Journal of Oil, Gas and Petrochemical Technology
سال چهارم شماره 1 (Summer and Autumn 2017)

Crude oil fouling of the equipment surfaces is a troublesome issue which leads to operating difficulties, economic penalties, increased environmental impacts, and health and safety hazards in petroleum industry. With a rough estimation, a minimum cost of equal to 4 million barrels of oil/year is required to be invested to offset the costs of crude oil fouling in Pre-heat Trains of Iranian oil refineries. Considering the price of each oil barrel equal to 50$, crude oil fouling cost is predicted to be 200 million$/year. Additionally, burning extra fuel leads to emission of a great portion of CO2, which is associated with a highly negative environmental and economic impacts. Therefore, crude oil fouling mitigation methods such as controlling the operating conditions, utilizing additives, and surface modification techniques have received a great deal of attention. Surface modification in terms of modification of its geometry and texture and/or surface energy can help mitigate fouling to a large extent.

Thermodynamic analysis of the cracking of hexane has been conducted by the Gibbs free energy minimization method and second law analysis of overall reactions. By-products have been divided into three groups of methane, alkynes and aromatics and their possible production paths have been discussed. Effect of operating conditions such as temperature and steam-to-hexane ratio on the cracking performance has been investigated. The principal set of compounds considered in the modelling is hydrogen, water, ethane, ethylene, acetylene, propane, propylene, methyl acetylene, butane, butylene and hexane. Hexane conversion increased with increase of temperature and steam content. As temperature increases, the equilibrium olefin yield shows a volcano-shaped trend. In presence of methane, the maximum olefin yield declined and shifted to lower temperatures. When aromatics were considered in the product list, the light olefins yield is negligible. Equilibrium predicts that adding steam to the feed stream led to decrease of coke deposition through suppressing of aromatization reaction.

In recent years, the production of oil and gas has been developed in deep water depths which exceed 500m. Deep water developments are being followed strongly in different parts of the world (Caspian Sea, Gulf of Mexico, etc.). The movement of floater causes severe stress at the touchdown point (TDP) in steel catenary risers (SCR). The main objective of this study was to simulate the exact behavior of the riser in the vicinity of the touchdown zone (TDZ) by implementing linear SCR-seabed interaction model. Hence, present study attempted to investigate the riser-seabed interaction during lateral cyclic pipe movements and also the influence of seabed evolution around the TDZ based on the vertical cyclic movements. Moreover, The significance of the soil types in the response of riser pipeline at TDP was analyzed based on the vertical and lateral interaction. The fully non-linear time domain finite element model was utilized to simulate the riser behavior.

Due to the importance of energy consumption in a steam network of oil refinery as a significant unit, present study is concerned with the optimization of an oil refinery steam network. Here, the attempt was made to use concepts such as first and second thermodynamic laws, thermo-economic, environmental and economic discussions to investigate three different scenarios about Tehran refinery steam network. The first scenario was a base case in which boiler efficiency was 67%. The second scenario was the same as the first scenario, except that boilers efficiency was 86%. The third scenario was also similar to the base one. However, the difference was that one of the boilers was eliminated from the site. Instead, two gas turbines with heat recovery steam generator were introduced and the boiler efficiency was 86%. The obtained results showed that the annual cost of second and third scenarios fell to the rate of 22% and 42% respectively compared to the first scenario. To carry out thermodynamic modeling of some equipment such as steam turbines, gas turbines, and thermal recovers, Star software was utilized. In this paper, there has been an attempt to use concepts such as first and second thermodynamic laws, economic, exergoeconomic, environmental discussions in order to investigatethree different scenarios around Tehran refinery steam network. Finally, the annual cost of second and third scenarios has fallen down to the rate of 22% and 42% respectively compared to the first scenario. In order to carry out thermodynamic modelling of some equipment such as steam turbines, gas turbines and thermal recovers, Star software was utilized.

In this work, an equation of state has been utilized for thermodynamic modeling of aqueous electrolyte solutions. The proposed equation of state is a combination of simplified statistical associating fluid theory (SAFT) equation of state (similar to simplified PC-SAFT) to describe the effect of short-range interactions and mean spherical approximation (MSA) term to describe the effect of long-range interactions. In this model, the salt- based approach or restricted primitive model has been used to adjust the four parameters of the model. The salt (ion) parameters have been estimated through simultaneous fitting to experimental mean ionic activity coefficient and liquid density data of strong electrolytes. Four strong electrolytes, three 1:1 and one 1:2 electrolytes have been used. Using adjusted ion parameters, osmotic coefficient of solvent has been predicted with 0.79% average relative deviation (ARD%). Results show that simplified SAFT, in combination with the MSA term has ARD% about 1% and less for correlating of density and mean ionic activity coefficient of electrolyte solutions.

Well test analysis of multi-layer reservoir comprises several parts. The first part concerns the estimation of parameters values and next considers finding an appropriate method to determine the unknown reservoir parameters. If the initial estimations are less accurate and weak, the final assessment may lead to incorrect results, which are totally different from the reality. Utilizing Automated Type-Curve Matching method by means of computers is effective and successful. In addition, it has priority over the ordinary analysis methods, and numerical calculations are performed with higher speed thereby causing fewer errors. In this study, first, a numerical simulation of reservoir was conducted by means of Eclipse 100 software and then its production and pressure results were introduced to Ecrin software of well test analysis. Different states were investigated in the analyzer to obtain the minimum error, and suggestions, including effect of regression point selection, initial guess, and effect of using each layer production were made to minimize the error. The final analysis results were compared with numerical simulation data to determine the performance of Ecrin software, and then a real well test was investigated in the gas field of South Pars by using this method. Furthermore, parameters of each layer were obtained so that applying the mentioned method caused the analyzer error to decrease to a favorable desired value.