مجله پژوهش نفت
پیاپی 77 (خرداد و تیر 1393)

The hydrate formation of hydrogen sulfide in the presence of thermodynamic inhibitors has been modeled in this study. A thermodynamic model has been employed for predicting the hydrate formation of the following systems: H2S + Water + Salts (NaCl، KCl، and CaCl2)، H2S + Water + Alcohols (methanol and ethanol)، and H2S + Water + ethylene glycol. The extended-UNIQUAC (E- UNIQUAC) model has been used for predicting the activity coefficient of water in the liquid phase. The structural parameters of E-UNIQUAC model have been extracted from literature but the interaction parameters of this model have been obtained by fitting the model with the experimental data. The results of the developed model show good agreement with the experimental data and the absolute average deviation of the model from experimental data is 3. 82%.

In this study، a rubber gasket with the dimensions of 1500 mm × 500 mm was fabricated using a reverse engineering method and utilizing a special rubber gasket as a reference. In order to identify the components in the reference gasket، some analyzing techniques such as pyrolysis، solvent extraction، and thermogravimetry as well as several analytical instruments including FTIR، EDAX، and XRD were used. In addition، some thermal characterizing instruments such as DSC and TGA were utilized to characterize the reference gasket and those fabricated herein. After assuring that the properties of the reference gasket were almost the same as rubber plates produced in laboratory، a number of rubber gaskets were produced using an industrial mold. To evaluate the quality of the fabricated gaskets and compare their properties with the reference gasket، some of the fabricated gaskets together with the reference gasket were placed inside an industrial amine heat exchanger for 35 days. The gaskets were then removed from the heat exchanger and tested for tensile strength، elongation at break، and hardness. This investigation showed that the rubber gaskets made according to the two rubber formulations in this work possessed almost the same properties as the reference gasket.

Albian to Campanian sequences in the Zagros sedimentary basin is called the Bangenstan Group (as named after the Bangestan Mountain) and is composed of the Kazhdumi، Sarvak، Sorgah، and Ilam formations. Kazhdumi formation with the age of Albian is important due to having potential hydrocarbon generation in most of the Iranian oil fields. Based on facies variations and correlation with geophysical well log data، it is interpreted that the Kazhdumi formation in Azadegan oil field has been deposited in the carbonate ramp type in three sub-environments، including tidal flat، lagoon، and open marine. The sequence stratigraphic analysis of Kazhdumi formation shows that this interval consists of one depositional sequence. This depositional sequence contains three system tracts including LST، TST، and HST. Its lower and upper boundaries are erosional and gradational respectively.

Nuclear magnetic resonance logging is considered to be a novel method for accurate access to the petrophysical parameters of hydrocarbon reservoirs in the oil industry. Using the presence of hydrogen nuclei in the reservoir fluids and employing the advantage of NMR method to determine the pore sizes، in this study، the bound water volume and free water volume of a carbonate well in the southwest of Iran have been determined in two ways and then، by using Coates and SDR models and Geolog software، NMR permeability was calculated. Similar results obtained from the two methods in determining the volume of bound fluid، with a correlation coefficient of 0. 9، show that the CBFV method for this well is valid. A correlation coefficient of 0. 7، obtained from the comparison of the NMR permeability and the core permeability، proves that the NMR technique can be a good alternative to the old costly methods.

In this study، zinc oxide/polymethylstyrene (PMSt) nanocomposite was prepared by in situ radical polymerization method. The applied ZnO nanoparticles were prepared by precipitation method. The obtained samples were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) continuously and the average crystallite size of nanoparticles was calculated and a crystallite diameter of 23 nm was obtained. The surface of ZnO nanoparticles was modified by silane coupling agent to obtain a good dispersion and to improve compatibility between inorganic nanoparticles and organic matrix. The modified ZnO nanoparticles were dispersed in methylstyrene and in situ radical polymerization were carried out in the presence of 2، 2’-azobisisobutyronitrile. The prepared materials were characterized by XRD، SEM، TEM، FT-IR، UV-Vis، and 1HNMR techniques. The effect of ZnO nanoparticles on the thermal properties and glass transition temperature of PMSt was investigated using thermo-gravimetric analysis (TGA) and differential scanning calorimetric (DSC) techniques.

Drilling fluids have the potential for reservoir damaging، which can be investigated in laboratories. Laboratory results indicate that the permeability of fractured reservoirs decreases due to using drilling fluid in pay zones. For reducing or returning the permeability of reservoirs many additives such as sized materials can play an important role in removing an increasing permeability of damaged sections. A set of experiments was performed which clearly showed that drilling fluids could cause large irreversible damage to fractures and then could dramatically reduce the productivity of wells producing from a natural fracture network. Using sized additives in drilling fluids can significantly reduce the depth and extent of formation damage. Laboratory results showed that sized calcium carbonate (CaCO3) were less effective comparing with acid soluble fibers; therefore، they were recommended for reducing pay zoon damage in fractured reservoirs. It is worth mentioning that according to the laboratory results aggregated fibers bridge across the face of the fracture and then bentonite in drilling mud forms an effective mud cake، which finally minimizes the invasion of solids and filtration to the formation and dramatically reduces formation damage (with filtration volume of 9 ml/5hr and 50% permeability improvement).

Determining the position of the oil-water contact (OWC) and improving the understanding of tilted OWC in fields help to explain risk analysis and development drilling. Oil-water contact has been defined in all wells of Civand (Sirri C) field utilizing petrophysical logs and confirmed using RFT data. Tilted oil-water contact has been established and presented in the field after providing isovalue map of OWC and using well correlation map in different directions. The oil-water contact has been tilted close to 0. 5 degrees westward. According to the results، the OWC tilting associated to hydrodynamic flow in Sarvak (Mishrif) aquifer in the east and west directions is a reliable indicate; moreover، because the petrophysical characterization of reservoir rock (porosity and permeability) is better in the west part of the field than the other side، transition zone thickness is decreased and oil-water contact level is increased.

A survey of the literature shows that the source of total acidity in crude oils is due to naphthenic acids available in their hydrocarbon matrices. On the contrary، our studies show that the emulsion water in crude oil is responsible for the main part of total acid number (TAN)، especially for heavy crude oils. In order to avoid metal corrosion in refining facilities and transport lines of crude oil، a special care is needed to control the acidity level of heavy crude oils. In the current work، a new technique based on chemical treatment and centrifugal separation was developed in order to decrease the total acid number of off-spec heavy crude oils. This method was ideally suited for the acid removal of heavy crude oils including water and salt at the level of 0. 05-20 vol% and 10-10000 ptb respectively.

Wax deposition is one of major challenges in petroleum production and transportation. The formation of wax deposition reduces the effective pipe radius and decreases flow capacity of the pipe. Highly waxy crude oils can cause a blockage of a pipeline because of wax deposition during production and transportation of the crude oil. Wax deposition costs can be significantly reduced if wax deposition can accurately be predicted. The target of wax deposition modeling is to predict wax content and the thickness of deposition with location and time. For wax deposition modeling، it is required to study this phenomenon in laboratory flow loop experiments to investigate effective operation conditions such as flow rate on wax deposition. For wax deposition modeling، heat and mass transfer coefficients should also be calculated. Studies show that in laminar flow conditions، mass transfer coefficient can easily be calculated from Chilton-Colburn analogy. The use of analogy in turbulent flow conditions for calculating mass transfer coefficient overestimates the amount of wax deposition. In this work، a computational wax deposition model combined with the wax precipitation kinetics in the boundary layer was developed. If wax precipitation kinetics can accurately be predicted، it can significantly reduce mass transfer coefficient in turbulent flow conditions. Herein، a wax precipitation coefficient model for the prediction of mass transfer coefficient is suggested and shows that when wax precipitation coefficient increases، mass transfer coefficient decreases.

The storage and disposal of greenhouse gases in underground aquifer reservoirs is a suitable option for the reduction of these gases in the atmosphere. Understanding the concepts and mechanisms involved in the storage process such as natural convection and their impact on the amount of time required for storage is very important. Natural convection is an effective mechanism to increase the solubility of carbon dioxide in the storage process. In this study، the injection of carbon dioxide (a major component of greenhouse gases) into aquifer has been studied and numerically simulated. The effect of aquifer salinity on the onset of natural convection phenomena has been studied. To this end، six scenarios revolving around the change of aquifer salt and keeping the other variables involved constant in the process are studied. The results reveal a direct effect of salinity on the activation of natural convection. Increasing aquifer salinity delays the onset of natural convection. As a result، the cumulative amount of gas dissolved after the specified time will be less.

Pinch technology has been employed as an important tool for the heat integration of petroleum refining processes. The thermal integration of heat pumping system is done by this technology. A heat pump is a system that takes low level heat from a source and delivers it to a sink where higher heat load and temperature levels are required. Heat pump integration in separation columns operates between the condenser as heat source and the reboiler as a heat sink. Therefore، it operates by extracting an amount of heat from a source with a relatively low temperature and delivering a larger amount of heat to a sink with a higher temperature by consuming high quality energy. In this study، the proper heat integration feasibility of a heat pump is done in the LPG process of Tehran oil refinery، which resulted in a $ 144،000 annual savings in energy cost.

Since the start of the graphene revolution in 2004، it has captured increasing attention and has shown great promise in many applications arising from its unique physicochemical properties. On the other hand، magnetite nanoparticles which separate the materials based on magnetic properties have attracted great attention. Herein، the magnetic properties of the magnetite nanoparticles and the high adsorption capacity of graphene are combined to fabricate a new nanocomposite for the removal of sulfur compounds from gasoline. The synthesized nanocomposite was characterized by several techniques and effective parameters were optimized. The kinetic and thermodynamic data of the adsorption process were analyzed to clarify the mechanism of adsorption. The results showed that under optimal conditions، 58% of thiophen was removed in 20 min and deep desulfurization could be achieved during 4 cycles. The isothermal data conformed well to the Langmuir model، and thus a monolayer adsorption occurred on a homogeneous nanocomposite surface. The maximum sorption capacity of the nanocomposite for thiophene was 113 mg. g-1.

This paper presents governing equations of the processes affecting oil and gas condensate slicks involving spreading، evaporation، dissolution، and vertical dispersion، which are important for numerical models of oil spill. These equations are used for crude oil، light oil، and gas condensate spill accidents according to their physical and chemical conditions and atmospheric conditions of the sea between Khark Island and Busher port and Assalouyeh marine region in the winter and summer. The evaporation of gas condensate is 42. 17% at a temperature of 24. 9 °C in the winter while it is 62. 24% at a temperature of 38. 4 °C in the summer after 48 hours. Moreover، the dissolution of gas condensate is 0. 0385% after 48 hours in the summer. The results also show that the evaporation of oil is 39. 74% at a temperature of 20 °C in the winter while it is 62. 025% at a temperature of 35. 5 °C after 48 hours in the summer. Additionally، the dissolution of oil is 0. 0537% after 120 hours in the summer. The results were compared with results of other studies which show good agreement.