مجله پژوهش نفت
پیاپی 72 (بهمن و اسفند 1391)

In this work, the SLD model is used to investigate the adsorption of pure gases and binary and ternary mixtures of them on solids. The volumetric properties of the fluid phase are described by PR and EDS equations of state. Three different procedures are used to estimate the parameters of the model. In the first and second procedures, the model is considered to have 2 and 1 adjustable parameters respectively. However, in the third procedure, none of the parameters are adjusted. In all the three cases, only the data of the pure compounds are used. The results show that although the adjustment of the parameters improves the results for pure compounds, it does not necessarily improve the prediction of the model for the mixture of gases, and even in some cases, less reliable results are observed. As a result, good predictions are observed without fitting the parameters of the model. The average absolute percentage of deviation for the calculation of excess adsorption for pure gases with PR EOS is 6.6%, 10.0%, and 11.6% for procedures 1, 2, and 3 respectively. The corresponding values for ESD EOS are 8.1, 10.4, and 15.9. For binary gas mixtures, the errors are 2.7%, 3.9%, and 4.2% for procedures 1, 2, and 3 respectively in case of using PR EOS; ESD EOS results in errors of 4.7%, 3.5%, and 4.8% for procedures 1, 2, and 3 respectively. A ternary gas mixture composed of methane, ethane, and ethylene is also examined; the average absolute percentages of deviations are 5, 4, and 15.6 in case of PR EOS and 6.9, 8.9, and 17.4 with ESD EOS for procedures 1, 2, and 3 respectively. The comparison of the equations of state used show that PR equations of state generally produce better results.

In this study, the kinetic effects of two ionic liquids (ILs), namely 1-butyl-3-metylimidazolium tetrafluoroborate ([Bmim][BF4]) and 1-butyl-3-metylimidazolium methyl sulfate ([Bmim][MS]), on the formation of carbon dioxide hydrate were investigated. The kinetic study confirmed that two ILs at concentration of 0.6 wt% and an initial pressure of 35 bar decreased the induction and nucleation time of carbon dioxide hydrate. Therefore, they can be considered as kinetic promoters. The promotion factor of [Bmim][BF4] and [Bmim][MS] were 68% and 52% respectively. Subsequent to the kinetic study of CO2 hydrate formation, the kinetic modeling of CO2 hydrate formation was carried out using the steady-state approach via a modified multi-step chemical reaction mechanism. The proposed model could reliably predict the pressure-time profiles; the experimental and the data calculated based on the integrated kinetic equations are in good agreement. The results showed that the proposed model could be used for the accurate prediction of the nucleation and crystal growth of CO2 gas hydrates.

One of the main problems in oil docks and offshore stuctures is the initiation of small cracks in fitting places. Maintenance engineers have always looked for a method to detect the crack at an early stage before crack growing and critical conditions initiate. Although several non-destructive testing methods have been proposed for the inspection of these structures, removing insulating layer and protective coating makes these methods inappropriate and expensive. In this paper, a new non-destructive pulse eddy current method is used to detect and characterize fine cracks under insulation layer without separating and removing the insulation from the structure. First, the theory of pulse eddy current method is briefly explainedand then the pulsed eddy current test is carried out on a steel plate having several simulated cracks with different depths. The results of the tests on the test plates with insulation layers and without insulation layers are presented and compared.

The optimization of hydrocarbon produced from the fields is one of the main concerns of the management of oil and gas reservoirs. In this respect, smart well technology developed in recent decades has been used. Among the main challenges of this important technology, one may refer to the optimized planning of intelligent control valves. This paper is based on the results of reservoir simulations, the behavior of smart wells, and use of experimental design Taguchi methods and response surface modeling and procedures are used to obtain and nonlinearly optimize the correlation between intelligent control valve settings and rate of oil production, and therefore to increase the rate of oil production while minimizing the rate of water production and calculation time.

Hydraulic fracturing, the process of creating cracks in the ground by injecting a viscous fluid into a well under high pressure, has been widely used in oil and gas industry to stimulate low-permeability petroleum reservoirs. The resultant field data from hydraulic fracturing operations exist mostly in the form of pressure-time curves and the determination of actual hydraulic fracture geometry using this data alone is impossible. Therefore, the design of hydraulic fracturing process and the prediction of fracture pattern are possible only by relying on the advanced mathematical and numerical models. Thus, several analytical and numerical models including 2D, pseudo 3D, and 3D models have been developed during last decades to predict the location, direction, and extension of hydraulic fractures in oil reservoirs. In the present paper, after introducing applications and the mechanism of hydraulic fracturing process, different approaches for analyzing the problem and predicting the crack pattern in petroleum reservoirs will be discussed. Finally, the framework and formulation of a numerical model with the capability of simulating 3D fractures and considering geomechanical reservoir effects and two-phase fluid flow will be presented.

In naturally fractured reservoirs, fractures play a main role in production, and fracture identification is very important in reservoir development and management. Borehole image log, which is a high resolution “pseudo picture” of the borehole wall, is a powerful tool for fracture study. These logs provide critical information about the orientation, depth, and type of natural fractures. Currently, there is no comprehensive algorithm for the automatic identification of fracture parameters in image logs, and the interpretation of these logs is often done manually. This process might become erroneous when the interpreter is less experienced. The present study uses image analysis and processing techniques, as well as genetic algorithms to detect fractures in image logs automatically. In this method, the points related to fractures are first extracted from the image by a classification method. Then, the number, depth, dip, and dip direction of fractures are determined on the extracted points by using genetic algorithm. This method is performed on a part of two image logs (4 and 8 pads) of two wells located in two oilfields in the south of Iran. Despite the sensitivity of the proposed method to the noises of the image, it successfully estimated the number, dip, and dip direction of fractures for both studied wells with an accuracy of 70%.

In this research, partial oxidation of butane was carried out in a fluidized bed reactor and in various operation conditions. In this way, at first, this reaction was carried out homogenous at various temperatures and fuel to air ratios. Results showed that the conversion was enhanced at higher temperatures. However, rate of increase was low at temperatures higher than 650 °C. Furthermore, optimum ratio of fuel to air was determined 6:1. Also, partial oxidation of butane was carried out using various zeolite supported catalysts. Results indicated that Ni/Y catalyst was the most appropriate catalyst with conversion 89% and Hydrogen selectivity 68%. Finally, Cu was used as promoter which improved stability of catalyst.

Biosurfactants are active surface components produced by some bacteria and fungi. These molecules reduce surface and interfacial tension in aqueous solutions and biphasic systems respectively. The most important application of biosurfactants is in oil industry to enhance oil recovery. The aim of this study is to isolate biosurfactant-producing bacteria and optimize the conditions such as temperature and pH for maximum biosurfactant production. Samples were collected from 8 selected points of oil-contaminated soils in the Sirri Island. Overall, 160 strains of bacteria were investigated in terms of isolation and morphological and gram stain. 59 strains had hemolytic activity and 46 strains had oil collapsing ability. Also, the results of oil displacement test were positive for 20 strains. Afterwards, 18 strains were selected and complementary tests such as foam formation and emulsification activity and surface tension were performed on them. Finally, two strains were found to be able to reduce surface tension more than 30 mNm-1 at 37 °C and a pH value of 7.0. Two strains with a high amount of biosurfactant production and emulsification ability were obtained in the present study. Regarding the high potential of the biosurfactant produced, it is suggested that it should be used in commercial applications such as enhanced oil recovery, bioremediation of soil and marine environments, and food industries.

Sulfosuccinates are widely used by virtue of their excellent wetting, foaming, emulsifying, and dispersing properties; commercial availability; and their wide range of applications. One of the sulfosuccinate derivatives is the sodium salt of dioctyl sulfosuccinic acid, which is commonly used in oil spill dispersant formulations. In this research, an attempt was made to modify the properties of commercial dialkyl sulfosuccinate by the ethoxylation of monoester of maleic acid derivative. This leads to an increase in the solubility of sulfosuccinate in hard water as well as improving its wetting properties. An unsymmetrical intermediate was formed either by the addition of polyoxyethylene group having different molecular weights (via ethoxylation) or the reaction of the monoester with polyethylene glycol; the intermediate product was consequently converted to sulfosuccinate sodium salt by being reacted withsodium disulfite. Since the dispersant formulation is capable of transferring crude oil and oil pollution into an aqueous column within a specific HLB range depending on the crude oil, the formulation is modified in an appropriate range using an agent to control HLB (rather than using pure sodium dioctyl sulfosuccinate). Furthermore, the agent has to possess biological degradability and non-toxicity. In the current work, the performance of a dispersant package having a high quantity of ethoxylated sodium sulfosuccinate (67%) was compared with that of a commercial sodium sulfosuccinate (33%). It was concluded that the ethoxylated sulfosuccinate had the potential to function properly in a dispersant formulation to disperse oil spills.

In this paper, some samples of supported carbon membranes are prepared with phenolic resin as a precursor. The effects of coating conditions including solvent type, resin concentration, and coating method on the preparation of a defect-free resin layer on the support surface are investigated. This layer is faced to carbonization operation to be converted to the carbon layer. To study the effect of support, two different supports with different materials and porosity are used. The results show that only resin concentration affects the preparation of the defect-free layer. A high concentration of resin can produce a complete layer on the surface of the support. But this layer is destroyed during carbonization and some cracks appear on the surface of the membrane due to the high thickness of resin layer. Similar experiments with supports having pores with smaller diameters show similar results. By repeating the coating-carbonization cycle, producing the complete resin layer is possible; but, this layer is also destroyed during carbonization and the produced membrane shows a little selectivity for gas separation.

Electrofacies is a deterministic or analytical way to practice the partitioning of well log data, which show a variation of geologic or reservoir characteristics. In this paper, we used three cored wells located in one of the oil fields in the south of Iran. Based on the core data (porosity-permeability), the three reservoir zones were identified to have different characteristics. Based on common well logs in all wells (Rhob, Nphi, Dt, and Rt) and MRGC method, an initial electrofacies model with 7 facies was developed. By comparing the results with the core data, those facies with the same reservoir quality were merged together. Thus, we obtained a new model with 3 facies. The new optimized model was then applied to 3 cored wells. It successfully separated poor, moderate, and good reservoir zones. Therefore, the above model was propagated into all wells. The results allowed creating a 3Dfacies model of the reservoir in the field. This model properly separated the poor, moderate, and good zones of reservoir.