PETROLEUM RESEARCH
Year:2014 | Volume:24 | Issue:79|Papers Count:18

One of the main limitations in the process of hydrate formation for its positive application is the requirement of high pressures and low temperatures. Establishing a unit with these conditions is expensive and unsafe. Therefore, finding the methods for the promotion of this process is very important. The utilization of ammonium salts in water noticeably promotes the hydrate formation conditions. One of these salts is tetra n-butyl ammonium fluoride (TBAF). In this research, the equilibrium data of semi-clathrate hydrate for the system of water/TBAF/methane have been measured and reported. Three concentrations of TBAF (2, 5, and 15 wt.%) were used for the experimental measurements. The comparison of the measured data with the simple hydrate (the hydrate for the system of water/methane) equilibrium data showed the high promotion effect of TBAF on methane hydrate formation. By increasing the concentration of TBAF, its promotion effect increases and the hydrate formation P-T curve shifts to the right side.

According to a recent seismic survey in the Oman Sea, hydrate bearing layers were detected through observation of significant bottom simulating reflector, flat spot, and bright spot attributes in the area of 27,000 km2. This paper estimates the minimum water depth required for gas hydrate formation in the Oman Sea. Also, the thickness of the gas hydrate stability zone (GHSZ) is modeled on the basis of the Oman Sea basin properties. This leads to the first estimation of the volume of hydrate-bound gas sequestered in the Oman Sea. Using Milkov and Sassen’s model, the thickness of the GHSZ is calculated. Considering three different gas compositions, the minimum water depth stability calculations suggest that gas hydrate may crystallize as shallow as ~430 m to a water depth of ~872 m and the average thickness of the GHSZ was estimated to be ~217–446 m in the Oman Sea. The estimated volume of hydrate-bound gas is 11–21×1012 m3 at standard temperature and pressure (STP) depending on the source gas composition, which is comparable to initial gas in place of South Pars gas field. Therefore, gas hydrate accumulation in the Oman Sea and free gas beneath could be a future energy source from which natural gas could be recovered profitably in the near future.

In this paper, the modified Ottengraf model (MOM), as a mathematical model, is applied to modeling the biofiltration process. The model facilitates considering both biological reaction and diffusion limitations simultaneously. The main advantages of this model are simplicity and an analytical solution compared with other mathematical models for biofiltration process. The modeling results show that the modified Ottengraf model can predict the experimental results for vinyl chloride removal from an air stream with an R-squared value higher than 0.95 and the relative errors between the model and the experimental results for first, second, and third column were 0.41, 0.59, and 0.54 respectively. Kinetic parameters such as reaction rate constant were estimated by fitting the measurements to the model for three columns as 1, 1.042, and 0.9957 g/m3.hr respectively. Using fitted parameters, it is possible to predict biofilter performance in other experimental conditions. According to the OSHA standard, for achieving an allowable VC concentration, during 8-hour work shifts in the outlet stream of the biofilter under consideration, the flow rate and empty bed residence time should be 0.129 m3/hr and 196 sec respectively. The removal efficiency of 90% was achieved using the mentioned empty bed residence time and flow rate.

Functionalized multi-walled carbon nanotube (MWCNT)/silica nanohybrid was synthesized and proposed as a stabilizing agent for water-in-oil pickering emulsion. The high cation content of the formation water balanced the hydrophilicity/ hydrophobicity of the structure and therefore stabilized an emulsion phase without any chemical or mechanical treatment. Bivalent cations, such as magnesium and calcium, changed the hydrophilic-lipophilic balance (HLB) more intensely than the sodium univalent cation. The experiments conducted on the formation water samples from two oil reservoirs, located in the southwest of Iran, revealed that other anions/cations did not impact the performance of the nanohybrid as the pickering emulsion stabilizer. The proposed nanohybrid may hold a great promise to be adopted in enhanced oil recovery (EOR) processes as it does not require any emulsifier and it is free of any mechanical treatments. The key factor, which affected the performance of the proposed nanohybrid, pertained to the type of the cation contained in water. Bivalent cations, such as magnesium and calcium, changed the hydrophilic-lipophilic balance (HLB) more intensely than the sodium univalent cation.

NMR logging is one of the most modern tools in oil wells, which is employed for obtaining petrophysical parameters. One of the most important abilities of NMR is hydrocarbon typing near the borehole. In this technique, there are two methods for hydrocarbon typing: dual TW method and dual TE method. The current paper studies the hydrocarbons in Asmari and Ilam formations of Ahwaz oil zone. At first, the petrophysical parameters of the reservoir such as porosity, water saturation, and viscosity were studied and it was found out that there was a good consistency in porosity data with the standard one; then, the hydrocarbon typing in this well was qualitatively investigated. Next, due to the presence of Twlong and Twshort at a depth of 3019 meter, the porosity of oil was obtained to be 0.027, which was exactly the same as the values obtained in the experimental data. The water saturation and viscosity were calculated using fluid substitution model and T2lm respectively.

The thermal cracking of hydrocarbons is one of the most important industrial processes producing olefin products including ethylene and propylene as desirable products. The undesirable process is coke formation, which causes several problems in thermal cracking reactors such as heat transfer reduction, increasing the pressure drop in the reactor, increasing fuel consumption, shortening the life of the reactor, and so on. Consequently, such undesirable affects can be decreased by choosing a proper alloy in reactor construction, using right feed, or some inhibitors. To prevent the formation of coke, some inhibitors were investigated. The variety of experiments showed that inhibitors like dimethyl disulfide and carbon disulfide could strongly decrease the coke formation. In this article, the reduction of coke formation and structural changes were investigated by using heavy naphtha as the normal feedstock entering the reactor, the above sulfide inhibitors, and stainless steel 304 as well as employing scanning electron microscope (SEM/EDAX) as an analysis technique.

In this paper, a modified formulation of class G cement for manufacturing and production has been proposed. Since the produced industry cements have no proper rheological properties, thickening time, and compressive strength, a new formulation has been proposed on the laboratory scale. The clinker was classified into a wide range of particle sizes and the final cement was prepared by mixing them with gypsum. The designed cement is non-uniform and coarser than conventional cements and 50 percent of particles are in the range of 3-30 mm, which shows a 20-30% decrease in the aforementioned range as compared to standard cements. Although the designed cement has very good rheological properties, thickening time, and lesser water usage about 10% which causes a higher 24-hour compressive strength, there is a lower early compressive strength when compared to standard cements. Hence the production system was changed from ball mill and sieves to production by ball mill alone and homogenous cement with the same specific surface area was produced. In addition to having all the desired properties, by a 10% decrease of water usage in the cement system, the early compressive strength was improved by 21% compared to standard cements based on quality control results. Moreover, this production system can completely be implemented at the production plants.

There are several methods to study the capillary behavior of multi-phase flow performance within reservoir rock. One is the actual determination of multiphase flow properties from measured data, and the other is the representation of the proposed functions for capillary pressure. It is essential that these functions have sufficient degrees of freedom to model the measured data. In this study, the new analytical correlation (LET function, proposed by Lomeland and Ebeltoft) is first defined and used to investigate the results of experimental capillary pressure by centrifuge for numerous samples from an Iran carbonate reservoir rock of southern oil fields. Then, by tuning the existing parameters in the function, a model was developed and completed to predict the capillary pressure curves. The results show that without any time and cost used for the experimental measurements of capillary pressure and only by applying the routine core parameters, the developed model can estimate the capillary pressure curves. This developed model is very simple to use and more accurate than other models. In order to demonstrate the validity of this correlation, the predicted results are compared with those obtained from several experimental measurements conducting a centrifuge method on several core samples from one of the Iran carbonated rocks. Regarding the amount of the calculated error (R2<0.18), this method has acceptable accuracy and is easy to use.

this work, agitated slurry-bubble reactor was simulated with the aid of computational fluid dynamics techniques. The effects of impeller flow direction on hydrodynamic behavior and the aeration quality of reactor spargers (terephthalic acid CTA, production in Shahid Tondgooyan petrochemical complex) were investigated. To this aim, an Eulerian multiphase approach and RNG k-e turbulence model were employed for large-scale CFD simulations. The results showed that up-flow impeller caused an increase in bubble residence time and mixing intensity in the higher zones of the reactor. Therefore, the length of the liquid path and the number of direction changes were greater in the case of up-flow impeller compared to down-flow one. As a result, the energy associated with the down-flow impeller (at the bottom of reactor) was much higher than the up-flow one; hence the turbulence intensity for the down-flow impeller was also relatively high. For down flow pattern, the outlet gas of spargers caused a reverse flow by the liquid flow and pushed the gas to the reactor center.

Fifteen billion barrels of recoverable oil accumulated in 17 oilfields make the Iranian sector of the Persian Gulf one of the most proliferous regions in the world. The elemental and isotopic analyses as well as gas chromatography were conducted on 33 oil samples selected from different reservoirs in order to study the physical and chemical properties and identify the probable source rock characteristics. Most of the oil samples were characterized as the high sulfur content. The sulfur contents increase as API decreases. The Asmari reservoir of Kharg-Dorood oilfield contains the highest sulfur content whereas the Surmeh reservoir of Resalat oilfield has the lowest content. Different hydrocarbon fraction contents such as n-alkane distribution, acyclic isoprenoids ratios of pristane and phytane, carbon preference index, and stable carbon isotope ratios were determined by conducting the column chromatography, gas chromatography, and stable carbon isotopic analysis. Based on the results, most of the oil samples could be classified under paraffinic oils probably sourced from Mesozoic marine carbonate bearing type II and II-S kerogen deposited under anoxic condition.

In this paper, the performance of a polymeric membrane was studied using a two-stage ultrafiltration treatment of produced water. At first, the effects of operating parameters, i.e. transmembrane pressure, temperature, and cross flow velocity on the flux decline caused by membrane fouling were investigated. In order to design the experiments and optimize the experimental results, the L9 (33) orthogonal array of Taguchi method was used. The analysis of variance was employed to determine the most significant parameters affecting the flux decline caused by membrane fouling. The optimum conditions were found at the first level of transmembrane pressure (1.5 bar), the second level of temperature (40oC), and the third level of cross flow velocity (1 m/s). In the second stage, the performance of ultrafiltration system by the polymeric membrane was studied under the optimum conditions, 99% oil and grease, 100% TSS, 99% turbidity, and 68% TOC removal were obtained. Moreover, the particles size of the feed decreased from the range of 200-800 nm to 1.5-3 nm.

The permanent storage of CO2 in deep saline aquifers is known as an effective method for reducing the greenhouse gas emissions. Predicting the long-term fate of the injected CO2 requires an understanding of the basic mechanisms involved in the storage process. CO2 injected in deep saline aquifers diffuses in resident brine, which increases the brine density and potentially leads to convective mixing raising the rate of dissolution. Hence it is important to realize the factors enhancing convection in deep saline aquifers. In this paper, a two dimensional, single-phase model is developed for modeling of the convective mixing. The scaling analysis of the convective mixing of CO2 in saline aquifers is presented and convection parameters are described as a function of system Rayleigh number. For the first time, in this study the start time of enhancement in CO2 dissolution due to convective mixing was studied quantitatively. The results indicate that the enhancement in CO2 dissolution due to convective mixing occurs at a time about three times of the onset time of instabilities. The results of this study increase our knowledge of the appropriate implementation of geological CO2 storage in deep saline aquifers, without the need for costly simulations.

One of the common methods for reservoir screeining in EOR projects is comparison of prosperous projects is comparison between successful carried out projects and available reservoirs in the whole world. Because of lack of similar samples in this method, some of reservoirs are not considered for injection, so casing of another EOR method is necessary. In this paper, at first, by combination of Experimental design and Compositional simulation, rock and fluid effective parameters are detected in N2 and CH4 gas injections for pressure maintenance in reservoirs. Then, indirect and interaction effect of these parameters are analyzed and compared for both gas injections. separately for both gases injection are analyzed and compared. Finally, for estimation of oil recovery factor, empirical correlation is proposed. This correlation is used for primary screening in N2 and CH4 injection projects.

In the present work, nanocomposites were processed and fabricated by mechanical mixing of epoxy resin with organoclay using an electric shear mixer. Methods of preparation, fabrication, and characterization of epoxy resin reinforced with organically-modified montmorillonite (OMMT) have been studied. The optimum scheme and procedure were selected and the effects of nanoclay concentration, rate and time of mixing, rule of solvent, sonication time were investigated. After that, the mechanical properties of fabricated samples were evaluated and compared with pure epoxy. It was found that using solvent in preparing the composites improved mechanical behavior. The X-ray diffraction (XRD) results showed intercalation, some degree of exfoliation, and increasing of d-spacing of silicate layers in the nanocomposites fabricated with the shear mixing because of well-dispersion when adding nanoclay up to 5 wt.%. By adding 5 wt.% nanoclay, tensile strength and modulus, and flexural modulus increased 13.4%, 21.5%, and 27.2% respectively.

In this study, the reasons for both sediment formation in a chlorinator instrument and erosion of some of its components have been investigated. This system was used to inject chlorine gas to cooling water. Visual examination clearly demonstrated the formation of gray sediments in the inner side of the chlorinator chamber along with the erosion. Furthermore, the excessive accumulation of white precipitated materials has blocked the glassy tube of the chlorinator. These events, however, have made the chlorinator system inefficient. The results of TGA, FTIR, and EDS analyses have clearly shown the best match between both unknown deposits and PVC materials. The portion of minerals in both gray and resinous white sediment materials was determined to be 28.51 and 16.7% respectively. Metallic elements such as iron and copper were also identified in the composition of sediment materials by EDS analysis. Additionally, the existence of intramolecular water in the mineral portion of the deposited materials was clearly demonstrated in the FTIR spectra. On the whole, it seems that wet chlorine has a crucial role in the erosion of chlorinator parts and subsequent deposit formation.

Relative permeability is one of the most important parameters affecting reservoir performance; it is determined from experimental measurements (e.g. cores),which can be time consuming and costly. Considering the relationship between relative permeability and resistivity, the relative permeability of phase diagrams (wet and nonwet) can be estimated by using resistivity data. This study determined the relative permeability by using resistivity logs in one of the Iran oil fields and compared it with experimental results. In view of the availability of resistivity logs from oil wells, this research can play an important role in the feasibility study of estimating the relative permeability by resistivity logs, which could be valuable in terms of saving time, economics, and dynamic reservoir simulation.