Iranian Journal of Oil and Gas Science and Technology

Abstract The present study deals with the geometry effects of the spherical pressure vessels (SPV) and the crack configuration on the variation of the stress intensity factor (SIF) through the crack line. The vessel is assumed to contain a semi-elliptical crack on the inner surface. The pressurized vessel is subjected to the pressure and thermal gradient (thermomechanical loading). The 3-D analysis of defective thick-walled pressurized spherical vessels is conducted using the numerical finite element method (FEM). This work covers various crack configurations in vessels with different geometries. The effect of the various parameters, such as thermal gradient, R_o/R_i, a/i, and a/t, on the variation of the dominant first mode of SIF through the crack front is studied. The obtained SIFs are compared with the mechanical loading results (without the thermal gradient). The results show that crack parameters (the aspect ratio and the crack depth), the wall thickness of the vessel, and the structural loading can significantly affect the distribution of the values of SIF through the crack front. Keywords: Semi-elliptical Crack, Spherical Pressure Vessel, Stress Intensity Factor, Thermomechanical Loading

Abstract Iran is ranked second after Russia, possessing about 91 trillion cubic meters of natural gas (equivalent to 81% of the world’s reserves). The optimal use of these vast reserves requires long-term precise scientific planning and a complete study and understanding of various related aspects. With huge gas reserves, Iran is known as the second country in the world with natural gas reserves, and from this point of view, it is at the center of international attention. The privileged strategic position of Iran, which is located in the center of crucial natural gas markets in the world, on the one hand, and the massive volume of the country’s oil reserves, which are generally in their second period of exploitation and require the injection of natural gas to increase the recovery rate, on the other hand, necessitate codified and long-term planning for gas allocation to achieve maximum benefits. This research aims to check whether a reservoir undergoing gas injection is profitable to inject or export gas and generalize its results to reservoirs under the same conditions.
The development of gas reservoirs such as South Pars has increased the gas supply in the country and created 
the necessary platform for using natural gas in various industrial and export sectors. There are different options for natural gas consumption in different sectors. Among other things, natural gas can be used in the development of petrochemical and steel industries, the development of gas exports, the injection of gas into oil fields, and the increase of oil recovery. Economic evaluation is one of the most essential criteria for gas allocation and allocation volume to each sector.
According to the implementation of petrochemical industrial projects and exports in the country, there is a reliable assessment of the economic efficiency of these sectors. However, it is necessary to provide a specific model for economic evaluation due to the technical and economic complexity of gas injection into oil fields. For this purpose, presenting a financial model based on the technical models of gas injection projects can help evaluate gas injection projects in the country so that the correct policy based on economic models can be made in this sector.
At first, it was checked from a technical and reservoir point of view by modeling with standard software that each amount of gas injected into the reservoir will increase the amount of production and how much this increase in production will add value to the output. In this section, the costs for gas injection, such as equipment and gas injection costs, were also obtained. Then, the output of the modeling done in several different scenarios was used in financial modeling in the majority of an investment project to inject gas into an oil field and generate income from the increased production of the field. The results were compared in the continuation of the relevant modeling concerning different sensitivity analysis parameters. Ultimately, it tried to obtain the minimum technical and economic conditions necessary for the profitability of gas injection into oil fields using modeling and evaluating the results.
This research examined gas applications based on different scenarios and sensitivity analysis, including injection and export. Then, the economic evaluation of each scenario was done to obtain the optimal state. Also, one of the reservoirs in the south of Iran was investigated, and the obtained information could be generalized to other reservoirs in the country with similar conditions.
A detailed investigation was conducted on the gas injection process in southern oil reservoirs using a sophisticated reservoir model and a commercial reservoir simulator. The analysis focused on both technical and economic aspects. The reservoir model consisted of 4 production wells and 3 gas injection wells, operated for 15 and 10 years, respectively. The impact of different injection pressures on the final recovery factor and cumulative oil production was examined from a technical perspective. It was observed that all gas injection scenarios resulted in an improved oil recovery factor, with injection at well bottom pressures of 3750, 4000, 4250, and 4500 psi leading to respective improvements of 10%, 12%, 13.7%, and 15% compared to natural depletion (no gas injection in the reservoir).
From an economic standpoint, a sensitivity analysis is conducted on various parameters related to production and injection, such as the price of produced oil, the price of produced gas, the cost of injected gas, and the discount rate. The results revealed that higher oil and gas prices increased the economic value of gas injection projects. Additionally, a comparison between the financial benefits of gas injection projects and gas export was made, considering parameters such as the price of export gas and gas export costs (both capital and operational). As the export gas price increased, gas export projects became more favorable than gas injection. Conversely, as the cost of gas export escalated, the desirability of gas export diminished compared to gas injection in the reservoir.
Overall, this comprehensive study provides valuable insights into the technical and economic considerations surrounding gas injection in southern oil reservoirs, highlighting its potential for enhanced oil recovery and economic viability compared to gas export projects.

Abstract Burning fuel oil presents a significant problem due to the harmful release of sulfur dioxide gases, which contribute to acid rain and environmental damage. Fuel oil contains a sulfur-rich asphaltene component, but the issues associated with burning this fuel oil can be mitigated through solvent deasphalting. This method isolates a portion of the asphaltene, thereby reducing the problems related to fuel oil combustion. In this study, the introduction of Nano-Fe2O3 into the fuel oil improved the efficiency of the solvent deasphalting process by up to 51% under optimal conditions (with a solvent-to-fuel oil ratio of 10 and a 5% weight percentage of Nano-Fe2O3). As a result, the sulfur content in fuel oil decreased from 3.5% to 2.71% by weight, reflecting a 22.5% reduction. Various analyses, including XRD, BET, FESEM, and FTIR, were used to examine the Nano-Fe2O3. Additionally, the Response Surface Method from Design Expert software was employed for statistical analysis and optimization. The experimental design included two numerical variables: the percentage of Nano-Fe2O3 (ranging from 1 to 5% by weight) and the solvent-to-fuel oil ratio (ranging from 5 to 10). The remaining sulfur in fuel oil and the efficiency of the asphaltene separation process were the dependent variables under investigation. Mathematical models were introduced to analyze these output variables, showing a high level of significance in predicting their behavior based on the independent variables, with predicted R2 values of 0.8218 and 0.9843, respectively.

Abstract This study examines and optimizes operational strategies in distillation units. Given rising energy costs, limited energy resources, and increasing environmental constraints, improving the energy efficiency of process industries has become critically important. This research aims to enhance the performance of distillation units by implementing dynamic process intensification, which involves alternating between two operational points with different concentrations. The study evaluates the use of Proportional-Integral-Derivative (PID) controllers and Model Predictive Control (MPC) to improve the efficiency of distillation columns. The results show that MPC controllers markedly enhance distillation performance compared to PID controllers. The findings further indicate that optimal periodic operation between the two operational points requires identifying the specific points and the time intervals during which the system should operate in each mode. This research demonstrates that using PID and MPC controllers to manage concentration transitions between operational points can dynamically improve the distillation of methanol and 1-propanol mixtures. As a result, energy savings of approximately 1.5% and 4.5% in the reboiler duty of the distillation column can be achieved without compromising product quality or throughput. Simulations performed in Aspen software validate these outcomes and underscore the positive effects of dynamic process intensification on distillation performance (Kister et al., 1992; Smith 2005).

Abstract Fourteen crude oil samples were collected from different oil fields in the southeastern region of Pakistan and analyzed for pH, density, kinematic viscosity, saponification value, distillation range, and fourteen metal ions (Ca, Cd, Cu, Co, Cr, Fe, K, Mg, Mn, Na, Ni, Pb, V, and Zn) using standard analytical procedures in accordance with ASTM methods. The metal ions were quantified by air–acetylene flame atomic absorption spectroscopy. Substantial variation in physicochemical properties and metal contents was observed among the different oil fields. The concentrations of V, Fe, Ca, and Ni were higher than those of the other elements. The metal ion data were further evaluated using correlation coefficient analysis, hierarchical cluster analysis, and principal component analysis.

Abstract The corrosion inhibition effects of two antibiotic compounds, tetracycline (TE) and streptomycin (ST), on the corrosion of copper sheets in 1 M hydrochloric acid were investigated using weight loss measurements, Tafel polarization, electrochemical impedance spectroscopy, scanning electron microscopy, molecular dynamics simulations, and quantum chemical calculations. The Tafel polarization results indicated that both inhibitors act as mixed-type inhibitors and showed that the inhibition efficiency of streptomycin is higher than that of tetracycline. In addition, the adsorption behavior of the inhibitors was found to be consistent with the Temkin adsorption isotherm. As a complementary approach, computational chemical studies were performed. Molecular dynamics simulations were used to evaluate the most stable configurations and adsorption energies of the two compounds on the Cu 100, Cu 110, and Cu 111 surfaces. The theoretical results provide substantial support for understanding the inhibition mechanism of the two antibiotic compounds and show good agreement with the experimental findings.