Sharif Digital Repository

As latency reduction is a key objective of upcoming mobile standards such as 5G, control applications over such channels have become of high interest in recent years. In this thesis, we will consider the problem of control over fading channels modeled by finite-state Markov chains. We will combine communication and control theory aspects of the problem and study stability of linear discrete-time plants which communicate with the controller over such fading channels. Two different scenarios are assumed for channel state information availability at encoder side, and the sufficient condition of almost sure asymptotic stabilizability is derived for each scenario. We will then examine the... 

Carbonate reservoir acidizing is one of the most important well stimulation operations that has been widely used in recent years. Modeling the operation prior to any laboratory tests has always been one of the motivations of scientists in recent years due to the complexity of modeling to consider both mass transfer and reaction phenomena. There are several models have been proposed to simulate the acid injection process in carbonate rocks in recent years, the most important one is the Two-Scale Continuum Model (TSCM). This model utilizes the combination of Darcy-scale transfer and reaction equations and a series of pore scale relations to investigate acid injection into two-dimensional... 

Crude oil is made up of dozens of chemicals which based on their structural similarity, SARA test separate it into four categories: saturates, aromatics, resins and asphaltene. Asphaltenes are recognized as the largest, heaviest and the most polarizable fraction of the crude oil which are in thermodynamic equilibrium with oil at reservoir conditions. Each of the physical, chemical, electrical or mechanical disruption of this balance during production can result in instability and asphaltene precipitation may occur and eventually led to deposition in the reservoir, wells, pipelines, etc. Due to the fact that most changes in temperature and pressure will generated in the wells, thus... 

Water-flooding, has been known as one of the most effective techniques to increase oil recovery efficiency. Many studies especially in the past decade have shown that by controlling the amount and type of ions of the injected water the recovery efficiency is significantly improved. It should be noted that inadequate design of flooding operation can disturbed the prevailing balance between the rock and fluids in the reservoir, hence damage the formation. Several different damages are reported such as the formation of unwanted emulsion, mineral and organic material deposition (such as asphaltene) that would affect the operation and hinder the recovery efficiency. Therefore, it is necessary to... 

Matrix acidizing as a well stimulation technique is performed to increase the production index by increasing the permeability and removing the formation damage in the near wellbore region. However, several challenges such as corrosion of the tubulars and iron precipitation in the formation are hindering this process. To encounter these challenges, different chemicals, or additives, such as corrosion inhibitors and iron control agents are added to the acid solution. Carbonate acidizing has been carried out using HCl-based stimulation fluids for decades. However, at high temperatures, HCl does not produce satisfactory results because of its fast reaction, acid penetration, and hence surface... 

Interfacial Tension (IFT) behavior of crude oil/CO2 system is recognized as the main factor affecting the efficiency of CO2 flooding during enhanced oil recovery (EOR) process. Adding paraffin group hydrocarbon to asphaltenic crude oils as an asphaltene precipitant component is aimed to mimic asphaltene precipitation process during crude oil production and transportation. Asphaltene precipitation would critically effects the IFT behavior of crude oil/CO2 systems. In the first part of this study, the equilibrium densities of oil samples which contain different heptane ratio were measured at different pressures and the temperature of 323 K. Then, the equilibrium IFT between CO2 and the crude... 

Additional to Temperature, Pressure and Compositional changes of crude oils, Electro-kinetics and Electrical potential effects are also known as the most influencing parameters on Asphaltene deposition during oil production and processing.Mechanisms of electro-kinetics and asphaltene charge generation are very complex and unclear. In the previous studies on asphaltene precipitation and deposition, mostly electro-kinetics effects are ignored.While, recent studies show the great effects of electrical filed on asphaltene deposition during production and processing phase of crude oils.At reservoir porous medium and crude flow line, an electrical field can be developed along the length of the... 

It is common to inject gas in naturally fractured reservoirs to maintain the reservoir pressure. Recovery will be the result of the complex interplay of several mechanisms such as viscous flow, extraction by molecular diffusion, gravity drainage, oil swelling and capillary force. Generally the main mechanism is gravity drainage However in many cases like low permeability of matrix, small matrix block size and high capillary pressure; gravity drainage may be very low or ineffective. Low permeability results inefficient viscous displacement too. Therefore in these cases the main mechanism is diffusion. The parameters influences the diffusion are: The nature of the injected gas, the composition... 

With the decline in oil discoveries during the last decades, it is believed that enhanced oil recovery (EOR) technologies will play a key role to meet the energy demand in coming years. Polymer flooding has been commonly used worldwide as one of the EOR processes. Literature reviews show that the active water-soluble polymers have a number of limitations related to their surface absorption, undesirable plugging, polymer concentration limitation,expensive, and low thermal, mechanical, bacterial, and salt tolerance. Up to now, five different polymer categories (i.e. polyacrylamide, hydrolyzed polyacrylamide, acrylamidebased resistant copolymers, associative copolymers, and thermoassociative...