Sharif Digital Repository

Today, increasing the productivity of reservoirs is more important than in the past, while the use of nanoparticles to change the wettability of rock and increase the recovery factor from the reservoir has been considered by many researchers. Despite previous studies on the use of nanoparticles to change the wettability of rock to gas-wet, the use of nanocomposites with super gas-wet at high temperature and pressure in the crude oil-gas system has rarely been considered. In this research, several nanocomposites with different structures have been synthesized in the laboratory and nanofluids with different formulations have been used to coat the rock thin sections and measure droplet contact... 

One of the most important parts of vehicles and most of mechanical machines is power transmission system, especially the Gearbox used in them.In order to optimize the use of energy, especially fossil fuel, researchers are looking for new mechanisms to refine the operation of vehicles and other machines.One of the mechanisms which absorbed researcher’s attention during recent years is the Continuously Variable Transmission. By using these gearboxes which are replaced with older samples, we can have the continuous range of aspect ratio between two constant values. This important property causes the decrease of the use of fuel.In recent decades many manufacturers have used different kinds of... 

After discovery of superconductivity in 1911 people try to find superconductors with higher Tc. High Tc superconductivity in cuprates and iron based superconductors was discovered in 1986 and 2008 respectively. However, there is not any unit theory for high Tc superconductivity in cuprates or iron based superconductors. Study of electronic and phonon structures of high Tc superconductor compounds can lead to find theory of high Tc superconductivity.
In this dissertation electronic structure of Ba1-xKxFe2As2, which belongs to class of 122 of iron based superconductor, under potassium doping x=0,0.5,1 has been studied. To this end ab-initio method and Density functional theory have been... 

The discovery of Iron-based superconductors with maximum transition temperature of 56 Kelvin and High critical magnetic field of the order of 50T at temperature 20K has created evolution in different fields of superconductivity including practical issues. BaFe2As2 family is one of the most important compounds of Iron-based superconductors and with different doping elements for instanse elements of the first column like Potassium inters superconducting state with critical temperature of 36K.
The purpose of this thesis is to localize the technology of making this compound in Iran which no project has been done in this field in the country before. In this thesis manufacturing, Optimization... 

Nowadays there are various means in the field of orbital mechanics used in different levels and their accuracy depends on the theory and complexity of the governing equations used in their development. Most of them just simulate the motion of an orbiting satellite while there exist some commercial products able to provide the user with the orbital performance specifications and almost none of them have a module to design an orbit, based on a required performance such as specific coverage / ground track, shadow/light duration, etc .... Although satisfying performance requirements and a set of orbital elements simultaneously only seems to be possible for some particular orbits, there is an... 

Foam injection for enhanced oil recovery is concerned by petroleum engineers because it decreases adverse effects of fingering and gravity segregation caused by the injected fluid .Obviously foam stability is an important factor in the efficiency of this process. So investigating it is an imperative. One of the ways that less studied and can improve foam stability is using of nanoparticles. In this project effect of nanoparticles on foam stability and displacement mechanism during foam flooding has been discussed.
Study consisted of two sets of experiments. In the first part, the static foam stability in the presence of silica nanoparticles has been investigated. Also influence of... 

Miscible displacement in fluid flowing through a porous medium plays an important role in many environmental and industrial applications; for instance, miscible displacements in enhanced oil recovery processes and pollutant spreading in groundwater. A large number of numerical approaches have been developed to solve the advection-dispersion equation that describes the behavior of miscible displacement in porous media. Most of these numerical models suffer from numerical dispersion. Random walk seems to be an effective method to overcome this problem especially in heterogeneous media. Here, a random walk model was developed and used for simulating miscible displacement in heterogeneous porous... 

Design and construction of an optical fiber sensor for liquid concentration detection are reported. This sensor operates based on light intensity modulation.Such modulation results from alteration of total internal reflection into partial reflection at the interface. It is well known that the extinction ratio is varied by changing the concentration.In this system,two optical fiber swere used, one transmitting the light source, another acting as the receiving fiber and a glass prism providing the total and partial reflections. The modulated intensity has been measured by using a receiving fiber. During the concentration measurements, when a liquid in a vessel touches the 45° faces of the... 

Various applications of speech processing systems are gaining more and more attention. Performances of these systems are dramatically affected in presence of background noise. Attempts toward improving quality of degraded speech have emerged into filed of speech enhancement which is one of the interesting topics in speech processing domain. In this thesis various single channel speech enhancement methods are studied briefly. Statistical methods as one of the most successful methods are studied more deeply. These methods are divided into two categories of short-term modeling of speech and long-term modeling. The aim of this thesis is to improve the performance of long-term methods of... 

One the basic challenges during drilling of both vertical and horizontal wellbores is due to mud filtrate invasion into the formation. Addition of nanoparticles to composition of drilling fluid has been recognized as a measure of control and reduction of filtrate invasion. Despite notable advances in formulation of nano-enhanced drilling fluids, effects of surface wettability of nanoparticles on their performance have not been studied with any precision. Moreover, return permeability of a grain packed porous media after extreme invasion by mud filtrate has not been experimentally measured in a radial system, yet. The last but not least, Generation and development of mud cake opposite the... 

Using foam for reducing undesirable effects of fingering and gravity segregation in enhanced oil recovery through gas injection has attracted a rapidly increasing interest in recent years. Lack of stability of foam often limits its application. However there is a lack of systematic study of effects of unmodified and in-situ modified silica nano-particle on foam stability and foam behavior in the presence and absence of oil and also polymer effects from the prospective of analysis of foam dynamic stability, size of foam bubbles, and foam flow behavior in Hele – Shaw cell. Main objectives of this study are mechanistic investigation of effects of polymer – surfactant systems and in-situ... 

Formation damage in oil and gas wells is mainly induced by drilling operations. Filtrate and particle invasion into formation as the sources of this damage caused serious problems, e.g. reduction of production rates. Therefore numerical modeling of this phenomenon helps us to better understand the process, and as a result, control and reduce formation damage associated with this impairment. In this research, a model to estimate the invasion depth and damage of mud filtrate from water-based mud is presented. Filtrate invasion into the formation is investigated by convection-diffusion equation with regard to dispersion term. The invasion depth is obtained from mud filtrate profile in the... 

Gas injection as an enhanced oil recovery (EOR) method usually suffers from low recovery efficiency. The low viscosity and density of gas as well as reservoir heterogeneity are the main reasons of early breakthrough and override of gas in oil reservoirs. To mitigate the poor sweep efficiency of gas injection, surfactants can be co-injected or injected in an alternating manner with gas to form foam within the reservoir rock. The foam formation can reduce the mobility of the injection fluids in porous media. A significant challenge of foam injection is the stability of the foam in formations and the foam liquid drainage rate is one of the key factors which characterize or show the efficiency... 

gas injection method is one of the common methods of EOR, which has a long history. In gas injection, molecular entry gas mixing is the controlling factor of oil play. Therefore, the exact value of this coefficient becomes an important requirement for the simulation and modeling of oil reservoirs, which can only be determined by laboratory consumption methods. In this research, the pressure decay method is used as a common laboratory method to determine the penetration coefficient of methane, nitrogen and gas enriched with intermediate compounds in crude oil of one of Iran's oil reservoirs. In most of the available records in the investigation of the mentioned gas diffusion coefficient in... 

In this work, flow transport, distribution, and dissolution of non-aqueous phase liquids (NAPLs) in heterogeneous porous media were modeled by focusing on the dissolution process in pore-level and field scale. First, by adopting advection-diffusion and mass transfer equations, dissolution process and NAPL distribution were investigated in a heterogeneous porous media using pore network modeling. The 2-D developed model was based on observations of micromodel tests. The pore scale simulator which adopted by this work was improved in some aspects in comparison to previous models in the literatures. First, in the phase displacement, by considering more realistic geometries for pore structure... 

Gas injection is one of the common methods for enhance oil recovery from oil reservoirs. At miscible injection condition, the efficiency of the process is majorly affected by the molecular diffusion coefficient of the gas in the oil. Therefore, the accurate value of this coefficient is an essential for applying in reservoir simulator. However, determination of this coefficient only is possible through experimental methods. In this study, pressure decay method was applied to determine the diffusion coefficient of nitrogen, methane and carbon dioxide gases in crude oil. The reasons for choosing this method are : accuracy in designing the experiment, covering a wide range of pressure... 

Due to the fact that, over 60% of oil reserves are located in fractured reservoirs, this type of reservoirs requires a great deal of attention. The presence of the fractures in porous media results in many complexities in the liquid path and production, consequently, simulation and modeling of flow equations is highly important. In order to achieve a more profound understanding of liquid flow in gravity drainage mechanism, the concept of capillary tubes is initially used. By using the capillary tube concept, at first, the gravity drainage mechanism is investigated in the first block in a stack of blocks and an analytical solution is presented for this case. Then, the stack of blocks is... 

Groundwater is one of the vital sources of drinking water worldwide, yet it faces the risk of contamination from organic and inorganic substances. These pollutants can persist in the environment for extended periods, leading to continuous contamination. One of the key factors in the rapid transport of these contaminants is the presence of fracture networks within porous media. These fractures play a crucial role in facilitating the movement of pollutants to deeper layers of groundwater aquifers. The fracture networks enable contaminants to migrate more rapidly and penetrate various regions, complicating pollution management. Additionally, the natural flow of groundwater acts as a driving... 

Fractured reservoirs have allocated a significant portion of Iran's and the world's oil and gas reserves, underscoring the importance of predicting the performance of these reservoir types in the oil and gas industry. Predicting the performance of fractured reservoirs by professional reservoir simulators, especially in enhanced recovery conditions, requires precise information on fracture flow functions, which is often limited. These functions vary for each reservoir based on the distinct characteristics of the rock and fluid, and the only way to determine them is through appropriate laboratory experimentation and modeling of the results. Currently, in simulation models, the relative... 

Most of oil content, especially in Iran, has been reserved in fractured reservoirs, so study and modeling of production mechanism of these reservoirs are great of importance. Gravity drainage is one of these effective production mechanisms in fractured porous media which dynamic pore scale modeling of this mechanism will lead to better understanding of it. In this work, the effects of variety of parameters such as oil gravity, interfacial tension between oil and gas, pore and throat size distribution, fracture aperture, and block to block interaction (capillary continuity and reinfiltartion) have been investigated. So developed simulator in this work has two main and separated parts, which...