Sharif Digital Repository

Process of casting with evaporative patterns and unbonded sand is a new method that due to different economic, environmental and technological benefits is considered to large and small industrial parts manufacturing in recent years. Different parameters are effective on the surface and metallurgical quality in this process, such as foam density, sand type and size, level and mode of vibration, sand compaction, coating and pouring time and temperature. If coating permeability that is function of type, thickness and concentration of coating is chosen improper, pyrolysis vapor of foam don’t exit completely and in this condition carbon of vapor deposit on the metal surface and produces defect... 

In this work, the effect of chemical composition on structural, mechanical, electrical and magnetic properties of nanocrystalline Finemet-type alloys with the composition of Fe73.5Si13.5B9Nb3Cu1 , Fe77Si11B9Nb2.4Cu0.6 and (〖Fe_0.5 Co_0.5)〗_77 Si_11 B_9 Nb_2.4 Cu_(0.6 )was investigated. The samples were prepared by vacuum arc melting of high purity constitution in order to obtain a nanocrystalline structure. The amorphous ribbons were then annealed under vacuum with the same conditions of temperatures and time to compare their properties. The structural and thermal properties of the samples were analyzed using various techniques such as X-ray Diffraction (XRD) and Differential Scanning... 

Real modeling of ceramic foam filters, because of their specific tortuosities is not possible and in case of possibility of real modeling of pores in filters, because of restriction of element’s dimensions, the number of elements increases and model can’t be run in a reasonable time with common computers which are accessible nowadays. The common computer simulation of filters in Computational Fluid Dynamic (CFD) and their effect on fluid flow pattern is done by use of permeability properties of porous media. In this research, ceramic foam filters which are used in casting are simulated by Forchhimer and Darcy models. SUT CAST software is used for simulation, because of its ability for... 

Oil and gas production from oil reservoirs is significantly affected by rock and fluid properties. Relative permeability and capillary pressure are two key flow functions that are used in the numerical modeling of processes related to the porous environment of oil and gas reservoirs at the core scale and above. The use of incorrect relative permeability and capillary pressure curves can lead to inappropriate prediction of the future behavior of the reservoir, which in turn affects future management decisions. Due to the time-consuming nature of obtaining flow functions from the steady state method, history-matching techniques are generally used to estimate these functions as accurately as... 

Mass or large-scale storage of hydrogen, as a clean source of energy, should be conducted in underground formations in order to be used as a reliable energy source at the peak of consumption. In this regard, underground formations such as aquifers and depleted hydrocarbon reservoirs are the most favorable and secured media for hydrogen storage. However, detailed understanding of the flow dynamics of hydrogen-water in these media is critical to maximize hydrogen storage and recovery and tackle the existing uncertainities which exist in the flow functions. To fill this gap, this research aims at a detailed pore-scale investigation of the effect of flow regime, hydrogen compressibility, and... 

During all operations in hydrocarbon reservoirs, there is a possibility of formation damage. These damages can reduce the production of fluids from reservoir. One of the major damages that can seriously affect the performance of a reservoir is the damage caused by drilling fluid. The main purpose of this research is to study the main mechanisms of formation damages when using oil-based drilling fluids and fixing or preventing these damages. Once the mechanisms are identified, it is tried to cure the damages but without acid-washing. The alternative method is surfactant-washing which is a surfactant-brine injection. This injection has been done for the first time. This study helps to industry... 

So far, many studies have been carried out on the core-scale regarding the effects of hysteresis on the macro-scale properties of systems including fluids and porous rock, however, many issues related to the physics of the problem (especially regarding the way fluids are distributed and the trapping of the non-wetting phase) at the pore-scale need further investigation. In the process of multiphase fluid flow in porous media, hysteresis refers to the dependence of the results of the fluids’ displacements on the history of fluid saturation and the direction of saturation changes (increasing or decreasing). The first step to investigate the hysteresis effect is to determine the amount of fluid... 

During the Acidizing process in oil and gas reservoirs, the injected acid reacts with the rock grains, changes the rock pore structure and affects the flow conditions. Due to the presence of a large concentration gradient at the vicinity of the rock grains and the continuous changes in rock-fluid interfaces of the porous medium, the continuum assumption has been remained debatable for the effective local mass transport and effective molecular diffusion coefficients and the porosity-permeability relation in the continuum scale modeling of this process. Therefore, the need for pore scale modelling is evident. The novelty of this study relies in adapting the grid refinement method on the... 

Clogging of the pores of the porous medium occurs in different processes such as geothermal injection pumps, hydrocarbon wells, and underground water extraction wells. We need a model that can simulate these blockages in order to predict how fundamental variables of the porous medium change under different flow regimes and different particle sizes in the fluid (for example, the relationship between porosity and permeability changes). The aim is to simulate clogging in a porous medium using a pore network model. Simulations should model pore clogging and show how the permeability of the sample changes due to pore clogging. In the pore network, there are often thousands (or millions) of pores... 

Determining the time of breakthrough of injected water is important when assessing waterflood in an oil reservoir. Breakthrough time distribution for a passive tracer (for example water) in percolation porous media (near the percolation threshold) gives insights into the dynamic behavior of flow in geometrically complex systems. However, the application of such distribution to realistic two-phase displacements can be done based on scaling of all parameters. Here, we propose two new approaches for scaling of breakthrough time (characteristic times) in two-dimensional flow through percolation porous media. The first is based on the flow geometry, and the second uses the flow parameters of a... 

The purpose of this research is to model transport and separation of single and gas mixtures through pore network modeling in dense membranes. In the first part of the project, the mass transfer and governing mechanisms of transport are investigated. In the second part of the project, simulation of membrane pore network in 3D of Cartesian coordinate is done. In the third part of the project permeability of single gas and ideal selectivity of binary gases for an actual membrane by desired mechanism are calculated. Then the results of pore network modeling were compare with the results from molecular dynamic simulation for single gas in polyurethane membrane with reasonable agreement. In this... 

Wettability of reservoir rock is one of the effective parameters in determining the mechanisms of production and consequently the amount of residual oil inside the porous media. In addition, the salinity of injected water is important factor in the recovery of reservoir oil in waterflooding.On the other hand, the role of the hysteresis on the residual oil saturation as well as the flow functions such as relative permeability curves is very important. In this project, the effects of reservoir wettability and injected water salinity on the hysteresis and residual oil saturation in two-phase water-oil flow systems are studied. Core-scale experiments were carried out using sandpacks and were... 

In order to prevent a blow out, cooling the bit, displacement of drilling particle, etc., it is necessary to use a suitable fluid called drilling mud. The construction of drilling mud, especially the oil base, has a high cost and covers more than 20% of drilling costs, so maintaining and proper use of it is important, as well as drilling the reservoir layer due to the higher permeability of this layer than Other layers allow the drilling mud to influx into the formation, which in addition to the cost of fluid loss, damage to the reservoir, reduce its permeability and many problems during production. Therefore, in order to investigate the phenomenon of fluid loss, measure its size and... 

In this research oil production decline curve of heterogonous reservoirs was investigated. Heterogeneity is modeled by percolation theory and using Petrel software and mass balance equations are solved by Eclipse simulation software. In primary production stage which oil flows up the reservoir spontaneously by reservoir high internal pressure, decline curve is exponential. Changes in the characteristic parameter of the exponential decline curve with occupation probability and permeable objects size were investigated.In secondary production stage, after reducing the natural production potential of the reservoir, water injection is used to increase and stabilize the pressure and increase the... 

Today, the Oil industry, much progress has been made in terms of increasing the productivity of reservoirs. In this method, generally one or more fluids are injected into wells to help, extract more oil from the reservoir. Knowledge of the main parameters in this flow of two or three phase fluid in the reservoir is most important. If fractured reservoirs are studied, the multiphase flow are much more complex and require more information about that. Unfortunately, due to the complexity of fractured reservoirs and fluid flow within them, little research has been done on them. The studies about two or three phase flow in fractured reservoirs are classified in two groups, modeling and laboratory... 

In this paper we have tried to mention a proper method of upscaling permeability data in a typical Iranian reservoir. Firstly a literature review is made on some common upscaling methods witch have been used so far. We introduced common upscaling methods like full tensor method, streamline method, stone method , vertical equilibrium method and also Kyte & Berry method. Additionally we have explained their advantages and also disadvantages. After selecting two upscaling methods, Kyte & Berry method and vertical equilibrium method, we applied these algorithms for upscaling of permeability data of Soroosh Oil Field. Soroosh oilfield is a heavy oil, Iranian reservoir located in Persian Gulf.... 

Determining the parameters of the porous media and fractures in order to properly understand the processes governing these environments is very important. Traditionally, these parameters are determined in the laboratory. In recent years, with the advancement of computational capabilities, numerical methods have been considered to determine the parameters of the porous media. In the last few decades, the lattice Boltzmann method has been considered by the researchers as a class of computational fluid dynamic methods for simulating fluid flow. The advantages of the lattice Boltzmann method include simplicity in applying to complex media and the ability to simulate different phenomena. In this... 

Formation damage is defined as any process that reduses the reservoir permeability relative to its normal state. Two major causes of this problem are filtrate and solid invasion into the pore spaces of reservoir rock.Therefore, the drilling fluid used for drilling the reservoir sections should prevent such a problem as much as possible.The goal of this study is to optimize the weighting additive particle size distribution to prevent permeability damage in one of the southern Iranian oil fields. By analizing the capillary pressure data of core samples, it seems that fracture presence in rock matrix leads to poor quality of mudcake, resulting peremabilty reduction in near wellbore region.... 

Production of solid particles is a phenomenon that occurs in most oil and gas well. This phenomenon can cause many problems in every life stage of a well such as erosion of surface equipment, subsurface equipment and environmental problems associated with solid particles disposal. On the other hand, this phenomenon can increase the permeability of near wellbore areas, which is considered to be the advantages of solid particles production. In this study, nine sandstone samples were prepared and different pressure ratios have been used for evaluation production of sand in different situations. Also, in the next step, by numerical simulations, studies of stresses around a well and... 

In recent years, the reductive dehalogenation of the chlorinated hydrocarbons using nanoscale zerovalent iron (nZVI) represents a promising approach for underground remediation. Regarding commercialization of this technique, instability and unknown nature of nZVI particle are still challenging tasks that should be considered.
In the current work, Nanoscale zero-valent iron (nZVI) and palladized iron (Pd/Fe) bimetallic particles were synthesized and employed to react with chlorinated compound (PCE) in water to investigate its degradation behaviors. The results show that the reactant ratio, stabilizer amount and temperature are the main parameters with the considerable effect on PCE...