مجله پژوهش نفت
پیاپی 84 (آذر و دی 1394)

The effect of operating conditions such as temperature, pressure, and H2/nC5 molar ratio on the hydroisomerization of n-pentane over Pt/ZSM-5 was investigated. It was found that, because of increasing the cracking reactions, by increasing temperature the n-pentane conversion was incremented, but the selectivity towards iso-pentane was decreased. Furthermore, an increase in pressure had a desirable influence on the n-pentane conversion and iso-pentane selectivity. The other important parameter studied in the current work is H2/nC5 molar ratio. The results showed that at the low ratios of H2/nC5, conversion was decreased with increasing this ratio, since the active sites was occupied with hydrogen. On the other hand, the hydrogenation of surface alkanes resulted in decreasing the cracking reactions and consequently increasing the selectivity towards iso-pentane. At the higher ratios of H2/nC5, increasing hydrogen amount had no effect on the selectivity and led to a low decrease in the n-pentane conversion.

The objective of this research was the design and economic study of biodiesel production from animal fat. Nowadays, biodiesel is mostly produced from edible sources such as soybean. Wastes of tallow as an abundant, cheap, and inedible source can be used instead of these sources. High amounts of free fatty acid of animal fats are why the process needs to be performed in two sections, namely esterification and transesterification reactions, and the purification process was conducted by water washing in an extraction column. The simulation results of Aspen Hysys software shows the production of 5000 kg of biodiesel of 5000 kg of tallow. Additionally, glycerol was purified as a by-product of the process. Aspen Icarus software was used for the economic study of the process and the economic results by Aspen Icarus software shows that the NPV is M$ 4.733 after 10 years, which confirms that this design is cost-effective. Furthermore, the payback period from the plant start-up is 7.7 years.

The outcrop of carbonate reservoirs is generally water-wet. However, in many cases, water film stability depending on surface charge between oil/water and rock/water interfaces is collapsed and the wetting condition changes from water-wet to oil-wet or intermediate wettability. The main cause of this phenomenon is resulted from the adsorption of some fatty acids in oil phase. Thus, due to the negative amount of capillary pressure, spontaneous imbibitions will not accomplish and consequently ultimate oil recovery will decrease. The utilization of surfactants is one of the available routes for wettability alteration of reservoir rock from oil-wet into water-wet. These materials can diffuse into water/oil or rock/oil interfaces through interfacial reduction and can consequently cause the wettability alteration of the trapped oil. Thus studying wettability alteration mechanism using surfactants has been emphasized by recent researchers. This work focuses on presenting a process mechanism, which has a direct effect on surfactants behavior in oil field usage by using analysis techniques such as zeta potential, TGA, and the injection of surfactant solutions in porous media via core flooding apparatus. The results show that cationic surfactants have the greatest effect on wettability alteration at above critical micelle concentration (CMC) because of the electrostatic attraction between surfactant and adsorbed fatty acids in crude oil, whereas anionic and nonionic surfactants have less performance in the wettability alteration of carbonate rocks.

With respect to the fact that most of the Iran oil reservoirs have elapsed their period of natural depletion, the usage of gas injection techniques renders necessary for EOR purposes. The formation of organic precipitates such as asphaltene and its subsequent precipitation over reservoir rock during the gas injection process is considered a critical problem due to causing damage to the formation. Therefore, prior to conducting any industrial gas injection projects, it is necessary to perform experimental research with the same type of reservoir rock/fluid, and then a field-scale project can be implemented, once the analysis of the experimental results and the simulation of the reservoir are completed. In this research, the effect of pressure of injecting natural gas on asphaltene precipitation and alteration of core characteristics is analyzed. Live oil samples from one of the Iran offshore fields were used. The permeability reduction before and after gas injection were determined. In addition, the produced fluid was sampled at different time scales and its asphaltene content was determined using the IP143 standard. Using the mass balance equations, the reduction in core porosity and the power relation between permeability and porosity in the damaged core were established. The results suggest that the asphaltene coagulation and precipitation should increase along with gas injection, which causes permeability reduction. Such damages tend to decrease by lowering pressure, and the analysis indicates the mechanism of precipitation to be of mechanical blockage.

Sand production during extraction and exploitation from oil wells is one of the most important problems in delaying the exploiting operations. Different methods are presented to predict sand production in the field the reservoir rocks of which are sandstone or carbonates. This methods are typically comprised of rock mechanics tests (such as uniaxial compressive strength and triaxial tests), and mineralogical analyses or using of well logs. Rock mechanics tests and mineralogical analyses, as well as other tests used to analyze oil and gas wells, are very time consuming and costly in comparison with conventional well logs. Therefore, in this paper, well logs are used for the prediction of sand production in the southwest of Iran. For this purpose, by having traditional petrophysical logs such as sonic logs, the uniaxial compressive strength and elastic modulus in rocks are first calculated, and then the values of pore pressure are computed; these values are also calibrated with the real data. Since in situ stresses at deep depths are very necessary for the prediction of sand production, by using values obtained for elastic modulus, uniaxial compressive strength, and pore pressure, the vertical and horizontal stresses were obtained. Finally, Mohr-Columb criteria and caliper log data were used to obtain the optimum safe mud window for the prediction of local zones that have the potential of sand productions.

In the current research, polyvinylchloride (PVC)-based nanofiltration membrane was prepared by using a mixture of N, N dimethylacetamide (DMAC) and tetrahydrofuran (THF) at a constant ratio of 85:15 as the solvent. The membranes were fabricated by a phase inversion method and casting solution technique. The effects of different ratios of anionic sodium dodecyl sulfate (SDS) in casting solution on membrane performance and phase inversion time were investigated. Flux, selectivity, water content, and the SEM of cross sectional of membranes were studied. The SEM results indicate a denser top layer for the membrane containing SDS compared to the pristine one. Also, the modified membrane containing 0.45 wt.% SDS showed better performance compared to the others.

The upper Jurassic Surmeh formation (Arab equivalent) is one of the most important oil reservoirs in the Persian Gulf. In this study, different rock typing approaches were used for the reservoir characterization of this formation in an oil field in the central Persian Gulf. Lithologically, the upper Surmeh formation is mainly composed of dolomite and anhydrite. Petrographic studies have led to the recognition of 10 microfacies grouped into four facies associations (belts) as supratidal, intertidal, lagoon, and shoal settings. The observed facies indicate a carbonate ramp as the depositional environment of the Surmeh formation. In order to relate the recognized microfacies with petrophysical rock classes, the porosity-permeability of cores was plotted on standard diagram and accordingly four distinct rock types (classes) were identified. In addition, electorofacies determination was applied by using the multi resolution graph-based clustering (MRGC) technique. The clustering technique has led to the recognition of six electorofacies in the upper Surmeh formation. Hydraulic flow units and reservoir/non-reservoir units were identified in the studied intervals by using the flow zone indicators (FZI) and a stratigraphic modified Lorenz plot (SMLP) respectively. Predicted porosity and permeability data were used to construct a continuous stratigraphic profile of reservoir/non reservoir units. Accordingly, six hydraulic flow units and nine reservoir units were identified and closely correlated in the studied wells. A comparison between the results of all rock-typing methods and petrographic data also reveals close correspondence. An integration of different rock typing approaches results in partitioning of three final rock types in the upper Surmeh formation.

Present study revises the biostratigraphy age of the Asmari formation in Dezful embayment in the southwest of Iran. Asmari formation thickness reaches 417.5 meters and it mainly consists of dolomite, sandy dolomite, limestone, sandy limestone, sandstone, and shale. Carbonate units comprise wackestone, packstone, grainstone, and less boundstone facies. According to the recognized assemblage zones and the previous Sr isotope data, new biozonation are defined for the Asmari formation in this filed. As a result, the Asmari formation is subdivided into five bio zones as follows:1. Borelis melo melo-Borelis melo curdica Assemblage Zone, Early Miocene (Burdigalian);2. Indeterminate Zone, Early Miocene (Aquitanian-Burdigalian);3. Miogypsina - Elphidium sp14 - Peneroplis farsensis Assemblage Zone, Early Miocene (Aquitanian);4. Archaias asmaricus-Archaias hensoni-Miogypsinoides complanatus Assemblage Zone, Late Oligocene (Chattian);5. Lepidocyclina-Operculina-Ditrupa Assemblage Zone, Late Oligocene (Chattian).Due to non-accompanied Lepidocyclina microfossils with Nummulites microfossils in the bio zone five, the related age is considered to be Late Oligocene (Chattian). Nummulites microfossils relating to Rupelian were not distinguished in the studied section of this filed.

The Sarvak formation (Late-Albian-middle Turonian) is one of the main oil and gas reservoir units in the southern and southwest of Iran after Asmari formation (Oligo-Miocene). It hosts an important amount of hydrocarbon reserves in this region. Detailed thin section studies of this formation in the Siri field led to the identification of 9 major microfacies, which are deposited in four facies belts (basin, outer-ramp, mid ramp, and inner ramp) in a homoclinal ramp-type platform. Main diagenetic processes affecTed carbonate of this formation are neomorphism, bioturbation, micritization, dolomitization, extensive dissolution, cementation, stylolitization, and fracturing. Diagenetic processes at the upper part of the Sarvak formation and the relative timing indicate that these processes occur in three main diagenetic environments, including marine, meteoric, and burial. The correlation between the porosity and permeability values of core data shows that the reservoir quality is affected by sedimentary environment, sedimentary facies, and subsequent diagenetic processes. Thus the rudists facies (grainstone, rudstone, and floatstone) have a maximum porosity and permeability.

Semblance analysis is one of the common methods in the seismic velocity estimation, which is based on the summation of samples in the velocity analysis window. In the case of deep reflection events or low offset data, the velocity spectrum of this method has a low resolution. An increase in the resolution of the semblance results in an improvement in the accuracy of the estimated velocity for NMO correction and stacking. In this paper, the bootstrapped statistical method was introduced to improve the resolution of velocity spectra. In semblance method, if the selected velocity for NMO correction is slightly different than the actual velocity, the traces inside the analysis window are not fully horizontal. Nevertheless, due to the small time difference between the adjacent traces, the semblance value calculated for this case is nearly identical to the value of the actual velocity and causes the extension of the peak of the velocity spectrum. If the velocity of the analysis window is different from the correct value, the bootstrapped method increases the time difference of two adjacent seismic traces by displacing them. By defining a new measure to compute semblance, this procedure can be useful to estimate the correct velocity and increase the resolution of seismic velocity spectra. The efficiency of this method is evaluated by applying it to both synthetic and real seismic data and it is compared with the result of semblance method. The obtained results show that the velocity spectrum of the bootstrapped method has a better resolution than that of the conventional semblance method.

In this study, the influence of the parameters affecting the ozone diffusion into the oil compound polluted soil was investigated. The soil was polluted with anthracene, which is a multi-ring aromatic hydrocarbon, was sieved, and its humidity was removed. It was then kept in vessels with closed caps in dark conditions for one week. The considered parameters were soil column height, soil particles size, the amount of pollutant, ozonation time, and humidity. The pilot employed in this study included a vessel containing phosphoric acid diluted by deionized water (pH=2) followed by a cylindrical reactor in Plexiglas type with a diameter of 3 cm and a height of 25 cm. To inject ozone into the soil uniformly, a glass distributor was inserted at the bottom of the reactor. The maximum amount of diffusion and removing efficiency were 83% and 92% respectively. According to the experimental design, it was observed that any changes in the size of the soil did not have any considerable effect on the amount of diffusion, while any changes in the amount of pollutant, the height of the soil column, and humidity had a significant influence on the diffusion. It was also observed that the highest diffusion rate was happened in the initial 10 minutes of the ozonation process. In the next step, by obtaining the equations dominant on the ozone decomposition by pollutants, organic and inorganic compounds, active sites of the soil, and ozone self decomposition, it has been tried to present a model for the investigation of the ozone diffusion into the soil. This model was obtained by comparing the experimental results with the results obtained from the speed coefficients model of the kinetic reactions of ozone with pollutants, organic, and inorganic compounds, active sites of the soil, and ozone self-decomposition.

At the level of preservation of oil wells in upstream oil industries, complicated experimentations, called PVT, are done for the recognition of reservoir fluid properties. Problems such as probable dangers, time consuming, and the inaccuracy of samples and limitations in temperature and pressure have led to tend to increase the use of intelligent methods in this field. In this study, in order to avoid the mentioned problems and find the complex and nonlinear relationships between data and PVT experiments, artificial neural network has been used. Because the suitable choice of the initial weights increases the neural network efficiency, genetic algorithm is used in order to adjust the initial weights. For evaluating the proposed approach, Iran oil reservoir fluid properties are implemented. The results of research showed that the use of genetic algorithm-based artificial neural network, in contrast to the classical methods, predicts the reservoir fluid properties in a shorter time and with high accuracy. Therefore, the proposed neural network can be seen as a powerful approach toward the prediction of Iran oilfield oil PVT properties.

Geological studies and mapping of surface and sub-surface structures have always attracted the attention of geologists. The main purpose of this study is the identification of salt domes in strait of Hormuz using subsurface data. The study area is located in the south of Iran، which is known as Block E for oil companies at longitude of 55-56° east and latitude of 25°30’-27° north. Seismic data، well data، and UGCtime map are used for three-dimensional modeling of the subsurface salt structures by Petrel software. In this work، the locations of 17 burial and non-burial domes in the Hormuz strait are mapped and the coordinates of the center of each dome with burial depths are written. Most of these diapirs concentrated on the western part of the strait of Hormuz and is likely that the thickness of Hormuz formation in the western part is higher than the central and eastern parts. Finally، eight domes were added to the dispersion salt domes map in Iran. The distance between each of the domes is estimated to be about 35 kilometers in marine sector and it was found that the salt diapirs in the southern Iran matched NE-SW direction or Hendurabi lineament.

Total organic carbon (TOC) is one of the important parameters for the evaluation of the hydrocarbon generation potential of source rocks. The measurement of this parameter requires conducting geochemical analysis on cutting samples، which is expensive and time consuming. In general، organic rich rocks are characterized by higher porosity، higher sonic transit time، lower density، higher gamma ray، and higher resistivity compared to other rocks. In this study، the linear and non-linear genetic algorithm models were used to estimate TOC from petrophysical data for the Kazhdumi، Gurpi، and Pabdeh source rocks in Ahwaz oilfield. The linear genetic algorithm model provided more reliable and acceptable results than the non-linear model. The genetic algorithm solutions for fitting coefficients to TOC equations were compared to a regression analysis. Performance analysis based on MSE and correlation coefficient indicates the higher performance of the intelligently derived equations in comparison to the statistical regression analysis. In the next step of the study، a cluster analysis technique was utilized for the classification of the estimated TOC log and the identification of geochemical zones. In the light of the acceptable results of the GA model، source rocks were classified into the organic-rich and organic-lean facies by using a cluster analysis method.

In the present study، a geostatistic model of the Asmari reservoir based on petrographic، geophysical، and petrophysical data of 90 drilled wells in Mansuri oil field is prepared by using reservoir modeling system (RMS) software. Based on the petrophysical data and their correlation with thin sections، the Asmari reservoir in Mansuri oil field is mainly carbonate-sandstone and subdivided into 8 zones. Zone 1 is at top، below the cap rock، and zone 8 (deepest zone) overlies Pabdeh formation. Between these zones، the upper zones are less affected by destructive diagenetic processes and have a good reservoir quality. Based on geophysical data، the Mansuri oil field has not been affected by tectonic activities as seen on the underground contour map. Moreover، a statistical reservoir model correlating petrographic، petrophysical، and geophysical data was prepared. The results indicate that zones 1-3 of Asmari formation are only productive، among which zone 2 is the best reservoir zone with 65% oil in place. This can be deduced by using petrophysical properties distribution (such as porosity، water saturation، and net to gross ratio) in the oil field. Fractures density contour map shows that، in the Mansuri oil field، fractures does not affect the reservoir to increase the qualities. The reservoir quality is better in the east-north east of Mansuri oil field based on porosity and water saturation contour maps. Thus one can focus on these areas for well planning، production control، and enhanced recovery in the future.

In this study, iron oxide (Fe3O4) magnetic nanoparticles were synthesized and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques and the observation of magnetic properties. Activated carbon nanoparticles magnetic nanocomposites were then synthesized by two in situ synthesis of the iron oxide magnetic nanoparticles on activated carbon and the addition of activated carbon during the synthesis of the magnetic nanoparticles. The observation of magnetic properties showed that the in situ synthesis of the iron oxide magnetic nanoparticles on activated carbon does not result in activated carbon nanoparticles magnetic nanocomposites. The magnetic nanocomposites were also characterized by XRD and SEM techniques. The XRD and SEM results of the samples prepared by the method of the addition of activated carbon during the synthesis of the magnetic nanoparticles revealed the formation of the iron oxide magnetic nanoparticles on activated carbon. The synthesized activated carbon nanoparticles magnetic nanocomposites can be used to adsorb petroleum contaminants from water and can be separated simply by applying a magnetic field.