Sharif Digital Repository

Two phase flow through porous media is one of great interests which have been studied for decades in petroleum sciences and even other fields, e.g. hydrology and physics, to solve problems such as enhanced oil recovery, contaminated groundwater or CO2 sequestration projects. Flow in porous media typically predict by means of Darcy’ law which in two phase flow lead to equations such as Buckley-Leverett or Koval, but today it is well approved that compact prediction of flow pattern by these equations may be accompanied by enormous errors and it’s because flow in certain condition is fractal. In this work a new mechanistic model has been used for simulating of immiscible drainage process and... 

MPD technique manages drilling pressure to keep bottom hole Pressure balanced in the well. The objective to this studs, is to approximate the well pressure to formation pressure to prevent entry of fluid into the well. MPD is a new method drilling in which, driller controls the annulus pressure in order prevent drilling problems. the circulating fluids system employed by MPD technology is more akin to that of a pressure vessel. In this thesis, using in laboratory-made machine, reacts with sudden changes in pressure at the bottom hole in the shortest possible time. Basically, this system is a system where well bore pressure management is obtained by adjusting the pressures along the well bore... 

Fracture reservoir modeling is an important subject since a lot of oil and gas resources around the world are preserved in them. One of the enhanced oil recovery methods in these reservoirs is gas injection and especially CO2 injection because of environmental issues. In one part of this research, a new diffusion mechanism called “double cross-phase diffusion” is introduced and applied to simulate the non-equilibrium gas injection process into fractured rocks. This new mechanism represents additional multicomponent gas diffusion into the crude oil through the water phase, existing in porous media as initial water saturation. Therefore, a lab-scale simulator, by implementing the generalized... 

Chemical flooding such as surfactant flooding in oil reservoirs can change the wettability and interfacial tension between oil and water and so reduce the residual oil saturation in the reservoir. Some of these materials can be adsorbed a lot on the surface of carbonate rocks, so it is difficult to predict the oil recovery factor in such process. Therefore it is necessary to survey the adsorption amount of surfactants in chemical EOR injections.In this thesis, the adsorption of a nonionic surfactant on the surface of carbonate rock is experimented and the proper model is obtained. Then the surfactant is injected in a core saturated with oil to observe the efficiency of this surfactant in... 

One of the most important EOR methods in oil reservoirs is surfactant and polymer flooding. Surfactants cause decreasing in interfacial tension between oleic and aqueous phases. However, polymers give us efficient mobility control in displacing oil by increasing the viscosity of aqueous phase. Therefore, oil is displaced in aqueous phase by viscous forces.
One of the most important challenges in surfactant flooding is adsorption. The net surface charge distributed on the rock surface depends strongly on pH. When we inject surfactant in reservoir, electrostatic charge on rock surface causes the first-layer adsorption. After that we have had second-layer adsorption.
In this thesis we... 

In the absence of appropriate control, several accidents in the nuclear power, lead to serious consequences including core melted and radiation leakage outside reactor containment. In all these events, when core melted, the reactor operation is always finished and all efforts are then directed to environmental impacts of radioactive materials to the external environment. However, the occurrence of events that would bypass reactor containment, have special significance, because all possible efforts in order to limit the leakage of radioactive materials to the external environment are ineffective. In this respect the occurrence of such incidents, as most of which is considered the worst... 

The rapid evolution of artificial intelligence (AI) technologies has led to the widespread adoption of AI systems in diverse research and industrial fields. Deep neural networks, at the forefront of AI's power, demonstrate high performance by leveraging large volumes of training data. However, acquiring such vast amounts of data requires collaboration among individual data owners, who may have concerns about privacy. To address these concerns, various privacy-preserving methodologies have been proposed. These methodologies share a common goal of striking a balance between preserving privacy and maintaining data utility. This study aims to explore and analyze these privacy protection... 

Aphron drilling fluids or CGA fluids are the wellknown updated drilling fluids in recent years.this kind of drilling fluids can control the mud loss into the formation and thus reduce formation damage and drilling costs. its structure consists of two phase fluid (gas and liquid) that the aphrons are the micro bubbles with 10 to 100 micrometer diameter that have strong stability in liquid phase compared to foamy drilling fluids. Generally aphron drilling fluids are made of base drilling fluid and surfactants, for more stability, mixed surfactant-polymer additive is so beneficial. in the last two decades, the Lattice-Boltazmann method is introduced for computational fluid dynamic area and... 

With the development of science and technology and its application in IT (e.g. internet, intranet and URL) the sharing of manufacturing resources reaches higher research attention, where resource virtualization enables new possibilities in terms of collaboration. As a result of these changes, with the intention of sharing optimum allocation of cloud manufacturing resource and capability among service providers and service users, the concept of service composition was introduced. Cloud services can be combine to build virtual manufacturing chain, so a strategy focusing on the evaluation and selection of virtual manufacturing resources to fulfill given services is fundamental exercise to... 

In the near future, it is expected that the microgrids become widespreed due to issues such as reliability, increased penetration of renewable energy sources and distributed generation, environmental concerns and shortage of fossil fuels. Different control methods have been suggested to regulate the frequency and voltage of the system so that these quantities remain in their permissible range upon islanding and in the islanded operation mode. However, in emergency conditions, such as shortage of generated power compared to the load of microgrid, frequency or voltage reduction occures due to imbalance. In this situation, it is invitable to shed extra load to maintain the stability and... 

The consumption of fossil fuels (oil, gas and coal) increased the concentration of greenhouse gases in the atmosphere that cause increase of earth atmosphere temperature and lots of environmental problems. Using appropriate alternative energy sources is one way to control this emission, while considering energy infrastructures shows this is a far solution. An early way for decreasing the emission of greenhouse gases in the atmosphere is injection of CO2 in geological formations. Since approximately 50 years ago some researches in this area have been developing. The most important limit of these projects is its costs so it is wise to combine them with gas injection projects in gas and oil... 

Carbonate matrix acidizing using hydrochloric acid which causes CO2 generation is one of the most popular well stimulation techniques in recent decades. Lots of the wormhole propagation models developed for laboratory scale, assumes that the cores are fully saturated with aqueous solution and no CO2 gas is produced. Final purpose of this research is to develop a geochemical model describing equilibrium composition of a 3 phase system of acidic solution-gas-rock accurately in common pressure and temperature conditions of carbonate matrix acidizing to obtain main inputs of acid reactive flow in porous media from it. In this regard, concept of the “extent of the reaction” is defined and after... 

Pulsating heat pipes (PHP) are complex heat transfer devices which unlike conventional heat pipes do not contain any wick in their structure. The effective parameters consist of; working fluid, volumetric filling ratio, operational orientation and input heat power have been investigated here. The experimental set-up we have contemplated, fabricated and tested included five turns, made of copper tube coupled with two glass tube of internal diameter 1.8 mm. The height of evaporator, condenser and adiabatic section was 60, 60 and 150 mm, respectively. The evaporator was heated with electrical element connected to an AC variant power supply and the condenser was connected to a constant... 

The ultimate goal of this study is to provide a general framework for assessing the reliability of different layouts of marine structures. This reliability is a yardstick for determining the safety level of marine structures at any given time. Using this criterion, it is possible to prioritize structures for maintenance operations and, by performing appropriate operations, create a uniform level of safety for all marine structures in a region, or the best type of fixed platform arrangement for structural strength He chose economics and so on. This framework is flexible and expandable, which means that its generalization to various hazards and the various effects of these hazards is possible... 

One of the best stimulation methods for oil and gas wells is matrix acidizing in order to increase the near wellbore permeability. in acidizing, good acid coverage in different layers is one the main goals. so, various methods have been presented. important part in using these methods is to not damage formation and economic matters. modern methods utilize VES acids for this purpose. viscoelastic characteristics of these materials by formation of miscellaneous, increases the apparent viscosity by a large degree. for this reason, VES fluids can be used to improve acid divergence in acid injection operation. acid system based on viscoelastic surfactants that is changed to gel instantly, can be... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

In this work, a basic model for numerically simulating matrix acidizing in carbonate formations is developed. This model employs laboratory linear acid core-flooding data and avoids any fitting parameters. Wellbore-scale numerical simulation is based on finite-volume method with Cartesian coordination and cubic meshing. Mass transfer equations are based on fluid front tracking and the momentum transfer equation is the Navier-Stokes equation for flow in porous media. The effect of fine-scale dissolution phenomena of carbonate rocks are translated into the coarse-scale by homogenization. In this work, it is tried to achieve a simple but logical approach towards a correct simulation, avoiding... 

The aim of this research is to model the separation and transport of multi-component gas mixture through a nanoporous membrane by using pore network models (PNM).
The first part of this project represents the membrane simulating by means of the PNM. A three-dimensional network is used to represent the membrane’s pore space and it consists of two parts; pore and throat. The pores are the main parts of the network and their diameter is characterized according to the pore size distribution of the membrane. Every throat connects two pores and the number of throats which is connected to each pore is named "coordination number". Using a variety size of pores and throats leads to production of... 

Shape Memory alloys are a kind of intelligent materials developed in recent years due to their comprehensive use in medical, robotics, and other advanced sciences. Two main characteristics of them are shape memory effect and superelasticity put these materials in the category of advanced materials. Recently, the new branch of them attracted many studies which is the porous shape memory alloys. The importance of this class of material is related to their properties such as bio-compatibility, superelasticity and shape memory effect. Since shape memory alloys are usually expensive, a new field is developed known as functionally graded porosity distribution. This method is performed by...