مجله پژوهش نفت
پیاپی 62 (تابستان 1389)

Modified nanoclay with a double bond on its modifier structure was employed to study the confinement effect of nanoclay in the atom transfer radical polymerization of styrene. The clay-attached and free polystyrene chains were used as evidence to such a kinetic study. The variations of monomer conversion and the linearity of semi-logarithmic kinetic plot, evidence of the living polymerization and constant radical concentration in the reaction medium, were revealed by the use of gas chromatography technique (GC). Number- and weight- average molecular weights and polydispersity index of polymers were also derived from GPC data. According to the gel permeation chromatography (GPC) results, the number-average molecular weight increases linearly against the monomer conversion indicating the living nature of the polymerization. Free chains which showed higher molecular weights than the attached ones exhibited closer molecular weights values to the theoretical ones. In addition, lower PDI values were obtained in free polystyrene chains. In the case of free polystyrene chains, the initiator efficiency was lower than 1 and by increasing clay content, higher molecular weights were obtained. Attached chains revealed lower molecular weights and their initiator efficiency was higher than 1. By adding clay content, an increase of PDI value and a decrease of molecular weight were observed in attached polystyrene chains. Moreover, all the samples experienced a falling of PDI value from nearly 2 to almost 1.2 as the reaction progressed. FTIR results revealed an interaction between clay surface and monomer causing acceleration in the polymerization kinetic.

In this study, based on a comprehensive mathematical model, a regenerator reactor in fluidized catalytic cracking unit is modeled. In this model, the regenerator is divided into two sections, namely dense and dilute sections; in each section, mass and energy balance for all components are solved simultaneously. The kinetics of reactions happened in regenerator consists of two reactions for coke combustion and two reactions for combustion of carbon monoxide via homogenous and heterogonous routes. After process modeling and computer programming in MATLAB, the modeling outputs are compared by experimental data presented in the literature as well as experimental data obtained from a pilot plant in our research center. The results show that mathematical modeling can predict system performance in different operating conditions with high accuracy and there is good agreement between the modeling predictions and the experimental data.

By development and improvement of oil industry, the tendency to increase the production of oil fields has been paid more attention. The growing need to increase the output and ultimate recovery by enhanced oil recovery (EOR) methods has received great significance as far as mature oil fields are concerned. Water Alternating Gas (WAG) injection also is one of these methods. WAG is defined as the injection of both water and gas into the same reservoir. WAG injection is an oil recovery method initially aimed to improve sweep during gas injection mainly by using water to increase the contact surface of injected fluid with the reservoir; it is also to control the mobility of the displacement and create stable mobility front. This including definition covers MWAG (miscible), IWAG (immiscible), HWAG (hybrid), SWAG (simultaneous), SSWAG (selective simultaneous). In this study, the various scenarios of WAG injection have been simulated in one of the reservoirs of National Iranian Oil Company by the GeoQuest commercial software package and ECLIPSE100 module; the efficiency coefficient, total oil production in factors effective on injection such as injection cycle, injection type and injection method (IWAG, HWAG, SWAG and SSWAG) are studied and compared. Then, the scenarios of water, gas, and WAG injection are studied and compared to choose the appropriate method of injection in the interested field. At last, by designing various scenarios of water, gas, and WAG injection in four- and five-spot injection patterns, the efficiency, residual oil saturation, and total oil production are studied and compared in various methods in the above patterns in order to find the optimal and appropriate pattern of injection. The results show that by choosing suitable parameters, the efficiency and production of WAG method will be higher than water and gas injection.

In this paper the desulphurization of gas streams by using aqueous ferric chelate solutions as washing liquor is studied mathematically and experimentally. The desulphurization is accomplished by a precipitation reaction that occurs when sulfide and ferric ions are brought into contact with each other. The absorption experiments of H2S in aqueous ferric chelate solutions were carried out in a packed-bed scrubber. The experiments were conducted in different operating conditions (gas flow rate: 2.2-4.1 lit/min, ferric chelate flow rate: 0.2-2.0 lit/min, hydrogen sulfide concentration: 130-230 ppm and packing height: 0.3-0.3 m). A dynamic mathematical model was used to predict the removal efficiency of the packed-bed scrubber for H2S absorption into a ferric chelate solution. From mass balances in the scrubber, a set of partial differential equations, relating the species concentrations in the gas and liquid phases, along the axial direction in the scrubber were formulated. These relationships were numerically solved to give performance profiles. The validity of the model was examined by comparing the results of the model with our experimental data. The predicted results of the model are in good agreement with the experimental data obtained in different operating conditions.

The Fluid Catalytic Cracking (FCC) is an important process for profitable conversion of heavy hydrocarbons into valuable products. In this study, a CFD simulation of hydrodynamic and heat transfer of FCC gas-liquid-solid riser reactor was carried out by considering the evaporation of liquid droplets. Since there is no symmetry in fluidizing steam, catalyst particles, and atomized liquid droplets, the reactor was modeled as a 3-D system. An Eulerian model was used for both gas and catalyst particles, which is comprised of continuity and momentum, species, heat transfer equations for gas and solid phases, and an equation for solid granular temperature. The hydrodynamic and heat and mass transfer (evaporating liquid droplets) were modeled using Lagrangian approach. The reactor hydrodynamic model predictions were compared with corresponding experimental data reported in the literature to validate the model. The distributions of gas and catalyst velocity are in good agreement with the experimental data. The multiphase results include flow field, distributions of volume fraction of each phase, temperature profiles of gas and solid phases as well as variation of atomized liquid droplet diameter and temperature. The simulation results indicate that the heating of liquid droplets takes place proportional to their initial size and immediately. Therefore, this step is not the controlling part of FCC riser operation. When the evaporation of the liquid starts, rate of droplet evaporation and reduction in droplet diameter are low. When the droplet temperature reaches the boiling point, the droplet diameter decreases faster and the total mass of liquid droplet evaporates in a fraction of riser reactor. In this research, a correlation for droplet evaporation time was also developed.

Ilam Formation is the reservoir rock of Maleh-Kuh oilfield located in folding-thrusting Zagros zone in Lurestan province. It is mainly composed of mud-supported lithofacies varying from mudstone to wackestone. The most important identified diagenetic processes are compaction (physical and chemical), aggrading neomorphism, different replacement (pyritization, dolomitization, glauconitization and silicification), cementation, several generations of fracture, and burial dissolution. The main recognized pore types are moldic, vuggy, stylolitic, intercrystalline, and intragranular. Paregenetic sequence interpretation of Ilam Formation indicates that a set of diagenetic processes such as syndepositional diagenesis in marine environment, as well as post-depositional shallow to deep burial diagenesis, and uplift have affected this reservoir rock. Porosity and permeability data plots show that these facies have very low reservoir quality and most diagenetic processes have not had a major effect on increasing reservoir quality, and, only in some cases, permeability has been increased by stylolitization and fracturing.

In this article, desulphurization from the gas streams containing hydrogen sulfide by aqueous iron chelate solutions in a turbulent contact absorber is mathematically and experimentally investigated. The desulphurization is accomplished by a precipitation reaction that occurs when sulfide and ferric ions are brought into contact with each other. Absorption experiments (Mobile Bed Absorber) contained low density hollow plastic balls as packing, which were entangled between two perforated plates. The experiments were conducted in different operating conditions (Gas flow rate: 22-28 lit/min, Iron Chelate flow rate: 0.2-0.5 lit/min, Hydrogen Sulfide Concentration: 3000-4000 ppm and Static Packing Height: 13 and 23 cm). A mathematical model was used to predict the removal efficiency of H2S absorption into a ferric chelate solution in the Mobile bed absorber. From mass balances in the absorber, a set of ordinary differential equations, which relate the species concentrations in the gas and liquid phases, along the axial direction in the scrubber were formulated. These relationships were numerically solved to obtain the performance of the absorber. The validity of the model was examined by comparing the results of the model with our experimental data. The predicted results of the model are in good agreement with the experimental data obtained in different operating conditions. The effects of the liquid (aqueous catalyst solution) flow rate, static height of the packing, and packing size on the absorption efficiency were also studied.

Well stimulation by means of acidizing has been extensively conducted for enhancing the productivity or injectability of producing and/or abandoned wells in southern Iranian oilfields, and matrix acidizing is considered as the major stimulation method in this region. Permeability improvement and consequently reaching a negative skin is the main objective of this type of stimulation. The aim of this research is to evaluate the performance of the carried out matrix acidizing and put forward some alternative methods to improve this kind of operation. The post production results of acidizing show an inefficient outcome of the majority of these operation in the investigated oilfield. The history of performed matrix acidizing operation in some of the southern Iranian oilfields in recent years has been introduced in this study. By employing Pansys software, the evaluation of pre and post stimulation jobs has been applied to nine wells. Also, Nodal analysis has been performed by Pipesim software in the investigated oil wells to study the production systems of these nine oil wells. By utilization of the results of this study and assessment the literature review of the related studies, matrix acidizing operation will be discussed in detail in this paper. The results show that among the nine oil wells studied in this research, wells 20, 22, and 38 are the best candidate for matrix acidizing operation. Finally because of the associated difficulties with matrix acidizing and in order to bypass various types of formation damage, the authors of this paper recommend Iranian upstream industry to considering Hydraulic Fracturing operation as a replacement stimulation method.