PETROLEUM RESEARCH
Year:2018 | Volume:27 | Issue:96 |Papers Count:13

Pore types distribution in reservoir rocks are the main factors controlling reservoir quality. Because, Pore type and pore distribution in carbonate reservoirs are very important because the pore types control fluid flow and permeability in porous media. In this study, pore types based on elastic and petrophysical behavior are classified into 3 classes (Stiff, Reference and Fracture) and 8 subclasses (Intraparticle, Moldic/Vug, Microporosity, Interparticle, Intercrystalline, Fracture, Intergranular, and Shale microporosity). Each pore type is identified based on Velocity Deviation Log (VDL) and core data along the studied wells. For the determination of petrophysical behavior of pores, their distribution is investigated within the hydraulic flow units based on Flow Zone Index method. After determining pore types and their petrophysical properties along the studied wellbores for extrapolation of the results in to the field, seismic attributes are used. Post-stack seismic data are inverted, and finally 3D model and maps of pore type distribution by using of seismic attributes are established. This model is useful to determinate reservoir and non-reservoir zonation in the field-scale.

Analyzing methods for immiscible injection have been subdivided into numerical and analytical methods, a numerical method needs a lot of time and also needs rock and fluid properties decisively, but analytical methods need less input data, therefore these methods are more suitable to make decision for managers. Among the analytical approaches, Capacitance- Resistance Model, CRM, as one of the most recent models, has been developed in basis of the injection rate and well flow pressure fluctuations. CRM just takes injection rate and well flow pressure as input data, moreover, this simplicity leads to increase estimation speed but has some problems. Injection fluctuations necessity can be mentioned as one of the main problems which confronts applied works because in applied program, injection rate doesn’t have enough fluctuations. Another problem can be mentioned for previous work is the range of history matching, in the previous works, rang of history matching has broken into number of time intervals which confronts reservoir nature because whole range of history matching has effect on estimation time. In this research some correction on CRM solution have been suggested that can decrease wrong and unapplied assumptions. Results show that estimation accuracy by CRM has been improved, and some of the confining assumptions have been removed.

The combination of extraction methods and oxidative desulfurization due to high efficiency and good operating conditions can be considered as a viable alternative for conventional desulfurization methods. In this study, the oxidation/extraction desulfurization method was investigated to remove sulfur-containing compounds from gasoil fuel. Gasoil with a total sulfur content of 1550 ppm was selected as feed. Hydrogen peroxide-formic acid system was used as the oxidation system. The gasoil desulfurization and recovery after oxidation were 96.38% and 20.64%, respectively. Three polar solvents (i.e., acetonitrile, dimethylsulfoxide and dimethylformamide) were considered as potential candidates for the extraction of oxidized sulfur-containing compounds from gas oil. Acetonitrile solvent was rejected due to its low density close to gasoil density. Thus, the effect of solvent to fuel ratio (0.5-2) and number of extraction stages (1-3) were investigated for dimethylsulfoxide and dimethylformamide. It was found that the achieved desulfurization for dimethylformamide was higher than that of dimethylsulfoxide. But, the gasoil recovery after the extraction was higher for dimethylsulfoxide in comparison with dimethylformamide. The highest gasoil desulfurization and recovery were obtained 97% and 96%, respectively.

In this research, a novel micro-model is designed to investigate the performance of silica nanoparticles on the increment of the effectiveness of water flooding. The micro-model is constructed with spherical or non-spherical glass beads or mineral grains like sandstones. These grains are put between the glass plates of the micro-model with an especial method. Afterwards, it is heated in an oven to prepare the heterogeneous porous media. This micro-model in comparison with previously developed one has lots of advantages and can represent the real reservoir porous media. Contact angle, inherent viscosity and micro-model flooding experiments are performed to investigate the effect of the nanoparticles on the recovery factor. In contact angle experiment, wettability alteration from oil-wet to water-wet is observed due to silica nanoparticles adsorption and deposition. Inherent viscosity is increased with adding silica nanoparticles in high reservoir temperature. In micro-model flooding with silica nanoparticles, increasing oil recovery and oil emulsion formation is observed in comparison with polymer injection. The hybrid injection of silica nanoparticle-polymer leads to more decrease in interfacial tension and increase in oil emulsion formation during water flooding. The designed micro-model provides an appropriate tool for 3D view of fluid displacement.

Preparing drilling fluids is the most important part of the drilling operation of oil and gas wells that the use of advanced and beneficial technologies in their production can be closer to their performance and efficiency than the ideal values. Colloidal gas Aphron (CGA) based drilling fluids with advanced technology of aphron micro-bubbles and particular for Under Balance Drilling (UBD) are one of the newest technology that is used in the drilling of low pressure reservoirs. With production of aphron oil-based drilling fluid can be achieved together positive and valuable properties of oil-based drilling fluids along with special properties such as lost circulation of aphron based drilling fluids. Stability over time is the most important characteristic of aphron based drilling fluids that can be influenced on desirable rheological properties and control of lost circulation in this type of fluids. In this study, aphronized fluid with 2.14 mole percent surfactant and 15.01 kg/m3 polymer concentration has the highest stability over time, lowest yield loss and the lowest bubble size changes that these concentrations are presented as optimal concentration of surfactant and polymer.

The purpose of this research is to remove greenhouse gases CO2 and CH4 by using ZnO nanoparticles produced from aqueous solution of zinc acetate dihydrate and ethanol by sonochemical method, and comparison of its performance with commercial ZnO. The prepared ZnO nanoparticles were analyzed by XRD, UV-vis, FTIR and SEM. Also, the photocatalytic conversion of CO2 and CH4, and photoreduction products were identified by means of GC-TCD and FTIR in gas medium. SEM images indicated that prepared ZnO nanoparticles were uniform. UV-vis spectrum showed that, after calcination, the range of ZnO absorption was proceeding toward the visible region. Also, XRD spectrum showed that, after calcination, pure ZnO has been produced. According to the results, nano ZnO with the efficiency about twice of commercial ZnO, leads to conversion of 14.3 and 14.7 % for CO2 and CH4, respectively.

Several factors can be affected the lost circulation, which the modeling of all items is complex. In this research, the fuzzy zoning is presented according to the fluid mud loss and using the improved Gustafson-Kessel fuzzy clustering algorithm. It is capable to model complex processes and integrate the various layers of information. To evaluate the algorithm, different information layers including circulation losses, geological zoning and drilling mud weight (with respect to the spatial location of the studied features) were utilized and four combinations of different information layers were considered. To determine the optimal number of zones, we employ the various fuzzy validity indices comprising in comparison with Partition Coefficient (PC), Classification (Partition) Entropy (CE), Partition Index (SC), and Xie and Beni›s Index (XB). The best combination of information layers was determined consisting of mud loss, and geological zoning regarding to the coordinate of the samples, the optimal number of zones was computed as 12 zones and the optimal fuzzy exponent was obtained about 1.1. In the improved Gustafson-Kessel fuzzy clustering algorithm, weighting factor was employed for scaling between the covariance of all data and within clusters, and the optimal value was determined as 0.4. Finally, three-dimensional fuzzy zoning in the studied field was executed and the Fisher›s discriminant analysis was approved that the obtained zoning from clustering method was better performance than the common geological zoning (Fisher index 0.088 vs. 0.011) for modeling and zoning the mud loss.

Stress dependent permeability is a great problem in petroleum engineering and natural fractured reservoirs. Permeability in a fractured porous medium is mainly controlled by the geometry and interaction of the pores and fractures as well as stress state. Interaction between stress and permeability in jointed reservoirs is a crucial factor during different stages of life of a reservoir such as assessment, productivity and management. Also, reduction in reservoir pressure significantly influence on the reservoir permeability. In this study, it is intended to find the relationship between the stress sensitivity and production rate. For this purpose, distinct element code is used to develop numerical modeling of a reservoir to evaluate the relationship between stress sensitivity and productivity rate. The results of numerical simulations indicated that with increasing the bulk modulus of rock joints, the skin factor increases and consequently the well productivity decreases.

One of the most promising methods in order to mitigate asphaltene precipitation is to use asphaltene dispersants. In this study, the effect of two dispersants of toluene and dodecylbenzene sulfonic acid on asphaltene precipitation of a dead and a live oil sample has been investigated. Investigations on dead oil were conducted using IP143 standard test and for studying live oil in the presence of asphaltene dispersants high pressure microscopy was used. The obtained pictures from high pressure microscopy were analyzed using a picture analysis software. According to the results, this dispersants in dead oil create an optimum point for asphaltene precipitation. In live oil, this dispersants reduce asphaltene precipitation, moreover, for dodecylbenzene sulfonic acid, the reduction in asphaltene precipitation reaches down to 70 percent. Also, it was observed that in the effect of injection of these dispersants, the average size of asphaltene flocculation has reduced, which this reduction was much more for dodecylbenzene sulfonic acid in comparison with toluene.

In this paper, anionic emulsifiers of disodium lauryl ether sulfosuccinate and sodium lauryl ether sulfosuccinate ethoxylated were synthesized in laboratory scale. These chemicals were used in preparation of diesel/saline water and diesel/tap water emulsions, and the stability of the emulsions were examined with a procedure adopted by National Iranian South oil Company. Accordingly, by addition of one mililitre of water solutions containing 25, 37 and 50 weight percent of the emulsifiers (synthesized chemical) to 100 mililiter mixtures of diesel/saline water and diesel/tap water having volume ratios of 60.40 and 70.30, and then homogenizing the mixtures with homogenizer working at high speed, a series of emulsions were prepared. By examining the stability of the emulsions at room temperature (for 24 hrs) and °90C (for 4 hrs), the performance of the synthesized chemicals as emulsifier in preparation of water-based emulsion drilling fluids were evaluated. The results of these experiments confirmed that the chemicals, in comparison with a commercial sample, had acceptable performance, because sodium lauryl ether sulfosuccinate ethoxylated in formulation of diesel/saline water and diesel/tap water, and also disodium lauryl ether sulfosuccinate in emulsions of diesel/ saline water showed being stable emulsifiers. In order to study the environmental effects of the synthesized chemicals, their aerobic biodegradation processes were examined by measuring the amount of carbon formed in their water solutions against incubation time, in comparison with a control sample. The results of the experiments showed that the two chemicals can be safely used as biodegradable emulsifiers in formulations of water based emulsion drilling fluids.

Gas injection is one of common EOR methods in oil reservoirs. However, it might not contact with whole oil and ride over the liquid phase or channels through the high permeable paths of the reservoir and bypasses some oil. Marangoni phenomena is an effective mechanisms in bypassed oil production and causes convective flow from a point with low IFT to one with high IFT. This study reports the role of thermal Marangoni phenomena in the recovery of bypassed oil experimentally. Core flooding experiments have been conducted under high pressure at various temperature, in immiscible regime due to the existence of interface between phases and into two categories of “isothermal” and “non-isothermal”. In isothermal design, the degree of freedom is zero, and there is no Marangoni flow. But also, in non-isothermal category, Marangoni flow might increase or decrease the amount of recovery based on the interfacial tension gradient direction. Analytical investigation of experiments have been conducted through dimensionless analysis and evaluation of viscose, capillary, gravity and molecular diffusion forces. Therefore, experiments have been designed by determination and investigation of dimensionless numbers in such a way that similarity of cross-flow forces like gravity, capillary and viscosity have been considered. Therefore, the role of Marangoni flow can be verified by comparison of recovery factor. Furthermore, carbon dioxide is used to be injected in fracture due to widespread application of this gas in the oil industry. The results of experiments show that Marangoni flow is one of the effective mechanisms in recovery of bypassed oil under high pressure and temperature. This phenomena can dominate capillary force and move the trapped oil in matrix. The magnitude of this flow is proportional to temperature difference of gas and oil in their interface. Increase or decrease in oil recovery of similar experiments, indicate the role of this phenomena in porous media.

This study was performed to assess the petrochemical wastewater containing Terphthalic acid for discharge to the environment and reuse it. In this project, the ozonation process was used for the degradation and mineralization of the wastewater containing 60 mg 1-1 of Terphthalic acid in semi-continuous reactor under the variable amounts of ozone and pH. The ozonation process is performed at pH of 5, 7, 9 and 11. After 30 min of the treatment process, at pH of 9 and the optimal level of ozone concentration (8.6 mg/L) the degradation of the pollutant was about 99.3% and at a pH of 5, 7 and 11, the amount of degradation was 79.7, 90.5 and 93%, respectively. Results showed that the formation of hydroxyl radical was more at alkaline than acidic media. The removal rate decreased significantly by increasing the concentration of the Terephthalic acid. About, 58.5% of chemical oxygen demand (COD) is removed at pH of 9 and 90 min of reaction. The removal rate of Terphetalic acid was more than the removal of COD, because the produced intermediate compounds were resistant against degradation. The degradation rate of pollutants was pseudo first order, and the rate constant (k) and the half-life time of reaction (t2.1) were determined.