Year:2006 | Volume:40 | Issue:2 (96)|Papers Count:17

The objective of this research is to investigate the effectiveness of “Genetic Algorithm” technique to optimize the performance of hydrocarbon producing wells. Through this paper, a new method for analysis of an oil and gas condensate production system is presented. This method is a new stochastic method which enables us to analyze a system of mathematical equations containing a great number of decision variables and determine the optimum values of them resulting in the most economical profit. The presented method is referred to as “Genetic Algorithm” (GA). A mathematical approach is initially obtained for well model and surface facilities and then it is analyzed and optimized, based on the economical profit, using GA approach. The performance of a production well is a function of several variables. Examples of these variables are tubing size, choke size, and separator pressures. Changing any of the variables will alter the performance of the well. The production facilities considered in this paper consist of tubing, choke, and separators. The method applied is able to consider dual sized tubing (combination of tubing and casing). Furthermore, it is able to determine the optimum number of separators. The developed code in MATLAB environment based on GA is able to obtain the most optimum size(s) for the tubing (single size or dual sized tubing), the depth at which the tubing size should varies (in case dual sized tubing is selected), choke size, number of separators, and separator pressures resulting in the most amount of hydrocarbon liquid production. Finally, this method and the developed code have been applied to production system of a real oil field and the obtained results have been compared to those of Prosper simulator. The results show that GA is a powerful tool to analyze production system of hydrocarbon fields.

Double base propellants are among the most powerful solid propellants and due to their high energy, specific impulse and large range of burning velocities are used very frequently and are preferred to many composite propellants. For the increase of rocket travel range the increase of specific impulse is very important in such a way that a 5% increase in this parameter results in a 45% increase in the range of travel. In this work production of double base propellants on laboratory scale has been carried out in order to reaching a specific impulse of minimum 240 Sec for a combustion pressure of 1000 Psi and exit gas pressure of 14.7 Psi. High energy double base propellant contains material such as Cyclotrimethylen tetranitroamine (HMX), Cyclotrimethylen trinitroamine (RDX), Amonium perchlorate (AP) and Aluminum (Al) which can be produced by both extrusion and casting. High energy double base propellants used in this investigation have been AP and Al which have been produced by the in solution extrusion method. In this study the software CEC is used to calculate the specific impulse and other parameter of the twelve samples and formulations produced in the laboratory. After optimization of various parameters in the mixture and checking the physical and chemical properties as well as the results of the static test using a laboratory rocket motor, a formulation is found which results in theoretical specific impulse of 260 Sec. This theoretical value corresponds to a practical standard value of 254 second which is a considerable increase in the present specific impulse of current double base propellants.

Distribution coefficients of Zr and Hf cations were determined in aqueous solution at different concentration of sulfuric acid and in presence of some kinds of organic solvents, by a cation exchange solfunated polystyrene resin. The effect of temperature, type and amount of solvent were studied in batch experiments. On the base of extracted results from batch experiments, separation of the mentioned cations were carried out in packed bed of the mentioned resin by a three stage chromatographic elution method. It is concluded that elution of the preloaded resin bed with Zr and Hf solution, by 0.5 N sulfuric acid solution followed by a mixture of 2 to 1 volumetric ratio of 1N sulfuric acid to methanol, can cause outlet of the major part of Zr and, at the final stage, using 2N sulfuric acid Hf cations can cause elution of remained Hf from the bed.

The influence of NaCl on interfacial properties is studied by measuring foamibility, foam stability and equilibrium. The surfactants chosen in these experiments are sodium dodecyl sulfate (SDS), Ethanol, n-propanol, 1-buthanol and Aniline.Symbol of foam stability is considered as the time that the height of column becomes zero.It seems that the relation between foam stability and NaCl concentration for all alcohols is the same. When the concentration of surfactants increases the foam stability, at constant NaCl concentration increases and with increasing NaCl at constant concentration of surfactants, this result is observed. For SDS the time stability is the maximum value and this is because SDS is an anionic and strong surfactant. The mixture of SDS and NaCl, causes the more stability.

In this article, new software has been developed for the simulation of naturally fractured reservoirs using discrete fracture modeling. Discrete fracture modeling in contrary to the double porosity modeling is able to simulate the real fracture distribution of a reservoir. In this modeling, non-ordered gridding has been used. Fractures are placed on the grids’ lines. Therefore, the geometry and the orientation of fractures are preserved. Also, in more heterogeneous region of a reservoir, smaller grids can be defined in order to increase the degree of accuracy in the calculation. In discrete fracture modeling, all connections of matrix-matrix, matrix-fracture, and fracture-fracture are used and the transfer function of double porosity model is not necessary and excluded. Also, a new approach has been used for the construction of triangular grids. This approach is the combination of Delaunay triangulation and the frontal advance method. For the numerical solution of equations, the finite volume method has been used. Finite volume method can be used in non-ordered grids with different size and geometry. The software in this work is developed for both 2-D and 3-D models and is tested by material balance for each grid. Also, this software is compared with commercial software in a case study. The accuracy of the developed software is confirmed.

The main object of this paper is to evaluate and discuss the cloud point temperature dependence on the solution nature in the crude oil. A correlation was also developed to predict the cloud point temperature in paraffin precipitation. The cloud point temperature is an important parameter to see whether there will be paraffin precipitation or not. So, we interested on the parameters that affect the cloud point temperature of pure paraffinic hydrocarbons. Therefore, besides literature survey, some experiments on paraffin precipitation and deposition have been performed and evaluated. We mean heavy paraffinic hydrocarbon components by the pure paraffins. Based on our experimental observations, the most important parameters that affect the hydrocarbon cloud point temperature are the apparent molecular weights of solution and solute, and solute weight fraction. These are the basic parameters of our developed correlation. In other words, the correlation is based on the intensive properties of the solution components such as their molecular weights and melting point temperatures, and the extensive properties such as weight fractions. Through the regression process different equations have been used and a complex nonlinear polynomial equation was selected to obtain a correlation which predicts the cloud point temperature with less than 1.8 percent error. This modeled correlation is very simple to use and less time consuming with respect to the other models.

Microwave energy has several possible benefits in textile processing. Substitution of conventional heating methods by microwave irradiation may result in faster and more uniform heating. The objective of this paper is to study the effects of microwave heating on dying of polyester fiber. All the dyed samples were closely studied using SEM and the effects of different variables are discussed throughout the article in detail.

In the present research, a military helmet is designed and fabricated using polymer matrix composites. The manufactured helmet stands an MP5 rifle shot from a 5 meter distance. The composite has been made of three layers of composites with different inclusions. In this research work, the polymeric resin and the number of composite layers plus the influence of arrangement of layers are studied and the best combination is found.

The purpose of this study is evaluation of complicated kinetic models by means of Genetic Algorithm. Because of importance of sulfur removal from oil products to control environmental pollution as well as preparation of low/ free sulfur feed for reforming process, hydrotreating of oil cuts is one of the most important reactions in refining processes. Rigorous HDS reaction kinetics is nonlinear models which are carried out on bi-functional catalysts. Two parallel reactions; Hydrogenolysis and Hydrogenation, are the major reactions which are carried out on the surface of non-homogeneous catalysts as Ni-Mo/g-Al2O3. In this study, appropriate models of Langmuir-Hinshelwood type kinetics for Hydrogenolysis and Hydrogenation were investigated. The experimental rate data at high constant pressure in different temperatures with different concentrations of dibenzothiophene (heavy sulfur compound), hydrogen and hydrogen sulfide were used for each model. By implementation of GA the best model and Arrhenius parameters were obtained, directly.In this study, a comparison with Levenburg-Marquardt Algorithm has been investigated. It is concluded that LMA is sensitive to the first guesses and there is possibility to trap in local optimum in contrast GA. In conclusion, GA can be used to modeling of rigorous and nonlinear kinetics, without consuming time for writing partial differentiation as we have to do in LMA, and GA is a convergent method to global optimua if we use a reasonable interval for the unknown parameters

This paper deals with bacterial leaching of copper dust emanating from furnaces at Sarcheshmeh copper complex. Regarding the considerable amount of acid leachable copper, a sulphuric acid leaching process was performed prior to bacterial leaching. Some shake flask and then bioreactor tests were conducted using a mixed culture of Acidithiobacilli and the effect of significant parameters such as culture medium; pulp density and bacterial inoculation rate were investigated. By increasing the pulp density because of higher toxicity and shear stress much more microorganisms and richer nutrient medium were needed. Favourite condition governed to agitated bioreactors caused a remarkable promotion in metal dissolution rate in comparison with shake flask. Copper recovery by bacterial leaching in shaking flasks and chemical leaching after 22 days were 87% and 38%, respectively. At the same condition, the maximum copper recovery in bioreactor was 91% within 6.5 days.

Cyanide, widely used in chemical and mining industry, is one of the most important environmental issues due to the acutely toxic properties of many cyanide compounds to humans and aquatic life. This research is aimed at investigating a feasible and economical technique for the detoxification of cyanide from tailing wastewater of Muteh gold mine. Cyanide detoxification was achieved through the oxidation of cyanide by using calcium and sodium hypochlorite using various concentrations of oxidant solutions at alkaline pH levels and temperatures between 12-65°C Cyanide titrated using Rhodanine solution and silver Nitrate. Cyanide concentration in waste water was measured 270 mg/lit.  Removal was achieved at optimum pH of 12.3 for both solutions.  However, at higher temperatures, cyanide removed completely at this pH level. Optimum Doses of calcium and sodium hypochlorite for perfect cyanide removing, were 1.43 and 8.64 gr/lit, respectively.

One of the most important parameters in designing grout mixtures is to determine type and size of the existing particles in the grout admixtures which are directly related to the size, shape and geometric configurations of the soil particles to be grouted. Generally, the ratio of the smallest soil particles to the largest cement particles in the grout admixtures is defined as the groutability ratio. To date, groutability ratios are mainly determined via experimental results and/or empirical equations. However, in order to properly analyze soil groutability, it is important to develop analytical methods to account for the most effective and determinative parameters. In this paper, a new mathematical approach is developed to compute the effective voids diameter and also to determine the smallest effective diameter of voids that may exist among soil particles which can be used to classify the quality of grouting performance.

In this study, stability of Pardis tunnel, east of Tehran, is analyzed by means of three dimensional profiles of displacements and stresses around tunnel. These profiles are obtained from numerical models created by FLAC3D software and provide complete insight about state of displacements and stresses around tunnel. By compare of these displacements with respect critical values, stability of tunnel could be assessed. Also in this study, state of support system in clay zone of tunnel was discussed and importance of support penetration in tunnel floor and effect of this phenomenon on tunnel stability was showed.

Determination of open pit-underground mining limit for deeply depth deposits that have possibility of open pit and underground mining is one of the primary decisions that should be taken in mining design process. The model that has been presented by Nilsson was based on choosing the depth with maximum total net present value (NPV) both open pit and underground mining. In this Project after using some corrections in determination of open pit–underground mining limit and providing some necessary parameters to maximize the net present value, the Nilsson’s model completed and based on corrected model software was developed with visual basic programming language. This software has been used to determination of open pit-underground mining limit of Chahar-Gonbad copper mine with studying of seven alternatives. To supply the necessary input data of software, in the first, the mine deposit was estimated in ordinary kriging method by Datamine Studio of version of 2.1. Then ultimate pit limits related to alternatives that their bottoms are placed in 2378, 2346, 2330, 2314, 2298 and 2250 respectively and with cut off grade of 0.3 in percent were designed by Datamine then ore and waste tonnage related to those were calculated. Based on University of British Colombia (UBC) method and the software that developed for mining method selection based on UBC method and with due attention to in-field experiences about underground mining exploitation, cut and fill stopping was chosen as the best method. One underground mine was considered with cut off grade of 0.5 in percent for each open pit mine. The income and costs were estimated and finally the software import data were prepared. The results of software indicated that level of  2330 has maximum both open pit (12996 million Rials) and total of open pit and underground (14775 million Rials) NPV, therefore this is either open pit or open pit - underground mining optimum limit. With considering of two concentrate prices in years of 2001 (3285034 Rials per ton) and 2005 (3353218 Rials per ton), the effect of the cut off grade and interest rate variations on this limit were studied. The results showed that depth associated to this limit goes upward when these two parameters increase, but as an increasing of the price, it dose not vary and only NPV associated to alternatives increases.