: Knowing the effects of different parameters on drilling fluid is one of the essential issue in the oil industry. Drilling fluids go into the wellbore through drill string and come out to surface via annulus. In this way, it is affected by high temperature and high pressure conditions. High temperature conditions cause the fluid in wellbore to expand, while high pressure conditions cause fluid compression. Failur to take these two opposing effects into account can lead to error in the estimation of bottom-hole pressure. In this study the effect of temperature and pressure on phisical properties of drilling fluid are explored. A Bingham plastic model is used to simulate the temperature and pressure dependent rheological behavior of drilling fluid studied. A simulator is prepared in MATLAB software to simulate the wellbore during circulation. This simulator can develop the temperature and pressure profiles of a wellbore during circulation, compute the bottom-hole pressure and equivalent circulating density (ECD) taking into account the temperature and pressure conditions in the wellbore. The effects of variation in circulation rate, geothermal gradient and fluid heat capacity are explored and discussed in this work for both oil base mud and water base mud. Also, the effects of frictional presure loss, pressure loss in drill bit and drillstring rotation are considered as internal heat sourece in wellbore. Results show that increasing flow rate and heat capacity of drilling fluid cause decreasing in bottom-hole temperature and greater geothermal gradient leads to greater bottom-hole teperature. Also, taking into account the temperature and pressure influence on rheological properties of drilling fluid cause decreasing in bottom-hole pressure that this is more significant in water base muds. To validate the model, the results of numerical solution compared with field data and previous model and show a good agreement.

Gas-liquid cylindrical cyclone (GLCC) separators are one of the most compact and cheapest cyclone separators that are developed by the Tulsa university Separator Project team (TUSP) and the Chevron company. This separator includes a vertical tube as the main body. The flow enters the cyclone from a tangential inlet, which is located in the middle of the body. It also has two outlets that are located at the top and the bottom of the main body and will be used for the gathering of the separated liquid and gas. Due to gravity, below the inlet is mainly occupied with liquid and the upper part with gas. Because of the tangential inlet, the swirl is induced and it results in creating the centrifusal force and a liquid vortex in the body. This research provides modeling and computational fluid dynamics (CFD) calculation of the single-phase liquid flow and two-phase gas-liquid flow in gas-liquid cylindrical cyclones. The objective of this study is to understand the characteristics of the flow in this geometry better and to examine the effect of different parameters on the operations of these separators. For achieving the hydrodynamic characteristics of the flow in this kind of geometry, we simulated the swirling liquid single-phase flow and utilized different turbulence models such as Spalart-Allmaras, RSM and k-ε models with different near wall treatments. By comparing the results, we realized the k-ε models give the closest results to the experimental data. In the next step, we studied different kinds of inlet and by comparing the results, it turned out the separator with quadratical inlet works better than the circular inlet. In the two phase gas-liquid flow simulation's section, we used water and air as the working fluids. The k-ε models were used to model the turbulence; as we found in the single-phase part, they have the best performance while simulating such flows. In this research we employed the VOF model as the multiphase flow model and the calculations suggested this model with split inlet gives better results than the mixture fluid in the inlet. From the results of this research, we concluded that the geometry and the angle of the inlet have a considerable effect on the performance of this kind of separators. Based on the results of the single phase flow simulation, we proved that the quadratical inlet gives better answers. Eventually we studied the performance of the separator based on the different types of inlet, such as constant cross section inlet and also dual inlet and different inlet angles toward the horizon.

For many years, particle-induced erosion has been a common issue in many industries, including oil and gas production and refinery. Oil and gas wells which produce petroleum from a sandstone layer are in the risk of erosional damage. Based on this, the aim of this research is to evaluate the erosion in oil well and determine the severity of the damage for various production conditions. Computational Fluid Dynamics (CFD), as a powerful tool for fluid flow and heat transfer calculations, has been employed in this research. In the present study, erosion calculation is accomplished in three steps which are solving of the flow, particle tracking and recording erosion on the walls which results from particle impingements. Validation of erosion calculation, for two sets of single and two-phase flows elucidated the capability of numerical models which are implemented in this study. Amongst them, two-phase flow calculations because of their inherent complexity, has a significant influence on the overall accuracy of erosion calculations. Then, these models have been employed to estimate the erosion in petroleum wells. Erosion calculation for wells has been carried out with a two-step procedure. At first, one-dimensional flow of oil and gas is solved from the well’s bottom-hole to the wellhead’s downstream using SPT Group OLGA software and phase properties and flow conditions in the selected regions are obtained. The second step is consisted of detailed solution of oil, gas and solid flow in these regions and erosion calculation for different sections of the wall. This 3-D solution is accomplished by utilizing ANSYS FLUENT package. For the wide range of examined conditions, erosion in the region near the ground surface is always an order greater than the erosion in the region closer to the bottom-hole. However, for the highest erosion rate with common sand production rates, the annual erosion rate is well below the maximum allowable rate.

One of the problems in steam turbine blades is the appearance of cracks in them. To understand this problem, it is necessary to analyze the flow and Heat transfer that occurs on the blades. In this study, flow and heat transfer in Intermediate-Pressure steam turbine (row 27) was simulated. Heat transfer analysis was performed both on the fluid and the blade at the same time (conjugate heat transfer). This simulation was comprised of three main stages: geometric modeling, grid generation and 3D flow solving. Stage 27 of the steam turbine in this study included 62 fixed blades and 134 moving blades. The geometry of the fixed blade was modeled using experimental measurements and the moving blade geometry was modeled using a three-dimensional scanning camera (cloud of points technique). The computational grid should encompass the complex geometry of the blades using minimum number of cells and the best possible quality. Computational flow area around the blades was discretized with a 3D structure grid based on hexahedral cells. To consider the effect of conjugate heat transfer, due to blade complex cross-sectional profile, unstructured grid based on tetrahedral cells were used to mesh the body of the blades. Disturbances were modeled using the k-ω model, and the governing equations were solved with finite volume method using the commercial Ansys CFX code. Simulation of flow and Heat transfer in row 27 of the turbine, which included fix and moving blades, were performed by considering a sliding grid in the interface of the two blades. The results were compared with experimental data from Ramin power plant steam turbine and they were in a good agreement. Numerical results include static and total pressure distribution, static and total enthalpy distribution, velocity distribution, total and static temperature distribution and total and static temperature distribution in the body of the blades. Results showed that the stator output pressure increases with height from the root to tip and variations in temperature. This is also the case for pressure. Fluid maximum velocity occurs at the outlet of the stator root level and it decreases by increasing height. Temperature levels close to the tip and the leading edge is the highest compared to other sections, therefore, crack occurrence is more likely in this area.

 With considering world economic situation and big oil companies competition on gaining more benefits with less investment and in shorter time intervals, simulation of reservoir has been accelerated in recent decades. This researches are focused on prediction of production scenario and time interval of economical production before needing to reinvestment for work over. So each one of these companies has made their research and development team and generated their exclusive simulation software. In this research radial three-phase flow in a gas-cap reservoir that has cylindrical shape and a single well is located at center of it, has been modeled. Total flow rate is assumed to be constant and outer boundary is assumed non permeable. With these assumption a reservoir with initial condition of under saturate and a reservoir with saturate initial condition has been compared. In first case, gas saturation will decrease at the beginning of production period but when reservoir reaches bubble point pressure, gas saturation will increase. The reason is dissolved gas that will be free when reservoir reaches bubble point pressure. In the second case gas saturation will increase all the time.

 Controling surface temperature during continuous casting billet, especially in the secondary cooling zone is the most important factors that can affect the quality of the final product; because reheat of the strand surface when the strand passes from one spray zone to the next (or to the radiation zone) can cause cracking. In this study three-dimensional model of solidification process and heat transfer of billet in continuous casting machine of National Iranian Steel Group is simulated by using Gambit and Fluent softwares. In this study, by using user defined function (UDF) of Fluent the boundary conditions were simulated with very high precision. In this simulation, billet temperature and metallurgical length changes are computed at varying casting speed, secondary spray cooling water flow rates and molten temperature. The results show that by increasing the casting speed at a constant water flow (heat transfer rate constant), the metallurgical length increased and solid shell thickness is reduced in any section. In this case, if the metallurgical length of the secondary cooling zone is increased and enters the radiation zone, due to the low rate of radiation heat transfer, surface reheating phenomenon occurs. Finally, according to the results, by optimizing water spray rates to different areas of the secondary cooling surface in any casting speed can be considerably reduced surface reheating phenomenon. Result shows that superheat has a little effect on temperature distribution and metallurgical length of strand while casting speed has significant effect. The results of simulations are validated with data of the previous researches.

In this study, gas-liquid two-phase flow in underbalanced drilling (UBD) of oil and gas wells using directional drilling (horizontal and inclined) is numerically simulated. Directional drilling is a type of controlled drilling in the predefined and specified path in order to reach the target. The governing equations of transient two-phase flow in underbalanced drilling is two one-dimensional mass conservation equations for two components of liquid and gas and a mixture momentum equation which is based on drift-flux model. These equations is discretized using first order implicit upwind scheme and is solved using Newton's method. Steady state condition, is solved using mechanistic model based on the drift-flux approach and has been modified to account for inclined well. In order to validate steady state flow model, the simulation results is compared with empirical data for Maspk 53 (vertical) and Persian 074 (directional) wells. The Comparison of the results with empirical data shows the steady state model has around of 5% error. Validation of the model for transient flow have been made for Lopez well (vertical) and a horizontal tube with two different inputs. Then the effect of changes in volumetric flow rate of gas, liquid and output pressure (Pressure chock valve) as a function of time on the bottom-hole pressure of the well for general conditions (vertical, inclined and horizontal) have been studied in two different modes. The results show that the proposed model can properly predict bottom-hole pressure of the well in underbalanced drilling operations in the transient condition.

In this thesis, analysis and feasibility study of several proposed Plan for energy recovery in Kroat oil facility is considered. In this regard, units and sections of process with high energy loss or energy saving potential have been identified and Introduced. Afterwards, four different plans were proposed to recover and reuse lost energy in the process. In the first three plans, the goal is to eliminate the desalting unit heaters by designing a CHP system. It should be noted that the main difference between these three Plans is in heat source which supplies required energy. in order to design a CCHP system, an ammonia-water chiller and Some proper heat exchangers were designed in the fourth plan to use recovered energy for cooling the natural Gas. Also in other part of this plan, the required energy for eliminating the desalting heaters has been provided by designed heat exchangers. At last by evaluation all the mentioned plans and doing economic calculations, the efficiency of each plan has been determined. It is worth mentioning that the time needed for returning the investment for the fourth plans are calculated to be 7, 12, 11 and 6 months respectively. In between, the fourth plan with saving about 1157.5 m3/h of natural gas and about 3290.8 kW in electricity energy and also having more than 2 million dollar annual profit, is the most efficient plans in this research.

In this study the non-isothermal multiphase wellbore flow of oil, gas, and water was numerically simulated. Governing equations of wellbore flow include three one-dimensional mass conservation equations for oil, gas, and water and one pressure drop equation and one energy conservation equation. First-order implicit upwind scheme has been used for discretization of these equations, and the resulting system of equations has been solved using Newton method. Also, In order to include the slip between gas and liquid phases, drift-flux model has been used. Properties of the fluid of wellbore and reservoir have been calculated by using Black-Oil model. Appearance and disappearance of the gas phase of wellbore blocks is one of the difficulties of solving multiphase flow during well testing. Consequently, if the mass conservation equations are formulated according to volume fraction, it will lead to numerical problems. To avoid this, formulation of the preceding equations has been based on mass fraction. Additionally, many of previous models have been provided by use of a standalone wellbore model along with a steady stay IPR which may lead to unreal results, since wellbore dynamic behavior is significantly correlated with reservoir’s one. Therefore, a one-dimensional radial three-phase reservoir has been modeled numerically, and implicitly coupled to wellbore model. It has been essential to simulate heat transfer between wellbore and its surroundings, as rigorous calculation of the temperature of wellbore fluid has been one of the main aims of the study. Hence heat transfer between wellbore fluid and surroundings including tubing, annulus fluid, casing, cement, and liner has been examined both analytically and numerically. After providing governing equations, few cases of multiphase flow have been solved and the results have been compared with those of other researchers and also Olga software. The results indicate that this model is highly capable of the prediction of temperature and pressure of the wellbore particularly during well testing.

A new type of drilling oil and gas wells which has attracted interest,dueto the positive features, is theUnderbalanced Drilling or briefly UBD. In this method, by reducing the hydrostatic weight of the drilling fluid through the injection of two-phase fluid, the well bottom pressure is kept lower thanthe reservoir pressure. The application of this method is less considered in the horizontal and inclined drilling. Therefore, in this study, numerical simulation of two-phase isothermal non-permanentflow using four-equation model of compressible fluids in horizontal, inclined and vertical wells is considered. After expressing the governing equations and theirhyperbolic analysis, numerical analysis method combines Advection Upstreamsplitting Method (AUSM) which does not need to calculate the system Jacobian matrix, will be introduced. The numerical simulations show that this numerical method has a high ability in the analysis of two-phase flows. In order to validate the code written for horizontal, inclined and vertical pipes, several two-phase flow problems have been studied and then several simulated sample wells is considered. The results indicate that in all flow conditions in the annulus, because of the pressure drop due to friction and gravity, the pressure decreases and the gas volume fraction and the velocity of the two-phase flow increases.Also, in the horizontal drilling pipe, due to friction, the pressure decreases and the gas volume fraction and the velocity of the two-phase flow increases.But in the drilling pipe flow in inclined regions, due to the weight of the column of fluid, the pressure increases and the gas volume fraction and the velocity of the two-phase flow decreases.

 In overbalanced drilling operation, due to the pressure difference between the drilling fluid and formation, one can observe a mud filtration which develops cake filtration on the sides of a wellbore wall. Fortunately, the presence of mud cake on the sides of the formation is a beneficial occurrence, as it can reduce the amount of filtrate, which subsequently decreases the formation damage. On the other hand, filter cake becoming thick contains several demerits, such as: (1) excessive torque when rotating the drill string, and (2) excessive drag when pulling it. The proccess of the cake filtration occurs as a result of three inter-related mechanism: flow of drilling mud in the annulus, invasion of fluid base of the mud into the formation, as well as filter cake formation on the borehole wall. In this research we took advantage of a numerical procedure for modeling and simulation of the cake growth in which, firstly flow field of drilling mud has been computed and next, permeation flux of the filtrate and the rate of cake growth has been calculated. To implement the mentioned procedure, first has been assumed that borehole wall is solid, in order to obtain the equation of motion of drilling mud. In that equation, the rheological properties of fluid expressed by Power law model and have been executed in both concentric as well as eccentric annulus case. Finally, the mentioned equation has been solved using numerical methods. In this study, the Darcy equation has been utilized in order to compute permeation flux as well as rate of cake growth, which the former, calculated by means of force analysis on the cake surface. The validation procedure has been accomplished using a two-step strategy: At first, validation of the flow field in both case of concentric and eccentric annulus has been done. After that, for cake computation, the thickness of the cake in an eccentric case has been computed and compared to relative articles. Finally, the effect of average flood velocity, rotation of the drill string and relative eccentricity has been investigated. The simulation results indicate that the increase of power law exponent can result in the increase of the thickness of the cake along with the decrease of permeation velocity (flux). Moreover, the increase in the eccentricity of the drill string not only leads in increase of maximum cake thickness, but also can enlarges difference between the maximum and minimum of the cake thickness