مجله پژوهش نفت
پیاپی 88 (امرداد و شهریور 1395)

The aim of this work is to study stability and mobility of modified nanoparticle-stabilized foam. Adding oppositely charged surfactant to the hydrophilic silica nanoparticle leads to variation in the hydrophobicity of nanoparticles. Surfactant’s adsorption on the nanoparticle’s surface is compared with different mixtures by a new criterion which is calculated by measuring conductivity. The adsorption criterion in domain of surfactant concentration has a maximum close to 1 CMC where nanoparticle reaches to maximum hydrophobicity. NPS-stabilized CO2 foam formed with simultaneous injection of CO2 and foam agent dispersion through a glass bead pack at reservoir pressure. Nanoparticle alone is not surface active. By adding appropriate surfactant concentration to nanoparticle dispersion¡ it becomes surface active. The complementary study of both pressure behaviour and morphology of foam using foam’s dynamic characterization apparatus¡ shown in the domain of surfactant concentration¡ apparent viscosity of the foam has a maximum about 6.034 cp which is consistent with the maximum adsorption criterion. Also¡ adding nanoparticle to the solution of surfactant forms more uniform¡ and the smaller foams and the apparent viscosity increase significantly. Increasing at a CO2 injection rate will also increase the size of the bubbles and reduce the apparent viscosity which means an increase in mobility.

The low salinity water flooding caused an increased secondary and tertiary oil recovery in many laboratory and field tests. The extent of the reactions and interactions of this type of flooding led researchers to investigate and find the main mechanisms¡ governing this process. To describe the interactions¡ numerous mechanisms such as¡ fines migration¡ increase in pH¡ multiple ion exchange and electric double layer effect have been noted¡ but none of them¡ has not been accepted as a comprehensive mechanism due to the complexity of the crude-oil-brine-rock interactions. So far¡ most of what has been suggested in previous research was creating a favorable wettability state with dilute brine injection. In this laboratory experiments that take place on sandpacks¡ the effects of brine salinity¡ aging of oil in packs and the fines have been investigated on recovery of oil¡ end point water relative permeability in each salinity and wettability alteration. The obtained results from dilute brine injections show that without the presence of minerals and divalent ions and with NaCl brine¡ tertiary recovery was increased¡ and of course this increase was higher for the aged sample. Also¡ the wettability alteration towards more water wet has been probed by means of flooding data.

In this study¡ an industrial unit of ethane dehydration which uses 3A adsorbents molecular sieve was simulated by using of mass¡ energy and momentum equations. For modeling of this process¡ rate of adsorption is approximated by linear driving force expression. The second form of Langmuir isotherm was employed in predicting adsorption equilibrium for water content in gas and solid phases. The mentioned mathematical equations were solved simultaneously by Matlab software. Then the simulation results were validated by using the experimental data and the simulation studies were performed to investigate the effect of changing various process variables¡ such as¡ diameter of absorbent¡ regeneration gas flow rate¡ feed pressure and temperature on water content of the product. The results shows that water content in the product increased by increasing of adsorbent diameter and feed temperature. While water content in the product decreased by increasing feed pressure and regeneration gas flow rate.

In this study¡ with added nitrogenated and metal based additive to standard diesel fuel¡ physicochemical properties of fuel and emission of exhaust gas from diesel engine were investigated. Nitromethane and manganese oxide were selected as nitrogenated and metal based additive¡ respectively. Nitromethane blended with diesel fuel 10% in volume¡ and 100 mg of MnO2 added per kg of diesel fuel. The experimental tests were carried out on ECE R-96 8modes. The results showed that by increasing additives cetane index ¡viscosity would be decreased contrast with sole diesel. These tests were measured according to ASTM D 976 and ASTM D 445¡ respectively. On the other hand¡ the density which was measured according to ASTM D 1298 did not change significantly. Besides¡ exhaust emission¡ such as¡ smoke concentration for fuel with nitrogenated additive 25% and metal based additive 16% would be reduced. In general low BSSOOT emission was measured with these additives.

Distillation column is one of the most important units of an oil refinery¡ that operates based on differences in boiling points of crude oil constitutes. Performance of more units after the column directly depends on its operation¡ and any disturbance instantly affects its performance in other refinery units. Therefore¡ designing an appropriate controller able to deal with input and output disturbances for distillation process is very important. The main objective of the distillation column control is to maintain product compositions within their set points and reduce energy consumption.To serve this purposes¡ the controller should be able to identify the states of the system and predict disturbances and noise of the process continuously. Furthermore¡ it should be able to deal with the problem resulted by multiple delay and high interactions existing among different control loops. With regards to ability of the developed predictive controllers to control the multivariable systems with multiple time delay¡ this strategy is followed in this paper. Moreover¡ a low-pass filter is considered in the predictive model to reject the effect of input and output disturbances and reduce the noise effect on process. The functionality of the proposed system is validated by simulation study that show strong performance in noise attenuation and disturbances rejection.

One of the approaches for improving the protective performance of organic coatings is to add organic corrosion inhibitors in the formulation. The scope of this research is to investigate the corrosion behavior of mild steel in 3.5% sodium chloride solution with zinc phosphate anticorrosion pigment (ZP) and 2-mercaptobenzimidazole as organic inhibitor through taking advantage of electrochemical impedance spectroscopy (EIS) and polarization measurements. The results which were obtained from electrochemical tests on the samples within 24 hours of immersion in the solution indicated superior protective performance of the combination of zinc phosphate anticorrosion pigment and 2-mercaptobenzimidazole inhibitor compared to only the zinc phosphate pigment. In general¡ time variations of parameters charge transfer resistance (Rct) which was obtained from electrochemical impedance spectroscopy and polarization resistance (Rp) as well as corrosion current density (icorr) which were extracted from polarization curves implied precipitation of a protective layer on the surface in the presence of 2-mercaptobenzimidazole inhibitor.

The Fahliyan Formation belonging to Khami Group is a main reservoir rock in Abadan Plane oil fields¡ and this formation is related to Neocomian age. Thickness of this formation in studied wells is about 580 meters. In the Abadan Plane¡ the Fahliyan Formation transitionally overlays the argillaceous limestone of the Garu Formation and its upper boundary transitionally changes into marl and argillaceous limestone of the Gadvan Formation. Petrographic studies of thin sections have been prepared from cuttings and cores resulted in to recognition of 13 microfacies and 2 lithofacies. This formation consists of two carbonate and mixed carbonate –detritalclastic (mixed zone) members. The carbonate member deposited in various sub-environment of basin¡ outer/mid ramp and inner ramp and the mixed member is composed of 3 parts: clay¡ sand beds and argillaceous limestone. Apparently¡ the sedimentary sequences of the carbonate member deposited in a homoclinal ramp¡ containing important shoal facies and lagoon expansion. The mixed member sucession shows shallow marine carbonate features along with claystone and thin sand beds. The Fahliyan Formation consists of three type 3 sequences with sb2 sequence boundary where termination of sb3 in mixed zone changes into sb1 in the Gadvan Formation.

Structural geology studies are important stages of exploration and production of oilfields since familiarity with the existing structures could have a substantial role in the development of oilfields. Salman oilfield located in the Persian Gulf is among those which have been formed in salty dome regions where several faults have been created by diapers. Since stress is the main factor in the formation of tectonic structures, in this study the main stresses on Salman oilfield were studied. For this purpose, contribution of stresses in creation and evolution of tectonic structures of the region was investigated. Then, fault plane of the oilfield designed and distribution pattern of faults and their displacement were studied by using Petrel software. In this regard, UGC maps and Fault Stick data were considered as input parameters. The results indicate compressive stress of Arabian plate movement towards Iran causing the formation of Salman oilfield dome. After three-dimensional modeling of faults plane, it is concluded that these faults were formed in two stages during different tectonic phases. The faults arrangement particularly is manipulated by direction of stresses which formed perpendicular to the tensile stresses. Measurements performed on the faults indicate increase in dip by increase in burial depth until it reaches near normal sate. Vertical displacement of the faults decreased relative to depth which could be in association with increase in fault plane dip. Finally, by considering observing horizontal displacements along fault planes, it is delineated that the main type of Salman field faults are normal with strike-slip component.

Functionalization of carbon nanotubes (CNTs) was applied, during preparation of Fischer–Tropsch synthesis (FTS) cobalt nanocatalysts, to modify the surface properties of CNTs supports. Carbon nanotubes functionalization effects on the particle size, dispersion, activity and selectivity of Co/CNTs nanocatalyst in FTS werw investigated. CNTs were functionalized with ozone and hydrogen peroxide. 15 wt.% Cobalt was impregnated on the functionalized and un-functionalized supports. Catalyst samples were characterized by different methods and assessed in a fixed bed micro reactor. Optimal catalyst activity is usually dependent on the size of the active metal phase, so the catalyst metal particles on the support with finer particles showed higher activity due to higher distribution, than the catalyst with larger size and poor dispersion. This phenomenon is the consequence of the existence of more metal particles which are more accessible to the reactants. In this work, the presence of functional groups decreased the active metal particle size to 8.8 nm. Furthermore, functionalization increased the percentage conversion of carbon monoxide by a factor of 1.16%. In addition, rate of catalyst deactivation decreased by 46% during 20 days continues synthesis. Finally, synthesis products showed a slight shift to lighter hydrocarbons.

In this paper, nanostructure of fullerene was synthesized in laboratory by KRASHMR- HOFFMAN method based on arc mechanisms. First, fullerene nanofluid was prepared at 1wt.% in order to use in gas hydrate formation and investigation the effect of fullerene on yield of process and storage capacity. Second since fullerene is not stable in water, SDS was used as surfactant for increasing the stability of the nanofluid. It was shownthat the prepared nanofluids had good stability. Third, in the process of natural gas hydrate formation containing 92.6% methane, fullerene nanofluid accelerates the gas solubility in water and reduces induction time of the process 53.2%. Angstrom pore structure due to the spherical shape of fullerene is great place to keep gas molecules. Therefore, the storage capacity of gas hydrates increased 5.5% by fullerene. It was observed despite that the presence of fullerene nanostructure reduced 1.3% of hydrate stability, but in the presence of this nanostructure results in increase of the residual gas hydrate after reaching the self presentation phenomenon and thorough stability.

Disposal of storage tanks’ sludges due to the high concentration of hydrocarbon involved in them and environmental hazards are a major concerns in oil depots. In this study, reducing concentration of hydrocarbon in petroleum sludge by applying a low cost absorption was investigated. For this purpose, natural zeolite of Semnan zone was applied. In the first stage, modification of the zeolite surface was performed by different acids and the modified zeolites efficiencies were studied. According to obtained results, modification of zeolite surface improves hydrocarbon adsorption, so that HCl-modified zeolite provides maximum adsorption. In the second stage, the influence of physical and chemical parameters on the process was studied using Taguchi methods at two levels. The results show that contact time, the amount of adsorption and temperature are effective on the adsorption process. In the last stage, adsorption isotherm of process was examined, and it was found that the hydrocarbon adsorption on the modified zeolite follows the Temkin isotherm. Finally, the results of this study show that hydrocarbon concentration of sludge can be reduced to 83% using just 0.28 gr of low cost zeolite per 1 gr of sludge.

In this study, demulsification of water-in-crude oil emulsions was investigated under various conditions by means of electrostatic dehydrator. The effects of various parameters including temperature, voltage, surfactant concentration, salinity, and water content of the West Paydar crude oil emulsion on the separation efficiency were evaluated. To evaluate the effect of temperature, concentration of surfactant and salinity, emulsions of 20 vol% of water in crude oil were prepared. To overcome the effect of asphaltene and resin of the crude oil in stabilizing the emulsions, SDS was used as a demulsification reagent. Emulsions containing 30 wt% of SDS in water were prepared. By increasing the electrice field from 0 to 6 kV/cm, at 22˚C, efficient separation of West Paydar crude oil emulsions was occurred. The normal separation at ambient temperature was 62% which was increased to 86% at 44˚C. Increasing the temperature up to 53 °C increased the separation of water up to about 92% while applying 6 kV/cm. Increasing the concentration of surfactant from 0 to 2.3 vol% at 6 kV/cm and 28˚C increased the water separation up to 75%. Increase in the water salinity of the West Paydar crude oil emulsion decreased the water separation. Increasing the water content of the emulsion from 10 to 30 vol% increased the water separation from 30 to 84%.

In petroleum industry, results from changes in seismic waves reflection amplitude versus offset can be used in extracting elastic properties and hence lithology and pore fluids identification in reservoirs. AVO analysis is one of the quantitative study methods related to seismic data which is applied on pre-stack data. Before performing AVO analysis studies, processing steps accuracy should be ensured so that changes in reflection amplitude will be only relative to changes in elastic properties of layers. One of the major parts of AVO analysis is investigation of common AVO attributes such as AVO intercept, AVO gradient and Poisson’s ratio or a combination of them. The cross plot method which compares two attributes simultaneously can play an efficient role in AVO analysis. In this study, AVO analysis is executed on a loose and unconsolidated sand stone reservoir and well logging data were used to calibrate real seismic data. Fluid Replacement Modeling (FRM) using well data and Gassmann’s equation showed that AVO behavior in every conditions of reservoir (with changes in fluid type and fluid saturation percentage) belongs to class IV of Rutherford and William’s classification which is in consistent with real data. The hydrocarbon boundary in seismic data which is obtained using attributes, their cross plots and also attributes plotting as structural sections of estimation considered horizon are in accordance with gained location from well data.

Pore pressure is defined as the pressure of the fluid inside the pore space of the formation, also known as the formation pressure. When the pore pressure is higher than hydrostatic pressure, it refers to as overpressure. Overpressure can make many problems such as kicks, blowouts, wellbore instability, hole washouts and loss of drilling mud circulation. Overpressure is generated due to different mechanisms; such as, compaction disequilibrium, oil to gas generation, buoyancy effect and lateral transfer. Each mechanism effects on exceed pressure in a significant way. So far, several methods have been proposed in pore pressure prediction using well logs and seismic data. Each method relies on a consideration that over pressure is resulting from a specific mechanism as the main factor, and it is also provided an empirical formula for estimation of pore pressure. Hence, geological studies to understand the overpressure generation mechanism and also choose the appropriated pore pressure estimation method are very important. The main objective of this study is to determine the mechanism of high pressure using well log information and provides the best method of estimating the pore pressure in one of hydrocarbon fields in southern Iran. To obtain this goal, the overpressure mechanism generation is studied from sonic log, density log, pore pressure and vertical effective stress information. The results suggest more disequilibrium compaction as the main mechanism and less unloading mechanism behind the overpressure. So, the Eaton and Bowers methods are used to estimation pore pressure and the results show agreement with the pore pressure prediction from formation pressure test.

Ab-Teymour oil field located in 25 km of southwestern of Ahwaz oil field and mid-north of Dezful embyment with concurrent and smooth anticline and by NW- SE proximate course. In this study, by using well and three dimensional seismic data, petrophysical and stratigrahic analysing on Bangestan reservoir of Ab-Teymour field introduced zone-2 of the Ilam formation and subzone-D from zone 4 of the Sarvak formation as high efficient zones. Also, with using Gama log and sedimentary facies, four third- order sedimentary sequences for the Sarvak formation and three third order sedimentary sequences for the Ilam formation suggested. Then location of the efficiency zones in these sequences was identified. The seismic sections was interpreated using seismic attributes, and well data were interpretated, and after identifying seismic sequences, location of efficiency zones on this sequences was recognized. In addition, seismic study illustrated that the sedimentary environment of the Ilam formation is shallow ramp and open marine for Sarvak formation suggested.

Formation of condensates around the wellbore in gas condensate reservoirs reduces the efficiency of well performance, and it can be intensified depending on the fluid type, reservoir and well properties. Adequate and appropriate information can be helpful for accurate modelling of gas condensate reservoirs. Disregarding the dependence of gas-oil relative permeability on capillary number and high the velocity flow (non-Darcy flow) may cause miscalculations and poor estimations in gas condensate reservoirs. In this paper, a sector model of South-Pars gas condensate field located in the Persian Gulf was simulated using ECLIPSE-300, and the effect of the capillary number and non-Darcy flow on cumulative condensate production and condensate formation near the wellbore and in the reservoir were investigated. Obtained results reveal that production increases as the bottom-hole pressure decreases and/or the production flow rate increases; however, more pressure drop and condensate blockage were occurred. Thus, bottom-hole pressure and the production flow rate should be optimized for efficient production. In addition, taking into account the effect of the capillary number on relative permeability decreases condensate formation near the wellbore and in the reservoir. Non-Darcy flow increases pressure drop, resulting in more condensate blockage near the wellbore. Ignoring the effect of the capillary number and non-Darcy flow in simulation process will strongly affect the accurate prediction of well performance in gas condensate reservoirs.