Iranian Journal of Chemical Engineering (IJChE)

Abstract Nanostructured SAPO-34 zeolites were synthesized using TEA/morpholine as dual templates through a hydrothermal approach, with the crystallization time as a key parameter. Different characterization methods of XRD, FESEM, EDX-dot mapping, BET, and FTIR were used to analyze these materials. The results demonstrated that the crystallization time was an efficient factor for determining the crystalline phase and uniformity of the final products. Additionally, the size and uniformity of cubic SAPO-34 particles enhanced in longer crystallization times. It was found that the SAPO-34 catalyst synthesized in the crystallization time of 72 h had an optimal distribution of silicon within the crystal lattice structure, resulting in a significant enhancement of its catalytic performance. This catalyst demonstrated the moderately stable production of highly desired olefins, maintaining the selectivity of 58% for ethylene and 38% for propylene over 10 h on stream. The possible reaction mechanism for the MTO process utilizing the prepared SAPO-34 material is proposed. 

Abstract Polymeric gels can be injected into reservoirs to regulate fluid dynamics and enhance oil recovery by creating physical barriers to redirect water flow. In this study, a polymer gel system was developed using sulfonated polyacrylamide combined with chromium acetate. Silica nanoparticles were synthesized via the sol-gel method, and their effects on the polymer gel system, including the gelation time and gel strength, at the concentrations of below 1% weight were evaluated through the bottle test. The performance of the polymer gel containing silica nanoparticles and the silica nanoparticle gel in formation waters was assessed. Furthermore, homogeneous microscopic models and heterogeneous two-layer microscopic models, which included regions with high and low permeability, were constructed to evaluate the functional effectiveness of the polymer gel and silica nanoparticle gel in porous media environments. Factors influencing oil recovery were examined in relation to the volume of injected pore water. The results indicated that silica nanoparticles enhanced the gel strength and increased its swelling capacity under saline conditions. Microscopic model testing in both homogeneous and heterogeneous configurations demonstrated that the silica nanoparticle gel provided better blockage in high-permeability regions and fractured zones, compared to the polymer-only gel. In the heterogeneous microscopic model, oil production rates were 55.60% for the polymer gel and 57.21% for the silica nanoparticle gel, while in the homogeneous model, these rates were 62.6% and 68.24%, respectively.

Abstract To reduce water production from oil and gas reservoirs, it is necessary to block certain fractures and layers of hydrocarbon formations. Although polymer gels are employed as water shut-off agents to reduce water production, they face challenges due to inefficiencies. This study aims to examine silicate-polymer gels, based on the factors influencing the formation of gel by focusing on controlling the gelation time of the silicate-polymer gelants at various temperatures and investigating the stability of gels. An experimental design was conducted based on 5 levels and 2 parameters, where these two parameters are the concentration of the polymer ranging from 0.06% to 0.3% by weight and the temperature ranging from 20 to 100 degrees Celsius in the presence of a crude oil from the southwest of Iran. Experimental results indicated that citric acid successfully covered the ions and effectively controlled the gelation time. Sodium silicate proved to be one of the main components, along with formation water, citric acid to mitigate the impact of formation ions on the gelation time, and the polymer itself. The presence of formation water led to an increase in gel strength and a decrease in the gelation time. Moreover, elevated temperatures resulted in shorter gelation times and lower viscosity in the polymer gel. Doubling the concentration of the polymer reduced the gelation time by 43%, while a two-fold increase in temperature decreased it by 54%. Increasing the concentration of the polymer indicated a decrease in the gelation time, and an increase in both gel strength and gel viscosity.

Abstract Research has shown that many Bentonite in Nigeria are unsuitable for oil well drilling in their natural states. Their modification and blends with some additives could increase the yield and boost their suitability. Many indigenous polymers have become very popular due to environmental friendliness and their ability to modify rheology of clay suspension. However, the common natural polymers are characterized with excessive fluid loss, low gel strength at typical reservoir conditions. The aim of this study is therefore to examine the influence of selected polymers on the physicochemical and rheological properties of Nigerian clay-water suspension. Mud samples were prepared with polymers according to mud formulations currently used in the wells drilling with properties varied and optimized in a Reduced Central Composite Design (RCCD). The physico-chemical (pH, mud weight), rheological (plastic viscosity, yield point) and fluid loss were measured out on the studied muds. The results show that, the rheological characteristics of studied muds (PV (19.4 ± 1.50 cp) and Yp (21.5 ± 0.79 lbf/100ft2), the Fluid loss (10.12 ± 0.45 ml/30 minutes/100 psi) and 10 min and sec Gel value (4.6 ± 0.05 and 5.1 ± 0.01 lb/100ft2) were clearly improved. However, the mud weight values recorded (8.6 – 8.9 lb) though satisfied the minimum 8.6 lb/gal ceiling value but was due to the local barite that this study evaluated. The barite is characterized with low specific gravity and we recommend its modification prior to use to avoid high sand content.

Abstract In this study, response surface methodology (RSM) based on central composite design (CCD) was applied for investigation of the effects of ultrasonic waves, temperature and solvent concentration on viscosity reduction of residue fuel oil (RFO). Ultrasonic irradiation was employed at low frequency of 24 kHz and power of 280 W. The results showed that the combination of ultrasonic waves and solvent injection caused to further reduce of viscosity. To obtain optimum conditions and significant parameters, the results were analyzed by CCD method. In this method, maximum viscosity reduction (133 cSt) was attained in ultrasonic irradiation for 5 min, temperature of 50 °C and acetonitrile volumetric concentration of 5 % by means of experimental and three dimensional response surface plots. The kinematic viscosity decreased from 494 cSt to 133 cSt at the optimum conditions. In addition, a multiple variables model was developed by RSM which the second-order effect of ultrasonic irradiation time was significant on viscosity reduction of FRO. Finally, a comparison between the RSM with artificial neural network (ANN) was applied. The results demonstrated that both models, , were powerful to predict of kinematic viscosity of RFO. The results demonstrated that both models, RSM and ANN, with R2 more than 0.99 were powerful to predict kinematic viscosity of RFO.

Abstract In this essay, lipase from Burkholderia cepacia was immobilized into 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS) derived sol-gels. GPTMS:TMOS molar ratio of 1:3 was found to yield the best result. The morphological characteristics were investigated based on SEM and BET analysis. Sample mean pore diameter was 39.1 nm, it had a specific surface area of 60 m2/g prior to enzyme addition which decreased to 7.49 m2/g after immobilization. The enzyme activity was assessed through transesterification of waste cooking oil in the presence of ethanol with optimal conditions of: 40 ᵒC, 15 % immobilized lipase, 9:1 alcohol to oil molar ratio in 24 h of reaction which resulted to 91.70 % biodiesel production. In six-hour reaction time, 86.87 % biodiesel was obtained which is much shorter than conventional enzymatic transesterification which is 72 hours. Ethyl esters were characterized by determining their viscosity, density, and flash point based on ASTM D 6751-07b standards.

Abstract Examination of the available ignition delay time data and correlations in the case of methane, butane, heptane, decane, kerosene, Jet-A and ethylene fuels, allowed the derivation and recommendation of standard equations for this property. In this study, a new accurate substance dependent equation for ignition delay time as a function of pressure, number of carbon atoms, mixture equivalence ratio, fuel mole fraction and temperature has been developed to estimate ignition delay time of some hydrocarbon fuels. With the presented model, ignition delay time has been calculated and compared with the data reported in literature. The accuracy of the obtained model has been compared to the mostly used predictive models and the comparison indicated that the proposed correlation provides more accurate results than other models used in the previous works.

Abstract "> In the present study, transesterification of soybean oil to Fatty Acid Methyl Ester (FAME) was carried out in the microreactor. The system performance was investigated in the presence of hexane as a cosolvent. Furthermore, the effect of number of micromixer’s inlets on the mixing was one of the objectives in this work. For the goals mentioned above, three different experiments were done with and without cosolvent in two and three inlet micromixers under optimum conditions. Both flow pattern observations and Gas Chromatgoraphy (GC) characterization of FAME samples demonstrated that cosolvent technique and micromixer application could significantly influence the FAME yield in biodiesel production.

Abstract Waste cooking oil (WCO) is being generated large scale all over the world; hence it has devised serious problems of its waste management. Organised collection of WCO in voluminous quantity is mainly used for the production of biodiesel. Most researchers focus primarily on the biodiesel generation from WCO, although other applications are also important and require attention. Objective of this review article is to highlight most of the aforementioned possible applications of WCO which may help in its utilization apart from biodiesel. It can be processed to obtain pyrolytic oil, hydrogen gas, biodiesel or electricity production by direct burning. Applications like combined heat and power generation (CHP) can utilize WCO with utmost efficiently. It can also be processed chemically to obtained biodegradable polyurethane sheets, greases, biolubricants, soaps and alkyd resins. Properly purified and sterilized WCO can be used as a carbon source in fermentation processes for the production of rhamnolipid biosurfactant and polyhydroxybutyrate (PHB). Waste cooking oil therefore can be considered as a potential waste which can be utilized as energy source and raw material for chemical or biological processes.

Abstract orption ofcontaminants in soil and sequestration in soil particles is a process, the mechanisms of which are not well understood as yet. The aim of this study was to investigate sequestration and bioavailability of crude oil as a contaminant in three different soils. For this purpose, three different soil samples with different textures (loamy sand, loam, and clay loam) but with the same organic carbon were collected. After sterilization, the soils were spiked with crude oil. Each soil sample was contaminated as aged and fresh, and inoculated with a consortium ofthree bacterial isolates. Respiration was analyzed on days 0, 30, 60, and 90 after inoculation. Bacterial population was also assessed at the beginning and at the end ofthe bioremediation and residual contaminant at the end ofthe bioremediation process. The results showed that in soils with the same organic carbon, texture is an important parameter in aging and sequestration of the contaminant. In addition, it was observed that the best degradation was accomplished in the loam soil, due to more bioavailability as compared to the clay loam soil and less inhibitory effect of the contaminant on microbial growth, resulting from lower bioavailability, as compared to the loamy sand soil.

Abstract Marun oil field is located in the southwest of Iran and consists of two oil reservoirs named Asmari and Bangestan. Asmari oil reservoir has been producing sweet oil and gas since 1964, but for the first time a high amount of hydrogen sulfide gas was observed in one well of this reservoir in 1980. Moreover, the Bangestan oil reservoir is located deeper than the Asmari oil reservoir and has been producing sour oil and gas since 1972. This paper represents the conducted study on the determination of hydrogen sulfide oil pollution sources in the Asmari oil reservoir. There are two hypotheses for sources of hydrogen sulfide oil pollution in the Asmari oil reservoir; first, hydrogen sulfide gas migration from Bangestan oil reservoir and second, sour gas injection migration. Data of well souring history, hydrogen sulfide gas concentration of wells, volume of gas injection and RFT analysis were used to investigate these hypotheses. The results showed a similar trend of gas injection volume and hydrogen sulfide gas concentration of wells, which decreased over time. Also, the results demonstrated that the migration of gas injection is a source and cause of spreading of hydrogen sulfide gas in the Asmari oil reservoir.

Abstract Eventual realization of a hydrogen economy requires cheap and readily available hydrogen sources and a technology to convert them into pure hydrogen in an efficient and sustainable manner. The objective of this paper is the computational investigation of the hydrogen production through thermal decomposition of sour natural gases containing CH 4 and H 2S inside a solar reactor. In this study a solar reactor has been used to absorb solar power and allow it to concentrate in a graphite nozzle in the middle of the reactor and transfer it to a flow reactant thereafter. From an economical standpoint, the main issue is the production of two valuable products, hydrogen (H 2) and a high-value nano-material of carbon. The effects of H 2S to CH 4 feed ratio and reactor temperature on hydrogen, carbon black, S2 and CS 2 formation are investigated. The results show complex behavior in the products because of the difference in CH 4 and H 2S pyrolysis temperatures. It can be seen that for H2S/CH 4>2, the yields of H2 and CS 2 reach a local and global maximum at H2S/CH 4=5, respectively. A comparison performed between the presented results and the results of Towler and Lynn, and Abanades demonstrates a good agreement.

Abstract Monte Carlo simulation is adopted to study the aggregation of asphaltene phenomenon in crude oil. Simulation is accomplished by applying two different potential functions to allow for asphaltene-asphaltene, asphaltene- resin and resin-resin interactions to take place. Asphaltene molecule is considered as a flat molecule, consisting of seven spheres. Resin molecule is considered to be a single sphere and the other hydrocarbons molecules contained in crude oil are modeled as a continuum media. The effect of media on intermolecular interactions is described by definition of a parameter that is composed of two dielectric and Hamaker constants. The effects of asphaltene concentration, temperature and solvent type on the aggregation of asphaltene molecules are investigated by applying both of the potential functions. The predicted results are compared.

Abstract In gas condensate reservoirs, by reservoir depletion, pressure decreases below the dew point pressure of the fluid and condensate forms in the reservoir. This heavy part of the gas has found many applications in industry and also in daily life. When condensate drops out in the reservoir not only is this valuable liquid lost, but also its accumulation results in forming a condensate bank near the wellbore region. The created bank makes a considerable reduction in gas well productivity. These facts demonstrate that finding an economical way to increase the condensate recovery from condensate reservoirs is essential. In this study gas injection has been simulated in a gas condensate reservoir to increase the condensate recovery factor. In addition, capability of injection of different types of gas in condensate recovery has been compared through different injection schemes. The injection schemes that have been considered are: different injection rates, different reservoir pressures at which the injection is implemented and different injection durations. A compositional simulator was applied to simulate a simplified gas condensate reservoir model. The injection pattern was a one-eighth of a five-spot pattern with finer grids near the producer and injector. The simulation results showed an increase in condensate recovery from 5% to 30% in all injection cases. Many parameters can affect the decision of selecting the injection scheme, other than the gas and condensate recovery factor. Therefore, an economical evaluation and analysis is inevitable to take them all into account to determine the optimum scheme.

Abstract Morphological and thermal properties of PA6/NBR nanocomposites prepared through a direct melt mixing process in an internal mixer were studied. The effects of the NBR content (10, 30, and 50%) and nanoclay loading (3, 5, and 7%) on the microstructure properties of nanocomposites have been reported and compared with PA6/NBR blends as well. The thermoplastic elastomer (TPE) nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), volume swelling in oil, differential scanning calorimeter (DSC) and dynamic mechanical thermal analysis (DMTA). XRD results show that Cloisite 30B is exfoliated into the PA6 and NBR. TEM image of the PA6/NBR/nanoclay composite confirms partial exfoliated structure of silicate layers dispersed into the both NBR and PA6 phases. The SEM photomicrograph of PA6/NBR nanocomposite shows an increasing of the rubber particles size in comparison with unfilled PA6/NBR TPE. By the presence of nanoclay, improved oil resistances of the prepared TPE nanocomposites were achieved. DSC studies show that loading of the nanoclay reduces the degree of crystallinity of the nanocomposite samples. The DMTA test shows that storage modulus of the PA6/NBR nanocomposite increases in comparison with the PA6/NBR blend. It also explains a reduction in damping by loading of the nanoclay.

Abstract Stuck pipe is one of the most serious drilling problems, estimated to cost the petroleum industry hundreds of millions of dollars annually. One way to avoid stuck pipe risks is to predict the stuck pipe with the available drilling parameters which can be employed to modify drilling variables. In this work, Artificial Neural Network (ANN) was used for stuck pipe prediction according to the fact that this method is applicable when relationships of parameters are too complicated. Based on the drilling fluid condition from one of the Iranian oil fields, stuck pipe instances were divided into static and dynamic types. The results of this study show more than 90% accuracy for stuck pipe prediction in the investigated oilfield. The methodology presented in this paper enables the Iranian drilling industry to estimate the risk of stuck pipe occurrenc during the well planning procedure.

Abstract In this contribution Artificial Neural Network (ANN) modeling of the hydrocracking process is presented. The input–output data for the training and simulation phases of the network were obtained from the Tehran refinery ISOMAX unit. Different network designs were developed and their abilities were compared. Backpropagation, Elman and RBF networks were used for modeling and simulation of the hydrocracking unit. The residual error (root mean squared difference), correlation coefficient and run time were used as the criteria for judging the best network. The Backpropagation model proved to be the best amongst the models considered. The trained networks predicted the yields of products of the ISOMAX unit (diesel, kerosene, light naphtha and heavy naphtha) with good accuracy. The residual error (root mean squared difference) between the model predictions and plant data indicated that the validated model could be reliably used to simulate the ISOMAX unit. A four-lumped kinetic model was also developed and the kinetic parameters were optimized utilizing the plant data. The result of the best ANN model was compared to the result of the kinetic model. The root mean square values for the kinetic model were slightly better than the ANN model but the ANN models are more versatile and more practical tools in such applications as fault diagnosis and pattern recognition.

Abstract A static to dynamic approach to modeling Asphaltenes has been developed and validated. A new algorithm for static asphaltene modeling uses a multi-solid thermodynamics approach where the equality of fugacity for each component and phase is applied at equilibrium conditions. This is required for minimizing the Gibbs free energy. The fractal distribution function used for the splitting and characterization of heavy components provides accurate results. The precipitation and re-dissolution of asphaltenes are investigated for a relatively heavy crude oil from an Iranian field. A
series of experiments are designed and carried out quantitatively to obtain the permeability reduction in a slim tube. Using a dynamic reservoir simulator, a 3-dimensional asphaltene model is developed to simulate the precipitation, flocculation, deposition and its impact on permeability in a slim tube. With this approach, the asphaltene is defined as a set of component(s) that can precipitate depending on their molar percentage weight in the solution. The simulated permeability reduction due to asphaltene deposition shows good agreement with our experimental data.

Abstract One limitation in the use of hydrophilic polymers as implantable devices is their inherently poor mechanical strength. Using interpenetrating polymer networks (IPNs) consisting of both hydrophilic and hydrophobic networks is an effective method to strengthen these polymers. In this work, a series of poly(dimethyl siloxane) /poly(acrylic acid) sequential IPNs was synthesized and the polymerization kinetics of acrylic acid in the presence of ethylene glycol dimethacrylate as the crosslinker was investigated using ampoule polymerization experiments and DSC analysis. The results from conversion measurements revealed the occurrence of gel effect during acrylic acid polymerization. The properties of the produced IPNs including swelling, morpho-logical, and mechanical properties were also investigated.

Abstract Silica fume is a by-product of silicon metal or ferrosilicon alloys in smelters using electric arc furnaces. It consists of 85% to 95% amorphous silicon dioxide (SiO 2). Each individual particle of silica fume is spherical with average diameter 0.15-0.3 μm (100 times finer than cement particle); therefore its specific surface area is high. Silica fume particles are water wet and absorb excess water in cement slurry when cement slurry is extended by water. Silica fume thickens the cement slurry, so rheological properties are controlled by dispersants. In this paper, optimal concentration of silica fume and other additives for preparing 90 pcf cement slurry for liner cementing in one Iranian oilfield is determined. The criteria of designing slurry formulation are slurry density, rheological properties, fluid loss, free water, thickening time of cement slurry, and compressive strength and permeability of set cement. Finally, based on experimental results, the preferable slurry compositions are selected. This formulation can be used for cementing of oil and gas wells where moderate and light weight cement density is needed.

Abstract Production optimization ensures that wells and facilities are operating at their peak performance at all times to maximize production. This paper describes a procedure, to develop Inflow Performance Curves, Tubing Performance Curves and Choke Performance Curves, for one of the Iranian southern oil wells, from the results of a multiphase flow simulator (PIPESIM). The goal of this project is to optimize the production from one of the southern Iranian oil fields. Increasing the choke size leads to maximizing production, and causes an optimum reduction in wellhead pressure and bottomhole flowing pressure. Controlling flow patterns in all sensitivity analysis play a major role in selecting the proper variables. Using 7in. OD tubing size rather than 95/8 in. casing size and selecting 9/16 in. choke size rather than 7/16 in., the wellhead pressure between 700 to 1180 psia will be the result and optimum range in selected well No. 305b. The results show a successful experience in optimization of well No.305b and the production can be increased from 2000 BOPD to 3150 BOPD.

Abstract Wettability alteration of outcrop obtained from Asmari formation was investigated using surfactants. Three different surfactants including a cationic surfactant: dodecyltrimethylammonium bromide (DTAB), an anionic surfactant: sodium dodecylbenzenesulfonate (SDBS) and a non-ionic surfactant that was Triton X-100 were used.
Wettability alterations in the presence of each surfactant for the three surfactant concentrations from 0.1 to 0.3 wt% in brine and at four different temperatures, from 25 to 80°C were examined. Surfactant solution droplets were placed on the rock surfaces after being saturated with brine and placed in crude oil. The potential of surfactants to alter the wettability was determined by estimating the contact angle (0) between the surfactant droplet and the surface of the rock. The results indicated that Triton X-100 could change the wettability condition from oil-wet to water-wet more than other surfactants with the same concentrations and temperatures.

Abstract Implicit pressure-explicit saturation method (IMPES) is widely used in oil reservoir simulation to study the multiphase flow in porous media. This method has no complexity compared to the fully implicit method, although both of them are based on the finite difference technique. Water coning is one the most important phenomenon that affects the oil production from oil reservoirs having a water drive source. Since the water coning affects final oil recovery, identification of this phenomenon is very important. In order to study this phenomenon, one should determine the critical production rate, the breakthrough time and watercut percentage. The scale of the problem hinders the numerical simulations, IMPES included, for a long running time. A corrected IMPES method is used here to overcome the long running time problem by choosing larger the time step for the coning problem. A water-oil phase flow system in the cylindrical coordinate that is commonly used to simulate water coning phenomenon is solved by the corrected IMPES method. The validity of the model is checked against Aziz and Settari’s model, which is based on a complicated fully implicit method.  The effects of the production rate and the thickness of the oil zone on the breakthrough time have been investigated. The results were found to be in good agreement with the results of previous studies.

Abstract Precipitation ofsolid paraffins is one ofthe most common problems in the oil industry, imposing high operating costs. There have been a great many efforts for the prediction of solid paraffins precipitation up to now. Most of them were based on activity coefficient models accounting to solid phase non-ideality or the multi-solid model to calculate the number ofprecipitated solid phases. In this work, solid phase behavior is predicted by a solid equation of state. At first, by using the thermodynamic method (subcoled liquid) for pure solid phase fugacity from pure liquid fugacity, the solid EOS parameters are tuned. The tuned solid EOS can then be directly applied for the prediction of the amount of precipitated solid paraffins (waxes) in the oil samples. The proposed equations system in this work is solved by a proper mathematical method. The obtained results of wax precipitation in this work are in good agreement with the experimental data.

Abstract The influence of different factors on the asphaltene stability in three iranian crude oils was evaluated. Compositional studies and structural characterization of resins and asphaltenes were carried out in order to study a possible relationship between these properties and asphaltene deposition behavior. Low hydrogen to carbon ratios and high aromaticities were the main characteristics of the asphaltenes from more unstable crude oils. According to these results, the stability behavior of asphaltenes was influenced strongly by their structural characteristics. Colloidal stability indexes such as the (aromatic+resins)/(asphaltene+saturates) ratio and (aromatics+resins)/ asphaltene ratio do not play a key role in the asphaltene stability for the studied crude oils.