مجله پژوهش نفت
پیاپی 69 (فروردین و اردیبهشت 1391)

In this research, polyacrylamide based hydrogels were made on the basis of solvent method, and their rheological properties and performance were evaluated by bottle testing and a rheometer under Iran south oil reservoir conditions. Based on the results of the bottle test, the polymeric gel formed by 15000 ppm polyacrylamide and 2500 ppm chromium (III) acetate and kept at 90 °C for 24 hrs was selected as a basic polymeric gel. Based on the results of rheometric tests at temperature of 25°C, the elastic modulus almost remains constant in frequency range of 0.1 to 10Hz and the strain range up to 100%, whereas this module decreases from 8 Pa at 25 °C to 4 Pa at 90 °C. Studying the effect of the applied yield stress on the polymeric gel indicates that for a sample each of three strain points of 100%, 3280%, and 6470% could be considered as a yield point, but it could not be found decisively because of wall slip effect around the rheometer wall. Also, the polymeric gel system does not tear up to the strain of 6470% and the elastic properties are superior to the viscous nature of the system below this point

In this study، the steady-state simulation and optimization of two continuous bulk styrene polymerization processes have been developed to compare the performance of industrial processes. The first process consists of two continuous stirred tank reactors (CSTR)، followed by a tubular reactor. The tubular reactor has been subdivided into six temperature-control zones. The second process consists of an auto-refrigerated stirred tank، followed by a tubular reactor. The tubular reactor of this process has been subdivided into three temperature-control jacket zones. Similar kinetic mechanism and assumptions were used to simulate both processes. The models can predict monomer conversion، number-and weight-average molecular weights، polydispersity index، and temperature at the output of reactors for each process. The genetic algorithm (GA) is used for the maximization of the monomer conversion، the minimization of the final polydispersity index in the product، and to control the number average molecular weight in the range of the common commercial grade. Simulation and optimization results show that the first process is able to produce just one grade of polystyrene while the second one can produce different grades of polystyrene.

Recent evidence on the efficiency of microorganisms and their metabolic products in the oil extraction rate, which is also called microbial enhanced oil recovery, has been reported. In this work, the oil samples produced from Gachsaran oil reservoirs were evaluated in order to isolate and identify bacteria by using public and private media and to consider the ability to produce bio surfactant. In order to determine the best conditions for cell growth, carbon sources (whey, soy, starch, molasses, peas, and water) were added to the medium and bacterial growth curves were plotted over a period of 7 days for each of the bacteria. Best carbon sources for bacterial growth were whey, starch, and soy. The identification of bacteria was also done by molecular and biochemical methods. On the whole, according to the results of biochemical and 16sr RNA tests, these bacteria were classified in the Bacillus genus. Moreover, the sample No. 5 from bacteria Bacillus Licheniformis with ID 1455550 and the sample No. 7 from bacteria Bacillus Subtillis, with ID 1455557 were registered in the NCBI GenBank of America.

The presence of nanoemulsion water droplets in diesel fuel during combustion phenomena causes micro explosions. This process provides more oxygen for fuel and therefore improved combustion efficiency. Diesel fuel nanoemulsions were obtained by using surfactant packages such as long chain fatty acids and their salts, fatty esters, ethoxylated fatty acids and together with co-surfactants such as linear alcohols, butanol and hexanol in the presence of 5-15% of water. These compositions were stable and transparent during long period of time. These fuels were tested in diesel engine OM314 and their performance such as exhaust emissions fuel consumption and engine performance were compared with conventional diesel fuel. The presence of 5-15% water in these fuel compositions causes the exhaust emissions, i.e. nitrogen oxides (0.44-12.9%), soot (17.35-43.9%), and unburned hydrocarbons (0.82-6%) to decrease, but thermal efficiency in diesel engine and lubricity improve. In addition, the presence of water and additives in the fuel reduces heating value, and despite improving the quality of micro explosion phenomenon and increasing the thermal efficiency of combustion (3-4.8%) it causes engine power to decrease by 4.5-13.5%.

The determination of fluid saturation is vital for the estimation of hydrocarbon in place which is the base for economic decision making about reservoir production. Archie’s equations are the most prevalent equations used for saturation calculation. One of the important parameters in these equations is saturation exponent. Saturation exponent has fundamental difference comparing with other parameters which are cementation exponent and tortuosity. Cementation exponent and tortuosity mostly depend on rock type but saturation exponent depends on the distribution of fluids and therefore the hysteresis of saturation during imbibitions and drainage and also wettability. The purpose of this research is an investigation into the effect of saturation hysteresis and wettability on saturation exponent. The saturation exponent was measured from primary drainage to secondary drainage with a four-electrode system at reservoir temperature with reservoir fluids on some cylindrical core samples. Dynamic porous plate technique was used، for which full capillary pressure curves and wettability with combined Amott-USBM were determined simultaneously. It was concluded that the saturation hysteresis affects saturation exponent in different samples during imbibition and drainage and cause it to range from 0. 1 to 0. 66; the variations were higher in oil-wet samples than water-wet samples.

It is very important to recognize faults and fractures in order to enhance oil recovery and to develop oil fields. Seismic coherency attribute is one of the common techniques in discontinuity characterization. Seismic coherency defines continuity of seismic events using the measurement of lateral changes in seismic responses. The rate of seismic continuity is a sign of geological continuity. In areas where are changed by faults and fractures، seismic traces have a low similarity with their neighboring traces. In this study، coherency attributes were determined using two algorithms based on cross correlation and semblance. These algorithms applied on a 3D seismic data cube from one of the Iranian oil fields in Persian Gulf. The performance of algorithms was evaluated to detect faults and fractures at lower member of Fahliyan reservoir. The results show that the semblance based algorithm provides a better coherency cube than the cross-correlation algorithm. The quality of the recognized discontinuities، especially fractures، was further increased by applying appropriate filters on stacked data cube and using reflectors dip and azimuth information. According to the results، the main orientation of faults and fractures at Fahliyan reservoir is NW-SE. This orientation is in accordance with the orientation detected by FMI log at the same depth from nearby well.

In the current work، azotobacter beijerinckii microorganism provided from Germany microbial bank is used. According to previous reports and the experiments conducted، it is inferred that the microorganism is able to accumulate poly (hydroxyl butyrate) granules in media containing high amounts of carbon sources and limited amounts of nitrogen sources. The effect of the different concentrations of carbon and nitrogen sources (glucose and ammonium chloride) on the cell dry weight (CDW)، the amount of glucose used by the microorganism، and the amount of the produced biopolymer is investigated. Ammonium chloride with concentrations of 0. 5 and 2 g. l-1 and glucose with concentrations of 30، 40، 50، and 60 g. l-1 were used as nitrogen and carbon sources respectively. The most of biopolymer was produced by glucose with a concentration of 60 g. l-1 and ammonium chloride with a concentration of 0. 5 g. l-1. The highest biomass efficiency (Yx/s) was obtained by glucose with a concentration of 30 g. l-1 and ammonium chloride with a concentration of 2 g. l-1 and the highest production efficiency (Yp/s) was gained using a concentration of 30 g. l-1 of glucose and a concentration of 0. 5 g. l-1 of ammonium chloride. The maximum productivity (Qp) was acquired in the media containing glucose with a concentration of 50 g. l-1 and ammonium chloride with a concentration of 1 g. l-1. The amount of biopolymer obtained through laboratory method was compared with response surface statistical method and the precision of the experiments conducted were examined. After extraction، Fourier-transform infrared (FT-IR) spectra and nuclear magnetic resonance (NMR) spectroscopy both verified the formation of biopolymer.

Perovskite dense membranes of La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF), Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and SrCo0.8Fe0.2O3-δ(SCF) were prepared by complexation method with EDTA-citrate. The perovskite phase structure of the samples was characterized by X-ray diffraction and experimental formula and stoichiometry of the metal ions for the prepared perovskite were confirmed by atomic absorption spectroscopy and inductively coupled plasma. The oxygen permeation flux through the perovskite dense membranes was measured and optimized by change in oxygen partial pressure, temperature, membrane thickness, and the used composition in perovskite structure. The oxygen permeation flux was measured in the range of temperature within 1073–1223 K and the partial pressure of 0.1–1.0 bar. The flux increases in the order of LSCF < SCF< BSCF membranes and the calculations of crystallography parameters such as lattice energy and free volume can confirm this point. The linear changes of oxygen flux versus ln(P2/P1) states that bulk diffusion through the membrane is the rate-limiting step.

In oil industry acidizing operation (matrix acidizing and acid fracturing) is performed to reduce or eliminate formation damage and increase permeability and productivity; also، acidizing is probably the most widely used work-over and stimulation practice in the oil industry. By dissolving acid-soluble components of rock formations، or removing material at the wellbore face، the rate of flow of oil or gas out of production wells or the rate of flow of oil-displacing fluids into injection wells may be increased. In this study، some laboratory work with different acid types was conducted on the carbonate rock samples of the Bangestan reservoir of Ahvaz oil field to find out the amount of the solubility of the carbonate rock samples in the acids. The effects of acid type، acid strength، and temperature on rock solubility were investigated. For this study، different acids such as HCl، acetic acid، hybrid acid، and emulsion acid at three different temperatures of 25 °C، 60 °C and 100 °C were used. The main goal of this study is to find out the optimum acid spot time at the formation to achieve the most productivity of the well without any formation damage creation and at the same time to select the most effective acid system for carbonate layer stimulation. The results show that 28% HCl acid has the most dissolving power between the tested acids in the experiments. In addition، the temperature has a direct effect on the solubility of the rocks in acids; i. e.، the higher the temperature is the higher the solubility is. The laboratory results showed that the time needed for dissolving about 50% of Bangestan reservoir rock at 100 °C is 700، 25، and 30 minutes for organic acid (10% acetic acid)، hybrid acid of 50:50 ratio of 10% acetic acid and 15% HCl، and hybrid acid of 80:20 ratio of 10% acetic acid and 15% HCl respectively. It is also found out that the hybrid acid system of 50:50 ratio of 10% acetic acid and 15% HCl has an effective role in dissolving formation core at high temperatures.

The mechanism and control of premature disbondment of three-layer polyethylene (3LPE) coatings have been the subjects of many research activities which are still going on. Also، the substitution of 3LPE with better coatings has been the aims of different research works and this paper is going to discuss it. Based on what is mentioned above، the quality and performance of two polyurethane and one polyurea coating samples were closely examined by running important standard tests including adhesion، cathodic disbondment، impact، bendability (flexibility)، water absorption، surfaces hardness، and dielectric strength. The results of cathodic disbondment tests of these three samples were compared with that of 3LPE coating. In this research، it was shown that polyurethane had better cathodic disbondment results than 3LPE coating. With reference to the fact that there is no report in the literature on the early disbondment of polyurethane from pipe surface، and that the coating is applicable on-site with one third thickness of 3LPE، polyurethane is recommended as a suitable substitution for 3LPE. Moreover، it was found the cathodic disbondment result of the polyurea was comparable with that of 3LPE. With reference to the same reasons argued for polyurethane، polyurea can be a good substitute for 3LPE as well.