etched depth as well as surface heterogeneity of constructed models were investigated. A new correlation has been proposed that relates the laser parameters to the pore morphology of the glass micro-models. The proposed exponential expression provides a reasonably accurate and fast tool for controlling micro-model characteristics. In addition, microscopic observation showed that sensible heterogeneity on glass surfaces induced by laser can be controlled by adjusting the resolution ratio, and is a good representation of reservoir rock surfaces. The permeability of the constructed models by a laser device is a better representation of real reservoir rock conditions. The results of this work can be helpful for designing and constructing micro-models with controlling pore morphology. [ABSTRACT FROM PUBLISHER]

Gravity drainage is the main production mechanism in the gas invaded zone in naturally fractured reservoirs. However, there are large ambiguities and complexities, resulting from the dynamic of oil depletion from matrix blocks toward the fracture network. Visualization of drained oil at pore scale using glass micromodels provides the opportunity to better understand the effects of different parameters which might affect oil recovery from fractured reservoirs. In this work a micromodel apparatus generated by laser etching is used to perform some gravity drainage tests on the network patterns. The experiments were performed on double block systems using crude oil. The block to block interactions and the formation and changes of capillary bridges between matrix blocks were visually investigated. A suitable empirical model of gravity drainage is used for the prediction and evaluation of experimental data. The empirical model will be used for sensitivity analysis of fracture dip angle which might affect oil recovery efficiency and oil drainage rate, and as seen in experiments this parameter has a direct relationship to and positive effect on oil recovery. We also found the important rule of the block to block effect on the recovery of blocks and the higher recovery of upper matrix blocks than lower ones shows this reality; also it was claimed that the threshold height of fractured reservoir blocks doesn't show the true matrix capillary pressure of matrices, because of the block to block effect that helps the gravity forces in the matrix draining procedure. By increasing the block tilting angle up to α = 90 -- tan--1(y/x) as y and x are the 2-dimensional block sides lengths, the recovery of the block will increase but its initial drainage rate will decrease. ItŠs a result of an increase in effective block height and increasing the capillary bridges stability which increases recovery, and the decrease of rate is due to capillary bridges frequency decreasing, which decreases the area open to flow. [ABSTRACT FROM AUTHOR]

The authors studied deposition and entrainment of asphaltene particles as major mechanisms that occur in porous media. Deposition mechanisms that contribute to permeability reduction and entrainment of deposited particle improve the damaged permeability value. While in most previous works the effects of entrainment mechanism are considered negligible, in this study miscible CO2 injection tests were conducted by core flood apparatus to investigate the effect of asphaltene deposition on permeability and porosity alterations. Results indicated that proposed model for entrainment mechanism is affected by deposition mechanism. The asphaltene deposition core's characteristics have undeniable roles in core impairment. [ABSTRACT FROM AUTHOR]

In this investigation, an accurate high pressure and temperature diffusion setup was applied to measure the diffusion coefficients of methane in Iranian heavy oils in presence and absence of porous media by using the pressure-decay method. The solvent diffusivity in heavy oil was determined by both graphical and numerical methods. In addition, the effects of the porous medium and the temperature on the molecular diffusion coefficient of the solvent gas in the liquid phase were discussed and finally, using experimental data, a functionality dependence of molecular diffusivity on temperature and porous medium characteristics was proposed. [ABSTRACT FROM AUTHOR]

The objective of this study was to experimentally investigate the performance of water-alternating gas (WAG) injection in one of Iran's oil reservoirs that encountered a severe pressure drop in recent years. Because one of the most appropriate studies to evaluate the reservoir occurs generally on rock cores taken from the reservoir, core samples drilled out of the reservoir's rock matrix were used for alternating injection of water and gas. In the experiments, the fluid system consisted of reservoir dead oil, live oil, CO2, and synthetic brine; the porous media were a number of carbonate cores chosen from the oilfield from which the oil samples had been taken. All coreflood experiments were conducted using live (recombined) oil at 1,700 psi and reservoir temperature of 115°F. A total of four displacement experiments were performed in the core, including two experiments on secondary WAG injection and others on the tertiary water and gas invaded zones WAG injections. Prior to each test porosity and permeability of dried cores were calculated then 100% water-saturated cores were oil-flooded to obtain connate water saturation. Therefore, all coreflooding tests started with the samples at irreducible water saturation. Parameters such as oil recovery factor, water cut, and gas-oil ratio and production pressure of the core were recorded for each test. The most similar experimental work with the main reservoir condition, indicated that approximately 64% oil were recovered after 1 pore volume of WAG process at 136,000 ppm brine salinity. Although tests show ultimate recovery of 79% and 55% for secondary and tertiary injection in gas and water invaded zones, respectively, immiscible WAG injection efficiency in the gas and water invaded zones will not be proper. In the similar test to field properties, the average pressure difference about 70 Psig was observed, which shows stable front displacement. These experiments showed that there was significant improvement in the oil recovery for alternating injection of water and CO2, especially in the secondary recovery process. Water breakthrough time in almost all of the tests shows frontal displacement of injected fluid in cores and produced gas-oil ratio changes a little whenever the injection is miscible and increases rapidly in immiscible processes. [ABSTRACT FROM AUTHOR]

This experimental study is aimed at evaluation of the performance of secondary WAG injection in carbonate cores at different pressures. To do so, a comprehensive series of high-pressure high-temperature (HPHT) core flooding tests are conducted. The fluid system includes reservoir dead and live crude oil, CO2, and synthetic brine while the chosen porous media consists of a number of fractured carbonate core samples. Parameters such as oil recovery factor, water and oil production rates, and pressure drop along the core are recorded for both dead and live oil. According to results, at first increasing pressure improves the oil recovery, but this improvement after MMP is not as significant as it is before MMP. Also recoveries of dead and live oils at same pressure show different values due to differences in miscibility condition of injected gas. Then as the graphs demonstrate, relative permeability reduction due to hysteresis effect has dominant effect on pressure drop curves. Finally, as the production rate curves show, nearly all of the remained oil after breakthrough is produced as the gas is being produced and almost no oil can be recovered during water production portions. [ABSTRACT FROM AUTHOR]