مجله پژوهش نفت
پیاپی 89 (مهر و آبان 1395)

Study of two-phase flow in the reservoir has an important role in management and predicting the performance of oil and gas reservoirs. This includes solving the nonlinear equations, time-dependent hybrid equations in heterogeneous reservoirs. The most important issue in this regard is to generate the best mesh for the reservoir network leading to the best answer. In this technique, the variables of permeability distribution, well locus and streamlines are combined to generate the background grid. Using one of the techniques for mesh generation, the computational grid is generated. Two-phase flow modeling is developed on finite volume basis and the results are compared to the fine grid.

The Late Jurassic Arab Formation, as an excellent example of the classic carbonate-evaporate sequences, constitutes one of the most prolific hydrocarbon reservoir in the Persian Gulf and adjacent areas. In this study, regarding the importance of dolomite reservoirs throughout the world, and the effects of anhydrite mineralization on these reservoirs, the impact of anhydrite texture, its distribution and abundance within the dolomite intervals of the Arab Formation is investigated. In this respect, the integration of the results from core description, petrographic studies as well as core poroperm values and the mercury injection capillary pressure data have been used. The petrographic analysis indicates that there is a strong relationship between the percentage, texture and distribution of anhydrite in the reservoir. Anhydrite has been developed as uniform and patchy distribution in the reservoir with poikilotopic, nodular, pore filling and bedding textures. Generally, the reservoir intervals with the uniform anhydrite distribution are correlatable with the high percent anhydrite samples, and nodular and pore filling textures. In contrast, the intervals with patchy anhydrite cover the reservoir dolomites with low percent anhydrite and poikilotopic texture. The assessment of poroperm data and parameters extracted from the mercury injection capillary pressure tests indicates that the dolomites with patchy anhydrite, poikilotopic texture and low anhydrite content, due to the large pore throats radius, comprise the best reservoir units of the Arab Formation.

In this study, hydrogen production by steam reforming of methane has been investigated. Due to its wide applications and important role as a future fuel, hydrogen is a valuable material. Steam reforming of methane is one of the most common and the most important hydrogen production processes which are carried out industrially at 700-900°C. High temperatures can cause problems; such as, sintering of catalysts, rising of costs, coke formation on the catalyst, and increasing safety concerns. In this study, prevalent catalyst of this process (Ni/Al2O3) is used at medium temperatures (450-650°C) to investigate the reasons for reduction in hydrogen production at these temperatures. Increasing time, increased and after a specific time sharply decreased the methane conversion. This sharp decline in methane conversion occurred after 210 min at 600°C and 275 min at 650°C. The peaks in XRD test indicate oxidation of catalyst during the process. In the stable time of catalyst at 650°C, methane conversion and hydrogen mole fraction were 99% and 80%, respectively. Rising steam methane ratio in the range 2.5-6 increased the methane conversion and hydrogen mole fraction and decreased the selectivity of CO. At medium temperatures, nickel can produce hydrogen by steam reforming of methane, but due to deactivation of catalyst, this process cannot be carried out continuously.

Produced water is one of the major drawbacks of petroleum production. Desalination is the most important step in controlling the produced water. Capability of electrodialysis in desalination of produced water was demonstrated by a sample containing a TDS of 4393 ppm using a flow rate of 0.3 L/min in an electrodialysis stack for 360 minutes. Desalination of %62 implied that this method was viable to produce required water for livestocks and agricultural uses from relatively thin produced water. To figure out the influences of feed flow rate, applied voltage, and duration of the process on the performance of electrodialysis, L9 array of Taguchi method was used to design the experiments. After conducting all designed experiments, it was concluded that the duration of the process and the applied voltage had direct relationships with the amount of separation, while there was an inverse relationship between the feed flow rate and the desalination of electrodialysis. Among the process variables, the period of the process had the most noticeable influence on the separation, while the feed flow rate had the least effect on desalination. In the vicinity of implied operating conditions the voltage of 7 V, flow rate of 0.3 L/min, and time duration of 200 min were obtained as the optimum conditions for desalination of produced water.

Oil contamination in soil affects the geotechnical properties of soil and may lead to hazards. In this research, the effect of oil contamination on shear strength and permeability of sandy soils has been studied. To perform geotechnical tests, four sandy soil samples including poorly graded sand, well graded sand, muddy sand and clayey sand have been produced, then standard proctor test, atterberg limit test, direct shear test and permeability test have been carried out on samples. Crude oil used as the oil contaminant has been taken from Tehran Refinery and has been added to specimens with weight ratio of 12, 8, 4 and 16 percent by dry weight of soil. Total of 60 sandy specimens have been produced with different crude oil percentage, and geotechnical tests have been carried out on each specimen. Results of direct shear tests have showed that friction angle in all of sandy specimens is reduced by increasing oil content. The results also showed that oil contamination in well graded sand, poorly graded sand and muddy sand creates an artificial cohesion and decreases cohesion of clayey sand. Effect of oil components’ evaporation on shear strength has been studied on %16 contaminated specimens and direct shear test results have been discussed. Permeability tests showed that by increasing the crude oil, permeability coefficient of clayey sand increases permanently, while permeability coefficient in poorly graded sand, well graded sand and muddy sand first increases and then begins to decrease.

Problems associated with heavy organic deposition during the production, transportation, and processing of crude oils are one of the important issues in oil industry. Thus, accurate identification of asphaltene structure and surface morphology of asphaltene should be investigated. In this experimental study, thermal and thermal-evaporating de-asphaltene method for asphaltene separation at two different temperatures is used. The effect of temperature as precipitating agent and toluene as solvent agent on the structure and surface morphology of asphaltene is explored and compared by XRD and SEM technique. The results of SEM are shown the dependence of asphaltene morphology on the method of asphaltene separation. In all SEM images, pore, cavities and also agglomerated and smooth surfaces of asphaltene have been observed. Appearance of pores in the SEM images has been used as an indicator of the resin detachment. At thermal de-asphaltene method cylindrical asphaltene shapes change to smooth surface by altering the separation method to thermal - evaporation de-asphaltene. XRD results are shown that characteristic parameters, such as, layer distance between aromatic sheets have the same values for all de-asphaltene methods and are in agreement with other researches investigations, while the average height of stack aromatic sheets and the number of aromatic sheets in a stacked cluster by decreasing the temperature slightly increased. In thermal – evaporation method, this increasing of the number of aromatic sheets in a stacked cluster is observable. It›s indicated that asphaltene particles has more tendencies to aggregate and has smoother crystallite structure at mentioned conditions.

Organic deposits particularly, asphaltenes cause detrimental effect on the petroleum industry, because it causes to decreases produced oil and clogging the oil facilities. Generally, dispersants and inhibitors or asphaltene solvents are using for chemical controlling of asphaltene precipitation. The asphaltenes content in crude oil are stable under the certain conditions, but there is no certainty about the stability of system in another operational condition. So it is important to study the kinetics of asphaltene settling and deposition. In this work, we investigated the kinetics effect of the three dispersants on the stability of asphaltene aggregates using turbidity measurement and particle size distribution methods. Turbidity measurement showed as the dispersant strength rises;moreover, the turbidity of unstable sample containing dispersant less declines versus time. Asphaltene particle size distribution measurements showed that adding dispersant decrease the average diameter of asphaltene aggregates. Also, in this study the kinetics of asphaltene settling using power law model and the relations of the diluted suspensions was developed. The result of model showed the settling velocity of asphaltene has been decreased by adding dispersants.

The increasing worldwide demand for propylene has led extensive research to be deployed for establishing economically feasible alternative methods for propylene production. The oxidative dehydrogenation of propane is a promising route for propylene production that does not suffer from the any drawbacks of traditional methods. However, selectivity control in oxidative dehydrogenation of propane is the only main challenge to industrialization of this process, because propane and propylene can convert to COx and other products. In this investigation, titania- silica supported Nickel-Vanadium catalysts were synthesized and evaluated in oxidative dehydrogenation of propane. Catalysts were characterized by XRD, BET, FT-IR, and SEM tests. The propane oxidative dehydrogenation reactions were carried out in fixed-bed reactor. All samples were tested in the temperature range of 350-550°C The best performance among these prepared catalysts was obtained for 7.5%Ni- 7.5%V/Si: Ti(1:1) with propylene yield of 14.33% at propane conversion of 41.84% at 550°C

In off-shore fields, whenever a mixture of sea water and produced water is used for reservoir pressure maintenance and, or recovery factor improvement, necessary precaution should be considered for the control of mineral scale formation. Incompatibility between sea water and produced water causes serious problems; such as, formation damage as well as flow restriction in producing wellbore and pipelines. In this project, experimental studies have been carried out as to investigate strontium sulfate scale due to the mixtures sea water and produced water under the temperature reservoir. Results have been shown when the ratio of produced water to sea water is increased, strontium sulfate formation intensifies. With the mixture of %60 sea water and %40 produced water, scale Formation is Maximum. Furthermore, experimental results have had reasonable match with the Jacques model.

Asphaltenes constitute the main hydrocarbon precipitants of crude oil which have been formed and deposited due to the effect of changing temperature, pressure and composition.. The phase separation of these heavy solid precipitates could alter rheological properties of reservoir fluids (e.g. by increasing pressure drop in pipes, reducing well productivity and ultimately stopping production). Detection of the time and location of phase separation is one of the major challenges in production assurance. To achieve this target, the thermodynamic conditions that induce precipitation of Asphaltenes in the oil medium (a.k.a. onset of precipitation) needs to be determined. On the other hand, the content of precipitation is important to characterize the thermodynamic behavior of Asphaltene. Viscosity is a reliable parameter for detection of phase separation Asphaltene precipitation in both onset point and content. In this study, the viscosimetry method is used for detection of onset of precipitation and the results are compared with that of other common methods of solid detection. The results indicate that the viscosity method has acceptable accuracy for crude oils with an API range of 18 to 40 and a wide pressure range (atmospheric to high pressure conditions). Solid solution theory is used for the modeling of thermodynamic behavior. In our study, Asphaltene is introduced as an individual component in Solid-Liquid-Vapor Equilibrium calculation. So rather than common solid model our modification take it easy to use the real physical properties of Asphaltene; such as, molecular weight and molar volume.

In this study, formation of composite coating containing silicon carbide amplifiers on ASTM A106-Gr B steel surface was investigated using the gas tungsten arc welding process. Therefore silicon carbide particles with different volume percentages on the steel surface were placed, and by changing the current density, melting and mixing process were done with the base metal. The study coating microstructure by optical microscopy and scanning electron microscopy (SEM) was conducted alongside the spot analysis. The results showed that the dendritic structure of the resulting coating which contained silicon carbide is capable of reinforcing. Besides, the capability of reinforcing could be improved hardness and wear behavior of the coatings. Hard coatings by a micro-hardness measurement and with slab vickers and wear behavior of the coatings was evaluated by testing the wear-trip basis. Microhardness test results showed that increased hardness was created (about 650 to 1200 Vickers) to compare with uncoated samples (about 200 Vickers) is. Conducting reviews of wear behavior of coatings represents significant improvements in their wear behavior due to the effect of adding silicon carbide reinforcement. The main wear mechanism of uncoated delamination wear samples, surface oxidation and the samples which were coated with a mixture of delamination wear, surface oxidation and adhesive wear were detected.

Precipitation and deposition of asphaltene are one of the serious problems in oil industry and has drawn the attention of many researchers in recent decades. The application of aromatic solvents is the most common method of asphaltene removal, especially in oil wells. Xylene, one of most applicable aromatic solvents, creates many environmental issues. Then it is needed to reduce the use of xylene either by co-solvents or replace it with environmentally friendly solvents. The main purpose of this paper is to find an alternative solvent to replace or reduce consumption of aromatic solvents. Firstly, the efficiency of xylene has been evaluated in the presence of co-solvents including kerosene and diesel at different temperatures. Then, terpene as an environment-friendly asphaltene solvent has been studied at ambient temperature and 80 ⁰C. The results show that efficiency of xylene in the presence of kerosene is higher than diesel. Moreover, temperature increase leads to more asphaltene dissolution. Finally, terpene has shown an acceptable solubility compared to aromatic solvents while its efficiency is being reduced dramatically in the presence of kerosene and diesel.

In skimmer tanks, the reduction of oil pollution from wastewater is a function of the geometry and the location of baffles inside these systems. The performance of a skimmer tank, existing in a desalination plant, with a diameter of 8 meters and a height of 10 meters has been unsatisfactory at the time of its launch because of lack of proper design of the tank and its internal equipment and thus, it has been out of service. In order to improve its performance, its aspects and sizes must be considered as problem’s constraints, and the problem solution must only be solved by locating its internal equipment. In this study, the arrangement of the polygon baffle of this skimmer tank has been extracted using geometrical similarity of an existing tank’s geometry with suitable performance. After that, three-dimensional turbulent flow within the tank has been simulated numerically using Fluent package. In order to validate the results of numerical simulation of flow in the tank, the pressure at the inlet pipe has been examined, and it can be shown that this amount is consistent with hydrostatic pressure. The performance of the skimmer tank has been assessed by establishing baffle and changing the diameter of the outlet pipe of water and doing numerical simulation. The results show that the new design of the skimmer tank will lead to increase the resident time of oil particles as well as to increase oil particles’ path through the water outlet pipe. Therefore, by installing the polygon baffle inside the existing tank and changing the diameter of the water outlet pipe, this tank can be used for operational purposes.

In this study, different ratios of methanol and hexane were used for lipid extraction from lyophilized microalgae and wet biomasses with 70 and 85 % moisture content. The amount of extracted crude lipid showed an increasing trend up to 1:1 volumetric ratio of methanol and hexane. Nevertheless, the increasing trend was diminished by further increase of methanol. A significant decrease of extracted crude lipids was observed with increase of moisture in low ratios of methanol. The highest amount of extracted fatty acids was achieved when same ratio of methanol and hexane were used, and amount of it was 2.30±0.53. The fatty acid recovery was decreased by increasing the moisture content. However, the profile of extracted fatty acids for different solvent mixture was nearly the same as dried microalgae. The best performance of extraction belongs to 1:1 hexane/methanol ratio which was 2.2±0.33 and 0.95±0.16 for 70 and 85% moisture content of biomass, respectively. The effect of temperature on the performance of extraction was also investigated, and the results showed that the recovery of both crude lipids and fatty acids was improved by increase of temperature, in which the crude lipid and fatty acid recovery was increased by about 17 and 36% at 65 oC comparing to the 25 oC. UNIQUAC thermodynamic model was employed to investigate the influences of moisture content and solvent ratio on lipid extraction process. Energy interaction parameters of the model were obtained by utilization of experimental data. Estimated results with AAD (%) inferior to 8.65 proved accuracy of it.

Core testing is the most accurate and most expensive method of measuring permeability. A lot of effort has been carried out for finding alternative methods to estimate permeability. One of the indirect methods of estimating permeability is using Stoneley waves. The main advantage of this method is to record Stoneley waves intrinsic property affected by the permeability and by quantifying the relationship between the physical parameters of waves and permeability, a continuous log of permeability changes around the wellbore can be prepared. This method results are influenced by many parameters; such as, porosity,lithology, accuracy of permeability measurement done by core or MDT tools and calculated Sotoneley slowness in rock matrix. In this study, the effects of the above parameters in the calculation of quantitative values of permeability have been studied. Based on the results, the parameters of porosity and slowness of Stoneley wave in rock matrix have more influence on accuracy of determining permeability. The observation shows that by absence of the accuracy in calculation of Stoneley slowness in rock matrix, the permeability values of some points will be negative. In addition when the porosity parameters is used in permeability , the results are more in tune with permeability values derived from the MDT tools.

Pore network characteristics control the fluid condition in reservoir rocks. In carbonate reservoirs, fluid flow status is independent of primary depositional texture, so network properties must be directly included in the process of facies determination to accomplish them and make them be applicable for analyzing the reservoir real conduct. A compilation of petrographic, petrophysical and reservoir engineering studies is carried out to characterize pore throats and lithofacies using Self-organizing Map Neural Network in Dalan and Kangan formations of South Pars Gas Field in this paper. Five pore-facies with unique petrophysical, geological and reservoir features are determined by the applied network. A sharp decreasing trend in reservoir quality recognized from pore-facies 1 toward 5 based on their extracted properties. Meanwhile, Support Vector Machine (SVM) which was used for prediction of pore-facies identified in previous steps from wireline well logs. The accuracy of the model in prediction of pore-facies is 78% which indicates an acceptable result for the model in the South Pars Gas Field.