مجله پژوهش نفت
پیاپی 91 (بهمن و اسفند 1395)

Identification of geological and reservoir changes in accordance with changing rock types is possible through log-facies studies and confirmation of those facies with core data. In the present study, first, in order to determination of microfacies and diagenesis processes, the Asmarri formation has been studied using thin sections of cores. Then well logging and core data of 5 wellbores from Asmari reservoir in Gachsaran field were clustered with the aid of Self-Organizing Map Neural Network algorithm, and then 5 facies models were selected among log facies. The log facies were acceptably confirmed through consideration and comparison of these models with tow cases: (1) core data (porosity, permeability and capillary pressure curve) and (2) petrography. Afterward, the log facies were presented as reservoir rock types. Regarding the good results in distinguishing reservoir horizons, the model was propagated in other wellbores in which only logging data were available, and the trend of changes in rock types were investigated through the entire field.

The cooling systems are widely used in power plants, manufacturing industries and refineries for the sake of reducing system heats and an increase in operational efficiency. Copper is widely used in cooling systems due to its high thermal conductivity. Corrosion of copper is one of main problems in these industries. The use of corrosion inhibitors is a common method to control the corrosion in cooling systems. Various inhibitors are usually used to protect the different metals in cooling systems. The synergistic or antagonistic effect of inhibitors on each other may be influenced on inhibition efficiency. The inhibition effect of 1H-benzotriazole (BTA) on corrosion of copper has been investigated in simulated sea water in the presence and absence of sodium molybdate (SM) using weight loss, Tafel polarization and electrochemical impedance spectrometry (EIS) methods. The results indicated that adsorption of BTA and SM on copper surface obeyed from Langmuir adsorption isotherm. The adsorption energy values for BTA and SM on copper surface was obtained -33.88 and -21.22 kJ/mol, respectively. The absorption of sodium molybdate promoted the stability of surface oxides on copper surface which in turn has a synergistic effect on the inhibition effectiveness of BTA. The inhibition of SM and BTA has been attributed to stabilize the effect of surface oxides and the formation of a protective complex layer, respectively.

The impact of Co3O4 nanoparticles with concentration of 0.1 wt%has experimentally been studied on (1) interfacial tension, (2) asphaltene precipitation and (3) miscibility with the carbon dioxide, when the Co3O4 nanoparticles have been added to one of Iranian crude oils and synthetic oil solutions . To do so, the Vanishing Interfacial Tension (VIT) technique has been used for a pressure of up to 1200 psi. The results have been showed that in the presence of Co3O4 nanoparticles, IFT, Minimum Miscibility Pressure (MMP) and severity of asphaltene precipitation have all been reduced to some extent. Within the range of operating conditions attempted here, MMP has reduced as much as 32% and 19% for the synthetic and crude oils, respectively. The severity of asphaltene precipitation has also reduced approximately 13% for the asphaltenic synthetic oil and 7% for the investigated crude oil. The experimental results appear to show that Co3O4 nanoparticles served to adsorb asphaltene which would, in turn, facilitated the solubility of CO2 in synthetic and crude oils which consequently would lead to enhanced oil recovery.

Spent caustic wastewater is one of the most important environmental challenges due to high alkalinity, the presence of sulfur compounds and non-biodegradable pollutants. Therefore, in this research, the effective parameters of Electro-Fenton process including pH range (2-5), H2O2/COD (0.2- 0.745), temperature (20-60 °C), reaction time (45- 135 min) and current density (5-20 mA/cm2) have been investigated on the COD removal efficiency by adopting response surface methodology (RSM). The results indicated that H2O2/COD, temperature, pH, current density and reaction time have the most effect on the pollutants removal, respectively. The optimum conditions have been found at pH =4.8, current density =14.8 mA/cm2, temperature =57 °C, reaction time =63 minutes and H2O2/COD =0.63 with 96% COD removal efficiency. According to the results, by changing of initial COD within 12,500 to 60,000 mg/L range at the optimum conditions, the pollutant removal efficiency has been increased from 94% to 97%.

In this work, a new catalyst based on Dawson salt, H9P2W15V3O62, is presented for oxidation of high stable sulfur compounds. The new catalyst, H9P2W15V3O62/TiO2, is synthesized by sol-gel method. The structure of catalyst and salt has been characterized by FT-IR, XRD and UV spectrophotometry. The performance of catalyst has been studied in the oxidative desulfurization of aromatic components, benzothiophene and dibenzothiophene (ones of the most resistant sulfuric components to oxidation), mixed with n-octane under mild operation conditions (temperature less than 70 oC and atmospheric pressure). The reactor tests’ results illustrated that the synthesized catalyst has a suitable performance (achieved 100% conversion of debenzothiophene and 78% conversion of benzothiophene in less than 20 minutes) in oxidative desulfurization. The process conditions (temperature, catalyst loading and a mole ratio of oxygen to sulfur) have been optimized by Taguchi Experimental Design method. Our results show that at 50 oC, the mole ratio of 6 for oxygen/sulfur and catalyst loading 7.5 g/L are optimum conditions.

The Sarvak Formation is one of the most important carbonate reservoirs of Iran. This study presents an integrated geological and petrophysical reservoir characterization of the Sarvak Formation in a giant oil field in the Abadan Plain, SW Iran. On the basis of porosity-permeability data, core description and petrographic studies from two key wells, flow units were identified and interpreted. To identify flow units within the Upper Sarvak Formation, three different petrophysical methods including (1) Flow Zone Indicator (FZI), (2) Pore Throat Radius (R35) and (3) stratigraphic modified Lorenz plot (SMLP) were applied. The results indicate that the FZI and R35 methods cannot efficiently discriminate the different reservoir zones and flow units for this reservoir, because of the high changes in petrophysical properties have mainly inherited from the internal geological heterogeneity. In contrast, SMLP method successfully classifies the studied reservoir into discrete flow units by considering the relationship between petrophysical properties and depositional and diagenetic features. From depositional facies point of view, the best flow units are related to talus, shoal-biostrome and shallow open marine depositional facies, while lagoon and distal open marine commonly show low reservoir quality. In low reservoir quality units, calcite cementation and compaction are the dominant diagenetic processes, while dissolution is the main agent for enhancing of the reservoir quality in the reservoir units with high quality. The results indicate that the interpretation of flow units based on the depositional and diagenetic characteristics provides the crucial insight on distribution of reservoir zones within the heterogeneous carbonate reservoirs, such as, the Sarvak Formation.

Fractured carbonate reservoirs have low oil recovery efficiency due to wettability and tightness of rock matrix. One of the most applicable methods for enhanced oil recovery of carbonate reservoirs is to use smart water flooding. In addition using surfactants which have been obtained from Cedar leaf extract as a rich and cheap source leads enhanced oil recovery by improving the wettability properties. In this research, the effect of Ca2, Mg2 and SO42- concentrations in the smart water and also Cedar leaves extract concentration as a biosurfactant on wettability of carbonate rocks have been investigated. The analysis which is including contact angle measurments and cre flooding eperiments have been examined. Results showed the effect of Mg2 and Ca2 concentrations from 0.01 mol/L to 1 mol/L, SO42- concentration from 0.007 mol/L to 1 mol/L and biosurfactant concentration from 0.05 %(w/v) to 0.3 %(w/v) changes the carbonate wettability to water-wet, and oil recovery has increased from 35% to 57%. The contact angle has changed from 161 degrees to 41 degrees investigated in the 0.3 % (w/v) of biosurfactant concentration, which reflects the effect of the solution on the wettability of carbonate rocks.

In this study, an innovative approach is presented for modeling asphaltene deposition in the well column. The presented model predicts the time, location and amount of asphaltene deposited in the well column as a function of well, fluid and reservoir properties. The model is formulated based on thermodynamic equilibrium, heat transfer, mass transfer and empirical multi-phase flow equations. Asphaltene-containing oil is sampled from an oil well suffering from periodic deposition problems. The thermodynamic behavior of the oil and depositional characteristics of asphaltene have been determined via laboratory experiments and modeled accordingly using the Peng-Robinson equation of state and the modified solid model, respectively. The pressure profile in the well column was determined based on Duns and Ross two-phase flow model. The temperature profile in the well column has been determined based on a developed model derived from field measurements. Fluid flow and heat transfer equations have been solved simultaneously based on pressure and temperature profiles in the well column. The Escobedo-and-Mansoori model which has been used for mass transfer calculations was used to evaluate the rate of asphaltene deposition onto the wellbore at various depths. The simulated and reported field values of wellhead pressure and temperature were used for evaluation of model predictions. The model had over 95.5% and 99.1% accuracy in predicting the wellhead pressure and temperature, respectively, in a time window of over three months in the studied well.

Storing in unlined rock caverns is regarded as one of the major ways of underground oil storage where cavern stability and oil leakage are the most crucial parameters to be concerned. The stability assurance of the cavern can lead to safety of the underground structure during and after construction as well as preventing the oil leakage phenomenon. Therefore, stability assessment of the structure is considered as one of the most important parts of design, construction and operation. Thus, the important parameters affecting the stability of the cavern were recognized and discussed in this paper. It was determined that a suitable algorithm, independent of numerical methods, is required in order to conduct a reliable and applicable stability analysis. Accordingly, in addition to recognition of affecting parameters, an algorithm was introduced for stability assessment of unlined rock caverns. A case of a stability analysis for unlined rock caverns in Asmari formation via numerical methods is discussed. Geotechnical, geology and engineering geology information was employed for numerical modeling purposes. Prediction of deformation and displacement magnitude during excavation, and subsequently designing a support system consisting of rock bolt and shotcrete based on these predictions were the objectives of modeling. Finally, the sensitivity analysis of the important parameters on cavern stability and the designing support system was carried out.

Reservoir characterization is an important step for exploration and development of oil and gas fields. Shear and compressional wave velocity can provide the accurate data for petro-acoustic studies from a hydrocarbon reservoir. Compressional wave velocity (Vp) is very easily obtained from sonic logs that are available in most of oil and gas wells, but some wells, especially old wells, may not have shear wave velocity (Vs) data. In this research, shear wave velocity was predicted from porosity well log data (sonic, neutron and density) using Hybrid ACOR-BP technique. For this purpose a total 3190 data points from Asmari reservoir which have Vs and porosity log data were utilized. These data are divided into two parts, (1) one part included 2090 data points which are used for constructing model and (2) the other part included 1100 data points used for testing and validation model. Hybrid ACOR-BP has better performance in simulating reservoir characterization than NN-BP and ACO individual algorithms. Results of simulation in the test and validation stage calculated root mean squared error, and correlation coefficient 0.06 and 0.97, respectively. Results of this research show Hybrid ACOR-BP algorithm is a reliable intelligent method for estimation of Vs. This study is based on the data collected from the two wells of the Cheshmeh Khush oilfield; moreover, the results of the study can be generalized to other developmental wells.

Thermal maturity is the primary geological factor in petroleum exploration and source rock assessment. Besides, Thermal maturity is an index to determine the maximum temperature that the source rock which has endured at the different stages of an evaluation of hydrocarbon. Measurement of this parameter requires conducting geochemical analyses on cutting samples which is expensive and time consuming, therefore the main objective of the research is development of a new method for direct estimation of this parameter from well log and seismic using a metaheuristic algorithm called Ant Colony Algorithm. In this research, 2D-seismic and petrophysical data of the Pabdeh Formation from 3 wells of the Mansuri Oil field were used. Also, a Maturity Index Equation at the well location was used to predict Maturity Index values from well logs; such as, neutron, resistivity, sonic and density. These calculated values were used as inputs for a Multi Attribute Analysis. Seismic inversion was performed based on a Neural Networks Algorithm because of its high accuracy; moreover, the resulting acoustic impedance was utilized as an external attribute. Afterwards, a Probabilistic Neural Network was trained using the set of predicting attributes derived from multiple regressions. Subsequently, MI was estimated using seismic attributes with a correlation coefficient of 87%. In the next step, the nonlinear Ant Colony Optimization technique was utilized as an intelligent tool to estimate and product a Maturity Index seismic section. It calculates weight factors for each of seismic attributes. The correlation coefficient between the input and output data was estimated 91% by nonlinear ACO. Finally, MI seismic section was produced. The comparison of the results from PNN with ACO methods revealed that the accuracy of ACO model was higher than the PNN.

The exploration of hydrocarbon resources as a process is very complex and costly. In this process, multiple factors of geology, geochemistry and geophysics are prepared and combined together. Designing the best route to take seismic data and determine the best location for drilling exploration wells is extremely important because improper or careless determination of the location, time consuming and expensive during the operation. The aim of this study was to identify possible areas for oil and gas in the map of 1: 250,000 Ahvaz with 20 oil fields using multilayer perceptron neural network (MLP) and geographic information systems. For this purpose, 17 maps of factors including: the lowest and highest values (total organic carbon, potential for the production of hydrocarbons, peak Tmax, the production index, the oxygen index, the hydrogen index) and the proximity to areas of an high Bouguer gravity anomaly, an anticline axis and faults, map of the topography and the curvature of the yield curve Asmari subsurface were created by GIS functions. For the combined factor map, the multilayer perceptron neural network (MLP) that is data-driven methods was used. The validation results showed that the neural network 17×10×5 is better than the other models with a R = 0.8948 ,RMSE=0.0267 and the Kappa=9079. Besides, the neural network 17×10×5 is able to accurately predict the oil fields. On the other hands, Some fields could not be identified, and also, some areas were classified oil fields mistakenly.

In this paper, the mechanism of hydrogenation of carbon dioxide to the heavy hydrocarbons through Fischer-Tropsch synthesis iron catalysts is considered for the development of suitable kinetic model. For this purpose, three kinetic models for carbon dioxide hydrogenation are developed using Langmuir-Hinshelwood-Hougen-Watson (LHHW) method based on basic reactions of Fischer-Tropsch Synthesis and water-gas shift reaction. The kinetic parameters in these models are obtained using empirical results. The results show that the reaction of hydrogenation of carbon dioxide is limited by reaction between surface species of adsorbed carbon monoxide and hydrogen. The results show that the activation energy for hydrocarbon growth in CO2 hydrogenation is higher than Fischer-Tropsch synthesis (100 kJ/mol).

In this investigation, TiO2-ZrO2 combined support with composition of 25wt% ZrO2 and 75wt% TiO2 was prepared by coprecipitation method and impregnated with 5 wt% of Cr2O3 and 3 wt% of K2O. The synthesized samples were characterized by XRD, FESEM, EDX, BET, and FTIR techniques. All characterization studies revealed that the deposition of Cr2O3 and K2O on the TiO2-ZrO2 combined support had obvious effect on the surface and structural properties and catalytic activity in the oxidative dehydrogenation of ethane to ethylene by carbon dioxide as a soft oxidant. The XRD analysis confirmed the formation of crystalline TiO2 and ZrO2 in the synthesized samples. The FESEM and EDX images represented the formation of homogeneous spherical type agglomerates within the nanometer range and uniform dispersion over the surface with an average particle size of about 75 nm. The BET results depicted high surface area of synthesized samples. Cr-K/TiO2-ZrO2 catalyst exhibited high performance towards the selective conversion of ethane to ethylene in the presence of CO2 (C2H4 yield of 39% as well as 97% ethylene selectivity at 700 °C), wherein Cr2O3 improved the conversion of ethane as a redox active phase and K2O enhanced the selectivity of ethylene, acting as a basic promoter.

Foam injection for the purpose of Enhanced Oil Recovery (EOR) process is one of the approaches of chemical EOR. In this method, in addition to using the surfactant, other chemical additives are used to achieve ultralow IFT which result in mobilizing the residual oil of the primary and secondary recovery stage. Foam generation causes to achieve the mobility ratio of less than 1, and then the foam generation improves volumetric sweep efficiency. In foam flooding, foam stability is one of the determining parameters for increasing oil recovery. Generating the most stable foam is one of the subjects of the recent researches on this kind of EOR process in stand point of selection of type and concentration of chemicals. In this study, effects of salinity, surfactant concentration, and the type and the concentration of co-solvent were investigated on foam stability. Optimized stability was gained in different co-solvents. This optimum was used in flooding process to investigate its effect on oil recovery. Butyric acid and 1-butanol were two used co-solvent. The most stable foam was resulted from the samples which utilized butyric acid as co-solvent. Maximum oil recovery of 44% of OOIP has observed in solution with 1-butanol as co-solvent, which is not displaced by water flooding. Moreover, observing the maximum oil recovery validates the efficacy of this technique.

Formation of asphaltene deposition in reservoirs during primary production and enhanced oil recovery techniques; such as, gas injection, especially carbon dioxide, is a devastating problem which occurs in many oil fields in the world. The experimental studies to predict the formation of asphaltene precipitation to be necessary to avoid possible irreparable problems resulting from its formation in the reservoir and eventually it will provide access to the best recovery efficiency. As a result of the technical and economic importance and the necessity of studying and understanding the operating conditions of the formation of asphaltene deposition in reservoirs is inevitable. In this paper, the thermodynamic behavior of fluids in oil processing unit has been studied at Sahand University of Oil and Gas Research Institute, which has the capability of testing high temperatures and pressures. The amount of asphaltene precipitation has initially been saturated by the injection of carbon dioxide into the porous media (sand pack), and then the amount of asphaltene precipitation pressurized with oil sample, at constant pressure and temperature, but various residence times. And then to investigate the effect of temperature and pressure and Oil composition at residence time, respectively, the test is repeated at lower temperature and higher pressure and oil change from Asmari reservoir oil to Paydarshrq oil reservoir. At a constant temperature and pressure with an increase in the residence time, more of asphaltene deposition has been formed on filter paper. At higher pressures and lower temperatures, and changing the oil samples also increased the amount of asphaltene with increasing residence time.