مجله پژوهش نفت
پیاپی 120 (آذر و دی 1400)

Recently, nanoparticles of various types have been used in enhanced oil recovery (EOR) research studies. Their tiny size and unique structure made them potential additives to take part in fluid/fluid and fluid/rock interactions leading to increased recovery from depleted oil reservoirs. Among different nanoparticles, multi-walled carbon nanotubes, because of their functionalization and possibility of surface modification, an abundance of carbon sources and reasonable price have gained increased attention. In this work, a novel nano-complex has been synthesized by surface modification of functionalized multi-walled carbon nanotubes using cetyltrimethylammonium bromide (CTAB) surfactant and polyethylene glycol (PEG) polymer. The prepared nano-complex was then used as an EOR agent in a crude oil-low salinity seawater-dolomite system. The experimental results revealed profound reduction of IFT in the presence of the nano-complex where an IFT value of 0.5 mN/m at critical micelle concentration (CMC) of 60 ppm was recorded. Moreover, profound wettability alteration from oil-wet toward water-wet state and low adsorption of the nano-complex on dolomite surface further confirmed its applicability in EOR practices.

The fluid produced from oil and gas wells is usually two-phase, which due to the need to maximize the efficiency of two-phase separators, achieving accurate design of separator dimensions is essential. But one of the main problems in the country is the impossibility of accurate design of the dimensions of industrial two-phase separators. Therefore, one of the most important issues in the field of oil and gas industry is to achieve a reliable way to design the dimensions of separators that have the best operational efficiency in the process of separating the production fluid. In this study, a review of classical methods of designing two-phase separators based on theoretical and semi-experimental methods was performed. Then, in order to evaluate the two-phase separators in the laboratory, the laboratory pilot design of the separators was performed. Therefore, one of the main problems in this field, namely the lack of a suitable laboratory pilot to experimentally evaluate the performance of two-phase separators, was solved, and it was possible to determine the standard dimensions for accurate design of industrial separators. According to the results of experiments performed in different operating conditions and comparison with the classical design, a correction factor (α) was proposed to modify the classical relations. Finally, the dimensional analysis method was introduced to design the dimensions of the industrial separator using laboratory results. In order to validate the dimensional analysis method, standard dimensions for separating liquid droplets larger than 750μm in the produced fluid by one of the wells in South Pars field were presented and compared with the actual separator dimensions. It should be noted that the design error of industrial separator dimensions compared to the dimensions of separators used in industry, has been less than 4 percent.

The Sarvak Formation is known as one of the largest sources of crude oil in the Persian Gulf region. In this study, 28 oil samples were collected from the Sarvak reservoirs and analyzed based on geochemical data in order to determine the genetic relationship of oils, depositional environment of source rocks and its dominant conditions, thermal maturity and source rocks age. Using the geochemical parameters, the depositional environments of source rocks have been determined, which include the marine carbonate environment, mixture of marine shale and carbonate, and marine carbonate-marl environment. The chemical conditions of the depositional environments have been evaluated based on the biomarker data, thus the redox conditions of the depositional environments are determined the anoxic marine environment. According to the Gammacerane index and Moretane/C30 Hopane ratio, the water column stratification and salinity of the depositional environment were assessed, thus the source rocks depositional environments are determined the normal water salinity and non-stratified marine to low water salinity/stratification marine. The thermal maturity of oils has been determined based on the study of biomarkers including the terpenes and steranes. Therefore, the samples are determined in the mature oils range, and the most of source rocks are located at the beginning of the oil window. The C28/C29 steranes ratio suggests the Paleozoic and Jurassic source rocks for the central Persian Gulf samples (BL-A, BL-B, RE-A, NT-C and RD-A), while the Sarvak reservoir in other parts of this region is sourced from the Cretaceous carbonate source rocks.

The task of pressure reducing stations is to regulate the gas pressure in the standard range for different uses. The indirect water bath heater is used as part of the gas pressure transfer station to heat the gas before the pressure drops so that the condensate temperature in the gas does not reach the point of hydration formation during breaking and reducing the gas pressure. In this study, according to the characteristics of natural gas and heat transfer relations and mass survival and energy equations, an acceptable analysis of the thermal behavior of heaters has been done and the heater is modeled with appropriate accuracy and the effect of geometric parameters on the heat performance of the heater is investigated. By changing the heater geometry from cylindrical to cubic geometry, acceptable results were obtained by increasing efficiency and reducing fuel consumption.

Common methods for measuring permeability include well test data and core samples. In the laboratory, due to the low cost and high operating speed, the absolute gas permeability of plug samples is often measured. The permeability of the gas in the porous media depends on the average injection pressure and the type of used gas. It is obvious that by changing these parameters, different results are obtained. Therefore, it is necessary to measure the liquid permeability or determine the equivalent permeability of the liquid (Klinkenberg permeability). In this study, a total of 1245 porosity and permeability data were obtained from core analysis of Kangan and Dalan carbonate formations. The permeabilities of 111 samples were measured at 4 different pressures. The pressures were plotted versus permeabilities and the fluid equivalent permeability was calculated. Then, in this diagram, the slope of the fitted line was calculated for each sample, and the coefficient of variations was calculated for the slope of the samples in each rock type to find out the scatter of the samples. Results showed that determination of rock types by the used methods (Winland, flow zone indicator and Lorenz) has little effect on improving the results of this experiment (determination of the Klinkenberg coefficient). Among the methods used to determine the rock types, flow zone indicator parameters (porosity, permeability and matrix) have direct effects on the slope of the line (permeability-pressure regression line). This method also yields the highest coefficient of determination. It can also be concluded that it is not possible to obtain the equivalent liquid permeability of all samples using a constant correction factor. Comparison of the liquid permeability results with laboratory measured values shows that the method could be used for increasing the accuracy of the predicted permeabilities.

The dielectric properties of a substance are the properties by which the effect of the utilization of electromagnetic waves can be studied. These properties should be investigated to study the electromagnetic heating method and optimization. In this study, seven oil samples from different fields were investigated, including Asmari, Sarvak, Sohrab, Fahlian, Kuh Mond, Mansouri, and Yaran. In this study, organic compounds and functional groups in crude oil were identified, and their effect on the dielectric property of oil was investigated. By examining the parameters affecting the dielectric property, it was concluded that the more polar compounds the compound has, the higher the dielectric and, therefore, the higher the ability to absorb microwave waves. The amount of dielectric property of Kuhmand, which is part of super heavy oil equal to 2.853 and Fahlian which is part of light oil is equal to 2.006, which shows that the heavier the oil between these two oil samples, the more Its electricity is higher and ultimately has a higher ability to absorb electromagnetic microwave waves. On the other hand, the bonds in the oil themselves also affect the dielectric. According to the FTIR test, the OH, NH, CN and SH bonds in the samples are directly related to the dielectric. The higher the concentration of these bonds is, the higher the dielectric is. In this project, the required links and functional groups within oil samples have been studied and discussed.

The siliciclastic formations of Ojagheshlaq and Zeivar, as the reservoir rock of Moghan basin are of special importance. The sandstone facies of these formations are a unique example of unconventional reservoirs (tight sandstones) in Iran, which due to the textural and diagenetic characteristics affecting their pore system, have unstable production with pressure drop. In this study, the lithological and sedimentary characteristics of these formations were investigated by combining the results of core description, petrographic studies, scanning electron microscope images along with porosity and permeability data of the core obtained from outcrops and wells. The results show that the low mineralogical maturity of these sandstones, which mainly contain volcanic lithics and feldspar, has played an important role on modification and evolution of the pore system during their diagenetic history. In fact, the presence of volcanic lithics as compressible components is an effective factor in reducing the porosity of these sandstones during burial and compaction. Also, the alteration of these components along with feldspars has led to the formation of various diagenetic clays that have acted as cement inside the pores and have played an important role in developing micropores within the pore system. The dissolution process has also led to the development of isolated dissolution pores with limited expansion. In general, the interaction of three factors of compaction, diagenetic clays and dissolution in contrast to mineralogy, has played an effective role in the development of pore system and reservoir quality of Moghan basin sandstones, as a result of which tight sandstones with a compacted texture and pore system with a poor connection consisting of isolated dissolution pore types and micropores have been developed.

In this study, thin film nanofiltration membranes were modified by using Ar-Air plasma. The effect of plasma time, power and the composition of plasma gases on physico-chemical properties and separation performance of membranes were investigated. The results showed that the plasma treatment caused to increase in membrane surface hydrophilicity considerably. The surface modification of membranes by using plasma treatment led to enhancement of water flux through the membrane obviously. The separation efficiency of membranes due to surface modification was also changed broadly compared to unmodified membrane. The separation efficiency of modified membranes at 35 W and 180 s, 25 W and 120 s, and 15 W and 60 s plasma treatment measured ~30%, 76%-92%  and 77%-89% respectively. The selectivity for un-modified membrane was also measured ~90%. Among all studied membranes, the modified membrane at 50-50 (v/v) Ar-Air plasma, 25 W and 120 s treatment with considerable enhancement of water flux compared to pristine membrane was selected as the optimum sample.

Injection of different acids is one of the methods that can improve the permeability of the damaged near-wellbore areas. The efficiency of the carbonate acidizing processes depends on the propagation of wormholes in porous media. Creation of these high permeable flow paths is mainly dependent on the flow rate of the injected acids, the composition of the system, and the structure of the porous media. Indeed, experimental studies have indicated that there are optimum injection rates for different acids in different systems. In this study, the injection of several acids into the damaged formations in an oilfield is simulated using the Well book software. The results of this study indicate that it is probable to implement an optimized acidizing operation in this well. The obtained optimum injection rate for HCl is slightly higher than the maximum injection rate that the carbonate layers can tolerate. In addition, the simulation results indicate that using formic acid instead of acetic acid helps to achieve a higher reduction of the skin factor. Moreover, using coiled tubing can contribute toward the uniform distribution of acid in different sections, which results in the increase in the productivity index in all production layers. According to the simulation results, injection of hydrochloric, acetic and formic acid in the determined optimized condition can result in the increase in the oil production rate from the primary value of 300 bbl/day to 544, 511, and 441 bbl/day respectively.

Asphaltene precipitation, as stated in previous studies, plugs the pores in the porous media and causes various problems, including permeability reduction, wettability alteration, and ultimately reduces production. The results of this study showed that this surfactant is able to prevent asphaltene precipitation and is effective in different aqueous phases (DW, SW and CW). In addition to increasing recovery factor in the core flooding test, it was able to alter the wettability of the pores surface from oil-wet to intermediate.