مجله پژوهش نفت
پیاپی 128 (فروردین و اردیبهشت 1402)

Surface separators play a very important role in oil and gas-producing fields. For this reason, their optimal design is very important for field applications. Semi-experimental design is a basic method to determine the dimensions of separators. Due to the simplifying assumptions used in semi-empirical design methods, they are only used for approximate estimation of the dimensions of the separators. The two-phase separator laboratory unit consists of a horizontal two-phase separator on a laboratory scale, pumps, compressors, and a static mixer to create a two-phase flow and a liquid filter to trap liquid droplets from the outlet gas flow. The separation efficiency is determined by weighing the trapped liquid droplets and by imaging the maximum diameter of the liquid droplets in the exhaust gas flow. In this research, the optimal dimensions of the separator are presented using a new combined method. In the proposed new combined method, CFD simulation of the two-phase separator was first carried out on a laboratory scale. Then the simulations were validated using laboratory data. Also, the optimal range for the slenderness ratio of the separator was determined. Finally, by using the new relationships presented in the form of dimensional analysis, the dimensions of the separator were determined, and then the performance of the designed two-phase separator was validated using the CFD simulation model. Validation results showed that the presented new method has a high capability in the design of gas-liquid separators. The relative error value between the results of the developed CFD model and the laboratory data was less than 7%. In order to use the presented new method in the field, the dimensions of the surface two-phase separator were determined for one of the production wells located in the South Pars gas field. One of the most important achievements of this research is providing the necessary platform for the optimal design and construction of surface separators for field use.

The Dariyan Formation with the Aptian age is one of the most important prolific oil reservoirs in the Zagros and Persian Gulf. In the current study, different rock typing approaches were integrated and applied for the reservoir characterization of this formation in an oil field in the eastern Persian Gulf. Petrographic studies on the thin sections of the studied formation have led to the recognition of nine microfacies grouped into four sub-environments, including basin, outer, middle and inner ramp. The observed facies indicate a carbonate ramp as the depositional environment of the Dariyan Formation. The most important diagenetic processes observed in thin sections are dissolution, dolomitization, fracturing, micritization, (mechanical and chemical) compaction, and bioturbation. Based on the porosity-permeability of cores, six hydraulic flow units (the flow zone indicators = FZI method), four Winland rock types, and three Lucia rock classes were identified. Predicted porosity and permeability from log data were used to identify five hydraulic flow units (from the FZI method) and based on the stratigraphic modified Lorenz plot (SMLP), six reservoir/non-reservoir units were identified. In addition, using the multi-resolution graph-based clustering (MRGC) technique, seven electrofacies were determined. A comparison between the results of all rock-typing methods and petrographic data also reveals close correspondence. In a general view, the reservoir potential of the Dariyan Formation is higher in the Highstand System Tracts, which are mainly composed of grain-supported fossil-bearing and boundstone facies of the inner ramp sub-environment that could be a target zone for the field development. In contrast, the mud-dominated facies of the basin and outer ramp sub-environments in the Transgressive System Tracts are the poor reservoir units within the Dariyan Formation.

In oil and gas wells, the quality of cementation behind the casing and liners has a significant role in maintaining safe production and reducing costs due to possible future repairs of the wells. Proper cementing prevents interlayer flows behind the casing, reduces the severity of corrosion of the outer surface of casing, prevents leakage of the annulus and the edge of liners, prevents water movement from deep to the upper reservoir zones of the space be-hind the pipes and prevents subsidence due to the infiltration of water from deep into the surface layers of the earth. The results of this study show that apart from the method of cementing operations and cement compositions, the property of rock and fluid also affects the quality of cementation. In drilled wells of Khangiran gas field, mainly the quality of cementation in certain zones of sedimentary formations is inappropriate. In this study, after applying petrophysical zoning on the formations of Khangiran field, first the sub-zones in which the quality of cementation is usually low were identified. Such as zone3 of Abderaz Formatiom. Then, the possible reasons for this event were investigated. For example, Existence of high permeability in zone1 of kalat formation. and finally, some suggested solutions to prevent the recurrence of this phenomenon in drilling future wells were presented. Such as changing the depth of casing point. The most important zones in which cementing are weak include porous and permeable zones and gas zones.

In this article, the combination of a flat plate solar collector with a solar still is used for water desalination. The purpose of this study is to increase the output of the solar still by improving its performance by using a whole flat plate and investigating the effect of solar water on the amount of distilled water produced. Various effects, environment, water depth, environment, speed, and solar radiation have been studied to increase productivity. The results showed that coupling solar still with a solar collector increases the efficiency by 48%. Also, the amount of water depth in the distillation device affects the production of distilled water, and it is clear that by decreasing the depth from 3 cm to 2 cm, the amount of freshwater produced increases by 8.5%. The results obtained from the tests showed that the volume of distilled water output from the device, for an average depth of 2 cm to 4 cm, is 4.6 to 9.5 L/day using the collector and 2.4 to 1.3 L/day. It is without using it. The average radiation intensity and wind speed during the test with the collector were 1035 W/m2 and 3.7 m/s, respectively, and in the test without the collector, it was 980 W/m2 and 4.2 m/s.

Determining reservoir parameters is very important which is usually conducted in laboratories, but, it is an expensive, time consuming and difficult process.Therefore, in this study, NMR log has been used to determine porosity, permeability, capillary pressure in the upper part of Dalan Formation in well SP-A of South Pars gas field. In this method, the capillary pressure versus Sw was plotted from the T2 distribution of NMR log and then compared with the curves obtained from mercury injection in the studied well. High Correlation coefficient of 0.93 and 0.98 are obtained by comparing core derived versus NMR porosity and Timur permeability (mean NMR Timur permeability 80 md) for the reservoir zone (k4). According to well log and software evaluation mean total porosity is 15.5% and mean effective porosity is 11.9 % for the study area. Low shale volume, adequate porosity showed that talent the reservoir of the study area is high.

The first and most important task of drilling fluid is to help clean the borehole and transport drilling cuttings to the surface. In addition, approximately twenty-five percent of unwanted waiting time on drilling rigs is due to time spent on well cleaning. With the acquisition of powerful computer systems, the processes of simulating well-cleaning operations and preparing models of operational wells are expanding, and this practice, while increasing accuracy and productivity for implementation in operational fields, avoids spending a lot of time and money. In the present research, an attempt has been made to design and validate a model based on experimental tests conducted in the flow loop of the drilling laboratory by using computational fluid dynamics, and by examining the current model with a number of similar CFD models and laboratory results, the optimal mesh and its effect on increasing the accuracy of the results have been studied as well as the efficiency and speed of the simulation. Also, by comparing the new experimental model and the previous experimental model, physical improvements for simulating the wellbore environment, such as adding a nozzle and bit and replacing the flow output is observed, and a CFD model designed based on the old experimental model and this optimized CFD model designed based on the new experimental model has also been compared. and by checking the accuracy and execution time of each one, the optimal mesh is selected.

Fractured network modeling is the main prerequisite for fluid flow simulation in many applications such as groundwater resource management, oil and gas reservoir simulation, geothermal energy resource modeling and etc. The aim of this study is to develop an iterative object-based algorithm for fractured network modeling that considers both statistical parameters and spatial connectivity of fractures. The presented algorithm uses the functions of fracture neighborhood matrices in image processing to make clear the fracture continuity and to determine their spatial distribution using the matrix of interconnected fracture cell detection, Sobel matrix, Prewitt matrix and Laplacian matrix. The objective function defines the differences between the features of the reference fracture network and the stochastic generated fracture network using a norm of two. To solve this objective function, optimization algorithms of Gravitational search, particle swarm and hybrid of these two metaheuristic algorithms have been used. In this paper, the metaheuristic algorithm of particle swarm optimization enjoys more validity in fracture network modelling. Therefore, among the metaheuristic algorithms, PSO algorithm regenerates the reference fracture network with the accuracy of 98.89%.

Dariyan Formation (with Aptian age) is considered as one of the important oil reservoir of the Zagros and Persian Gulf sedimentary Basin. This formation in the studied field in southeast of the Persian Gulf, is considered as the most important oil reservoir rock. In this study, microscopic thinsections that prepared from the cores of the Dariyan Formation, were investigated. The study of the microfacies of the Dariyan Formation in this field led to identification of seven carbonate microfacies and one mixed carbonate-clastic microfacies, which were deposited in four facies belt including the inner ramp, middle ramp, outer ramp and deep basin. The investigating of the fauna in the studied microfacies shows a relatively shallow marine environment (in some intervals representing the deep marine environment), generally. Uniform facies changes and the absence of rudists and corals which are reef-building faunas as well as the replacement of Lithocodium algae with less ability to form the large reefs, represent the homoclinal carbonate ramp environment, which contain «patch reefs». Importanat diagenesis processes such as: cementation, bioturbation, pyritization, phosphatization, dolomitization, dissolution, Mechanical and chemical compaction and fracture has affected the carbonate rocks of this Formation. Correspondence of porosity and permeability data of the cores indicates that the reservoir quality of the Dariyan Formation in the studied field was affected by facies, sedimentary environment and diagenesis factors, so the lithocodium- bearing facies (boundstone-flootstone) have the most porous facies.

Surfactant flooding is one of the most effective methods of the enhanced oil recovery (EOR) technique since it can reduce the interfacial tension (IFT) and wettability of the crude oil oil/rock/formation brine system. The aim of this study is to investigate the effect of ions (NaCl and Na2SO4) on the efficiency of two ionic liquids (ILs) namely 1-dodecyl-3-methyl imidazolium chloride ([C12mim][C])) and 1-octadecyl-3-methyl imidazolium chloride ([C18mim][Cl]) with different alkyl chain lengths on the IFT reduction and wettability alteration using works of adhesion and cohesion and spreading coefficient. Based on the critical micelle concentration (CMC) measurement, the efficiency of ILs at three different concentrations (C), C<CMC, C=CMC, and C=CMC, are investigated to evaluate the wettability alteration on the dolomitic carbonate rock surface and oil spreading coefficient. The results show that the performance of IL with longer chain length depends on the salt type, although the importance of surfactant concentration is dominant compared with salt type effect. To sum up, it seems that the IFT reduction can improve the performance of the solution for wettability alteration. The worth mentioning point is that the highest spreading coefficient is obtained for the IL with shorter chain length ([C12mim] [Cl]) in the presence of NaCl salt.

In seismic methods, the estimation of formation pressures is acquired by transforming the seismic velocity to the pore pressure and contrasting it with the velocity log and effective pressure obtained during the well-test program. This study is regarding the velocity studies in one of the oilfields in SW Iran, which is generally carbonated. Except for the Kazhdumi Formation, they do not have shale interbeds. This study is based on information from 23 wells and seismic interpretation. Compressional (Vp) and shear velocity (Vs) models are determined from combined geostatistical models and compared with the value-volume fractal method, especially the velocity-volume model. Based on vertical Seismic Profiling (VSP) data, the maximum Interval velocity is 2760-2900 m/s in the northeast of the field related to the Gotnia Formation. In order to determine the formation fracture pressure, the shear velocity cube is modeled using exploratory well-cores and dipole sonic imager (DSI) shear velocity logs. The final cube with a coefficient of 0.95 has been determined for the shear velocity data obtained from the porosity, lithology, and primary DSI shear velocity data. The final amounts of inverted acoustic impedance (AI) in the deeper formation of the field are mainly in the range of 8000-15000 [(m/s)*(gr/cm3)], which it could be referred to as calcareous formations. Based on the calculation of the logratio matrix obtained from the Velocity-Volume (Vp-V) fractal model, the maximum overall accuracy (OA) in the dominant limestone intervals is 0.74. It indicates a high correlation of the compressional velocity cube model obtained from a combination of sequential Gaussian simulation (SGS) and co-kriging models with acoustic impedance inversion (AI). In the final Vp cube’s vertical Variogram, the sill is 0.34, and in major and minor is 0.96. Anisotropy range for vertical variogram range is 96 meters and for major and minor directions is 11850 meters.